Variations in Estrogen, Progesterone, and Nocturnal Physiology Are Not Associated with Performance and Sleep Within and Between Menstrual Cycles

Purpose: To investigate performance, recovery, sleep, nocturnal physiology, ovarian hormone concentrations, and menstrual cycle symptoms within- and between- menstrual cycle phases and establish within-phase reliability of these measures. Methods: Twenty naturally cycling, trained female participants (age 27 ± 5 years) completed a repeated measures study design. Serum estradiol and progesterone concentrations, countermovement jumps, isometric mid-thigh pulls, a repeated 5km cycle time trial, and two nights of sleep architecture were measured in phases one, three, and four of two menstrual cycles. Sleep and wake measures from activity monitoring, nocturnal heart rate (HR) measures from Oura ring, and menstrual cycle symptoms were monitored daily. Statistical analyses included linear mixed models and reliability measures. Results: Estradiol concentrations were significantly lower in phase one vs three, one vs four, and three vs four (p<.001 to 0.04) in both menstrual cycles. Progesterone concentrations were significantly lower in phase one vs four, and three vs four (p<.001) in both menstrual cycles. Symptoms were significantly higher in phase one vs three and four (p<.001) in cycle one only. No significant differences between-phases were found for performance, recovery, and sleep in either cycle, except for the non-rapid eye movement stage three (N3%) sleep in cycle two. Nocturnal average HR was significantly lower (p<.001) and HR variability higher (p<.001) in phase one vs four in both cycles. Ovarian hormone concentrations were highly variable within each phase (CV 28-95%), while performance and recovery demonstrated minimal variability in both cycles. Conclusions: Performance, recovery, and sleep in trained female participants remained consistent despite ovarian hormone fluctuations. Consequently, practitioners should test athletes when convenient, using accurate and reliable assessments rather than synchronising testing with specific menstrual cycle phases.