Effects of concentric and repeated eccentric exercise on muscle damage and calpain–calpastatin gene expression in human skeletal muscle

The purpose of this study was to compare the responsiveness of changes in Ca 2+ -content and calpain–calpastatin gene expression to concentric and eccentric single-bout and repeated exercise. An exercise group ( n = 14) performed two bouts of bench-stepping exercise with 8 weeks between exercise bouts, and was compared to a control-group ( n = 6). Muscle strength and soreness and plasma creatine kinase and myoglobin were measured before and during 7 days following exercise bouts. Muscle biopsies were collected from m. vastus lateralis of both legs prior to and at 3, 24 h and 7 days after exercise and quantified for muscle Ca 2+ -content and mRNA levels for calpain isoforms and calpastatin. Exercise reduced muscle strength and increased muscle soreness predominantly in the eccentric leg ( P