London, June 29 (IANS): If you stop using your legs just for two weeks, you would lose a third of your muscular strength even if you are quite young and strong, says a new study.

Researchers from the University of Copenhagen examined what happens to the muscles in younger and older men after a period of high inactivity -- for example when we are injured, fall ill or simply take a very relaxing holiday.

"Our experiments reveal that inactivity affects the muscular strength in young and older men equally. Having had one leg immobilised for two weeks, young people lose up to a third of their muscular strength, while older people lose around one fourth," said researcher Andreas Vigelsoe.

"A young man who is immobilised for two weeks loses muscular strength in his leg equivalent to ageing by 40 or 50 years," Vigelsoe added.

With age, our total muscle mass diminishes, which is why young men have around 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," said co-researcher Martin Gram.

"But even though older people lose less muscle mass and their level of 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," Gram added.

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

"Unfortunately, bicycle-training is not enough. If you want to regain your muscular strength following a period of inactivity, you need to include weight training," Andreas 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 have lost," Gram added.