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Therapeutic exercise is the foundation of physical therapy, and a fundamental component of the vast majority of interventions. Prescribed accurately, therapeutic exercise can be used to restore, maintain, and improve a patient's functional status by increasing strength, endurance, and flexibility. Therapeutic exercise enables the patient/client to

  • remediate or reduce impairments
  • enhance function
  • optimize overall health
  • enhance fitness and well-being.

When prescribing a therapeutic exercise program it is important to consider the functional loss and disability of the patient.

Energy Systems

Muscles are metabolically active and must generate energy to move. The creation of energy occurs initially from the breakdown of certain nutrients from foodstuffs.


The energy required for exercise is stored in a compound called adenosine triphosphate (ATP). ATP is produced in the muscle tissue from blood glucose or glycogen. Fats and proteins can also be metabolized to generate ATP. Glucose not needed immediately is stored as glycogen in the resting muscle and liver. Stored glycogen in the liver can later be converted back into glucose and transferred to the blood to meet the body's energy needs.

If the duration or intensity of the exercise increases, the body relies more heavily on fat stored in adipose tissue to meet its energy needs.


During rest and submaximal exertion, both fat and carbohydrates are used to provide energy in approximately a 60% to 40% ratio.

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.
      • The short-term energy system: provides energy for muscle contraction for up to 15 seconds.
    • Anaerobic glycolysis (glycolytic system): a major supply of ATP during high-intensity, short-duration activities.
      • Muscle glycogen is the initial substrate. Stored glycogen is split into glucose, and through glycolysis, split again into pyruvate acid and lactic acid as the end product, with no oxygen being directly involved. The energy released during this process forms ATP.
      • Although unable to produce as much energy per unit time as the phosphocreatine system (i.e., unable to sustain maximum sprinting speed), it lasts considerably longer before intensity must be further reduced.
      • The intermediate energy system: provides the majority of energy for a sustained performance lasting between 20 seconds and 2 minutes (sprinting 200 to 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 to generate ATP.
    • The long-term ...

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