Release of muscle proteins after downhill running in male and female subjects

The release of muscle proteins after downhill running, which mainly include s eccentric muscle action, was compared in females (F; n=9) and males CM; n =9). They performed 20 min of downhill treadmill running with 16% decline w ith a target heart rate of 70% of the individual VO2peak, which was determi ned two weeks before. Blood samples were drawn before, 6 and 24 h after exe rcise to measure plasma levels of skeletal troponin I (sTnI), myosin heavy chain fragments (MHC), creatine kinase (CK), and myoglobin (Mb). Baseline l evels before exercise mere significantly higher in males compared to female s for the cytoplasmic proteins CK and Mb but the difference for MHC and sTn I was not significant. Both groups displayed marked and significant early ( 6 h) increases (P<0.05) for sTnI (median: F: 8.2 <mu>g/L; M: 22.0 mug/L), M b (median: F: 86.8 mug/L; M: 407 mug/L), and CK (median: F: 162 U/ L; M: 33 9 U/L), a significant (P<0.05) but delayed (24 h) increase was found for MH C (median: F: 482 <mu>U/L; M: 651 muU/L), The absolute values for all four parameters were significantly (P<0.05) higher in males compared to females; however, no difference was found for the relative increases and the time c ourse of all parameters between females and males. We conclude 1) that ther e were no significant differences in the basal concentrations of predominan tly bound proteins, and 2) that there were no differences in the relative m uscle protein release between females and males before and after one bout o f high-intensive eccentric exercise. The higher plasma concentrations of al l measured muscle proteins in males are probably caused by the higher muscl e mass compared to females.