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A Week or Two on the Couch Makes You Weak |
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Written by Superhuman
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Thursday, 17 January 2008 |
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Exercises such as weight training and running disturb local muscle and total-body regulation of metabolism. In response …
tissues adapt so that subsequent exercise is less stressful. Intense weight training, for example, causes small muscle injuries. Repair processes heal the injuries and make the muscles stronger to prevent future stress. Detraining (i.e., stop exercising) causes the reverse. Maintaining muscle mass and strength is metabolically expensive, so the body reverts to lower levels of muscle size and function during deconditioning. A study conducted by an international team of scientists led by Mikel Izquierdo showed that four weeks of detraining (no exercise) following 16 weeks of intense weight training caused a 6 percent to 9 percent decrease in strength and a 14 percent to 17 percent decrease in power (power is the ability to exert force rapidly). Two weeks of tapering— gradually decreasing training volume while maintaining intensity— caused a 2 percent increase in strength, but no change in power. Insulin-like growth factor (IGF-1) increased during detraining, while insulin-like hormone-binding protein (IGFBP-3) increased during tapering. The significance of these chemical changes is not known. Taking a month off from training will decrease power more than strength, while tapering will increase strength without affecting power. (Journal Strength Conditioning Research, 21:768–775, 2007)
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