The Principle of Reversibility – What Happens When You Stop Exercising?

The Principle of Reversibility as it applies to exercise and fitness training means: If you don’t use it, you lose it. This principle is well-grounded in exercise science and is closely related to the biological principle of Use and Disuse. (1)

While rest periods are necessary for recovery after workouts, extended rest intervals reduce physical fitness. The physiological effects of fitness training diminish over time, causing the body to revert back to its pretraining condition.

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

The Principle of Reversibility does not apply to retaining skills. The effects of stopping practice of motor skills, such as weight training exercises or sport skills, are very different.

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

Tips on How to Apply the Principle of Reversibility

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

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

3. Increase exercise gradually and progressively after a long break. Be patient about regaining your previous fitness level.

4. Do not attempt to lift heavy weight loads without proper conditioning after a long break. You will remember how to properly execute the lifts, but you may sustain an injury if you overestimate how much 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, S.K., Dodd, S.L., Noland, V.J. (2006). Total fitness and wellness (4th ed.). San Francisco: Pearson Education.

2. Costill, D. & Richardson, A. (1993). Handbook of sports medicine: Swimming. London: Blackwell Publishing.

3. Schmidt, R.A. & Wrisberg, C.A. (2000). Motor learning and performance: A problem-based learning approach (2nd ed.). Champaign, IL: Human Kinetics.

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