The reversibility principle, as applied to exercise and fitness training, means: If you don’t use it, you lose it. This principle is well founded in the science of exercise and is closely related to the biological principle of use and disuse. (1)

While rest periods are necessary for recovery after workouts, long rest intervals reduce fitness. The physiological effects of physical training diminish over time, returning the body to its pre-training condition.

Detraining occurs within a relatively short period of time after you stop exercising. Only about 10% of strength is lost 8 weeks after training is stopped, but 30-40% of muscular endurance is lost during the same period of time. (2)

The reversibility principle does not apply to skill retention. The effects of not practicing motor skills, such as weight training or sports skills, are very different.

A skill once learned is never forgotten, especially if it is learned well. Coordination appears to be stored in long-term motor memory and remains nearly perfect for decades, particularly for continuous skills (eg, biking, swimming). If you stop training, you will lose strength, endurance, and flexibility over time, but you will remember how to execute the skills involved in performing exercises and activities. (3)

Tips on how to apply the reversibility principle

1. After long intervals of rest, begin a conditioning program to rebuild your base of strength and endurance.

2. For sports, take an active break to minimize the effects of detraining during the off-season.

3. Increase exercise gradually and progressively after a long rest. Please be patient to regain your previous physical condition.

4. Don’t try to lift heavy loads without proper conditioning after a long rest. You will remember how to perform the lifts correctly, but you can be injured if you overestimate the amount of weight you can lift.

5. Emphasize stretching exercises to regain joint flexibility. This is particularly important for older adults who participate in senior sports.


1. Powers, SK, Dodd, SL, Noland, VJ (2006). Fitness and total well-being (4th ed.). San Francisco: Pearson Education.

2. Costill, D. and Richardson, A. (1993). Sports Medicine Manual: Swimming. London: Blackwell Publishing.

3. Schmidt, RA and Wrisberg, CA (2000). Performance and motor learning: a problem-based learning approach (2nd ed.). Champaign, IL: Human Kinetics.

Leave a comment

Your email address will not be published. Required fields are marked *