Influence of early follicular and mid-luteal phases of the menstrual cycle on aerobic performance, perceived exertion, and cardiac autonomic responses in eumenorrheic women: a randomized crossover trial

Purpose The aim of the present study was to compare aerobic performance, anthropometry, heart rate variability (HRV) pre-exercise and during graded exercise testing (GXT) on HRV threshold (HRVT), heart rate (HR) and rate of perceived exertion (RPE) between the early follicular and mid-luteal phases of the menstrual cycle. Methods Sixteen eumenorrheic women (28.8 ± 6.7 years) randomly completed two GXT (starting at 50W and increasing 25W every two minutes until exhaustion), one in the early follicular phase and another in the mid-luteal phase. Cardiac autonomic responses were continually monitored via HRV indices, recorded pre-exercise and during GXT, throughout the HRVT, HR and RPE. Results There were no differences between early follicular and mid-luteal phases for body mass (67.2 ± 10.1 vs. 66.6 ± 10.1 kg, p = 0.08), time to exhaustion (753.0 ± 193.8 vs. 730.8 ± 179.5 s, p = 0.10), peak power (181.9 ± 40.4 vs. 177.3 ± 37.4 W, p = 0.10), maximal HR (176 ± 13 vs. 176 ± 13 bpm, p = 0.80), and maximal RPE (median: 19.0 vs. 18.5 units, p = 0.37), respectively. In addition, no significant differences were observed between early follicular and mid-luteal phases for pre-exercise HRV indices ( p  > 0.05). There were also no significant differences between early follicular and mid-luteal phases for power output and HR at HRVT identified during the GXT ( p  > 0.05). However, the RPE at the HRVT identified using vagal index (SD1) was ( p  = 0.03) higher in the early follicular phase (median: 12.0, interquartile distance 10.8 to 13.8) than in the mid-luteal phase (median: 10.5, interquartile distance 9.0 to 12.0). Conclusion In eumenorrheic women, endurance performance and cardiac autonomic responses were similar in early follicular and mid-luteal phases, but RPE of the exercise intensity at which a shift in autonomic nervous system balance occurs is higher in the early follicular phase than in the mid-luteal phase.