'Use it or Lose It' Is True for Muscle Mass

New research discovers that even among young people, two weeks of not using your legs can cause a drop in muscular strength of more than 30 percent.

In fact, the loss of muscular strength can result in a young person having the strength of a person who is 40-50 years older than they are.

Researchers at the University of Copenhagen discovered that inactivity — whether from an injury or if we simply take a relaxing vacation — can cause a rapid decline in muscular strength.

Investigators examined what happens to the muscles in younger and older men after a period of high inactivity, by way of so-called immobilization with a leg pad.

“Our experiments reveal that inactivity affects the muscular strength in young and older men equally. Having had one leg immobilized for two weeks, young people lose up to a third of their muscular strength, while older people lose approximately one-fourth.

“A young man who is immobilized for two weeks loses muscular strength in his leg equivalent to ageing by 40 or 50 years,” says Andreas Vigelsoe, Ph.D.

Researchers explain that with age, our total muscle mass diminishes, which is why young men have about one kilogram more muscle mass in each leg than older men. Both groups lose muscle mass when immobilized for two weeks: Young men lose 485 grams on average, while older men lose approx. 250 grams. The participants’ cardiovascular fitness was also reduced while their one leg was immobilized in a pad.

“The more muscle mass you have, the more you’ll lose. Which means that if you’re fit and become injured, you’ll most likely lose more muscle mass than someone who is unfit, over the same period of time.

“But even though older people lose less muscle mass and their cardiovascular fitness is reduced slightly less than in young people, the loss of muscle mass is presumably more critical for older people, because it is likely to have a greater impact on their general health and quality of life,” said Martin Gram, a researcher at the university.

In the study, after two weeks of immobilization, the participants bicycle-trained three to four times a week for six weeks.

However, even with this training, strength remained suppressed.

“Unfortunately, bicycle-training is not enough for the participants to regain their original muscular strength. Cycling is, however, sufficient to help people regain lost muscle mass and reach their former fitness level. If you want to regain your muscular strength following a period of inactivity; you need to include weight training,” Vigelsoe said.

“It’s interesting that inactivity causes such rapid loss of muscle mass, in fact it’ll take you three times the amount of time you were inactive to regain the muscle mass that you’ve lost. This may be caused by the fact that when we’re inactive, it’s 24 hours a day,” Gram said.

Source: University of Copenhagen