The Summary
Researchers tested whether hormonal fluctuations affect high-intensity interval training (HIIT) performance. Thirty-five women completed four randomized cycling sessions comparing two work-to-rest ratios (1:1 versus 2:1) across low- and high-hormone phases. Work-to-rest ratios drove overall power output, with the 2:1 protocol generating higher average and peak power regardless of phase. However, participants experienced significantly greater fatigue during their low-hormone phase, specifically during the shorter-rest 2:1 protocol. Equal work-to-rest intervals (1:1) buffered against this phase-dependent drop in power, suggesting generous rest periods help stabilize performance across the menstrual cycle.
Why this is interesting
Many athletes assume monthly hormonal swings derail hard workouts. This study reveals a more nuanced picture: your peak power capacity does not change across your cycle, but you may fatigue faster during your low-hormone phase if recovery intervals are too short. Rather than backing off completely, women can optimize training by adjusting interval structures. Extending rest periods to match work intervals—such as one minute on, one minute off—allows women to maintain high power output and prevent premature exhaustion, regardless of where they are in their cycle.