How Long Does It Take To Lose Muscle Mass?

Have you ever been out of action with an injury and felt that you’ve lost your fitness in about a third of the time it took you to get it?

Well it seems there may actually be some truth to that.

The Blackmores Institute reports on new research that examines what happens to muscle after a period of inactivity.

READ MORE: Sports injuries

Blackmores Institute- About the research

Researchers from the University of Copenhagen, Denmark, have examined what happens to the muscles in younger and older men after a period of high inactivity, by way of so-called immobilisation 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 immobilised for two weeks loses muscular strength in his leg equivalent to ageing by 40 or 50 years," says Andreas Vigelsoe, PhD at the Center for Healthy Aging and the Department of Biomedical Sciences at the University of Copenhagen.

With age, our total muscle mass diminishes, which is why young men have approximately one kilogram more muscle mass in each leg than older men.

Both groups lose muscle mass when immobilised for two weeks - young men lose 485 grams on average, while older men lose approximately 250 grams. The participants' physical fitness was also reduced while their one leg was immobilised 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.” says Martin Gram, researcher at the Center for Healthy Aging and the Department of Biomedical Sciences.

YOUR GUIDE: Running with injuries

After two weeks of immobilisation, the participants bicycle-trained 3-4 times a week for six weeks.

"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” says Vigelsoe.

“If you want to regain your muscular strength following a period of inactivity; you need to include weight training.”

"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," Martin Gram concludes.

Source: Journal of Rehabilitation Medicine 2015 Volume 47, Issue 6 DOI: 10.2340/16501977-1961