Aging and the Motor Unit

It has long been known that humans have decreased strength and muscle mass with age, but the mechanisms behind this are still not completely understood. In his review, Degens [1] discusses some potential reasons for this loss in strength with age, concluding that the hypertrophy capability of a muscle fiber does not change as one gets older, but rather that there are fewer muscle fibers. The primary reasoning behind fewer muscle fibers is associated with restructuring and subsequent loss in motor units, as well as a lack of mechanical stimuli from physical activity.