The menstrual cycle changes heart-rate variability but not strength

By Dr. Priyom Bose, Ph.D.Reviewed by Lauren HardakerJun 23 2026

New research reveals that the menstrual cycle may influence how the heart's autonomic nervous system functions, while strength, motivation, and overall mood remain remarkably stable throughout the month. 

Study: Influence of menstrual cycle on autonomic nervous system, muscular strength and mood states. Image credit: Pormezz/Shutterstock.com

A recent Scientific Reports study investigated the impact of menstrual cycle phases on autonomic cardiac 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 cyclical fluctuations in pituitary hormones, including follicle-stimulating hormone (FSH) and luteinizing hormone (LH), and in steroid sex 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, notably the autonomic nervous system (ANS), neuromuscular performance, and mood. Although the MC phase is recognized as a factor influencing exercise performance and well-being, existing evidence remains inconsistent and is often hampered by the underrepresentation of women in sports science research.

Hormonal variation throughout the MC is thought to alter ANS activity, often assessed via heart rate variability (HRV). HRV serves as a non-invasive indicator of physiological stress, recovery, and adaptation, reflecting the dynamic interplay between parasympathetic and sympathetic branches. While indices such as the root mean square of successive differences (RMSSD), high-frequency power (HF), and the standard deviation of instantaneous beat-to-beat variability (SD1) are well validated, most studies have focused on male populations, leaving the influence of MC phases on HRV insufficiently characterized.

Neuromuscular performance, including force production, may also fluctuate across the MC, potentially enhanced by estrogen or weakened by progesterone. However, research findings are mixed, with reports ranging from notable performance changes to negligible variation in muscle strength and function over the cycle.

Critically, the combined regulation of HRV and muscle force across the MC has not been systematically investigated. This lack of integrative analysis is a significant research gap, hindering the development of personalized training and performance strategies for female athletes.

Assessing the impact of the MC phase on cardiac and physiological measures

The current observational study utilized a within-participant repeated-measures design to assess physiological and neuromuscular changes across three menstrual cycle phases: menstruation (Mens), estimated late follicular (Foll-late), and estimated midluteal (Lut-mid). After a one-month screening period, which included menstrual diary tracking and urinary LH testing, 15 healthy, recreationally active, naturally menstruating women, with a mean age of 24.3 years, were enrolled.

Eligibility criteria included engagement in 2–4 physical activity sessions per week, regular MC (21–35 days), at least six months without hormonal contraception, and a low risk of menstrual disturbances (LEAF-Q score <8). Participants using copper intrauterine devices (IUDs) were eligible; however, those with anovulation (confirmed by urinary LH testing), lower limb injury, or initiation of hormonal contraception during the study were excluded.

Each participant attended a familiarization session and three experimental sessions, each scheduled to coincide with a distinct MC phase. At each session, participants completed the Profile of Mood States (POMS) questionnaire, followed by a 5-minute 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 urinary ovulation testing: Mens (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 and progesterone). Testing schedules were individualized to match each participant’s cycle characteristics. Hormone concentrations were not directly measured.

Mid-luteal phase linked to lower vagal activity

Participants had an average LEAF-Q score of 2.7 ± 1.8, suggesting minimal risk for low energy availability and a low probability of MC disorders. The mean cycle length was 29.1 days, and menstruation lasted an average of 5.1 days. Participants were randomly assigned to start in various menstrual phases.

The menstrual phase significantly affected vagally mediated HRV indices, which were notably lower during the estimated mid-luteal phase than during the menstrual and estimated late follicular phases.HRV analyses included 14 participants because one participant's HRV data were excluded due to poor signal quality. 

Although a phase effect was observed for SD2, the post hoc comparisons were not significant. These findings indicate a reduction in cardiac vagal modulation during the estimated mid-luteal phase, supporting HRV as a sensitive marker of autonomic fluctuations across menstrual-cycle phases.

No significant differences were found in maximal voluntary contraction (MVC), rate of force development (RFD), electromyographic (EMG) activity, or neuromuscular efficiency (NME) across MC phases. Psychological outcomes, including motivation, total mood disturbance (TMD), and most POMS subscales, also showed no significant phase-related changes. An exception to the POMS depression subscale score was observed: it was elevated in the late follicular phase compared to the mid-luteal phase. Although TMD scores did not differ significantly across phases, some variability was observed.

Vigor was positively associated with EMG activity during the early force-development phase of contraction, whereas normalized frequency-domain HRV indices correlated with the rate of force development (RFD). Specifically, higher LFnu values were associated with greater RFD, whereas higher HFnu values were associated with lower RFD.

No significant correlations were found between HRV indices and psychological measures. No significant associations were found between HRV indices and maximal force, EMG, or NME. These results highlight select physiological and psychological interrelations, primarily linking autonomic and neuromuscular responses to certain psychological states, rather than broad cross-variable associations.

The researchers also reported substantial inter- and intra-individual variability, suggesting that physiological and psychological responses to menstrual cycle phases may differ considerably among women.

Most performance measures remained stable throughout

The current study demonstrated that HRV indices fluctuate across the menstrual cycle in healthy, naturally menstruating active women, with a notable decrease in vagally mediated HRV during the estimated luteal-mid phase.

These results indicate that autonomic cardiac function varies across menstrual-cycle phases and is consistent with hormone-related autonomic changes, although hormone concentrations were not directly measured. Conversely, muscle strength, overall mood, and motivation, except for higher scores on the POMS depression subscale during the late follicular phase, remained consistent 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 a low risk of menstrual disturbances. Therefore, they may not necessarily generalize to women with menstrual disorders, low energy availability, hormonal contraceptive use, or different athletic populations.

Because estrogen and progesterone concentrations were not measured directly, the findings should be interpreted as evidence of menstrual-cycle-phase differences in autonomic regulation rather than as proof that specific hormonal changes caused the observed HRV variations.

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