Changes in human skeletal muscle ultrastructure and force production after acute resistance exercise.
Gibala-MJ; MacDougall-JD; Tarnopolsky-MA; Stauber-WT; Elorriaga-A
J Appl Physiol 1995 Feb; 78(2):702-708
Muscle ultrastructure and contractile properties were examined before and after a single bout of resistance exercise (8 sets of 8 repetitions at 80% of 1 repetition maximum). Eight untrained males performed the concentric (Con) phase of arm-curl exercise with one arm and the eccentric (Ecc) phase with the other arm. Needle biopsies were obtained from biceps brachii before exercise (Base), immediately postexercise from each arm (post-Con and post-Ecc), and 48 h postexercise from each arm (48 h-Con and 48 h-Ecc). Electron microscopy was used to quantify the presence of disrupted fibers in each sample. Analysis of variance revealed a greater (P < or = 0.05) proportion of disrupted fibers in post-Con, post-Ecc, 48 h-Con, and 48 h-Ecc samples compared with Base. Significantly more fibers were disrupted in post-Ecc (82%) and 48 h-Ecc (80%) samples compared with post-Con (33%) and 48 h-Con (37%), respectively. Voluntary and evoked strength measurements recovered to Base values within 24 h in the Con arm but remained depressed (P < or = 0.05) for 72-96 h in the Ecc arm. These data indicate that both the raising and lowering phases of weightlifting produced myofibrillar disruption, with the greatest disruption occurring during the lowering phase.
Skeletal-system-disorders; Musculoskeletal-system-disorders; Muscles; Microscopy; Sampling; Sampling-methods; Muscle-physiology; Skeletal-system
William T. Stauber, Ph. D., Department of Physiology, West Virginia University, P.O. Box 9229, Morgantown, WV 26507-9229
Journal of Applied Physiology
West Virginia University, Morgantown, West Virginia