Menstrual Cycle And Menopause Influence On Creatine Kinase Response After Exercise-induced Muscle Damage

Abstract

Studies with animals have demonstrated that estrogens contribute to limit exercise-induced muscle damage. However, this effect is not entirely clear in humans, despite some benefits have been observed. For instance, estrogen replacement therapy has shown to increase strength and reduce exercise-induced muscle damage in postmenopausal women. PURPOSE: To evaluate the influence of sex hormones on creatine kinase (CK) response after an eccentric squat-based workout in well-trained females with different hormonal profiles. METHODS: Nineteen eumenorrheic females (28.6±5.9 years, 163.4±6.1 cm, 59.6±5.8 kg) and thirteen postmenopausal females (51.7±3.7 years, 161±5.31 cm, 56.6±8.1 kg) participated in this study. A resistance-based workout was performed by the eumenorrheic females in the early follicular phase (EFP), late follicular phase (LFP) and mid-luteal phase (MLP) of their menstrual cycle, in a counterbalanced and randomized order. Postmenopausal females performed the protocol in a single visit. Blood samples were obtained at baseline and 2h, 24h and 48h after the eccentric workout to analyse serum CK. An unpaired t-test was performed to compare CK values between postmenopausal and eumenorrheic females. RESULTS: At baseline, postmenopausal showed higher CK concentrations (136.2±45.5 U·L-1) in comparison to eumenorrheic women in the LFP (105.7±33.1 U·L-1, p=0.039) and MLP (100.7±29.8 U·L-1, p=0.012 ). However, these differences were not observed between postmenopausal and eumenorrheic women in the EPF (108.6±48.0 U·L-1, p=0.114). No differences were observed in post-exercise time-points between postmenopausal and eumenorrheic women in any of the menstrual cycle phases analysed. CONCLUSION: Lower estrogen and progesterone concentrations may elicit higher CK values at rest. However, the lack of post-exercise differences between groups may indicate that the supposed protective role of sex hormones is not as determinant as other factors like intensity or training status. The IronFEMME Study is supported by the Ministerio de Economía y Competitividad (Contract DEP2016-75387-P).