Menstrual cycle and hormonal contraception : associations between hormones, physical performance, and menstrual cycle -related symptoms

Abstract

Introduction. It has been reported that 42 % of exercising women feel that the menstrual cycle negatively affects their performance (Bruinvels et al. 2016). However, athletes must train and compete in each phase of the cycle and manage the possible symptoms associated to the hormonal fluctuation. The aim of this thesis is to evaluate whether the symptoms related to menstrual cycle and/or hormonal contraceptive cycle are associated with physical performance.

Methods. The participants were recreationally active women aged 19-37. There were 13 subjects in hormonal contraceptive -group (HC-group) and 16 subjects with normal menstrual cycles in non-hormonal contraceptive group (NHC-group). The study used a cross-sectional research design. The participants completed four identical measurements during different phases of menstrual cycle (1. menstruation 2. follicular 3. ovulation 4. luteal) or hormonal contraceptive cycle (1. withdrawal bleeding 2. first active phase 3. second active phase 4. inactive phase). The measurements consisted of venous blood sample collections and physical performance tests, which included one repetition maximum (1RM) and maximal voluntary contraction (MVC) of the leg extensor muscles and maximal oxygen uptake (VO2max) test by running. Also, the participants filled a menstrual diary throughout the study, in which they reported the symptoms. The statistical significance was set to p<0.05.

Results. Sex hormone fluctuation was more significant among the NHC-group compared to HC-group. VO2max and number of symptoms did not differ between the groups. However, strength performance was statistically significantly higher in NHC-group: 1RM in all the phases and MVC in the third phase. In NHC-group, VO2max was statistically significantly higher during ovulation compared to luteal phase, and number of symptoms was statistically significantly higher in luteal compared to follicular phase. In HC-group the concentration of SHBG, T3 and cortisol were statistically significantly higher compared to NHC-group in all the measurement points. In addition, these hormones were found to correlate with physical performance and number of symptoms. After merging the groups as one, serotonin was found to be inversely associated with number of symptoms whereas serotonin and VO2max were positively associated when regarding the relative changes of the variables between phases 1 and 4.

Conclusions. There were several associations found in this thesis. Yet, the relationship between the symptoms and physical performance remains uncertain and needs more investigation.