Effects of chronic exercise during aging on muscle and end-plate morphology in XXXX .

@entity35 @entity4833 @entity194
Terminal sprouting, myofiber @entity194 , and fiber type changes were studied in soleus and distal gastrocnemius muscles of 21- and 26-mo-old @entity35 and in @entity35 who performed treadmill running from 21 to 26 mo. End-plate structure and muscle fiber types were demonstrated by staining for @entity4833 and myosin ATPase activity. Terminal sprouting was expressed as the percentage of end plates with growth configurations. Fiber @entity194 was assessed as percentage of small-diameter fibers. In all three groups, the percentage of small-diameter fibers was significantly smaller and the percentage of growth configurations significantly larger in the soleus than in the gastrocnemius. The exercised-soleus group had a significantly higher percentage of growth configurations than the 26-mo controls, which had a higher percentage than the 21-mo controls. Percentages among gastrocnemius groups were not different. Fiber type was similar among gastrocnemius groups. However, the exercised-soleus had significantly more slow-twitch fibers than the controls. These data suggest that the soleus responds differently to chronic exercise during aging than does the gastrocnemius.
