Variations in Physical Activity Across the Menstrual Cycle in Healthy Women: A Focus on Step Count and Activity...

Physical activity patterns across the menstrual cycle may reflect evolutionary adaptations that optimize reproductive success by aligning heightened activity with the fertile window and lowered activity in the luteal phase, when the female's body prepares for a possible pregnancy.

This study examined variation in physical activity patterns across five arbitrary phases of the ovulatory menstrual cycle in 77 healthy women (age: 20-36 years). Based on ovulation tests and the date of the next menstruation, the menstrual cycle was divided into five physiologically distinct phases: menstrual, follicular, peri-ovulatory, luteal, and premenstrual. Daily physical activity was measured using a wristband accelerometer that tracked step count and activity duration at various intensities: sedentary, light, moderate, and intense, and the total 24-h duration of activity. Differences among phases were analyzed by repeated measures ANOVA, with corrections for multiple comparisons.

Step counts were higher in the follicular phase compared to the premenstrual phase (mean 10.2 vs. 8.9, respectively, p = 0.001), and total activity time was higher during the follicular phase than in the premenstrual phase (mean 99.3 vs. 90.8, p = 0.004). No other significant differences were observed.

Step count and total active time peaks in the follicular phase and declines during the premenstrual phase. Our study highlights the importance of accurately identifying phases of the menstrual cycle and analyzing various activity intensities for understanding physical activity behavior across the menstrual cycle.