Internist, Geriatric Specialist (elderly care)
27 years of experience

Accepting new patients
Northeast Ann Arbor
Ann Arbor Veterans Affairs Medical Center
2215 Fuller Rd
Ann Arbor, MI 48105
734-769-7100
Locations and availability (3)

Education ?

Medical School Score Rankings
University of Minnesota, Twin Cities (1983)
  • Currently 4 of 4 apples
Top 25%

Awards & Distinctions ?

Associations
American Board of Internal Medicine

Affiliations ?

Dr. Alexander is affiliated with 3 hospitals.

Hospital Affilations

  • University of Michigan Health System
  • Ann Arbor Veterans Affairs Medical Center
    2215 Fuller Rd, Ann Arbor, MI 48105
  • University of Michigan Hospitals & Health Centers
  • Publications & Research

    Dr. Alexander has contributed to 77 publications.
    Title Bedside-to-bench Conference: Research Agenda for Idiopathic Fatigue and Aging.
    Date September 2010
    Journal Journal of the American Geriatrics Society
    Excerpt

    The American Geriatrics Society, with support from the National Institute on Aging and the John A. Hartford Foundation, held its fifth Bedside-to-Bench research conference, "Idiopathic Fatigue and Aging," to provide participants with opportunities to learn about cutting-edge research developments, draft recommendations for future research, and network with colleagues and leaders in the field. Fatigue is a symptom that older persons, especially by those with chronic diseases, frequently experience. Definitions and prevalence of fatigue may vary across studies, across diseases, and even between investigators and patients. The focus of this review is on physical fatigue, recognizing that there are other related domains of fatigue (such as cognitive fatigue). Many definitions of fatigue involve a sensation of "low" energy, suggesting that fatigue could be a disorder of energy balance. Poor energy utilization efficiency has not been considered in previous studies but is likely to be one of the most important determinants of fatigue in older individuals. Relationships between activity level, capacity for activity, a tolerable rate of activity, and a tolerable fatigue threshold or ceiling underlie a notion of fatiguability. Mechanisms probably contributing to fatigue in older adults include decline in mitochondrial function, alterations in brain neurotransmitters, oxidative stress, and inflammation. The relationships between muscle function and fatigue are complex. A number of diseases (such as cancer) are known to cause fatigue and may serve as models for how underlying impaired physiological processes contribute to fatigue, particularly those in which energy utilization may be an important factor. A further understanding of fatigue will require two key strategies: to develop and refine fatigue definitions and measurement tools and to explore underlying mechanisms using animal and human models.

    Title Decreased Muscle Strength Relates to Self-reported Stooping, Crouching, or Kneeling Difficulty in Older Adults.
    Date January 2010
    Journal Physical Therapy
    Excerpt

    Bending down and kneeling are fundamental tasks of daily living, yet nearly a quarter of older adults report having difficulty performing or being unable to perform these movements. Older adults with stooping, crouching, or kneeling (SCK) difficulty have demonstrated an increased fall risk. Strength (force-generating capacity) measures may be useful for determining both SCK difficulty and fall risk.

    Title The Influence of Age and Physical Activity on Upper Limb Proprioceptive Ability.
    Date December 2009
    Journal Journal of Aging and Physical Activity
    Excerpt

    Our understanding of age-related declines in upper limb proprioceptive abilities is limited. Furthermore, the extent to which physical activity might ameliorate age-related changes in proprioception is not known. Upper limb proprioceptive acuity was examined in young and older (active and sedentary) right-handed adults using a wrist-position-matching task that varied in terms of processing demands. Older individuals were also classified according to their participation in tasks specific to the upper limb. Errors were greater for older than younger individuals. Older sedentary adults showed greater errors and performed movements less smoothly than older active adults. The nonspecific group showed greater errors and longer movement times than the upper-limb-specific group. In older adults, decreased ability to perceive limb position may be related to a sedentary lifestyle and declines associated with memory and transfer of proprioceptive information. Performing tasks specific to the upper limbs may reduce age-related declines in proprioception.

    Title Guest Editorial: Linking Thinking, Walking, and Falling.
    Date March 2009
    Journal The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences
    Title Executive Function and Gait in Older Adults with Cognitive Impairment.
    Date March 2009
    Journal The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences
    Excerpt

    Cognitive impairment has been shown to predict falls risk in older adults. The ability to step accurately is necessary to safely traverse challenging terrain conditions such as uneven or slippery surfaces. However, it is unclear how well persons with cognitive impairment can step accurately to avoid such hazards and what specific aspects of cognition predict stepping ability in different patient populations.

    Title Use of a Device to Support Standing During a Physical Activity Program to Improve Function of Individuals with Disabilities Who Reside in a Nursing Home.
    Date March 2009
    Journal Disability and Rehabilitation. Assistive Technology
    Excerpt

    To demonstrate the feasibility of an innovative program of physical activity using a standing-support device targeted towards adult residents of a nursing home who are unable to transfer or stand independently.

    Title Developing a Positive Emotion-motivated Tai Chi (pem-tc) Exercise Program for Older Adults with Dementia.
    Date February 2009
    Journal Research and Theory for Nursing Practice
    Excerpt

    Exercise, particularly Tai Chi, has many known benefits, especially in reducing fall risk. However, exercise studies have tended to exclude older adults with dementia (OAD), who may be at high fall risk but have difficulty participating in formal exercise programs. This paper describes development and feasibility testing of a Tai Chi fall risk reduction exercise protocol, the positive emotion-motivated Tai Chi (PEM-TC) program for OAD, and explores strategies that facilitate their participation in and adherence to exercise programs. Preliminary data indicates that difficulties in delivering exercise to OAD may be eased by using the Sticky Hands Tai Chi teaching technique. Family members may have the optimum advantage in using Sticky Hands because of established emotional connections with their OAD.

    Title Standing Balance and Trunk Position Sense in Impaired Glucose Tolerance (igt)-related Peripheral Neuropathy.
    Date September 2008
    Journal Journal of the Neurological Sciences
    Excerpt

    Type 2 diabetes mellitus (T2DM) and pre-diabetes or impaired glucose tolerance (IGT) affect a large segment of the population. Peripheral neuropathy (PN) is a common complication of T2DM, leading to sensory and motor deficits. While T2DM-related PN often results in balance- and mobility-related dysfunction which manifests as gait instability and falls, little is known about balance capabilities in patients who have evidence of PN related to IGT (IGT-PN). We evaluated patients with IGT-PN on commonly-used clinical balance and mobility tests as well as a new test of trunk position sense and balance impairment, trunk repositioning errors (TREs). Eight participants aged 50-72 years with IGT-PN, and eight age- and gender-matched controls underwent balance, mobility and trunk repositioning accuracy tests at a university neurology clinic and mobility research laboratory. Compared to controls, IGT-PN participants had as much as twice the magnitude of TREs and stood approximately half as long on the single leg balance test. People with IGT-PN exhibit deficits in standing balance and trunk position sense. Furthermore, there was a significant association between performance on commonly-used clinical balance and mobility tests, and electrophysiological and clinical measures of neuropathy in IGT-PN participants. Because IGT-related neuropathy represents the earliest stage of diabetic neuropathy, deficits in IGT-PN participants highlight the importance of early screening in the dysglycemic process for neuropathy and associated balance deficits.

    Title The Effects of Age and Step Length on Joint Kinematics and Kinetics of Large Out-and-back Steps.
    Date September 2008
    Journal Clinical Biomechanics (bristol, Avon)
    Excerpt

    BACKGROUND: Maximum step length (MSL) is a clinical test that has been shown to correlate with age, various measures of fall risk, and knee and hip joint extension speed, strength, and power capacities, but little is known about the kinematics and kinetics of the large out-and-back step utilized. METHODS: Body motions and ground reaction forces were recorded for 11 unimpaired younger and 10 older women while attaining maximum step length. Joint kinematics and kinetics were calculated using inverse dynamics. The effects of age group and step length on the biomechanics of these large out-and-back steps were determined. FINDINGS: Maximum step length was 40% greater in the younger than in the older women (P<0.0001). Peak knee and hip, but not ankle, angle, velocity, moment, and power were generally greater for younger women and longer steps. After controlling for age group, step length generally explained significant additional variance in hip and torso kinematics and kinetics (incremental R2=0.09-0.37). The young reached their peak knee extension moment immediately after landing of the step out, while the old reached their peak knee extension moment just before the return step liftoff (P=0.03). INTERPRETATION: Maximum step length is strongly associated with hip kinematics and kinetics. Delays in peak knee extension moment that appear to be unrelated to step length, may indicate a reduced ability of older women to rapidly apply force to the ground with the stepping leg and thus arrest the momentum of a fall.

    Title Measuring Activity Pacing in Women with Lower-extremity Osteoarthritis: a Pilot Study.
    Date September 2008
    Journal The American Journal of Occupational Therapy. : Official Publication of the American Occupational Therapy Association
    Excerpt

    OBJECTIVE: We examined how women with osteoarthritis naturally use activity pacing and how pacing relates to symptoms and physical activity within daily routines. METHOD: Thirty women with knee or hip osteoarthritis (mean age = 63.8 +/- 6.9) wore an actigraph accelerometer and repeatedly reported activity pacing, pain, and fatigue. Using the median split, symptom patterns were compared for low and high pacers. The relationship between activity pacing and physical activity was also examined. RESULTS: Activity pacing was low (1.4 +/- 0.9); pain and fatigue were mild (1.0 +/- 0.7 and 1.1 +/- 0.7, respectively). When compared with low pacers, high pacers had more severe, escalating symptoms. Activity pacing was related to lower physical activity (beta = -28.14, SE = 6.24), t(586) = -4.51, p = .0001. CONCLUSION. Pain, fatigue, and activity pacing use varied depending on average activity pacing level. High pacers may benefit from interventions to manage daily symptoms.

    Title Characteristics of Older Adults with Self-reported Stooping, Crouching, or Kneeling Difficulty.
    Date September 2008
    Journal The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences
    Excerpt

    BACKGROUND: Stooping, crouching, and kneeling (SCK) are fundamental components of daily living tasks, and nearly a quarter of older adults report a lot of difficulty or inability to perform these movements. This study examined characteristics associated with SCK difficulty to explore underlying mechanisms and remediation strategies. METHODS: One hundred eighty-four older adults with no, low, or high SCK difficulty underwent a comprehensive laboratory visit at the University of Michigan. RESULTS: Twenty-one percent of participants (n = 39) reported a lot of difficulty or inability to stoop, crouch, or kneel. Characteristics independently associated with increasing SCK difficulty were self-reported leg joint limitations, (odds ratio [OR] = 3.84; 95% confidence interval [CI], 1.64-9.01), Activities-specific Balance Confidence Scale score (OR = 0.97; 95% CI, 0.95-0.99), and knee extension strength (OR = 0.72; 95% CI, 0.55-0.94). CONCLUSIONS: Increasing SCK difficulty is associated with balance confidence as well as leg limitations. Remediation of SCK difficulty will likely require a program that encompasses both behavioral and physical issues.

    Title The Impact of Momentary Pain and Fatigue on Physical Activity in Women with Osteoarthritis.
    Date July 2008
    Journal Arthritis and Rheumatism
    Excerpt

    OBJECTIVE: To examine the daily life patterns of both pain and fatigue symptoms and objective physical activity (using ambulatory monitoring) in women with symptomatic lower extremity osteoarthritis (OA), and to evaluate how momentary symptoms impact physical activity levels. METHODS: Sixty women age >or=55 years (40 with knee or hip OA and 20 matched controls) participated in an observational study involving 2 laboratory visits and a 5-day home data collection period. During the home period physical activity levels were assessed continuously, and symptoms were inputted 6 times a day into an enhanced accelerometer at prespecified time points. RESULTS: In the OA group as compared with the control group over the 5-day period, average physical activity was significantly lower (P = 0.02) and peak physical activity tended to be lower (P = 0.06). Although pain and fatigue overall were of moderate severity in this cohort, fatigue escalated throughout each day. In a hierarchical linear model, fatigue was most strongly associated with physical activity (beta = -30.1, P < 0.0001). Pain was more weakly associated with physical activity and in the direction opposite to what was hypothesized (beta = 16.9, P = 0.04). CONCLUSION: Momentary reports of fatigue negatively predicted physical activity levels and were much more strongly related to physical activity than momentary pain. In order to help women with knee or hip OA manage symptoms and become more physically active, it may be important to emphasize fatigue management.

    Title The Effect of Lateral Stabilization on Walking in Young and Old Adults.
    Date December 2007
    Journal Ieee Transactions on Bio-medical Engineering
    Excerpt

    We tested how lateral stability affects gait as a function of age. A simple computational model suggests that walking is laterally unstable and that age-related decreases in motor and sensory function may be treated as noise-like perturbations to the body. Step width variability may be affected by active control of foot placement subject to noise. We hypothesized that age-related deficits may lead to increased step width variability. A possible compensation would be to walk with wider steps to reduce the lateral instability. The addition of external stabilization, through elastic cords acting laterally on the body during treadmill walking, would be expected to yield reduced step width variability and/or reduced average step width. We measured step width, its variability (defined as standard deviation), and metabolic energy expenditure in eight adult human subjects aged less than 30 years (Young) and ten subjects aged at least 65 years (Old). Subjects walked with and without external stabilization, each at a self-selected step width as well as a prescribed step width of zero. In normal walking, Old subjects preferred 41% wider steps than Young, and expended 26% more net energy (P < 0.05). External stabilization caused both groups to prefer 58% narrower steps. In the prescribed zero step width condition, Old subjects walked with 52% more step width variability and at 20% higher energetic cost. External stabilization resulted in reduced step width variability and 16% decreased energetic cost. Although there was no significant statistical interaction between age group and stabilization, Old and Young subjects walked with similar energetic costs in the stabilized, prescribed step width condition. Age-related changes appear to affect lateral balance, and the resulting compensations explain much of the increased energetic cost of walking in older adults.

    Title The Bath Environment, the Bathing Task, and the Older Adult: a Review and Future Directions for Bathing Disability Research.
    Date September 2007
    Journal Disability and Rehabilitation
    Excerpt

    PURPOSE: To review existing research studies to identify optimal intervention strategies for remediation and prevention of bathing disability and future directions for bathing disability research. METHOD: Bathing disability, defined as problems in the interaction between the person and the environment during bathing performance, is examined through a comprehensive, narrative literature review. RESULTS: Most studies focus on the relationship between the person and the environment (such as assistive device use and environmental hazards) while fewer studies focus on analysis of the bathing task or the interaction of the person, environment, and bathing task. Of intervention studies, most do not focus solely on remediation of bathing disability and outcomes vary widely. CONCLUSIONS: In order to help remediate and prevent bathing disability, it will be necessary to better understand and measure the person-environment-occupation interaction involved in bathing as it relates to specific groups of older adults.

    Title Maximum Step Length: Relationships to Age and Knee and Hip Extensor Capacities.
    Date August 2007
    Journal Clinical Biomechanics (bristol, Avon)
    Excerpt

    BACKGROUND: Maximum Step Length may be used to identify older adults at increased risk for falls. Since leg muscle weakness is a risk factor for falls, we tested the hypotheses that maximum knee and hip extension speed, strength, and power capacities would significantly correlate with Maximum Step Length and also that the "step out and back" Maximum Step Length [Medell, J.L., Alexander, N.B., 2000. A clinical measure of maximal and rapid stepping in older women. J. Gerontol. A Biol. Sci. Med. Sci. 55, M429-M433.] would also correlate with the Maximum Step Length of its two sub-tasks: stepping "out only" and stepping "back only". These sub-tasks will be referred to as versions of Maximum Step Length. METHODS: Unimpaired younger (N=11, age=24[3]years) and older (N=10, age=73[5]years) women performed the above three versions of Maximum Step Length. Knee and hip extension speed, strength, and power capacities were determined on a separate day and regressed on Maximum Step Length and age group. Version and practice effects were quantified and subjective impressions of test difficulty recorded. Hypotheses were tested using linear regressions, analysis of variance, and Fisher's exact test. FINDINGS: Maximum Step Length explained 6-22% additional variance in knee and hip extension speed, strength, and power capacities after controlling for age group. Within- and between-block and test-retest correlation values were high (>0.9) for all test versions. INTERPRETATION: Shorter Maximum Step Lengths are associated with reduced knee and hip extension speed, strength, and power capacities after controlling for age. A single out-and-back step of maximal length is a feasible, rapid screening measure that may provide insight into underlying functional impairment, regardless of age.

    Title A Kinematic Analysis of the Rapid Step Test in Balance-impaired and Unimpaired Older Women.
    Date June 2007
    Journal Gait & Posture
    Excerpt

    Little is known about the kinematic and kinetic determinants that might explain age and balance-impairment alterations in the results of volitional stepping performance tests. Maximal unipedal stance time (UST) was used to distinguish "balance-impaired" old (BI, UST<10s, N=15, mean age=76 years) from unimpaired old (O, UST>30s, N=12, mean age=71 years) before they and healthy young females (Y, UST>30s, N=13, mean age=23 years) performed the rapid step test (RST). The RST evaluates the time required to take volitional front, side, and back steps of at least 80% maximum step length in response to verbal commands. Kinematic and kinetic data were recorded during the RST. The results indicate that the initiation phase of the step was the major source of age- and balance impairment-related delays. The delays in BI were primarily caused by increased postural adjustments prior to step initiation, as measured by center-of-pressure (COP) path length (p<0.003). The Step landing phase showed similar, but non-significant, temporal trends. Step length and peak center-of-mass (COM) deceleration during the Step-Out landing decreased in O by 18% (p=0.0002) and 24% (p=0.001), respectively, and a further 12% (p=0.04) and 18% (p=0.08) in BI. We conclude that the delay in BI step initiation was due to the increase in their postural adjustments prior to step initiation.

    Title Dynamic Balance and Stepping Versus Tai Chi Training to Improve Balance and Stepping in At-risk Older Adults.
    Date January 2007
    Journal Journal of the American Geriatrics Society
    Excerpt

    OBJECTIVES: To compare the effect of two 10-week balance training programs, Combined Balance and Step Training (CBST) versus tai chi (TC), on balance and stepping measures. DESIGN: Prospective intervention trial. SETTING: Local senior centers and congregate housing facilities. PARTICIPANTS: Aged 65 and older with at least mild impairment in the ability to perform unipedal stance and tandem walk. INTERVENTION: Participants were allocated to TC (n = 107, mean age 78) or CBST, an intervention focused on improving dynamic balance and stepping (n = 106, mean age 78). MEASUREMENTS: At baseline and 10 weeks, participants were tested in their static balance (Unipedal Stance and Tandem Stance (TS)), stepping (Maximum Step Length, Rapid Step Test), and Timed Up and Go (TUG). RESULTS: Performance improved more with CBST than TC, ranging from 5% to 10% for the stepping tests (Maximum Step Length and Rapid Step Test) and 9% for TUG. The improvement in TUG represented an improvement of more than 1 second. Greater improvements were also seen in static balance ability (in TS) with CBST than TC. CONCLUSION: Of the two training programs, in which variants of each program have been proven to reduce falls, CBST results in modest improvements in balance, stepping, and functional mobility versus TC over a 10-week period. Future research should include a prospective comparison of fall rates in response to these two balance training programs.

    Title Can Initial and Additional Compensatory Steps Be Predicted in Young, Older, and Balance-impaired Older Females in Response to Anterior and Posterior Waist Pulls While Standing?
    Date October 2006
    Journal Journal of Biomechanics
    Excerpt

    The initiation of a single compensatory step in response to balance perturbations has been predicted with accuracies of up to 71%. We sought to determine whether similar methods also could be used to predict the onset of additional compensatory steps in both healthy and balance-impaired older females. Anterior and posterior waist pulls of five different magnitudes were applied to 13 unimpaired young (mean age 23 years), 12 unimpaired older (mean age 71 years), and 15 balance-impaired older (mean age 76 years) women. Body segment kinematic data were recorded at 100 Hz. A step was predicted when the time for the center-of-mass to reach the vertical projection of the boundary of the base-of-support fell below a certain threshold. The results show that 83% of all steps and non-steps were correctly predicted at an optimal time-to-boundary threshold (tau(opt)) of 0.78 s. Step prediction accuracy did not differ significantly by group: 86% of steps and non-steps by young, 84% by unimpaired old, and 82% by balance-impaired old women were correctly predicted at tau(opt) of 0.58, 0.67, and 0.78 s, respectively. Anterior steps and non-steps were predicted more accurately than posterior ones (94% vs. 79% correct at tau(opt) of 0.52 and 0.84 s, respectively) and initial steps were better predicted than additional ones (87% vs. 81% correct at tau(opt) of 0.77 and 0.34 s, respectively). We conclude that this step prediction method reasonably predicts initial and additional steps in the anterior and posterior direction by all three subject cohorts.

    Title Bath Transfers in Older Adult Congregate Housing Residents: Assessing the Person-environment Interaction.
    Date September 2006
    Journal Journal of the American Geriatrics Society
    Excerpt

    OBJECTIVES: To examine environmental feature utilization (EFU) and the types and prevalence of performance difficulties during a videotaped bath transfer and to determine the personal characteristics associated with total EFU and performance difficulties. DESIGN: Cross-sectional analysis. SETTING: Two congregate housing facilities in southeastern Michigan. PARTICIPANTS: Eighty-nine older adults who reported independence in bathing. MEASUREMENTS: Trained video coders recorded EFU (defined as upper extremity contact with features in the environment) and rated performance difficulties (defined as lack of fluid movement or difficulty negotiating the environment). EFU was measured by determining whether features used were safe (i.e., designed for use as a transfer support) or unsafe and by total EFU (i.e., number of environmental features used during the transfer). Personal characteristics included self-reported medical conditions, bath transfer difficulty, functional mobility, lower extremity strength, range of motion functional impairment, and falls efficacy. RESUTLS: For participants with a tub-shower, safe EFU was higher than unsafe EFU (85% vs 19%; P<.001). Participants with shower stalls had the same rate of safe and unsafe EFU (71%). In multiple regression analysis, self-reported bath transfer difficulty was associated with total EFU (P=.01). One-third of the sample had performance difficulties. In multivariate analysis, range of motion functional impairment (odds ratio (OR)=13.49, 95% confidence interval (CI)=1.11-163.53) and lowest quartile in falls efficacy scores (OR=5.81, 95% CI=1.24-27.41) were associated with performance difficulties. CONCLUSION: Unsafe EFU and performance difficulties were common in independently bathing older adults. Self-reported bath transfer difficulty appears to be a good indicator of high total EFU and may be used as a screening question for clinicians. Important strategies to reduce unsafe EFU and to increase falls efficacy include removing shower sliding glass doors and training older adults in safe transfer techniques.

    Title Gait Disorders: Search for Multiple Causes.
    Date August 2006
    Journal Cleveland Clinic Journal of Medicine
    Excerpt

    Gait disorders predict functional decline in older adults. They are often the result of multiple causes, so a full assessment should consider different sensorimotor levels and should include a focused physical examination and evaluation of functional performance. Exercise and medical and surgical interventions are effective and can reduce the degree of gait disorder, but usually not without some residual impairment. Orthoses and mobility aids are also important interventions to consider.

    Title Age Differences in Timed Accurate Stepping with Increasing Cognitive and Visual Demand: a Walking Trail Making Test.
    Date April 2006
    Journal The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences
    Excerpt

    BACKGROUND: Impaired vision, cognition, and divided attention performance predict falls. Requiring both visual and cognitive input, the ability to step accurately is necessary to safely traverse challenging terrain conditions such as uneven or slippery surfaces. We compared healthy young and older adults in the time taken to step accurately under conditions of increasing cognitive and visual demand. METHODS: Healthy Young (n = 42, mean age 21) and Older (n = 37, mean age 70) participants were required to step accurately on an instrumented walkway under conditions of increasing visual and cognitive demand. Based on the paper-and-pencil neuropsychological test, the Trail Making Test (P-TMT) A and B, participants stepped on instrumented targets with increasing sequential numbers (Walking Trail Making Test A [W-TMT A]) and increasing sequential numbers and letters (Walking Trail Making Test B [W-TMT B]), under conditions of Low as well as Normal lighting. RESULTS: W-TMT performance time increased with increased age (Older vs Young), decreased light (Low vs Normal), and increased cognitive demand (Trails B vs Trails A). W-TMT performance time was disproportionately increased in Low light and in the Older group under the highest cognitive demand (W-TMT B) conditions. Paired W-TMT A-B differences were three times higher in the Older group than in the Young group. In the Older group, the correlation between W-TMT results and P-TMT B was particularly strong (p <.001). CONCLUSIONS: The time to perform a stepping accuracy task, such as may be required to avoid environmental hazards, increases under reduced lighting and with increased cognitive demand, the latter disproportionately so in older adults.

    Title Compensatory Stepping in Response to Waist Pulls in Balance-impaired and Unimpaired Women.
    Date January 2006
    Journal Gait & Posture
    Excerpt

    An effective stepping response is often critical in avoiding a fall. Our objective was to study the effects of age and balance impairment on anterior and posterior compensatory stepping strategies in response to waist pull perturbations of 1-5% body weight (BW). Based on maximal unipedal stance time (UST), we tested 15 balance-impaired old (BI, UST < 10s, mean age = 76 years), 12 healthy old (O, UST>30s, mean age = 71 years), and 13 healthy young women (Y, UST >30s, mean age=23 years). Randomized anterior and posterior pulls of 1-5% body weight (BW) were applied to the waist while kinematic and kinetic recovery responses were recorded. Results show that O and BI required 0.5 more steps than Y to recover balance for posterior pulls of 4-5% BW (P < 0.01). For anterior pulls of 4-5% BW, only BI had a greater probability of step initiation (P<or=0.05 or <0.02) and mean number of steps required to recover balance (P < 0.03). The Y used 93% greater torso extension and 24% greater torso flexion in responding to anterior and posterior pulls, respectively. In the posterior, but not anterior direction, O employed smaller (P < 0.007), but more laterally-directed (P < 0.03) steps than the Y. The BI were less able to attenuate their momentum during the step landing in both directions. We conclude that the additional steps required by the BI in both directions occurred because their initial step failed to properly arrest their momentum. Controlling torso inclination before step liftoff and linear momentum after step landing are critical components of successful compensatory stepping.

    Title Trunk Repositioning Errors Are Increased in Balance-impaired Older Adults.
    Date January 2006
    Journal The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences
    Excerpt

    BACKGROUND: Controlling the flexing trunk is critical in recovering from a loss of balance and avoiding a fall. To investigate the relationship between trunk control and balance in older adults, we measured trunk repositioning accuracy in young and balance-impaired and unimpaired older adults. METHODS: Young adults (N = 8, mean age 24.3 years) and two groups of community-dwelling older adults defined by unipedal stance time (UST)-a balance-unimpaired group (UST > 30 seconds, N = 7, mean age 73.9 years) and a balance-impaired group (UST < 5 seconds, N = 8, mean age 79.6 years)-were tested in standing trunk control ability by reproducing a approximately 30 degrees trunk flexion angle under three visual-surface conditions: eyes opened and closed on the floor, and eyes opened on foam. Errors in reproducing the angle were defined as trunk repositioning errors (TREs). Clinical measures related to balance, trunk extensor strength, and self-reported disability were obtained. RESULTS: TREs were significantly greater in the balance-impaired group than in the other groups, even when controlling for trunk extensor strength and body mass. In older adults, there were significant correlations between TREs and three clinical measures of balance and fall risk, UST and maximum step length (-0.65 to -0.75), and Timed Up & Go score (0.55), and between TREs and age (0.63-0.76). In each group TREs were similar under the three visual-surface conditions. Test-retest reliability for TREs was good to excellent (intraclass correlation coefficients > or =0.74). CONCLUSIONS: Older balance-impaired adults have larger TREs, and thus poorer trunk control, than do balance-unimpaired older individuals. TREs are reliable and valid measures of underlying balance impairment in older adults, and may eventually prove to be useful in predicting the ability to recover from losses of balance and to avoid falls.

    Title Assessing Falls in Older Adults: a Comprehensive Fall Evaluation to Reduce Fall Risk in Older Adults.
    Date November 2005
    Journal Geriatrics
    Excerpt

    Falls account for significant morbidity and mortality in the older adult population. A comprehensive fall evaluation (CFE) is proposed, particularly for use in recurrent fallers, those who seek medical attention for a fall, and those with a gait and/or balance disorder. The CFE focuses on key factors in the medical and fall history, review of systems, and physical examination. Interventions utilize a multifactorial model, although balance exercise may be the most critical component. While some components may be marginally successful when presented individually as an intervention (such as correction of vision impairment or environmental hazard reduction), when presented together, fall risk can be significantly reduced.

    Title Tests of Stepping As Indicators of Mobility, Balance, and Fall Risk in Balance-impaired Older Adults.
    Date April 2005
    Journal Journal of the American Geriatrics Society
    Excerpt

    OBJECTIVES: To determine the relationships between two tests of stepping ability (the maximal step length (MSL) and rapid step test (RST)) and standard tests of standing balance, gait, mobility, and functional impairment in a group of at-risk older adults. DESIGN: Cross-sectional study. SETTING: University-based laboratory. PARTICIPANTS: One hundred sixty-seven mildly balance-impaired older adults recruited for a balance-training and fall-reduction program (mean age 78, range 65-90). MEASUREMENTS: Measures of stepping maximally (MSL, the ability to maximally step out and return to the initial position) and rapidly (RST, the time taken to step out and return in multiple directions as fast as possible); standard measures of balance, gait, and mobility including timed tandem stance (TS), tandem walk (TW, both timing and errors), timed unipedal stance (US), timed up and go (TUG), performance oriented mobility assessment (POMA), and 6-minute walk (SMW); measures of leg strength (peak knee and ankle torque and power at slow and fast speeds); self-report measures of frequent falls (>2 per 12 months), disability (Established Population for Epidemiologic Studies of the Elderly (EPESE) physical function), and confidence to avoid falls (Activity-specific Balance Confidence (ABC) Scale). Spearman and Pearson correlation, intraclass correlation coefficient, logistic regression, and linear regression were used for data analysis. RESULTS: MSL consistently predicted a number of self-report and performance measures at least as well as other standard balance measures. MSL correlations with EPESE physical function, ABC, TUG, and POMA scores; SMW; and peak maximum knee and ankle torque and power were at least as high as those correlations seen with TS, TW, or US. MSL score was associated with the risk of being a frequent faller. In addition, the six MSL directions were highly correlated (up to 0.96), and any one of the leg directions yielded similar relationships with functional measures and a history of falls. Relationships between RST and these measures were relatively modest. CONCLUSION: MSL is as good a predictor of mobility performance, frequent falls, self-reported function, and balance confidence as standard stance tests such as US. MSL simplified to one direction may be a useful clinical indicator of mobility, balance, and fall risk in older adults.

    Title Age-related Changes in Maximal Hip Strength and Movement Speed.
    Date May 2004
    Journal The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences
    Excerpt

    BACKGROUND: We quantified age-related decreases in the ability of female participants to generate whole leg movements about the hip. METHODS: We measured maximum hip strength and hip velocity in 12 young and 12 older healthy women. Both capabilities could help fall prevention by contributing to fast leg movements. We also measured maximum velocities as a function of isotonic load. RESULTS: Young participants produced 107.6 +/- 25.4 N-m (mean +/- SD) isometric torque in flexion and 109.3 +/- 22.3 N-m in extension. Older participants produced 22% and 31% lower torques, respectively (p<.001). Young participants generated maximum velocities of 362.8 +/- 51.5 degrees/s in flexion and 371.5 +/- 54.2 degrees/s in extension. Older participants produced 16% lower velocities in both directions (p<.001). Older participants also produced lower velocities as a function of load (p<.001), and lower maximum power (p<.001). CONCLUSION: Both maximum strength and velocity contribute to reduced ability to move the leg quickly with age.

    Title Oxygen-uptake (vo2) Kinetics and Functional Mobility Performance in Impaired Older Adults.
    Date September 2003
    Journal The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences
    Excerpt

    BACKGROUND: Measures of maximal oxygen uptake (VO(2max)) are limited in disabled older adults, and measures of submaximal oxygen uptake (VO(2)) may better predict functional mobility limitations. These measures may include oxygen-uptake kinetics at the onset of submaximal exercise or during recovery. We sought to determine whether the lag in oxygen uptake at the beginning of exercise (oxygen deficit) and excess oxygen uptake above rest following exercise (excess postexercise oxygen consumption) (a) predict physical performance in impaired older adults with decreased aerobic function, and (b) predict physical performance better than peak VO(2). METHODS: Two groups of community-dwelling volunteers aged 65 or older were recruited according to their performance on a maximal graded exercise test. Using the Social Security Administration criterion of disability of a peak VO(2) <or = 18 ml/kg/min, we compared the performance of an impaired aerobic capacity group at a peak VO(2) < 18 ml/kg/min (Impaired, n = 20, mean +/- SEM age 82 +/- 1 years) with an unimpaired group at Peak VO(2) > 18 (Unimpaired, n = 21, mean +/- SEM age 76 +/- 1 years). RESULTS: The mean +/- SEM peak VO(2) was 58% lower in the Impaired (14 +/- 1 ml/kg/min) than the Unimpaired (24 +/- 1 ml/kg/min) adults. The time constant for oxygen deficit, tc(deficit), was more than twice as high in the Impaired than the Unimpaired (p <.05), and the time constant for excess postexercise oxygen consumption, tc(EPOC), tended to be higher in the Impaired than the Unimpaired (by 43%, p =.09). Measures of submaximal oxygen-uptake kinetics were as strong or more strongly predictive of functional mobility performance than peak VO(2) in both Unimpaired and Impaired older adults. The major predictor of functional performance for the Unimpaired was a measure of oxygen deficit accruing during exercise (tc(deficit)), and for the Impaired, it was a measure of oxygen debt during recovery, tc(EPOC). CONCLUSIONS: Measurement of submaximal oxygen-uptake kinetics may provide a more practical and relevant assessment of deconditioning in frail older adults, and may eventually supplant maximal (peak) oxygen uptake as a predictor of functional disability in older adults.

    Title The Effect of Age and Movement Speed on Maximum Forward Reach from an Elevated Surface: a Study in Healthy Women.
    Date May 2003
    Journal Clinical Biomechanics (bristol, Avon)
    Excerpt

    OBJECTIVE: To test the hypotheses (1) that the maximum distance reached by young or older women when standing on a raised platform is independent of movement speed, and (2) the maximum forward momentum generated at comfortable and fast reaching speeds is independent of age. DESIGN: Repeated measures case-control study in a university laboratory setting.Background. Maximum forward reach distance is often part of a geriatric mobility assessment. The effect of movement speed, and hence momentum, on forward reaching behavior is unknown in young or older subjects, despite the fact that excess momentum might increase the risk of fall-related injuries, especially from an elevated surface. METHODS: Ten healthy young women (mean age 23.7 years) and 10 healthy older women (mean age 70.5 years) participated. Subjects stood on an instrumented force platform and forward reach body segment kinematics were measured optoelectronically. Whole-body center of reaction and center of mass trajectories were calculated during six maximum forward reach trials: three performed "at a comfortable speed", and three performed "as fast as possible". RESULTS: Subjects reached slightly further at a comfortable speed than when reaching as fast as possible (P=0.016). Fast reaches were associated with a 25% increase in momentum (P<0.001; however, under both speed conditions, older women developed less whole-body momentum than did young controls (for example, 4.1 vs. 6.1 kgm/s at comfortable speed, P<0.05). Three young and one older women lost their balance in at least one trial. CONCLUSIONS: Independent of age, these women reached further when reaching slowly than when reaching rapidly, and older women restricted peak forward momentum under both speed conditions when standing on the elevated surface. RELEVANCE: Interventions designed to reduce falls from raised surfaces might utilize the insights gained from these women that (1) at any age, one cannot expect to reach as far when reaching fast as one can when reaching slowly; and (2) comfortable reaching speed is reduced in older individuals.

    Title Floor-rise Strategy Training in Older Adults.
    Date December 2002
    Journal Journal of the American Geriatrics Society
    Excerpt

    OBJECTIVES: To determine the effect of a 2-week (six-session) training intervention to improve the ability of disabled older adults to rise from the floor. DESIGN: Prospective intervention trial. SETTING: Congregate housing in Michigan. PARTICIPANTS: Subjects aged 65 and older who admitted to requiring assistance (such as from a person, equipment, or device) in performing at least one of the following mobility-related activities of daily living: transferring, walking, bathing, and toileting. INTERVENTION: Participants were randomly allocated to individual training (n = 17, mean age 81) in strategies to rise from the floor (using for example, certain key intermediate body positions) or a control chair-based flexibility intervention (n = 18, mean age 80). MEASUREMENTS: At baseline and postintervention, residents were queried regarding their rise difficulty (difficulty scale) and symptoms (symptoms scale) associated with the rise and were tested in their ability to perform timed floor-rise tasks. These tasks varied in starting position (supine vs all fours) and in use of a support to assist in rising (no support, use of an end table, use of a chair). RESULTS: Using baseline performance as the covariate, by analysis of covariance (ANCOVA), the training group showed a significant (P <.05) improvement in mean number of rise tasks completed (baseline mean 6.6, postintervention mean 7.3) versus essentially no improvement in the controls. Similarly, by ANCOVA, the training group (compared with controls) showed a significant (P <.05) improvement on the difficulty and symptoms scales. There was no intervention effect for rise time. CONCLUSIONS: A short-term, strategy-based intervention improved floor-rise ability and perceived difficulty and symptoms associated with the rise. This approach, focusing on key intermediate body positions, may be useful in training floor-rise skills, particularly in older adults at risk for falls.

    Title Biomechanical Factors Affecting the Peak Hand Reaction Force During the Bimanual Arrest of a Moving Mass.
    Date September 2002
    Journal Journal of Biomechanical Engineering
    Excerpt

    Fall-related wrist fractures are among the most common fractures at any age. In order to learn more about the biomechanical factors influencing the impact response of the upper extremities, we studied peak hand reaction force during the bimanual arrest of a 3.4 kg ballistic pendulum moving toward the subject in the sagittal plane at shoulder height. Twenty healthy young and 20 older adults, with equal gender representation, arrested the pendulum after impact at one of three initial speeds: 1.8, 2.3, or 3.0 m/sec. Subjects were asked to employ one of three initial elbow angles: 130, 150, or 170 deg. An analysis of variance showed that hand impact force decreased significantly as impact velocity decreased (50 percent/m/s) and as elbow angle decreased (0.9 percent/degree). A two segment sagittally-symmetric biomechanical model demonstrated that two additional factors affected impact forces: hand-impactor surface stiffness and damping properties, and arm segment mass. We conclude that hand impact force can be reduced by more than 40 percent by decreasing the amount of initial elbow extension and by decreasing the velocity of the hands and arms relative to the impacting surface.

    Title Effects of Age and Gender on Toe Flexor Muscle Strength.
    Date June 2002
    Journal The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences
    Excerpt

    BACKGROUND: Toe flexor muscle strength determines the anterior limit of the functional base of support, thereby affecting a standing individual's maximum forward reach or lean capacity. We developed a method for measuring toe flexor muscle strength in order to test the null hypotheses that it is neither affected by age nor gender. METHODS: Gender-balanced groups of 20 healthy young adults (YA) (average age 22.8 years) and 20 healthy older adults (OA) (average age 73.2 years) participated in the study. Toe flexor isometric muscle strength, calculated as the maximum volitional moment developed simultaneously in the sagittal plane by the toe flexor muscles about a reference axis through the first metatarsophalangeal joint, was measured in three trials while subjects reached forward as far as possible while standing on a force plate. RESULTS: Significant age (p <.005) and gender (p <.0005) differences were found in maximum toe flexor muscle strength. OA were 28.9% less strong than the YA [mean (SD) 13.5 (5.7) Nm and 19.0 (6.8) Nm, respectively]. The men developed 39.1% greater strength than the women [20.2 (7.1) Nm and 12.3 (3.7) Nm, respectively]. However, when normalized by body size (body weight x height), the gender difference in strength no longer reached statistical significance. Across all subjects, the anterior limit of the functional base of support was significantly correlated with toe flexor strength (coefficient of determination: 0.84). CONCLUSIONS: Toe flexor muscle strength decreased significantly with age. This decrement underlies the known age-related reduction in the functional base of support.

    Title Task-specific Resistance Training to Improve the Ability of Activities of Daily Living-impaired Older Adults to Rise from a Bed and from a Chair.
    Date March 2002
    Journal Journal of the American Geriatrics Society
    Excerpt

    OBJECTIVES: To determine the effect of a 12-week intervention to improve the ability of disabled older adults to rise from a bed and from a chair. DESIGN: Subjects were randomly allocated to either a 12-week task-specific resistance-training intervention (training in bed- and chair-rise subtasks, such as sliding forward to the edge of a chair with the addition of weights) or a control flexibility intervention. SETTING: Seven congregate housing facilities. PARTICIPANTS: Congregate housing residents age 65 and older (n = 161, mean age 82) who reported requiring assistance (such as from a person, equipment, or device) in performing at least one of the following mobility-related activities of daily living: transferring, walking, bathing, and toileting. MEASUREMENTS: At baseline, 6 weeks, and 12 weeks, subjects performed a series of bed- and chair-rise tasks where the rise task demand varied according to height of the head of the bed, chair seat height, and use of hands. Outcomes were able or unable to rise and, if able, the time taken to rise. Logistic regression for repeated measures was used to test for differences between tasks in the ability to rise. Following log transformation of rise time, a linear effects model was used to compare rise time between tasks. RESULTS: Regarding the maximum total number of bed- and chair-rise tasks that could be successfully completed, a significant training effect was seen at 12 weeks (P = .03); the training effect decreased as the total number of tasks increased. No statistically significant training effects were noted for rise ability according to individual tasks. Bed- and chair-rise time showed a significant training effect for each rise task, with analytic models suggesting a range of approximately 11% to 20% rise-time (up to 1.5 seconds) improvement in the training group over controls. Training effects were also noted in musculoskeletal capacities, particularly in trunk range of motion, strength, and balance. CONCLUSIONS: Task-specific resistance training increased the overall ability and decreased the rise time required to perform a series of bed- and chair-rise tasks. The actual rise-time improvement was clinically small but may be useful over the long term. Future studies might consider adapting this exercise program and the focus on trunk function to a frailer cohort, such as in rehabilitation settings. In these settings, the less challenging rise tasks (such as rising from an elevated chair) and the ability to perform intermediate tasks (such as hip bridging) may become important intermediate rehabilitation goals.

    Title Effects of Functional Ability and Training on Chair-rise Biomechanics in Older Adults.
    Date September 2001
    Journal The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences
    Excerpt

    BACKGROUND: Difficulty in rising from a chair is common in older adults and may be assessed by examining the biomechanics of the rise. The purposes of this study were (i) to analyze the biomechanics of rise performance during chair-rise tasks with varying task demand in older adults with varying rise ability and (ii) to determine whether a strength-training program might improve chair-rise success and alter chair-rise biomechanics, particularly under situations of increased task demand. METHODS: A training group (n = 16; mean age, 82 years) completed a 12-week strength-training regimen while a control group (n = 14; mean age, 84 years) participated in a seated flexibility program. Outcomes included the ability to complete seven chair-rise tasks, and, if the chair-rise tasks were successful, the biomechanics of these rises. Chair-rise task demand was increased by lowering the seat height, restricting the use of hands, increasing rise speed, and limiting foot support. RESULTS: At baseline, increased chair-rise task demand generally required increased task completion time, increased anterior center of pressure (COP) placement, increased momentum, increased hip flexion, and increased hip and knee torque output. Those unable to rise at 100% knee height without the use of their hands (task NH-100), compared with those able to rise during task NH-100, followed this pattern in requiring increased time, more anterior placement of the COP, and increased hip flexion to rise in the least demanding tasks allowing the use of hands. However, the unable subjects generated less momentum and knee torque in these tasks. At 12 weeks, and compared with baseline and controls, the training group demonstrated changes in chair-rise biomechanics but no significant changes in rise success. The training subjects, as compared with the controls, maintained a more posterior COP, increased their vertical and horizontal momentum, maintained their knees in greater extension, and maintained their knee-torque output. CONCLUSIONS: These data demonstrate that subtle yet significant changes can be demonstrated in chair-rise performance as a result of a controlled resistance-training program. These biomechanical changes may represent a shift away from impairment in chair-rise ability, and, although the changes are small, they represent how training may reduce rise difficulty.

    Title How Quickly Can Healthy Adults Move Their Hands to Intercept an Approaching Object? Age and Gender Effects.
    Date September 2001
    Journal The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences
    Excerpt

    BACKGROUND: The upper extremities are often used to protect the head and torso from impact with an object or with the ground. We tested the null hypotheses that neither age nor gender would affect the time required for healthy adults to move their upper extremities into a protective posture. METHODS: Twenty young (mean age 25 years) and twenty older (mean age 70 years) volunteers, with equal gender representation, performed a seated arm-movement task under three conditions: Condition 1, in which subjects were instructed to raise the hands upon cue as quickly as possible from thigh level to a shoulder height target; Condition 2, in which subjects were instructed as in Condition 1 with the addition of intercepting a swinging pendulum at the prescribed hand target; and Condition 3, in which subjects were instructed as in Condition 2 but were asked to wait as long as possible before initiating hand movement to intercept the pendulum. Arm movements were quantified using standard kinematic techniques. RESULTS: Age (p <.01) and gender (p <.05) affected hand movement times. In Conditions 1 and 2, the older women required 20% longer movement times than the other subject groups (335 vs 279 milliseconds; p <.01). In Condition 3, shorter movement times were achieved by young men (20%; p =.002) and older women (10%; p =.056) as compared with their respective performance in Conditions 1 and 2 because they did not fully decelerate their hands. The other groups slowed their movements in Condition 3. CONCLUSIONS: Age, gender, and perceived threat significantly affected movement times. However, even the slowest movement times were well within the time available to deploy the hands in a forward fall to the ground.

    Title Age and Gender Differences in Peak Lower Extremity Joint Torques and Ranges of Motion Used During Single-step Balance Recovery from a Forward Fall.
    Date July 2001
    Journal Journal of Biomechanics
    Excerpt

    Previous studies have found substantial age and gender group differences in the ability of healthy adults to regain balance with a single step after a forward fall. It was hypothesized that differences in lower extremity joint strengths and ranges of motion (ROM) may have contributed to these observed differences. Kinematic and forceplate data were therefore used with a rigid-link biomechanical model simulating stepped leg dynamics to examine the joint torques and ROM used by subjects during successful single-step balance recoveries after release from a forward lean. The peak ROM and torques used by subjects in the study were compared to published estimates or measured values of the available maxima. No significant age or gender group differences were found in the mean ROM used by the subjects for any given initial lean angle. As initial lean angle increased, larger knee ROM and significantly larger hip ROM were used in the successful recoveries. There were substantial gender differences and some age group differences in peak lower extremity joint torques used in successful recoveries. Both young and older females often used nearly maximal joint torques to recover balance. Subjects' maximum joint strengths in plantarflexion and hip flexion were not good predictors of single-step balance recovery ability, particularly among the female subjects.

    Title Bed Mobility Task Performance in Older Adults.
    Date May 2001
    Journal Journal of Rehabilitation Research and Development
    Excerpt

    Difficulty in transferring, the ability to rise in and out of a bed and chair, is a common problem in older adults, particularly those residing in skilled nursing facilities. Focusing on one aspect of transferring, rising from supine to sitting position, we devised a set of bed mobility tasks to test key arm, leg, and trunk movements that likely contribute to successful rising from bed. Healthy young controls (YC, n=22, mean age 23), and older adults (aged 60 and over) either residing independently in congregate housing (CH, n=29, mean age 84) or undergoing rehabilitation in a skilled nursing facility (SNF, mean age 77) were assessed in the time to rise from supine to sitting and in the ability or inability to perform 16 other bed mobility tasks. Trunk function-related tasks, specifically those requiring trunk elevation and trunk balance, were most difficult for the SNF, followed by CH, and then YC. Tasks focusing on trunk flexion strength (sit up arms crossed, bilateral heel raise) and lateral trunk strength/balance were the most difficult for both SNF and CH, although there was minimal difference in the percent unable to complete each task. The major CH-SNF differences occurred in trunk elevation tasks where the upper limb was important in facilitating trunk elevation (sit up with head of bed elevation with use of arms, sit up with the use of a trapeze, or sit up with use of arms from a flat bed position). These findings suggest that to improve frail older adult performance on bed mobility tasks, and specifically in rising from supine to sitting, training should move beyond improving trunk function (i.e., trunk strength). There should be an additional focus, either through therapy or bed design modifications, on how upper limb movements and positioning can be used to assist in trunk elevation.

    Title Body Positions Used by Healthy and Frail Older Adults to Rise from the Floor.
    Date January 2001
    Journal Journal of the American Geriatrics Society
    Excerpt

    OBJECTIVE: The purpose of this study was to describe how older adults, particularly more physically impaired older adults, might differ from healthy controls in the body positions used to rise from the floor. DESIGN: Cross-sectional analysis of young, healthy older, and congregate housing older women. SETTING: University-based laboratory and congregate housing facility. PARTICIPANTS: Healthy young university student controls (n = 22, mean age 23 years); healthy old adults living independently in the community (n = 24, mean age 73 years); and congregate housing older adults (n = 29, mean age 81 years). INTERVENTION: Videotaping and timing of rising from a supine position on the floor to standing. MAIN OUTCOME MEASURES: In addition to the time taken to rise from the floor, 10 specific trunk and extremity positions used during the rise, termed Intermediate Positions (IP), were identified. RESULTS: The Young controls had the fastest rise time and used the fewest number of IP, whereas the Congregate residents had the slowest rise time and used the most IP, with the Healthy old adults intermediate in both time and IP use. Prevalence of certain IP, together with correlational and factor analyses, suggest that use of Sit and Crouch was the most preferred rise strategy for the Young controls, whereas use of Tuck, Crouch-Kneel, All Fours, and Bearwalk was the most preferred rise strategy among the Congregate residents. The Healthy old used IP common to both Young and Congregate residents, reflecting a rise strategy intermediate to the latter groups. A substantial subset of the Congregate residents (38%) were unable to rise without assistance and appeared to use certain preparatory positions (Sit, Kneel, Tuck) but were unable to get into presumably more challenging positions (Crouch-Kneel, All Fours, Bearwalk). CONCLUSIONS: With increasing age and physical impairment, body positions used during rising from the floor suggest a preference for maintaining upper and lower extremity contact with the floor, presumably minimizing the lower extremity strength requirements to rise and maximizing stability and postural control. These intermediate body positions may be useful as the basis for training older adults to rise from the floor.

    Title Self-reported Walking Ability Predicts Functional Mobility Performance in Frail Older Adults.
    Date November 2000
    Journal Journal of the American Geriatrics Society
    Excerpt

    OBJECTIVE: To determine how self-reported physical function relates to performance in each of three mobility domains: walking, stance maintenance, and rising from chairs. DESIGN: Cross-sectional analysis of older adults. SETTING: University-based laboratory and community-based congregate housing facilities. PARTICIPANTS: Two hundred twenty-one older adults (mean age, 79.9 years; range, 60-102 years) without clinical evidence of dementia (mean Folstein Mini-Mental State score, 28; range, 24-30). INTERVENTION AND MAIN OUTCOME MEASURES: We compared the responses of these older adults on a questionnaire battery used by the Established Populations for the Epidemiologic Study of the Elderly (EPESE) project, to performance on mobility tasks of graded difficulty. Responses to the EPESE battery included: (1) whether assistance was required to perform seven Katz activities of daily living (ADL) items, specifically with walking and transferring; (2) three Rosow-Breslau items, including the ability to walk up stairs and walk a half mile; and (3) five Nagi items, including difficulty stooping, reaching, and lifting objects. The performance measures included the ability to perform, and time taken to perform, tasks in three summary score domains: (1) walking ("Walking," seven tasks, including walking with an assistive device, turning, stair climbing, tandem walking); (2) stance maintenance ("Stance," six tasks, including unipedal, bipedal, tandem, and maximum lean); and (3) chair rise ("Chair Rise," six tasks, including rising from a variety of seat heights with and without the use of hands for assistance). A total score combines scores in each Walking, Stance, and Chair Rise domain. We also analyzed how cognitive/ behavioral factors such as depression and self-efficacy related to the residuals from the self-report and performance-based ANOVA models. RESULTS: Rosow-Breslau items have the strongest relationship with the three performance domains, Walking, Stance, and Chair Rise (eta-squared ranging from 0.21 to 0.44). These three performance domains are as strongly related to one Katz ADL item, walking (eta-squared ranging from 0.15 to 0.33) as all of the Katz ADL items combined (eta-squared ranging from 0.21 to 0.35). Tests of problem solving and psychomotor speed, the Trails A and Trails B tests, are significantly correlated with the residuals from the self-report and performance-based ANOVA models. CONCLUSIONS: Compared with the rest of the EPESE self-report items, self-report items related to walking (such as Katz walking and Rosow-Breslau items) are better predictors of functional mobility performance on tasks involving walking, stance maintenance, and rising from chairs. Compared with other self-report items, self-reported walking ability may be the best predictor of overall functional mobility.

    Title A Clinical Measure of Maximal and Rapid Stepping in Older Women.
    Date September 2000
    Journal The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences
    Excerpt

    BACKGROUND: In older adults, clinical measures have been used to assess fall risk based on the ability to maintain stance or to complete a functional task. However, in an impending fall situation, a stepping response is often used when strategies to maintain stance are inadequate. We examined how maximal and rapid stepping performance might differ among healthy young, healthy older, and balance-impaired older adults, and how this stepping performance related to other measures of balance and fall risk. METHODS: Young (Y; n = 12; mean age, 21 years), unimpaired older (UO; n = 12; mean age, 69 years), and balance-impaired older women IO; n = 10; mean age, 77 years) were tested in their ability to take a maximal step (Maximum Step Length or MSL) and in their ability to take rapid steps in three directions (front, side, and back), termed the Rapid Step Test (RST). Time to complete the RST and stepping errors occurring during the RST were noted. RESULTS: The IO group, compared with the Y and UO groups, demonstrated significantly poorer balance and higher fall risk, based on performance on tasks such as unipedal stance. Mean MSL was significantly higher (by 16%) in the Y than in the UO group and in the UO (by 30%) than in the IO group. Mean RST time was significantly faster in the Y group versus the UO group (by 24%) and in the UO group versus the IO group (by 15%). Mean RST errors tended to be higher in the UO than in the Y group, but were significantly higher only in the UO versus the IO group. Both MSL and RST time correlated strongly (0.5 to 0.8) with other measures of balance and fall risk including unipedal stance, tandem walk, leg strength, and the Activities-Specific Balance Confidence (ABC) scale. CONCLUSION: We found substantial declines in the ability of both unimpaired and balance-impaired older adults to step maximally and to step rapidly. Stepping performance is closely related to other measures of balance and fall risk and might be considered in future studies as a predictor of falls and fall-related injuries.

    Title Chair and Bed Rise Performance in Adl-impaired Congregate Housing Residents.
    Date May 2000
    Journal Journal of the American Geriatrics Society
    Excerpt

    OBJECTIVES: To examine the ability of activity of daily living (ADL)-impaired older adults to successfully rise, and, when successful, the time taken to rise, from a bed and chair under varying rise task demands. SETTING: Seven congregate housing facilities SUBJECTS: Congregate housing residents (n = 116, mean age 82) who admitted to requiring assistance (such as from a person, equipment, or device) in performing at least one of the following mobility-related ADLs: transferring, walking, bathing, and toileting. METHODS: Subjects performed a series of bed and chair rise tasks where the rise task demand varied according to the head of bed (HOB) height, chair seat height, and use of hands. Bed rise tasks included supine to sit-to-edge, sit up in bed with hand use, and sit up in bed without hands, all performed from a bed where the HOB was adjusted to 0, 30, and 45 degrees elevations; roll to side-lying then rise (HOB 0 degrees); and supine to stand (HOB 0 degrees). Chair seat heights were adjusted according to the percent of the distance between the floor and the knee (% FK), and included rises (1) with hands and then without hands at 140, 120, 100, and 80% FK; (2) from a reclining (105 degrees at chair back) and tilting (seat tilted 10 degrees posteriorly) chair (100% FK); and (3) from a 80% FK seat height with a 4-inch cushion added, with and then without hands. Logistic regression for repeated measures was used to test for differences between tasks in the ability to rise. After log transformation of rise time, a linear effects model was used to compare rise time between tasks. RESULTS: The median total number of tasks successfully completed was 18 (range, 3-21). Nearly all subjects were able to rise from positions where the starting surface was elevated as long as hand use was unlimited. With the HOB at 30 or 45 degrees essentially all subjects could complete supine to sit-to-edge and sit up with hands. Essentially all subjects could rise from a seat height at 140, 120, and 100% FK as long as hand use was allowed. A small group (8-10%) of subjects was dependent upon hand use to perform the least challenging tasks, such as 140% FK without hands chair rise and 45 degrees sit up without hands. This dependency upon hand use increased significantly as the demand of the task increased, that is, as the HOB or seat height was lowered. Approximately three-quarters of the sample could not rise from a flat (0 degrees HOB elevation) bed or low (80% FK) chair when hand use was not allowed. Similar trends were seen in rise performance time, that is, performance times tended to increase as the HOB or chair seat elevation declined and as hand use was limited. Total self-reported ADL disability, compared to the single ADL transferring item, was a stronger predictor of rise ability and timed rise performance, particularly for chair rise tasks. CONCLUSIONS: Lowering HOB height and seat height increased bed and chair rise task difficulty, particularly when hand use was restricted. Restricting hand use in low HOB height or lowered seat height conditions may help to identify older adults with declining rise ability. Yet, many of those who could not rise under "without hands" conditions could rise under "with hands" conditions, suggesting that dependency on hand use may be a marker of progressive rise impairment but may not predict day-to-day natural milieu rise performance. Intertask differences in performance time may be statistically significant but are clinically small. Given the relationship between self-reported ADL disability and rise performance, impaired rise performance may be considered a marker for ADL disability. These bed and chair rise tasks can serve as outcomes for an intervention to improve bed and chair rise ability and might also be used in future studies to quantify improvements or declines in function over time, to refine physical therapy protocols, and to examine the effect of bed and chair design modifications on bed and chai

    Title Muscle Activities Used by Young and Old Adults when Stepping to Regain Balance During a Forward Fall.
    Date April 2000
    Journal Journal of Electromyography and Kinesiology : Official Journal of the International Society of Electrophysiological Kinesiology
    Excerpt

    The current study was undertaken to determine if age-related differences in muscle activities might relate to older adults being significantly less able than young adults to recover balance during a forward fall. Fourteen young and twelve older healthy males were released from forward leans of various magnitudes and asked to regain standing balance by taking a single forward step. Myoelectric signals were recorded from 12 lower extremity muscles and processed to compare the muscle activation patterns of young and older adults. Young adults successfully recovered from significantly larger leans than older adults using a single step (32.2 degrees vs. 23.5 degrees ). Muscular latency times, the time between release and activity onset, ranged from 73 to 114 ms with no significant age-related differences in the shortest muscular latency times. The overall response muscular activation patterns were similar for young and older adults. However older adults were slower to deactivate three stance leg muscles and also demonstrated delays in activating the step leg hip flexors and knee extensors prior to and during the swing phase. In the forward fall paradigm studied, age-differences in balance recovery performance do not seem due to slowness in response onset but may relate to differences in muscle activation timing during the stepping movement.

    Title Age and Gender Differences in Single-step Recovery from a Forward Fall.
    Date March 1999
    Journal The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences
    Excerpt

    BACKGROUND: Previous work has found that healthy older men were significantly less able than young male adults to recover balance by taking a single rapid step upon sudden release from forward leans. In light of the higher rates of falls and fall-related injuries among older women compared to older men, we hypothesized that healthy older women would perform more poorly than either female young adults or older men in this test of abilities to recover balance rapidly. METHODS: Ten young (mean age 25.0 years) and 10 older (73.7 years) healthy women were released from forward leans and instructed to regain standing balance by taking a single step forward. The lean angle was incrementally increased from its smallest value, approximately 14 degrees, until the subject failed to regain balance as instructed. Lower extremity kinematics were measured, and findings were compared with those of the earlier study of healthy young and old men. RESULTS: Five of the 10 older women could not recover balance with a single step after release from the smallest of the imposed forward leans. For the 5 older women who succeeded in recovering as instructed from at least one lean, the mean maximum lean angle was significantly smaller than that for young women (16.2 degrees vs 30.7 degrees, p < .001) or older men (16.2 degrees vs 23.9 degrees, p = .014). In contrast, there was no significant difference in mean maximum lean angle between female and male young adults. CONCLUSIONS: Healthy older women, compared to either young women or older men, were significantly less able to recover balance by taking a single rapid step during a forward fall. The decreased abilities of older women appeared to result from limitations in the maximum speeds at which they moved their swing foot during recovery.

    Title Thresholds for Sensing Foot Dorsi- and Plantarflexion During Upright Stance: Effects of Age and Velocity.
    Date March 1998
    Journal The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences
    Excerpt

    BACKGROUND: The objective of this study was to determine in healthy young and old adult females the influence of age, rotation direction, angle, and speed on the threshold for sensing foot dorsi- and plantarflexion when standing and bearing weight on the limb. METHODS: Twelve young (YF, mean age 22 years) and 12 old (OF, 70 years) healthy adult females stood with their dominant foot on a servo-controlled platform and the other foot on a fixed platform. The platform induced either dorsi- or plantarflexion rotations at angular velocities of 0.1, 0.5, or 2.5 degrees/s to angles of 0.05, 0.1, 0.2, 0.4 or 0.8 degree. Subjects performed five trials at each velocity-angle combination and 30 dummy trials in which no platform rotation occurred, for a total of 180 trials. Success rates were determined for detecting both rotation (SRR) and rotation direction (SRD) for each test condition. The angular thresholds required to achieve an SRD of 75% were estimated using logistic regression. RESULTS: Age, rotation angle, and rotation speed significantly affected SRD (repeated measures ANOVA: p < .001). For the YF, DF thresholds were 0.04, 0.09, and 0.41 degree at the fast, moderate, and slow velocities, respectively. Threshold angles were three to four times larger in the OF than in the YF. A 10-fold reduction in the angular threshold was observed upon increasing the speed of rotation from 0.1 to 2.5 degrees/s. CONCLUSIONS: Both age and speed significantly affected the thresholds for sensing foot dorsiflexion and plantarflexion in women.

    Title Muscle Strength and Rising from a Chair in Older Adults.
    Date October 1997
    Journal Muscle & Nerve. Supplement
    Title What Leads to Age and Gender Differences in Balance Maintenance and Recovery?
    Date October 1997
    Journal Muscle & Nerve. Supplement
    Excerpt

    OA compared to YA have high rates of falls and fall-related injuries. OF have notably higher rates of falls and fall-related injuries than OM. Healthy OA compared to YA, and females compared to males of any adult age, have lower strengths and have development rates for at least some strengths that are lower. The results of the obstacle avoidance and balance recovery studies described suggest that OA are not notably more at risk than YA, nor are females notably more at risk than males, in avoidance and recovery tasks that are time-critical (TC), but do not have high strength (HS) requirements. The results suggest that for TC/HS avoidance and recovery tasks, OA compared to YA and females compared to males are substantially more at risk for injury. The source of these age and gender differences seems to lie primarily in differences in muscle strengths and speeds of muscle contraction once contraction is initiated, rather than in neural factors underlying the sensory processing or motor planning that leads to the initiation of muscle contraction. Perhaps these findings help to explain the high rates of falls and fall injuries among OA compared to YA, and among OF compared to OM.

    Title Summary of Work Group Ii: Small-scale Clinical Studies.
    Date October 1997
    Journal Muscle & Nerve. Supplement
    Title Rising from the Floor in Older Adults.
    Date June 1997
    Journal Journal of the American Geriatrics Society
    Excerpt

    OBJECTIVE: The primary goal was to determine the ability of older adults to rise from the floor. A secondary goal was to explore how rise ability might differ based on initial body positions and with or without the use of an assistive device. DESIGN: Cross-sectional analysis of young, healthy older, and congregate housing older adults. SETTING: University-based laboratory and congregate housing facility. PARTICIPANTS: Young adult controls (12 men and 12 women, mean age 23 years), healthy older adults (12 men and 12 women, mean age 73 years), and congregate housing older adults (32 women and 6 men, mean age 80 years). The healthy older adult women (n = 12, mean age 75 years) and a subset of the congregate housing women (n = 27, mean age 81 years) were identified for further analyses. INTERVENTION: Videotaping and timing of rising from the floor from controlled initial body positions (supine, on side, prone, all fours, and sitting) and with or without the use of a furniture support. MAIN OUTCOME MEASURES: Whether subjects were successful in rising, and if they were, the time taken to rise. Subjects also rated their perceived difficulty of the task as compared to the reference task, rising from a supine position. RESULTS: Older adults have more difficulty rising from the floor than younger adults. The healthy old took twice as long as the young to rise, whereas the congregate old took two to three times as long as the healthy old to rise. Although all young and healthy old rose from every position, a subset of the congregate housing residents was unable to rise from any position, 24% when attempting to rise without a support and 13% when attempting to rise with a support. Congregate old were most likely to be successful when rising from a side-lying position while using the furniture for support. The more able congregate old, as well as the young and healthy old, rose more quickly and admitted to the least difficulty when rising from the all fours position. CONCLUSIONS: The inability to rise from the floor is relatively common in congregate housing older adults. Based on the differences between groups in time to complete the rise, determining the differences in rise strategies, and the underlying biomechanical requirements of rising from different positions with or without a support would appear to be useful. These data may serve as the foundation for future interventions to improve the ability to rise from the floor.

    Title Abilities to Turn Suddenly While Walking: Effects of Age, Gender, and Available Response Time.
    Date April 1997
    Journal The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences
    Excerpt

    BACKGROUND: Falls may occur when an unexpected turn must be made quickly, in order to avoid colliding with an object in the gait path. Little is known about abilities, particularly about abilities of old adults, to turn suddenly. METHODS: Twenty young and 20 old (mean age 73.8) healthy and physically active adults, while walking straight ahead, were cued to make approximately a 90 degrees turn without advance knowledge of where the turn was to be made or whether it would be to the right or left. Subjects were given available response times (ART), the times between the cue to turn, and potential crossing of a specified forward limit line, of 375, 450, 600, and 750 ms. The rate of success (RS) in completing the turns as prescribed was determined. Regression analyses were used to estimate the additional ART that would be needed for other groups to achieve the same RS as did the young male subject group. RESULTS: For all ART, old subjects had a lower rate of success in completing the turns as prescribed than the young. At an ART of 375 ms, mean RS was 36% for the young and 6% for the old. The regression analyses suggested that, for RS from 30 to 95%, old adults needed 112 ms longer than young of corresponding gender to succeed as well. Females needed on the order of 50 ms longer ART than males of corresponding age. CONCLUSIONS: There are significant age and gender differences among healthy and physically active adults in the available response times they need when walking for successfully making sudden turns.

    Title Age Differences in Using a Rapid Step to Regain Balance During a Forward Fall.
    Date February 1997
    Journal The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences
    Excerpt

    BACKGROUND: Earlier studies showed that healthy old adults have substantially reduced abilities to develop joint torques rapidly. We hypothesized that this age decline would reduce abilities to regain balance once a forward fall is underway. The present study examined whether aging in fact reduces ability to regain balance by taking a single, rapid step upon release from a forward lean. METHODS: Ten young (mean age 24.3 yr) and ten old (72.8 yr) healthy males were released from a forward-leaning position and instructed to regain standing balance by taking a single step forward. Lean angle was successively increased until a subject failed to regain balance as instructed. Lower extremity motions and foot-floor reactions were measured during the responses. Total response time was divided into reaction, weight transfer, and step times. RESULTS: At small lean angles, responses of old subjects were similar to those of the young. However, the mean maximum lean angle from which old could regain balance as instructed was significantly smaller than that for young (23.9 vs 32.5 deg, p < .0005). Within each age group, maximum lean angle correlated strongly with weight transfer time and step velocity. CONCLUSIONS: Substantial age-related declines in the ability to regain balance by taking a rapid step exist among healthy adults when the time available for recovery is short. The source of the decline seems largely to lie in the decrease with age of maximum response execution speed rather than in the sensory or motor programming processes involved in response initiation.

    Title Postural Control in Young and Elderly Adults when Stance is Perturbed: Dynamics.
    Date January 1997
    Journal Journal of Biomechanics
    Excerpt

    Responses in maintaining or restoring standing balance were measured in 24 healthy young and 15 healthy elderly adults (mean ages 26 and 72) under four task conditions: two involving self-generated motions and two involving imposed disturbances. The two primary objectives of the study were to quantify the whole-body dynamics of these responses and to identify any age related differences in those dynamics. Response dynamics were analyzed using a seven-link biomechanical model. In terms of approximate population-mean values, maximum whole-body center of mass (CM) excursions ranged to 3 cm, maximum center of support-surface reaction (CR) excursions ranged to 8 cm, vertical reaction force changes ranged to 50 N, anteroposterior support surface reactions ranged to 30 N, maximum joint torques used per side ranged to 20 Nm and peak angular momenta about a transverse axis through the ankles ranged to 6 kg m2 s-1. The elderly adults, compared to the young tended to exhibit higher-frequency oscillations in excursions and larger horizontal excursions of their CM and CR, tended to develop larger support surface reactions and use larger response joint torques, and tended to arrest less of their angular momentum in their first cycle of response during the two imposed-disturbance tasks. Only some of these tendencies proved statistically significant. The results suggest that healthy elderly subjects with no apparent musculoskeletal or neurological impairments differ from healthy young adult subjects in their responses to modest perturbations of upright stance. However, the differences are generally not large and their magnitudes are perturbation-specific.

    Title Differential Diagnosis of Gait Disorders in Older Adults.
    Date December 1996
    Journal Clinics in Geriatric Medicine
    Excerpt

    The purpose of this review is to examine the causes of gait disorders in older adults, focusing specifically on the underlying diseases that are the primary causes of the disorder. A classification system for these diseases is proposed. Thus far, interventions used to reduce gait disorders yield only modest results and residual disability is common.

    Title Using Technology-based Techniques to Assess Postural Control and Gait in Older Adults.
    Date December 1996
    Journal Clinics in Geriatric Medicine
    Excerpt

    Increasingly sophisticated instrumentation and techniques to assess gait and postural control in older adults are now available. These technology-based methods may be most useful in understanding the mechanisms underlying age-related and disease-related changes in gait and postural control. Further work is needed to ensure that these methods: (1) are used in a hypothesis-driven manner; (2) are made more simple, portable, and user friendly; and (3) are used in an appropriate and cost-effective manner.

    Title Effects of Age on Rapid Ankle Torque Development.
    Date October 1996
    Journal The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences
    Excerpt

    BACKGROUND: When balance is disturbed, often only fractions of a second are available in which to make the initial responses needed for its restoration. Abilities to develop joint torques rapidly may be critical to such responses. We undertook this study to quantify age effects among healthy adults in abilities to develop ankle joint torques rapidly. METHODS: Ankle dorsiflexion (DF) and plantarflexion (PF) torque development during rapid isometric and during isokinetic (30, 60, 120, 180, and 240 deg/sec) exertions was assessed in 24 healthy young (mean age 23 years) and 24 healthy old adults (mean age 72 years). The effects of age, gender, and torque direction on the times needed to reach given torque magnitudes, maximum rates of isometric torque development (MRTD), and maximum isokinetic torques were examined. RESULTS: The old adults required substantially more time to reach given torque magnitudes than the young adults. For example, the young and old females needed approximately 236 and 337 msec to develop 15 Nm of DF torque, of which 141 and 164 msec were reaction times. Isometric MRTD were 25 to 36% lower in the old than in the young adults. The age declines in isometric torque development time were associated with losses in maximum isometric strength. Maximum isokinetic torques developed by the old were 20 to 40% lower than those of young adults. The percent losses in isokinetic torques with age were independent of joint angular velocity for PF, but increased with velocity for DF. CONCLUSIONS: We found substantial age declines in abilities of healthy old adults to rapidly develop ankle joint torques. The capacities of even healthy old adults to recover balance or to carry out other time-critical actions that require moderate-to-substantial strengths may be considerably degraded by these declines.

    Title Do Neural Factors Underlie Age Differences in Rapid Ankle Torque Development?
    Date August 1996
    Journal Journal of the American Geriatrics Society
    Excerpt

    OBJECTIVES: Rapid torque development is substantially slower in healthy old adults compared with young adults, but the underlying cause of this age-related loss remains unclear. Measurements of myoelectric signals in ankle dorsi- and plantarflexor muscles during rapid exertions were used to explore the extent to which the loss might be attributed to neural factors. METHODS: Myoelectric signals were measured in a laboratory setting in 24 healthy young and 24 healthy old adult volunteers during rapid isometric and isokinetic torque development. Premotor times, muscle activation rates, and myoelectric activity levels of agonistic and antagonistic muscles were quantified. RESULTS: There were few marked age differences in the premotor times or in the onset rates or magnitudes of agonistic muscles activities during maximum isometric and during isokinetic exertions. Premotor times were statistically associated with age but, in the mean, were only approximately 10 to 25 ms longer in the old. Age effects on agonist muscle activity magnitudes were significant only in the lateral gastrocnemius. Small decreases in antagonistic muscle activity levels with age were found. CONCLUSIONS: Given the outcomes of this study, the differences observed previously in rapid torque development abilities in healthy older adults, compared with healthy younger adults, seem attributable largely to differences in muscle contraction mechanisms rather than to differences in speeds of stimulus sensing or central processing of motor commands, or to differences in muscle recruitment strategies.

    Title Chair Design Affects How Older Adults Rise from a Chair.
    Date July 1996
    Journal Journal of the American Geriatrics Society
    Excerpt

    OBJECTIVE: To determine how modifications of key chair design aspects, such as seat height, posterior seat tilt, backrest recline, seat compressibility, and armrest placement, affect how older adults rise from a chair and the seating comfort they experience. DESIGN: Cross-sectional comparison. SETTING: Congregate housing facility and university laboratory. SUBJECTS: Two groups of volunteers, Old (n = 29, mean age 84) and Young (n = 21, mean age 23). MEASUREMENTS: Analysis of time to rise, body motion (determined by use of digitized videotaping), and self-reported difficulty when subjects rose from a variety of controlled chair settings thought to represent important chair design specifications encountered by older adults. Subjects also reported their comfort while being seated in these settings. RESULTS: Lowered seat height, increased posterior seat tilt and backrest recline, and perhaps increased seat compressiblity cause increased time to rise, increased body motion, and increased self-reported ratings of rise difficulty in both Young and Old groups. Under the most challenging conditions, the effect appears to be stronger in the Old than in the Young: a few Old were unable to rise, and the Old took disproportionately longer to rise and used disproportionately greater neck motion (P generally < 0.001) compared with the Young. Arm rest placement did not alter rise performance or ratings significantly. The conditions in which rise difficulty increases or decreases do not correspond exactly to conditions in which comfort increases or decreases. Some aspects that increase rise difficulty, such as tilt/recline and seat compressiblity, may also increase comfort. CONCLUSIONS: Aspects of chair design such as lowered seat height, increased posterior seat tilt, increased back recline, and increased compressibility interfere with chair egress in older adults. While decreasing ease of egress, however, these same factors may increase seating comfort. Furniture designers and manufacturers must find a balance between degree of sitting comfort, ease of egress and the degree to which the seating device facilitates functional independence, particularly to meet the needs of disable older adults.

    Title Gait Disorders in Older Adults.
    Date July 1996
    Journal Journal of the American Geriatrics Society
    Title Stepping over Obstacles: Dividing Attention Impairs Performance of Old More Than Young Adults.
    Date June 1996
    Journal The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences
    Excerpt

    BACKGROUND. Tripping over an obstacle is a common cause of falls in the elderly. An earlier study of abilities to avoid stepping on suddenly appearing obstacles found that, although healthy old adults had a lower rate-of-success than young adults, the magnitude of that difference was not large. The present study inquired whether dividing attention during such a task would differentially affect young and old healthy adults. METHODS. Rates-of-success were observed in 16 young and 16 old healthy adults (mean ages 24 and 72 years) in avoiding stepping on a band of light that was suddenly projected across their gait path while they walked at their comfortable gait speed. This virtual obstacle was placed at predicted next-footfall locations to give 350 or 450 msec available response times before footfall. During most of the trials the subjects were asked, in addition to trying not to step on the obstacle, simultaneously to respond vocally as quickly as possible when red lights near the end of the walkway turned on. These attention-dividing reaction time tests were of two types: synchronized, when only red lights lit at intervals synchronized with the appearance of the obstacle, and unsynchronized, when green or yellow lights lit in addition to the red lights, with lighting intervals not synchronized with the appearance of the obstacle. RESULTS. When synchronized and unsynchronized reaction time tests were conducted concurrently with the obstacle avoidance tasks, mean rates-of-success in avoidance decreased significantly in both young and old adults. With available response times of 350 msec, mean success rates decreased from their no-division values in the young adults by 14.7% for synchronized reaction and by 19.9% for unsynchronized reaction, attention-dividing tests. Corresponding mean decreases for the old adults were 32.0 and 35.7%. This age difference in the effects of dividing attention was significant. CONCLUSION. Both young and old adults had a significantly increased risk of obstacle contact while negotiating obstacles when their attention was divided, but dividing attention degraded obstacle avoidance abilities of the old significantly more than it did in the young. Diminished abilities to respond to physical hazards present in the environment when attention is directed elsewhere may partially account for high rates of falls among the elderly.

    Title Neuropsychological Predictors of Complex Obstacle Avoidance in Healthy Older Adults.
    Date October 1995
    Journal The Journals of Gerontology. Series B, Psychological Sciences and Social Sciences
    Excerpt

    Global cognitive impairment in older adults has been associated with a greater risk of falling, and tripping has been implicated as an important factor in a large percentage of these falls. In order to evaluate the role of specific cognitive domains in tripping and falling, 23 healthy older adults completed basic and complex obstacle avoidance tasks, as well as a battery of neuropsychological tests. Using multiple regression analysis, a select pattern of neuropsychological measures was found to predict the decrement in performance evident as avoidance task complexity increased. Whereas measures of problem solving, response inhibition, general anxiety, and variability in attention were found to be significant predictors (in that order) of the relative decline in successful obstacle avoidance, measures of visuo-spatial discrimination and memory did not.

    Title Association of Age with the Threshold for Detecting Ankle Inversion and Eversion in Upright Stance.
    Date June 1995
    Journal Age and Ageing
    Excerpt

    A randomized quadruple staircase method and probit analysis were used to measure the thresholds for sensation of ankle inversion and eversion by 18 healthy young and 18 healthy old subjects while standing with a foot in a servo-driven cradle. The results of over 3600 trials show that the mean threshold for detecting inversion with a probability of 75% was 0.35 degrees in the older subjects, a value significantly greater than the 0.06 degrees threshold found in the younger group. The corresponding thresholds in eversion were significantly greater in both old (0.52 degrees) and young (0.35 degrees) subjects. Significant, but smaller, age differences were also found in unipedal stance. Few significant sex differences were found. When the velocity of a 0.1 degree inversion movement was increased from 2 to 200 degrees/s the probability of detecting it rose by only 22.6%. Although significantly increased with age, the threshold for sensing rotation in the weight-bearing ankle was measured in tenths of degrees, an order of magnitude better than previously reported (non-weight-bearing) values.

    Title Maintenance of Balance, Gait Patterns, and Obstacle Clearance in Alzheimer's Disease.
    Date June 1995
    Journal Neurology
    Excerpt

    Patients with cognitive impairment, particularly as a result of Alzheimer's disease (AD), are at increased risk for falls, but it is unclear how, or if, they differ from normal adults in their balance, gait, or ability to clear an obstacle in their path. Using an optoelectronic camera system, we compared body motions and force output at the feet in patients with probable AD (n = 17) with those in healthy older adults (n = 15) while they stood on a force plate or on a beam attached to the force plate that was either stationary or accelerating. Using the same camera system and comparing this AD group with another group of healthy older adults (n = 24), we observed the AD patients during normal walking and while clearing 25- and 152-mm-high obstacles. None of the AD patients had extrapyramidal signs or musculoskeletal impairments. Compared with healthy older adults, normal walking speed was significantly slower in the AD group (p < 0.0001). While clearing either obstacle, the AD patients were significantly slower in their approach (p < 0.0001) and crossing (p < 0.0001) speeds and landed closer to the obstacle after having crossed it (p < 0.02). Moreover, the percent of trials in which a subject made contact with an obstacle was significantly higher in patients with AD (p < 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

    Title Healthy Young and Old Women Differ in Their Trunk Elevation and Hip Pivot Motions when Rising from Supine to Sitting.
    Date May 1995
    Journal Journal of the American Geriatrics Society
    Excerpt

    OBJECTIVE: To describe the differences between healthy young and older women in regards to trunk elevation and hip pivot motions when rising from a supine to a seated position. DESIGN: Cross-sectional comparison. SETTING: University laboratory. PARTICIPANTS: Two groups of healthy female volunteers: young adult female controls (n = 22, mean age 23.5 years) and community-dwelling older female adults (n = 17, mean age 73.8 years). MEASUREMENTS: Subjects were videotaped as they performed three controlled bed mobility tasks, starting from a supine position: (1) rising to a seated position at the edge of a firm plinth surface (SS); and rising to a seated position without moving to the edge of the bed while either (2) using hands (SUH) or (3) not using hands (SUNH). A series of movements involving the trunk were identified as subjects performed the SS task. RESULTS: The older women were more likely to rotate and laterally flex their trunks, particularly in the later phases of the SS task. In addition, during the SS task, the older group was more likely to bear weight on their hip/gluteal area, particularly in the later phases, and more likely to use a broad pivot base, consisting of the hip and the elbow. While all young and old performed the SUH task, less than half of the older group could complete the SUNH task. Moreover, the subgroup of older adults who could not complete the SUNH task may have accounted for much of the differences between the young and the old on the SS task. CONCLUSION: Healthy young and older women differ in their ability to rise from a supine to sitting position, primarily in the strategies used to elevate the trunk and facilitate a pivot. Trunk flexion ability likely contributes to the age group differences noted in rising. These data provide the basis for a biomechanical analysis of the critical body segment motions and the strengths required to perform bed mobility tasks.

    Title Effects of Age and Available Response Time on Ability to Step over an Obstacle.
    Date September 1994
    Journal Journal of Gerontology
    Excerpt

    BACKGROUND. Falls during walking are often triggered when a foot contacts an obstacle in its path. Yet little is known about the ability of individuals of any age to successfully negotiate obstacles, especially under time-critical conditions. METHODS. The gait of 24 young and 24 old healthy adults (mean ages 23 and 73 years) was studied as they approached and tried to avoid stepping on a band of light, not knowing when or where it might appear on an 8 m-long walkway. This virtual obstacle was placed at the predicted location of the next footfall with available response times (ART) before heel strike that were varied randomly in 50 ms increments from 200 to 450 ms. In addition, their gait was observed as they stepped over a fixed virtual obstacle and over an obstacle that appeared with approximately a 1000 ms ART. RESULTS. The old had an increased risk of obstacle contact while negotiating obstacles under time-critical conditions (p = .082). Mean rates-of-success (RS) in obstacle avoidance for the young ranged from .205 at a 200 ms ART to .969 at a .450 ms ART. Corresponding mean RS for the old were .157 and .920. Lower extremity simple reaction time (SRT) test made under static conditions showed that the mean SRT of the old were approximately 80 ms longer than those of the young. Regression analyses suggested that the old in fact would have needed only 30 ms additional ART to achieve RS equal to that of the young for obstacles appearing with ART from 300 to 450 ms. CONCLUSIONS. Reductions in ART significantly decreased RS. Delays as small as 50 or 100 ms in observing or reacting to obstacles in real-life situations may significantly lower the rate of success that subjects of any age have in avoiding them. Age differences in SRT do not always reliably indicate age differences in obstacle avoidance under time-critical situations.

    Title Stepping Responses of Young and Old Adults to Postural Disturbances: Kinematics.
    Date June 1994
    Journal Journal of the American Geriatrics Society
    Excerpt

    OBJECTIVES: When large disturbances of upright stance occur, balance must usually be restored by taking a step. We undertook this study to examine the biomechanics of stepping responses to sudden backward pulls at the waist. Primarily, response differences between young and old healthy adults were sought. DESIGN: A controlled laboratory study. SUBJECTS: Two groups of healthy and physically-fit adult females, 12 of mean age 22 (Young) and 12 of mean age 73 years (Old). MEASUREMENTS: Response kinematics were measured. From them, the stepping strategies of the subjects were derived, including the timing, length, and height of the first step taken and the rotations of major body segments and at major body joints that occurred. RESULTS: In response to sufficiently large backward pull forces, all subjects responded by taking one or more steps backwards. No significant age group difference appeared in the smallest disturbance for which subjects sometimes used a step response. A significant age group difference appeared in the smallest disturbance at which subjects began consistently to use step responses, and that disturbance was larger for the Old than for the Young. Distinct age group differences were found in stepping strategy. At large disturbance levels, the Young mostly responded by taking a single step, whereas the Old mostly responded by taking multiple steps. The steps taken by the Old, compared with those of the Young, were significantly shorter, had significantly smaller heights, and were taken significantly earlier in the responses. Body segment and joint rotations were generally modest, and few significant age group differences were found in these kinematics. CONCLUSIONS: In restoration of perturbed balance by step-taking, the responses of the healthy, physically-fit young and old adults studied here were similar in many respects, but they differed in some important features. Joint range of motion (ROM) limitations are unlikely to explain age group differences in stepping responses to postural disturbances among healthy subjects because the ROM actually used in any of the responses observed were substantially smaller than the ROM available.

    Title Postural Control in Older Adults.
    Date February 1994
    Journal Journal of the American Geriatrics Society
    Title Postural Control in Young and Elderly Adults when Stance is Challenged: Clinical Versus Laboratory Measurements.
    Date August 1993
    Journal The Annals of Otology, Rhinology, and Laryngology
    Excerpt

    The use of dynamic posturography (EquiTest) for the characterization of postural control biomechanics would be aided by specific knowledge of what the measured data imply about body segment movements. To investigate this issue, the biomechanics of a group of 15 healthy elderly subjects were compared to those of healthy young subjects by using both dynamic posturography and a laboratory movement and force measuring system. The results from EquiTest were analyzed by 1) routine clinical interpretation of data and 2) a clinical research interpretation by subjecting the EquiTest parameters to additional statistical comparison of mean performance of the young and elderly groups. The young-elderly differences from the 2 EquiTest analyses were then compared to the young-elderly differences derived from the laboratory protocol. The routine clinical interpretation of EquiTest data identified the same increases in sway shown by the laboratory study, but did not reveal the more subtle differences indicated by the laboratory study. When the EquiTest data were subjected to additional statistical analysis, the characterization of difference between young and elderly subjects was the same as that of the laboratory study, with the exception of issues of head versus trunk movement, a measure not made by EquiTest. This essential similarity in the characterization of elderly compared to young subjects by both systems suggests 1) that EquiTest is able to detect subtle differences in biomechanics of postural control between young and elderly healthy adult groups and 2) that implied movements of center of gravity, trunk versus lower limbs, and strength of reaction measures are consistently detected by both EquiTest and the laboratory kinematics and dynamics measurement systems.

    Title Biomechanical Analyses of Rising from a Chair.
    Date February 1993
    Journal Journal of Biomechanics
    Excerpt

    Quantification of the biomechanical factors that underlie the inability to rise from a chair can help explain why this disability occurs and can aid in the design of chairs and of therapeutic intervention programs. Experimental data collected earlier from 17 young adult and two groups of elderly subjects, 23 healthy and 11 impaired, rising from a standard chair under controlled conditions were analyzed using a planar biomechanical model. The joint torque strength requirements and the location of the floor reaction force at liftoff from the seat in the different groups and under several conditions were calculated. Analyses were also made of how body configurations and the use of hand force affect these joint torques and reaction locations. In all three groups, the required torques at liftoff were modest compared to literature data on voluntary strengths. Among the three groups rising with the use of hands, at the time of liftoff from the seat, the impaired old subjects, on an average, placed the reaction force the most anterior, the healthy old subjects placed it intermediately and the young subjects placed it the least anterior, within the foot support area. Moreover, the results suggest that, at liftoff, all subjects placed more importance on locating the floor reaction force to achieve acceptable postural stability than on diminishing the magnitudes of the needed joint muscle strengths.

    Title Quantitative Assessment of Bed Rise Difficulty in Young and Elderly Women.
    Date July 1992
    Journal Journal of the American Geriatrics Society
    Excerpt

    OBJECTIVE: To describe the motions which occur during rising from bed, specifically the motions that appeared to characterize difficulty in rising from a bed in older adults. DESIGN: Development of a Mobility assessment tool. SETTING: Retirement center and two university laboratories. PARTICIPANTS: Three groups of female volunteers: young controls (n = 17, mean age 24), community-dwelling older adults (n = 12, mean age 71), and retirement center-dwelling older adults who admitted to difficulty in rising from a bed (n = 15, mean age 86). INTERVENTION: Videotaping of motions occurring during controlled rises from a supine to sitting position. MAIN OUTCOME MEASURES: These motions were rated on the specially developed Bed Rise Difficulty (BRD) scale, a scale designed to measure movements that characterize difficulty in rising from a bed in older adults. Subject groups were compared in total BRD score, individual BRD item score, and total time to rise. Item relationships and scale reliability were also assessed. RESULTS: Older adults with no apparent difficulty in rising based on total time to rise or on the BRD score nevertheless showed differences in upper extremity use when compared to young controls. Older adult subjects with difficulty in rising from a bed, when compared to other older adults with no apparent difficulty, differed more often in their upper extremity and leg use to facilitate the rise. Five BRD scale items, including use of extremity pushes, discontinuity of trunk and leg motion, multiple shoulder/pelvic adjustments, multiple leg adjustments, and poor vertical heel clearance may have best indicated true bed rise difficulty. CONCLUSIONS: These data provide a reliable and valid method to characterize difficulty in rising from a bed and provide the basis for biomechanical analyses of the strength and joint ranges of motion required to rise from a bed.

    Title Postural Control in Young and Elderly Adults when Stance is Perturbed: Kinematics.
    Date June 1992
    Journal Journal of Gerontology
    Excerpt

    Increased postural sway and falling are associated with aging and are likely related to problems with postural control in the elderly. We investigated the motions of individual body segments in 24 healthy young adults and 15 healthy elderly adults (mean ages 26 and 72) in response to four tasks: (a) standing with feet flat on an anteriorly accelerating platform (Flat Translation); standing on a narrow beam support that was (b) stationary (Beam Standing) and (c) accelerating anteriorly (Beam Translation); and (d) standing on a rotatable but otherwise stationary springboard (Springboard Standing). An optoelectronic camera system was used to measure rotations of body segments, particularly regarding their maximum excursions, time to first rotation response, direction of initial rotation, and time to first rotation reversal. In general, larger rotation excursions were noted in the elderly compared to the young group, particularly in the Beam Standing and Beam Translation tasks, but the magnitude of rotation difference was small. All rotation magnitudes were well within the available ranges of motion of the body joints. In both excursion magnitudes and directions of initial rotation, the elderly showed greater variability than the young. In the Beam Translation task, the elderly group, compared to the young, tended to rotate their upper body segments more than in the Flat Translation task. These data suggest that healthy elderly adults with no apparent musculoskeletal or neurological impairments have small but consistent differences in postural control kinematics, particularly when more challenging conditions are presented. Moreover, these data provide the basis for biomechanical analyses of joint torques and other dynamic requirements of these responses.

    Title Stepping over Obstacles: Gait Patterns of Healthy Young and Old Adults.
    Date December 1991
    Journal Journal of Gerontology
    Excerpt

    Falls associated with tripping over an obstacle can be devastating to elderly individuals, yet little is known about the strategies used for stepping over obstacles by either old or young adults. The gait of gender-matched groups of 24 young and 24 old healthy adults (mean ages 22 and 71 years) was studied during a 4 m approach to and while stepping over obstacles of 0, 25, 51, or 152 mm height and in level obstacle-free walking. Optoelectronic cameras and recorders were used to record approach and obstacle crossing speeds as well as bilateral lower extremity kinematic parameters that described foot placement and movement trajectories relative to the obstacle. The results showed that age had no effect on minimum swing foot clearance (FC) over an obstacle. For the 25 mm obstacle, mean FC was 64 mm, or approximately three times that used in level gait; FC increased nonlinearly with obstacle height for all subjects. Although no age differences were found in obstacle-free gait, old adults exhibited a significantly more conservative strategy when crossing obstacles, with slower crossing speed, shorter step length, and shorter obstacle-heel strike distance. In addition, the old adults crossed the obstacle so that it was 10% further forward in their obstacle-crossing step. Although all subjects successfully avoided the riskiest form of obstacle contact, tripping, 4/24 healthy old adults stepped on an obstacle, demonstrating an increased risk for obstacle contact with age.

    Title Rising from a Chair: Effects of Age and Functional Ability on Performance Biomechanics.
    Date June 1991
    Journal Journal of Gerontology
    Excerpt

    Although difficulty in rising from a chair is common to elderly people, few studies have compared chair rise performance in young and elderly adults with differing functional abilities. Using an instrumented chair and a videotape analysis, controlled chair rise performances were quantified in three groups of volunteers: young adults (Young, n = 17, mean age 23 years), elderly adults able to rise without the use of armrests (Old Able, n = 23, mean age 72 years), and elderly adults unable to rise without the use of armrests (Old Unable, n = 11, mean age 84 years). Rises both with and without the use of hands were observed. The total time to rise and the percent of that time spent in the two distinct phases of the rise, the body segment rotations used, and the hand forces exerted were measured. Despite no apparent functional impairment, the Old Able compared to the Young spent a larger percent time in the first phase of the rise and rotated their body segments by different amounts. When rising with use of hands, the Old Unable compared to the Old Able group took more time and used different body segment rotations and larger ratios of hand force to body weight. These data quantify chair rise performance in young adults and in elderly adults with differing functional abilities and enable biomechanical analyses of the importance of joint torque strengths and postural stability in that performance.

    Title Stomas. Self-help Groups. Part 1.
    Date October 1982
    Journal Clinics in Gastroenterology
    Title The Endocrine Basis of Infertility in Women.
    Date February 1981
    Journal The Nursing Clinics of North America
    Title Towards Independence with an Ostomy.
    Date June 1974
    Journal Queen's Nursing Journal
    Title Sudden Turns and Stops While Walking: Kinematic Sources of Age and Gender Differences.
    Date
    Journal Gait & Posture
    Excerpt

    Background: Significant age and gender differences were found among healthy young and older adult subjects in their abilities to quickly turn or stop in order to avoid obstacles that suddenly appear in the gait path (Cao C, Ashton-Miller JA, Schultz AB, Alexander NB. Abilities to turn suddenly: effects of age, gender and available response time. J Gerontol Med Sci 1997;52A:M88-M93; Cao C, Ashton-Miller JA, Schultz AB, Alexander NB. Abilities to stop suddenly: effects of age, gender, gait phase, and available response time. Submitted for publication, 1997 (also available as a chapter in Cao C. Biomechanics of forward momentum arrest when walking: age and gender differences. PhD Dissertation, University of Michigan, 1996). The present study quantified the extent to which age and gender differences in those subjects' response kinematics affected the total time they needed to suddenly arrest their forward momentum. Methods: Age- and gender-group means of four measures of forward movement of the anterior surface of the abdomen were obtained: the duration of the first post-cue response phase, from the visual cue that initiated the arrest response to reaching peak velocity (T1); acceleration (A1) during this phase; and decelerations (D2 and D3) during two subsequent post-cue response phases. A three-line-segment representation of this forward velocity history was constructed. This representation was used to predict the differences in response time needed (NRT) to suddenly arrest momentum that resulted from measured age and gender differences in each of the four response kinematics measures. Results: The largest contributor to the age group difference found in NRT was the increase in T1 among the older adults. Among the older males, the next largest contributor was their larger value of A1, and among the older females, their substantially smaller value of D2. Among the young adults in sudden turns, no single kinematic parameter seemed primarily responsible for the gender difference found in the NRT. Among the older adults, the gender difference in D2 was almost fully responsible for the gender difference in NRT, in both sudden stops and turns. Conclusions: Much of the older adults' need for longer response times than those of the young was attributable to the lengthened first phase of their responses. Older females, in addition, needed longer response times than young adults or older males because, during the second phase of their responses, their decelerations were substantially smaller. These age and gender differences may have arisen in part from known age and gender differences in abilities to develop lower extremity joint torque strengths rapidly. Copyright 1998 Elsevier Science B.V.

    Title Age Differences in Abilities to Perform Tandem Stand and Walk Tasks of Graded Difficulty.
    Date
    Journal Gait & Posture
    Excerpt

    We quantified the abilities of 12 young (mean age 23.3 years) and 12 old (mean age 72.0 years) healthy women to tandem stand and tandem walk on a set of six beams, ranging from 15 cm down to 2.5 cm in width. Tandem stand tasks were conducted with eyes both open and closed. Tandem walk tasks were conducted with eyes open, and with both heel-to-toe and comfortable-distance step types. Significant age differences were found in the mean rate of successful performance for both tandem stand and tandem walk (P<0.001, rm-ANOVA). For both age groups, significant main effects for beam width were found for both tandem stand and tandem walk tasks. During tandem stand with eyes closed, young women were always successful on the widest beam while elderly women had an average success rate of only 62% and demonstrated an increased dependence on vision on narrower beams. Copyright 1998 Elsevier Science B.V. All rights reserved

    Title Effects of Age, Available Response Time and Gender on Ability to Stop Suddenly when Walking.
    Date
    Journal Gait & Posture
    Excerpt

    Background: Injuries may occur during walking when a sudden stop to avoid a gait path obstacle is called for unexpectedly, but cannot be completed in the time available. Little is known about abilities, particularly those of older adults, to stop suddenly. Methods: Twenty young (mean age 23.4 years) and 20 older (72.6 years) healthy and physically active adults with equal numbers of females and males in each age group were studied. While walking straight ahead at approximately 1.3 m/s, they were cued by a light at one of five possible locations to stop as quickly as possible. Subjects were given available response times (ART), the times between the visual cue to stop and potential passage through a virtual wall that was outlined by the array of lights used to cue the subjects, ranging from 375 to 825 ms in 75-ms increments. The rate of success (RS) in completing the stops as prescribed was determined and the effects on RS of age, available response time and gender were examined. Regression analyses were used to interpolate the RS data. Results: At all ART, older female (OF) subjects had a significantly lower rate of success (RS) than either older male (OM) or young adult (YA) subjects. At an ART of 525 ms, for example, RS was 58% for YA and 51% for OM, but only 23% for OF. The regression analyses suggested that OM in the mean would have needed 10 ms longer and OF 70 ms longer than YA to achieve a 50% RS. No significant gender difference in RS were found among YA. Conclusions: The healthy and physically active older female subjects in this study needed longer available response times, and thus longer available stopping distances, than did the young adults or the older males to succeed as well in stopping suddenly while walking at their comfortable gait speed. Copyright 1998 Elsevier Science B.V.

    Title Effects of High- and Low-velocity Resistance Training on the Contractile Properties of Skeletal Muscle Fibers from Young and Older Humans.
    Date
    Journal Journal of Applied Physiology (bethesda, Md. : 1985)
    Excerpt

    A two-arm, prospective, randomized, controlled trial study was conducted to investigate the effects of movement velocity during progressive resistance training (PRT) on the size and contractile properties of individual fibers from human vastus lateralis muscles. The effects of age and sex were examined by a design that included 63 subjects organized into four groups: young (20-30 yr) men and women, and older (65-80 yr) men and women. In each group, one-half of the subjects underwent a traditional PRT protocol that involved shortening contractions at low velocities against high loads, while the other half performed a modified PRT protocol that involved contractions at 3.5 times higher velocity against reduced loads. Muscles were sampled by needle biopsy before and after the 14-wk PRT program, and functional tests were performed on permeabilized individual fiber segments isolated from the biopsies. We tested the hypothesis that, compared with low-velocity PRT, high-velocity PRT results in a greater increase in the cross-sectional area, force, and power of type 2 fibers. Both types of PRT increased the cross-sectional area, force, and power of type 2 fibers by 8-12%, independent of the sex or age of the subject. Contrary to our hypothesis, the velocity at which the PRT was performed did not affect the fiber-level outcomes substantially. We conclude that, compared with low-velocity PRT, resistance training performed at velocities up to 3.5 times higher against reduced loads is equally effective for eliciting an adaptive response in type 2 fibers from human skeletal muscle.

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