Figure 5.

Older animal skeletal muscle exhibits a reduction in it's intrinsic force-generating capacity, particularly at high stimulation frequencies. This cross-sectional data were obtained from young (6–8 mos) and older (24 mo) rats by normalizing the electrically stimulated plantarflexor maximal force to the muscle weight. At the higher stimulation frequencies the older—but not yet senescent—muscle exhibited a greater than 30% reduction in its intrinsic force capacity. It should be noted that this reduction occurred in the presence of a very limited amount of atrophy. Modified with permission from Russ and colleagues (102) Modified figure approved by the corresponding author (D. W. Russ).