PRINCIPLES OF EXERCISE TRAINING

Design of exercise programs that are part of pulmonary rehabilitation programs should be founded on an appreciation of the principles of exercise training of healthy subjects. Training produces structural and biochemical changes in the muscles that exercise which increase the ability of the trained muscle to perform aerobic exercise. After training, a given level of heavy exercise engenders lower levels of blood lactate. This is associated with a lower requirement for oxygen uptake, carbon dioxide output, and ventilation. Although the precise mechanism by which training produces changes in the exercising muscles is unknown, characteristics of an effective training program have been defined. Healthy subjects must train for at least 30 min per day, 3 to 5 days per week for 4 to 8 weeks to achieve a physiologic training effect. More controversial is whether a critical training intensity exists. Further, it is not clear which yardstick to apply to quantitate training intensity. Finally, after a training effect has been achieved, regular exercise must be continued or the gains will be lost.