Changes in human skeletal muscle ultrastructure and force production after acute resistance exercise

J Appl Physiol (1985). 1995 Feb;78(2):702-8. doi: 10.1152/jappl.1995.78.2.702.


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.

Publication types

  • Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Electromyography
  • Humans
  • Isometric Contraction / physiology
  • Male
  • Microscopy, Electron
  • Muscle Fibers, Skeletal / physiology
  • Muscle Fibers, Skeletal / ultrastructure
  • Muscle, Skeletal / physiology*
  • Muscle, Skeletal / ultrastructure*
  • Myofibrils / physiology
  • Myofibrils / ultrastructure
  • Time Factors
  • Weight Lifting / physiology*