New research reveals that the menstrual cycle can affect how the heart’s autonomic nervous system works, while strength, motivation and overall mood remain remarkably stable throughout the month.
Study: Effect of the menstrual cycle on the autonomic nervous system, muscle strength, and mood states. Image credit: Pormezz/Shutterstock.com
A recent one Scientific Reports The study investigated the effect of menstrual cycle phases on cardiac autonomic function, neuromuscular performance and psychological states in naturally menstruating women.
Menstrual cycle and physiological functions
The menstrual cycle (MC) is a recurring physiological process characterized by cyclic fluctuations in pituitary hormones, including follicle-stimulating hormone (FSH) and luteinizing hormone (LH), and in sex steroid hormones such as estrogen and progesterone. These hormonal changes define the distinct phases of the cycle and drive a cascade of coordinated physiological adaptations.
Fluctuations in hormone levels regulate multiple systems, most notably the autonomic nervous system (ANS), neuromuscular performance, and mood. Although the MC phase is recognized as a factor affecting exercise performance and well-being, existing evidence remains inconsistent and is often hampered by the underrepresentation of women in sports science research.
Hormonal variation across the MC is thought to alter ANS activity, often assessed through heart rate variability (HRV). HRV serves as a noninvasive indicator of physiological stress, recovery, and adaptation, reflecting the dynamic interplay between parasympathetic and sympathetic branches. While indices such as root mean square of sequential differences (RMSSD), high-frequency (HF) power, and standard deviation of instantaneous beat-to-beat variability (SD1) are well validated, most studies have focused on male populations, leaving the effect of MC phases on HRV insufficient.
Neuromuscular performance, including force production, may also fluctuate along the MC, potentially enhanced by estrogen or attenuated by progesterone. However, research findings are mixed, with reports ranging from marked performance changes to negligible variation in muscle strength and function over the course of the cycle.
Essentially, the combined regulation of HRV and muscle force across the MC has not been systematically investigated. This lack of comprehensive analysis is a major research gap, impeding the development of individualized training and performance strategies for female athletes.
Evaluation of the effect of MC phase on cardiac and physiological measures
The current observational study used a repeated-measures within-participants design to assess physiological and neuromuscular changes in three phases of the menstrual cycle: menses (Mens), estimated late follicular (Foll-late), and estimated mid-luteal (Lut-mid). After a one-month control period, which included menstrual diary monitoring and urine LH testing, 15 healthy, recreationally active, naturally menstruating women with a mean age of 24.3 years were enrolled.
Eligibility criteria included participation in 2–4 physical activity sessions per week, regular MC (21–35 days), at least six months without hormonal contraception, and low risk of menstrual disorders (LEAF-Q score <8). Participants using copper intrauterine devices (IUDs) were eligible. However, those with anovulation (confirmed by urine LH test), lower extremity injury, or initiation of hormonal contraception during the study were excluded.
Each participant attended one familiarization session and three experimental sessions, each timed to coincide with a separate MC phase. In each session, participants completed the Profile of Mood State (POMS) questionnaire, followed by a 5-min resting HRV recording, a standardized warm-up, and three maximal voluntary isometric contractions (MVCs) of the knee extensors.
Menstrual cycle phases were determined by a combination of menstrual diaries and urine ovulation tests: Men (days 1–4, low estrogen and progesterone), estimated Foll-late (days 11–13, high estrogen, low progesterone), and estimated Lut-mid (days 21–23, elevated estrogen). Testing programs were individualized to match each participant’s cycle characteristics. Hormone concentrations were not measured directly.
The mid-luteal phase is associated with lower vagal activity
Participants had a mean LEAF-Q score of 2.7 ± 1.8, indicating minimal risk for low energy availability and a low likelihood of MC disorders. The average cycle length was 29.1 days and menstruation lasted an average of 5.1 days. Participants were randomly assigned to start at various menstrual phases.
Menstrual phase significantly influenced lung-mediated indices of HRV, which were significantly lower during the estimated mid-luteal phase than during menstruation and the estimated late follicular phases. HRV analyzes included 14 participants because one participant’s HRV data was excluded due to poor signal quality.
Although a phase effect was observed for SD2, post hoc comparisons were not significant. These findings indicate a decrease in cardiac vagal modulation during the estimated mean luteal phase, supporting HRV as a sensitive indicator of autonomic fluctuations in the phases of the menstrual cycle.
No significant differences were found in maximal voluntary contraction (MVC), rate of force development (RFD), electromyographic (EMG) activity, or neuromuscular efficiency (NME) in the MC phases. Psychological outcomes, including motivation, total mood disturbance (TMD), and most POMS subscales, also showed no significant phase-related changes. An exception was observed in the POMS depression subscale score: it was elevated in the late follicular phase compared to the mid-luteal phase. Although TMD scores did not differ significantly between phases, some variability was observed.
Vigor was positively correlated with EMG activity during the early force development phase of contraction, while frequency domain normalized HRV indices were correlated with rate of force development (RFD). Specifically, higher LFnu values were associated with greater RFD, while higher HFnu values were associated with lower RFD.
No significant correlations were found between HRV indices and psychological measures. No significant correlations were found between HRV indices and maximal force, EMG or NME. These results highlight selected physiological and psychological interactions, primarily linking autonomic and neuromuscular responses to certain psychological states, rather than broad intervariate associations.
The researchers also reported considerable inter- and intra-individual variability, suggesting that physiological and psychological responses to the phases of the menstrual cycle may differ significantly between women.
Most performance measures remained stable throughout
The current study showed that HRV indices fluctuate throughout the menstrual cycle in healthy, physically active menstruating women, with a marked decrease in lung-mediated HRV during the estimated luteal-mid phase.
These results indicate that cardiac autonomic function varies between phases of the menstrual cycle and is consistent with hormone-related autonomic changes, although hormone concentrations were not directly measured. In contrast, muscle strength, overall mood, and motivation, in addition to higher scores on the POMS depression subscale during the late follicular phase, remained stable throughout the cycle, indicating that these aspects of performance and well-being may be less affected by the MC phase.
The findings apply specifically to healthy, recreationally active, naturally menstruating women with regular menstrual cycles and low risk of menstrual disorders. Therefore, they may not necessarily generalize to women with menstrual disorders, low energy availability, use of hormonal contraceptives, or different athletic populations.
Because estrogen and progesterone concentrations were not directly measured, the findings should be interpreted as indicative of menstrual cycle phase differences in autonomic regulation rather than evidence that specific hormonal changes caused the observed HRV fluctuations.
