Chapter 17

Therapeutic exercise is a fundamental component of the vast majority of physical therapy interventions. Prescribed accurately, therapeutic exercise can be used to restore, maintain, and improve a patient's functional status by increasing strength, endurance, and flexibility. When prescribing a therapeutic exercise program it is important to consider the functional loss and disability of the patient.

### Energy Systems

The creation of energy for the metabolically active muscles occurs initially from the breakdown of specific nutrients from foodstuffs. The energy is stored in a compound called adenosine triphosphate (ATP), which is produced in muscle tissue from blood glucose or glycogen, of which glycogen is the initial substrate. Two of the most important energy generating systems that function in muscle tissue include the anaerobic and aerobic metabolism, both of which produce ATP:

• Anaerobic metabolism: this process metabolizes glucose to generate small amounts of ATP energy without the need for oxygen.
• ATP-PCr system: used for ATP production during high-intensity, short-duration exercise. Phosphocreatine (PCr) decomposes and releases a large amount of energy that is used to construct ATP—it is the short-term energy system and provides energy for muscle contraction for up to 15 seconds.
• Anaerobic glycolysis (glycolytic system): a major supplier of ATP during high-intensity, short-duration activities. While unable to produce as much energy per unit time as the phosphocreatine system (ie, unable to sustain maximum sprinting speed), it lasts considerably longer before intensity must be further reduced. This is the intermediate energy system—provides the majority of energy for a sustained performance lasting between 20 seconds and two minutes (sprinting 400 or 800 m).
• Aerobic metabolism (oxidative system): if exercise continues beyond a certain point the body can no longer rely solely on anaerobic metabolism and has to switch to this more complex form of carbohydrate and fat metabolism in order to generate ATP. This is the long-term energy system.

Ultimately, all exercise has an oxygen cost, and the faster this can be met during recovery, the better the preparation for the next high-intensity exercise bout. Delivery of oxygen to the fatigued muscles replenishes stores of PCr and lowers levels of lactic acid. This means the aerobic system must not be overlooked during rehabilitation.

In most activities, both aerobic and anaerobic systems function simultaneously with the ratio being determined by the intensity and duration of the activity. In general, high-intensity activities of short duration rely more heavily on the anaerobic system, whereas low-intensity activities of longer duration rely more on the aerobic system.

The normal and abnormal responses to exercise, and the signs and symptoms of exercise intolerance, are described in Chapter 11.

For motion to take place, the muscles producing movement must have a stable base from which to work from. Muscles perform a variety of roles depending on the required movement. These roles include

• Prime movers/agonists: a muscle that is directly responsible for producing ...

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