Key result
The early follicular phase was associated with significantly higher active energy expenditure compared to the late follicular phase (23.9 vs 22.4 kJ/kg), and peak estradiol strongly correlated with physical activity when delayed by two days.
Why the study?
The day-to-day relationship between the menstrual cycle and physical activity remains unclear.
Does physical activity (active energy expenditure) fluctuate across the menstrual cycle and correlate with estradiol levels in healthy menstruating women?
Observational (n=26)
Does physical activity (active energy expenditure) fluctuate across the menstrual cycle and correlate with estradiol levels in healthy menstruating women?
Standardized Mean Difference: 0.12
Absolute Event Rate: 23.9% vs 22.4%
p-value: p=0.0073
Objective wearable monitoring reveals that physical activity is higher during the early follicular phase and correlates with peak estradiol levels with a two-day delay.
Activity fluctuations across phases warrant cycle control in future studies; leaves open causal estradiol effects on energy expenditure.
Approximately 1.8 billion people experience hormonal changes caused by the menstrual cycle, which impacts work, school, and health factors like physical activity. Prior research shows high-level insights, such as reduced activity during symptomatic days, but the day-to-day relationship between the menstrual cycle and physical activity remains unclear. We performed a 28-day study monitoring physical activity in 26 healthy, naturally menstruating women using an inertial measurement unit on the shank. A validated model estimated energy expended per step. Physical activity was significantly higher during the early-follicular phase than the late follicular phase due to more steps. Energy expenditure was compared with open-source daily estradiol and progesterone data collected from different study cohorts of healthy, eumenorrheic women. Peak estradiol and physical activity showed a correlation ( r 2 = 0.64) when activity was shifted by 2 days, suggesting a delayed relationship. Precisely measuring movement with wearable sensors could help uncover menstrual cycle effects on activity and improve health management and workplace policies.
No takes yet. Share an insight, caveat, or question.
Rodriguez et al. (2026) conducted an observational in Healthy, naturally menstruating women (n=26). Early follicular phase vs. Late follicular phase was evaluated on Active energy expenditure (AEE) (Cohen's d 0.12, p=0.0073). The early follicular phase was associated with significantly higher active energy expenditure compared to the late follicular phase (23.9 vs 22.4 kJ/kg), and peak estradiol strongly correlated with physical activity when delayed by two days.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: