Reversibility

Reversibility is the “use it or lose it ”concept. The reversibility principle states that if we stop exercising, we will lose the physical capabilities that we are no longer using. This sequence occurs with many individuals when they are having problems with arthritis—they slowly decrease their activities and as a result lose flexibility, strength, and endurance. However, the principle works both ways; a person can reverse the effects of a sedentary lifestyle. With regular activity the body adapts and gains strength, flexibility, and endurance, regardless of the age at which one starts exercising.

This principle also applies to short periods of inactivity, such as being ill. If you have to stop exercising due to illness, you rapidly start to lose muscle mass and strength. As soon as you start exercising again, however, you can reverse the loss. As noted in the section on progression, you will need to decrease your exercise workload slightly upon resumption of your program. The longer you are not exercising, the more you will need to adjust your start-up level. Complete bed rest used to be the standard after surgeries and during illnesses, but we now recognize that complete rest is often not the best for healing. The rapid changes that occur in the body during bed rest may slow down healing. One of my jobs as a physical therapist is to help people get up and start moving, even the day after surgery. The changes are reversible, and the shorter the down time, the more rapid the recovery.