Influence of the Menstrual Cycle on Blood Markers of Muscle Damage and Inflammation Following Eccentric Exercise.

The aim of this study was to evaluate whether the menstrual cycle and its underlying hormonal fluctuations affect muscle damage and inflammation in well-trained females following an eccentric exercise. Nineteen eumenorrheic women performed an eccentric squat-based exercise in the early follicular phase, late follicular phase and mid-luteal phase of their menstrual cycle. Sex hormones and blood markers of muscle damage and inflammation -creatine kinase, myoglobin, lactate dehydrogenase, interleukin-6, tumoral necrosis factor-, and C reactive protein- were analyzed in each phase. No effect of menstrual cycle phase was observed (p > 0.05), while an interaction for interleukin-6 was shown (p = 0.047). Accordingly, a moderate effect size [0.68 (0.53)-0.84 (0.74)], indicated that interleukin-6 values 2 h post-trial (2.07 1.26 pg/mL) were likely to be higher than baseline (1.59 0.33 pg/mL), 24 h (1.50 0.01 pg/mL) and 48 h (1.54 0.13 pg/mL) in the mid-luteal phase. Blood markers of muscle damage and inflammation were not affected by the menstrual cycle in well-trained women. The eccentric exercise barely triggered muscle damage and hence, no inflammation was observed, possibly due to participants training status. The mid-luteal phase was the only phase reflecting a possible inflammatory response in terms of interleukin-6, although further factors than sex hormones seem to be responsible for this finding.