A sports medicine specialist is a physician who is trained to diagnose and treat injuries and conditions caused by participation in athletic activities.
These doctors are generally employed by professional sports teams to care for the athletes who are injured. They have extensive knowledge of the types of injuries that athletes are most susceptible to, such as stress fractures, sprains, concussions, muscle cramps, ACL injuries, and shin splints.
It is the responsibility of sports medicine specialist to clear athletes to return to the playing field when they are deemed fit. These doctors also advise athletes on how to avoid injury through proper care of their bodies while training.

Hospitalists are physicians who specialize in the care of patients in the hospital. The majority of hospitalists are board-certified internists and have completed the same training as other internal medicine doctors including medical school, residency and board certification examination.
Hospitalist activities include patient care, teaching, research, and leadership related to hospital care. They have more expertise in caring for complicated hospitalized patients on a daily basis since, unlike other specialists or primary care doctors, they spend most of their day in the hospital.
They often coordinate the care of their patients and act as the central point of communication among the different doctors and nurses involved in the patient's care. They are also the main physician for family members to contact for updates on a loved one.

A gastroenterologist is a specialist in diagnosis and treatment of conditions involving the digestive/gastrointestinal (GI) tract. These doctors are experts on how food moves through the digestive system and is chemically broken down, with nutrients being absorbed and waste excreted. You might see this kind of doctor if you are experiencing any number of stomach issues, some of which might be severe diarrhea, irritable bowel syndrome, hemorrhoids, ulcers, acid reflux, Crohn's disease and more.

An internist is a physician who focuses on the diagnosis and treatment of conditions that affect the adult population—both acute and chronic.
These doctors are often who adults see as their primary physicians because they treat a broad range of illnesses that do not require surgical or specialist interventions. They also work to help a patient maintain optimal health in order to prevent the onset of disease.
In addition to treating the common cold and flu, internists also treat chronic diseases like diabetes and heart disease.

A physiatrist is a doctor who specializes in the rehabilitation and physiological treatment of patients with an illness or injury that affects movement.
These specialists have extensive knowledge of the nerves, muscles, bone, and brain. Physiatrists are also experts in pain medication.
Some common conditions that physiatrists treat are rheumatoid arthritis, neurological and spinal disorders and injuries, chronic pain disorders, like fibromyalgia, and musculoskeletal issues, like broken bones and torn muscles.
These physicians also often coordinate a team of other specialists in order to maximize the patient's recovery, such as occupational therapists, speech therapists, neurologists, orthopedists, and counselors.