Influence of Estrogen on Markers of Muscle Tissue Damage Following Eccentric Exercise

This study tested the hypothesis that estrogen levels of women influences the development of a muscle-tissue damage (creatine kinase, CK) marker and delayed onset muscle soreness (DOMS) following eccentric exercise. Seventeen oral contraceptive (OC) users and ten eumenorrheic (EU) subjects completed a 30-min downhill run at ∼60% VO2max. The OC completed the exercise during the midluteal phase (day 22.9 ± 1.5; high estrogen) while the EU did their exercise in the midfollicular phase (day 9.6 ± 4.4; low estrogen) of the menstrual cycle, respectively. The CK activity and DOMS were assessed preexercise, immediately postexcercise, 24, 48, and 72 h postexercise. ANOVA results indicated that there was a significant increase in CK activity in response to the downhill run (p< 0.001), and the interaction of group x time was significantly different (p< 0.01). The OC group had lower CK at 72 h postexercise than did the EU group. Preexercise estrogen levels correlated with the overall mean CK (r= –0.43. p< 0.05) and 72 h (r= –0.38, p < 0.05) responses, respectively. Exercise caused an increase in DOMS in both groups (p< 0.001); but, no significant interaction was observed. These findings suggest that elevated estrogen levels have a protective effect on muscle tissue following eccentric exercise. The mechanism of this protective effect is unclear, but it may be related to the antioxidant characteristics and membrane stability properties associated with estrogen and its derivatives.