Influência do ciclo menstrual na modulação autonômica cardíaca pós-exercício físico

Abstract

The increasing participation of women in recreational and competitive exercise programs highlights the need to understand physiological particularities that may influence acute responses to exercise and post-exercise recovery. Among these factors, the menstrual cycle represents an important source of biological variability due to the hormonal fluctuations that characterize its phases, which may influence cardiovascular and autonomic regulation. Heart rate variability (HRV) reflects the dynamics of cardiac autonomic regulation, particularly vagal modulation, and is widely used as an indicator of physiological recovery following exercise, during which hemodynamic and autonomic adjustments occur to restore homeostasis. However, findings regarding the influence of menstrual cycle phases on autonomic recovery kinetics after moderate-intensity aerobic exercise remain inconsistent. Therefore, the aim of this study was to investigate the influence of the early follicular and mid-luteal phases of the menstrual cycle on cardiac autonomic modulation during post-exercise recovery in eumenorrheic women. Fourteen healthy women (≥18 years) with regular menstrual cycles (25–34 days), non-smokers and not using hormonal contraceptives, participated in the study. Participants were evaluated under two experimental conditions: early follicular phase (1st–5th day after the onset of menstruation) and mid-luteal phase (22nd–26th day of the cycle). In each experimental session, participants performed a standardized aerobic exercise protocol on a cycle ergometer lasting 60 minutes, consisting of warm-up (5 min <65% of heart rate reserve), main phase (50 min at 65–75% of heart rate reserve), and active recovery (5 min <65% of heart rate reserve), with continuous heart rate monitoring. Blood pressure was measured repeatedly, and post-exercise recovery was monitored for 60 minutes with autonomic and hemodynamic recordings at rest and at multiple time points during recovery. HRV was analyzed using time-domain indices (SDNN, RMSSD, and LnRMSSD) and frequency-domain indices (LF, HF, and LF/HF ratio). Statistical analysis was performed using mixed-model ANOVA (phase × time), followed by appropriate post hoc tests, adopting a significance level of 5%. The results indicated that anthropometric characteristics and baseline hemodynamic parameters did not differ between menstrual cycle phases, ensuring comparability between experimental conditions. Autonomic recovery was predominantly determined by post-exercise time, with no significant overall differences between phases for heart rate, blood pressure, and most HRV indices throughout the recovery period. However, a pattern of more efficient early vagal reactivation was observed during the mid-luteal phase, particularly evidenced by the behavior of LnRMSSD in the first minutes following exercise, indicating greater parasympathetic modulation during this phase. Nevertheless, this effect did not result in sustained differences in the overall recovery profile during the 60-minute recovery period. In conclusion, in eumenorrheic women performing moderate-intensity aerobic exercise, the early follicular and mid-luteal phases of the menstrual cycle do not promote substantial global alterations in cardiac autonomic recovery. However, the mid-luteal phase may subtly influence early vagal recovery kinetics, suggesting that markers measured during the first minutes of recovery are more sensitive to hormonal variations across the menstrual cycle.