Histological changes in the gastrocnemius muscle after 1

w and 6 w. Muscle samples from the exercised (left column, A, C) and non-exercised contralateral (right column, B, D) sides of gastrocnemius muscles after 1 w (A, B) and 6 w (C, D) of unilateral EMS/E. The sections are stained with H&E. Note the presence of atypical muscle fibers indicating muscle fiber regeneration in the exercised muscle (A) and fibers with internal nuclei (arrow) in the non-exercised muscle (B) after 1 w of EMS/E. Note also the large variation in the fiber size (A–D), the presence of small rounded fibers (C, D) and the marked fibrosis and inflammatory cell infiltration with extended duration of EMS/E (asterisks) (A, C, D) in both the exercised and non-exercised sides. Figure B and D shows presence of internal nuclei (arrows). (Bar = 50 µm).