Modification of vastus lateralis muscle homeostasis after an acute bout of unaccustomed exercise

Abstract

The purpose of this study was to investigate skeletal muscle changes during rhabdomyoly- sis induced by an acute bout of jumping exercise in sedentary individuals. Healthy volunteers (N=26) did a bout of jumping exercise (10 sets of 10 squat jumps to maximal jump height rest between sets was 1 min). Blood samples were drawn immediately before the exercise interven- tion and 6, 24, 48 and 72 hours after. The vastus lateralis was biopsied before (9 or 4 days) and 3 days post-intervention. Subjects were divided into two groups on individual CK responses on day 3 after exercise: high (n=10) and low responders (n=16). The cut-off limit used to diagnose rhabdomyolysis after exercise was CK≥1000 U/L. Structural (dystrophin staining) and ultra- structural (transmission electron microscopy) analysis of muscle fibres did not evidence any difference between high and low responders despite that the high responders perceived more muscle soreness than low responders. Moreover, high responders presented significantly high- er muscle myeloperoxidase (MPO) levels at both baseline and postexercise biopsies compared to the baseline of the low responder group. The results seems to indicate that rhabdomyolysis after exercise is caused by secondary inflammatory damage.