While they do not yet understand why the connections between muscles and nerves remain healthy in some people and not in others, the new knowledge could be used to delay old-age weakness by either slowing the decline or by increasing the success of nerve branching to rescue detached muscle fibres.
By the age of 75, individuals typically have around 30 to 50 per cent fewer nerves controlling their legs.
This made muscles waste away, but in older fitter athletes there was a better chance of them being "rescued" by nerves re-connecting. According to the study published in the Journal of Physiology, as people get older they start facing a number of muscle problems and have difficulty in walking, climbing staircase or sitting and getting out of the chair. It happens to everyone eventually, but there has been no sufficient explanation as to why.
Image copyright Piasecki et al Image caption Muscle loss: The femur bone is in the middle creating a black ring, muscles are shaded grey and fat is white.
But his research showed this changed significantly in old age.
There was a dramatic loss of nerves controlling the muscles - a 30-60% loss - which means they waste away.
"The muscles need to receive a proper signal from the nervous system to tell them to contract, so we can move around".
These researchers analyzed the functioning of each tissue by performing MRI (Magnetic Resonance Imaging) scans and recorded the electrical activity of each muscle in order to calculate the size and numbers of surviving nerves. This was more likely to happen to seniors with large, healthy muscles, McPhee said.