To better understand how atrophied muscles recover from prolonged non-weight bearing, we studied soleus muscles (in vitro at optimal length) from female rats subjected to normal weight bearing (WB), 15 days of hindlimb unloading (HU), or 15 days HU followed by 9 d of weight bearing re-loading (HU-R). HU reduced peak tetanic force (P_o), increased maximal shortening velocity (V_max), and lowered peak power/muscle volume. Nine days of re-loading failed to improve P_o, while depressing V_max and intrinsic power below WB levels. These functional changes appeared intracellular in origin as HU-induced reductions in soleus mass, fiber cross-sectional area, and physiological cross-sectional area were partially or completely restored by re-loading. We calculated that HU-induced reductions in soleus fiber length were of sufficient magnitude to over-extend sarcomeres onto the descending limb of their length tension relationship upon the resumption of WB activity. In conclusion, the force, shortening velocity, and power deficits observed after 9 days of re-loading are consistent with contraction-induced damage to the soleus. HU-induced reductions in fiber length indicate that sarcomere hyper-extension upon the resumption of weight bearing activity may be an important mechanism underlying this response.