Estrogen, muscle damage, and the repeated bout effect
PURPOSE: The aim of this study was to investigate estrogen’s effect on markers of muscle damage and the repeated bout effect in women following multiple downhill runs. METHODS: Thirteen moderately trained females (VO 2 max: 36-47 ml/kg/min), 18-35 years old, and who used hormonal contraception participated in the study. They completed two 40 min downhill runs (-10% grade) at 65-70% VO2 max during either the third week of hormone use (low estrogen group (LE), n=7) or the placebo week (high estrogen group (HE), n=6). Trials were separated by four weeks. Creatine kinase (CK) activity, pressure tolerance (front thigh, shin, and calf), and circumferences (thigh and calf) were measured before (pre) and at 24 hr, 48 hr, and 72 hr after exercise. Muscle soreness of the front thigh, shin and calf was reported immediately (0 hr) and at 24 hr, 48 hr, and 72 hr after exercise. Knee extension and ankle dorsiflexion peak torque were measured pre and 72 hr postexercise. RESULTS: A run effect was found in front thigh (P = 0.009) and calf (P = 0.02) pressure tolerance such that DH1 was lower than DH2. Soreness of the front thigh was lower following DH2 compared to DH1 (P = 0.05). A group x time interaction was observed for shin soreness such that soreness in LE was higher at 24 hr and 48 hr compared to 0 hr (P < 0.001; P < 0.001, respectively) and 72 hr (P < 0.01; P = 0.04, respectively). Following DH1, CK activity was higher at 24 hr (P < 0.001), 48 hr (P = 0.04), and 72 hr (P = 0.03) compared to pre-exercise. CK activity was lower at 24 hr following DH2 (P < 0.001) compared to 24 hr following DH1. No significant changes were noted for shin pressure tolerance, calf soreness, circumference, or peak torque measurements. CONCLUSION: Women with lower estrogen levels may show a greater response in markers of muscle damage following the initial bout of exercise as evidenced by increased soreness in the shin. The RBE was observed as evidenced by a less robust response to pressure tolerance, soreness and CK activity following DH2, with no group differences in the RBE response. Higher estrogen levels at the time of exercise may mitigate markers of muscle damage following an initial bout of eccentric exercise but does not seem to influence the repeated bout effect.
Sedlock, Purdue University.
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