Ceasing of muscle function with aging: is it the consequence of intrinsic muscle degeneration or a secondary effect of neuronal impairments?

Aging is associated with a significant decline in neuromuscular function leading to an eventual loss of independence and mobility of senescent people. Age-related sarcopenia, characterised by a reduction in muscle mass and strength, is considered one of the most striking features of aging at the level of the skeletal muscle. Morphological alterations in skeletal muscle can be considered as one of the consequences responsible for muscle weakness in the aged population. Beyond 60 years of age, human muscle undergoes a process of continuous denervation and reinnervation, due to an accelerating loss of motor units. It appears evident that phenotypic alterations in muscle depend on the motor drives provided by the nervous system. Because the peripheral nerves, the neuromuscular junction and motor neurons exhibit degenerative features during advanced age, sarcopenia does not seem to intrinsically develop, but is rather a secondary effect of impaired neuronal function. It is therefore recommended that elderly subjects undergo an exercise program that is aimed towards the improvement of coordinative skills and of muscle strength.