Use it or lose it? The facts of detraining

Hi Alice,

Why does it take me about six months to get really fit, then only about two weeks for my fitness to decline? I would have thought that it'd take the same amount of time to lose fitness as gain it.

Fitness Freak

Dear Fitness Freak,

Fitness industry professionals call the phenomenon you are describing "detraining". Basically, if someone trains aerobically or anaerobically (any physical activity), his/her body produces more enzymes for the muscles to grow and be maintained. When s/he stops working out, however, these enzymes break down, leading to muscle atrophy. This can occur as soon as one-and-a-half weeks after a person stops training or being physically active. Within two weeks, an individual can lose up to 80 percent of his/her gains.

Detraining can be influenced by fitness level, how long and intensely one has been exercising, and the length of inactivity. Studies conducted on aerobic fitness have shown that fit people who exercised consistently for a year and then stopped exercising for three months lost half of their aerobic fitness during their hiatus. The researchers also found that those who just begun an exercise program, who were exercising for two months and then stopped for two months, however, lost all of the cardiovascular gains they had previously made.

Here's the good news: muscle has memory, so when someone resumes his/her exercise regimen, his/her muscles will retrain more quickly! Many coaches actually recommend that athletes take two to four weeks off to detrain. Detraining aids in muscle recovery by strengthening muscle fibers when retraining begins, so that the body can reach an even higher level of fitness than before the break.

When returning from a period of inactivity, it's wise to begin at a slower and less intense rate of exercise and to increase activity gradually. A person can also maintain fitness level by not stopping exercise altogether. If someone is exercising at a certain level, s/he can decrease that level and can still keep his/her fitness capacity. For example, if someone works out three to four days per week, s/he can decrease his/her exercise regimen to one day a week for a few weeks and still maintain the same fitness level.

So, the term "use it or lose it" does indeed apply to fitness level. Fortunately, reducing the amount of time spent on training can still maintain fitness. And, if a break is taken, returning to a conditioned level can be accomplished relatively quickly.

Last updated May 11, 2015
Originally published Apr 01, 2005

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