SKELETAL-MUSCLE INJURY AND REPAIR IN MARATHON RUNNERS AFTER COMPETITION

  • 1 January 1985
    • journal article
    • research article
    • Vol. 118  (2) , 331-339
Abstract
Elevated serum creatine kinase MB isoenzyme (CK-MB) activity in marathon runners after competition may arise from injury to skeletal muscle, myocardium or a combined tissue source. Normal radionuclide myocardial scintigraphy and the selective increase in skeletal muscle CK-MB reported in such runners strongly suggest a peripheral source. Gastrocnemius muscles were examined by EM from 40 male marathon runners at intervals after competition and from 12 male nonrunners. Muscle from runners showed post-race ultrastructural changes of focal fiber injury and repair: intra- and extracellular edema with endothelial injury; myofibrillar lysis, dilation and disruption of the T-tubule system, and focal mitochondrial degeneration without inflammatory infiltrate (1-3 days). The mitochondrial and myofibrillar damage showed progressive repair by 3-4 wk. Late biopsies showed central nuclei and satellite cells characteristic of the regenerative response (8-12 wk). Muscle from veteran runners showed intercellular collagen deposition suggestive of a fibrotic response to repetitive injury. Control tissue from nonrunners showed none of these findings. The sequential morphologic changes in runners suggest that the increase in skeletal muscle CK-MB is a marker of cellular regeneration.