Active exercise is a term commonly heard in medical settings and rehabilitation centers, as well as in gyms and fitness centers. It is essentially any exercise in which a person must exert force to complete a motion. For an injured patient, this may mean simply raising a leg by himself, or sitting up and getting out of bed. The opposite of active exercise is passive exercise, in which another person moves the patient's limbs for him to keep muscles from atrophying or to encourage better range of motion. Passive exercises are very common in physical therapy settings in which a patient is recovering from a broken limb or torn muscle.
Most exercises performed at a gym or fitness center are generally considered to be active exercise. Lifting weights, for example, requires the user to actively initiate the movement of lifting. By contracting the muscle repeatedly, the lifter builds muscle. Some sorts of stretching, on the other hand, may be considered passive exercise because the limbs stay still while force is exerted upon the muscles to stretch them. Active exercise involves voluntary movement and is generally focused on building muscle or improving cardiovascular performance.
When a person is recovering from an injury, he or she may participate in two types of active exercise: simple active, and assisted active. Assisted active exercise is any exercise in which the patient must move limbs or muscles on his or her own, but with the assistance of a nurse or therapist. Therapy that has moved beyond passive exercise and into the active phase may begin with assisted active exercise because the muscles may not yet be strong enough to act completely on their own; a nurse may also assist to prevent further injury or instability in the patient.
Simple active exercises rely on just the patient for movement with not outside assistance from a nurse or therapist. This is a more advanced form of rehabilitation and generally happens after the patient has had sufficient time to heal. The patient will more than likely go through several days or weeks of passive exercise and assisted active exercises before attempting active exercises on his own to allow the muscles to recover properly and prevent re-injury. This phase of rehabilitation can go on for several weeks, months, or even indefinitely in more severe cases. The point of the active exercises is to get the muscles to remember how to function normally, and to build muscle memory so the muscles and joints can function well again.