Daily physical activity patterns across the menstrual cycle in eumenorrheic female athletes: an accelerometry-based...

Hormonal fluctuations during the menstrual cycle (MC) influence various physiological parameters, yet their impact on daily physical activity (PA) behavior in naturally menstruating women remains under-researched, often lacking rigorous hormonal verification.

This prospective observational study aimed to examine variations in daily PA intensity and energy consumption across MC phases in eumenorrheic, female athletes [classification as level II or level III athletes according to McKay et al. (2022)] using accelerometry as an objective tool to measure PA. Twenty female athletes (26.6 ± 5.9 years) with regular cycles were monitored using wrist-worn GENEActiv accelerometers over one complete natural cycle. MC phases were classified into seven stages (early, mid, and late follicular; ovulatory; early, mid, and late luteal) using a combination of self-reported bleeding, daily urinary luteinizing hormone (LH) testing, and serum hormone analysis (progesterone >16 nmol·L⁻¹ to confirm ovulation). PA intensity was categorized into six levels (sedentary to extremely vigorous) using validated triaxial cut-points, and energy consumption (kcal·kg^-1·min^-1) was estimated from accelerometry data.

No significant differences were found across MC phases for sedentary, light, or moderate PA p > 0.05. However, time spent in vigorous, very vigorous, and extremely vigorous intensities showed significant phase-dependent variations p = 0.004; 0.001 y 0.001 respectively, with the lowest values consistently recorded during the ovulatory phase. Energy consumption also reached its minimum during ovulation p = 0.009, while total wear time remained stable.

In eumenorrheic athletes, the MC does not substantially modify overall daily activity volume or lower-intensity behaviors. However, high-intensity activity and energy consumption are sensitive to cyclical hormonal fluctuations, specifically decreasing during the ovulatory phase. These findings suggest that higher-intensity activity domains may be more susceptible to menstrual cycle fluctuations than overall activity volume. Therefore, training prescription and load monitoring should consider individual cycle patterns and hormonal profiles rather than assuming behavioral stability across all intensity levels.