A new study published in the Journal of Physiology found that muscle loss during old age is mainly caused by a loss of nerves. Researchers claim that this change in the nervous system causes muscles to waste away, however, they suggest that physical exercise may give older people a fighting chance of re-connecting their nerves.
Scientists at Manchester Metropolitan University, the University of Manchester, and the University of Waterloo, Ontario, have found that by the age of 75, people have a 30 to 50 percent decline in muscle nerves in their legs.
To reach this conclusion, researchers examined nerve signals among 168 subjects and compared the results to individuals with an athletic background or those who were more physically fit. They checked muscle tissue in detail using magnetic resonance imaging (MRI) and estimated the size and number of nerves in the region by evaluating signal activity.
Scientists said that the aging process not only weakens the muscles but it also causes them to shrink.
This means that large areas of the muscle remain disconnected from the nervous system, which allows the brain and the muscles to communicate. Without this connection, the muscle areas weaken and die.
Professor Jamie McPhee, from the Manchester Metropolitan University, and senior author of the study said that young adults usually have 60 to 70 thousand nerves controlling movement in the legs from the lumbar spine. However, this number gradually declines with old age.
“The muscles need to receive a proper signal from the nervous system to tell them to contract, so we can move around,” Professor McPhee said.
Scientists explained that, when muscle loss occurs, people find it difficult to move, climb stairs and perform basic tasks such as getting up from a chair. This condition worsens if the individual is overweight.
According to the study, healthy muscles have a protective mechanism which allows the surviving nerves to generate new branches and save muscles from withering away. This mechanism is stronger among people with healthy muscle mass as well as those who are more physically fit.
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