A new study, published in The Journal of Physiology, suggests that muscle wasting of old age follows on from changes in the nervous system. The findings may pave the way for reversing the condition in the future.
Loss of muscle mass with age is called sarcopenia and affects around 10 to 20% individuals over the age of 65 years. The new study looked at 95 men aged between 65 and 90 years with various degrees of sarcopenia. Their muscles were compared along with the nerve activity with 48 healthy young men aged between 18 and 40 years.
The study results showed that the older men as expected had a lower muscle mass compared to the younger men. In older men who did not have pronounced sarcopenia however, the nerve activity in the muscles remained high. This means that whatever little muscle they had lost, the nerves compensated for it.
Of the older men in the study, 13 did not have sarcopenia while 53 were likely to develop sarcopenia with time and were termed “pre-sarcopenic”. Of the study population, 29 had already developed sarcopenia. The nerve bundles or motor units of the muscles were much (by 63 to 65%) lower among the older adults with or without sarcopenia.
Those with no sarcopenia had a 26% higher nerve activity than younger men. Similarly those with “pre-sarcopenia” had a 41% higher nerve activity than the younger individuals. Men with sarcopenia tended to have lower nerve activity.
The researchers could understand the muscle quality and quantity changes with age. They could say that maintaining healthy muscle mass with age could mean that quality of muscle activity was preserved for longer.
The study however was a one-time study and following up the participants over time would have proved deeper insights feel experts. Following up individuals over years with or without adequate physical activities would provide a deeper understanding of how muscle movement and activity helps prevent muscle mass loss.
Prof Jamie McPhee, from Manchester Metropolitan University, explained that while younger persons have 60-70,000 nerves controlling movement of their legs down from the lower back or spine, this number declines with age. Around 30 to 60% nerves are lost he explained, and that leads to muscle wasting.
The researchers suggest that older adults must maintain healthy diet and also regular physical activity to keep their muscles strong and functioning. They are advised 150 minutes of moderate intensity activity per week (30 minutes 5 days a week for example) and strengthening exercises are recommended at least twice a week.
The study authors concluded that losing the nerve fibres to the muscles early during the ageing process is well known. However this study shows how the body can adapt and increase the nerve fibres to the muscles to preserve muscle mass.