Matching mechanical load removes sex differences in creatine kinase response to intense eccentric exercise: a comparative study
Abstract
Abstract Background Men are frequently reported to exhibit greater creatine kinase (CK) responses to exercise-induced muscle damage (EIMD) than women, but the mechanisms underlying this apparent sex difference remain unclear. We investigated whether this difference reflects intrinsic sex-related biological mechanisms or is largely attributable to greater absolute mechanical loading in men resulting from sex-associated differences in maximal strength. Methods Two hundred participants (127 men and 73 women) performed a unilateral intense eccentric exercise (IEE) on a leg press at 85% of their theoretical maximal isometric strength for eight sets of 10 repetitions. Blood samples were collected before IEE, immediately post-IEE, and 24, 48, and 72 h after the IEE to assess CK activity. Principal component analysis was performed to explore the determinants of interindividual variability in peak CK increase, and CK response over time was analyzed using linear mixed-effects models. To examine the influence of absolute mechanical loading on the observed sex difference, men and women were matched for equivalent absolute mechanical loading. Results Men exhibited significantly greater CK response than women ( time, sex, and time x sex interaction , all p p p p = 0.74; sex x time interaction , p = 0.35). Conclusions The greater CK response observed in men was no longer evident when men and women were exposed to equivalent absolute resistance. These findings suggest that apparent sex…
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