Does Hormonal Phase Affect Acute High-Intensity Interval Training Exercise? An Evaluation of Performance and Fatigue.

Area of Science:

• Exercise Physiology
• Sports Science
• Endocrinology

Background:

• Fatigue significantly impacts high-intensity interval training (HIIT) performance.
• Female hormonal fluctuations may influence exercise capacity and fatigue levels.
• The interplay between hormonal phase and work-rest ratio in HIIT requires further investigation.

Purpose of the Study:

• To evaluate the impact of hormonal phase (low-hormone phase [LHP] vs. high-hormone phase [HHP]) on exercise performance and fatigue during two work-matched HIIT protocols.
• To compare exercise performance (average power [AP], peak power [PP]) and fatigue (power drop [PD]) between HIIT protocols with different work-rest ratios across hormonal phases.

Main Methods:

• Thirty-five women completed four randomized HIIT trials, two protocols (HIIT1:1 and HIIT2:1) during both LHP and HHP.
• HIIT1:1 involved 10 rounds of 1 minute on/1 minute off.
• HIIT2:1 involved 20 rounds of 20 seconds on/10 seconds off.

Main Results:

• HIIT2:1 yielded significantly higher AP and PP compared to HIIT1:1, irrespective of hormonal phase.
• Greater power drop (PD) was observed during the LHP compared to the HHP for the HIIT2:1 protocol.
• Across both protocols, overall PD was significantly greater in the LHP than in the HHP.

Conclusions:

• Work-rest ratio, specifically HIIT2:1, significantly influences HIIT power performance (AP, PP), but hormonal phase does not.
• Increased PD during the LHP suggests heightened physical fatigue, particularly with the HIIT2:1 protocol.
• Modifying work-rest ratios may be beneficial for optimizing power output and managing fatigue across the female menstrual cycle, especially during the LHP.