It’s no secret, our lower limbs get weaker as we age. Though our body overall weakens as we get older, the loss of leg strength have always fascinated scientists. A group of British and Canadian researchers believe they have identified the culprits: the nerves.
With age, the leg muscles become smaller and weaker, which can lead to difficulties in performing certain daily movements such as climbing stairs or getting up from a chair.
Though this reality hits a majority of aging people at different levels, its very nature remained a mystery.
Professor Jamie McPhee of the Manchester Metropolitan University in the United Kingdom and colleagues at Waterloo University in Ontario have found that the number of nerves that control the legs decreases by about 30% at the age of 75.
This loss, which directly influences the muscular strength of aging people, would be less important for people who train regularly. Researchers have indeed noticed a better ability to reconnect nerves in the latter.
The study shows a significant decrease in the number of these nerves with age.
“There has been a significant decrease in the nerves controlling the muscles – a loss of 30% to 60% – which leads to a decrease in energy capacities,” says Jamie McPhee, researcher at Manchester Metropolitan University, UK.
“The muscles have to get an appropriate signal from the nervous system to contract and allow movement,” McPhee says.
In this work, researchers examined muscle tissue in detail using magnetic resonance imaging (MRI). They were able to record the electrical activity that passes through the muscles to estimate the number and size of the nerves.
They found that healthy muscles have some form of protection, despite age. Nerves that survive can create new branches to help muscles and prevent their loss.
In addition, this “redirection” is more likely to occur in healthy people whose muscles are trained.
The details of this work are published in the Journal of Physiology.