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What Happens When You Stop Training: The Effects of Deconditioning

October 15, 2004 10:00 AM

By Jim Brown, Ph.D., Executive Editor, Sports Performance Journal (athletesperformance.com)

Serious exercisers and competitive tennis players worry about what will happen to their fitness and performance levels if they cannot work out because of injuries, family and work responsibilities, or other circumstances. Here is a summary of what we know about the physiological effects of detraining:

1. Highly trained athletes show a five percent drop in VO2max (the ability to take in, transport, and use oxygen for fuel) during the first three weeks of inactivity. But there is a slower decline over the following weeks.

2. Persons with low to moderate aerobic capacity show little effect of detraining during the first three weeks, but VO2max declines to untrained levels after several additional weeks.

3. Stroke volume (the amount of blood pumped with each heartbeat) begins to decrease as soon as training is stopped. One study showed a 10 percent decline within 12 days, while another indicated a 12 percent drop 2-4 weeks after the last training session.

4. Resting heart rates increase with inactivity, which indicates a decline in cardiovascular endurance. However, among well-conditioned athletes, the rates do not change significantly after the first 2-3 weeks of inactivity.

5. In highly trained individuals, an interruption of training causes a decline in performance. Swimmers showed a 14 percent decrease in maximal arm power after four weeks of not training. Marathon runners posted a 25 percent decrease in endurance time after 15 days of inactivity.

The exact effect of detraining on a person’s performance is difficult to measure because depends on physical condition, intensity and duration of training, and choice of exercise, among other variables. You can minimize the loss of conditioning by participating in alternate training methods. Water running and brisk walking are examples. These activities may not be as fun or as challenging as playing tennis, but doing something less taxing is better than doing nothing.

© 2004 HMS Publishing, Inc.
Jim Brown will be contributing new content to this site on a monthly basis. If you have a question for Dr. Brown please feel free to email him at




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