The effects of non-weight bearing on skeletal muscle in older XXXX : an interrupted bout versus an uninterrupted bout.

@entity1 @entity194 @entity4218 @entity35
Age-related changes in skeletal muscle, in combination with bed rest, may result in a poorer rehabilitation potential for an elderly @entity1 . The purpose of this study was to determine the effects of non-weight bearing ( @entity4218 [ @entity4218 ]) on the soleus and extensor digitorum longus (EDL) in older @entity35 . Two non-weight bearing conditions were used: an uninterrupted bout of @entity4218 and an interrupted bout of @entity4218 . Twenty-one @entity35 were randomly placed into 1 of 3 groups: control, interrupted @entity4218 (2 phases of 7 days of @entity4218 , separated by a 4-day weight-bearing phase) and an uninterrupted @entity4218 (18 uninterrupted days of @entity4218 ). Following non-weight bearing, the soleus and EDL muscles were removed. Fiber type identification was performed by myofibrillar ATPase and cross-sectional area was determined. The findings suggest that any period of non-weight bearing leads to a decrease in muscle wet weight (19%-45%). Both type I and type II fibers of the soleus showed @entity194 (decrease in cross-sectional area, 35%-44%) with an uninterrupted bout of non-weight bearing. Only the type II fibers of the soleus showed recovery with an interrupted bout of weight bearing. In the EDL, type II fibers were more affected by an uninterrupted bout of non-weight bearing (15% decrease in fiber size) compared to the type I fibers. EDL type II fibers showed more @entity194 with interrupted bouts of non-weight bearing than with a single bout (a 40% compared to a 15% decrease). This study shows that initial weight bearing after an episode of non-weight bearing may be damaging to type II fibers of the EDL.
