Physical rehabilitation in the form of wheel running does not exacerbate injury related intramuscular collagen content. Uninjured contralateral (A,C) and injured muscle (B,D) of SED and RUN groups, respectively were analyzed for intramuscular collagen content (E). Scale bar = 100 μm. Only tissue within the injured muscle (not in the defect area) was included for analysis. Values are mean ± SEM. n = 3-6 muscles/group; * denotes ≠ uninjured (contralateral); £ denotes ≠ sedentary uninjured; p < 0.05.