Anaerobic Threshold Variations during Different Phases of Menstrual Cycle: Effect of Substrate Selection

Hormonal variations throughout the menstrual cycle is usually associated with change in exercise performance. The purpose of the current study was to investigate the effect of menstrual cycle phases on aerobic performance, substrate selection, and physiological variables corresponding to anaerobic threshold (AT) in active women of Kerman city. 

Twelve active females owning regular menstrual cycle participated in the study. The subjects performed two standard incremental tests at their own middle of follicular or luteal phase until exhaustion. Breath-by-breath respiratory gases were measured throughout the test. AT (abrupt increase in oxygen equivalent (VE/VO2)), cross over point (COP) and Fatmax (using respiratory exchange ratio (RER)) were determined, then heart rate and oxygen consumption corresponding to them were extracted and compared between menstrual cycle phases using paired sample T-Test.

Estradiol and progesterone levels during luteal phase was significantly higher than those from follicular phases (P < 0.05). The values of oxygen (ml.kg.min) corresponding to AT (follicular: 30.8±3.3, luteal: 34.6±2.1), Fatmax (follicular: 16.2±1.6, luteal: 19.1±1.7), and COP ((follicular: 18±3.3, luteal: 21.8±4.5) were significantly different between the phases (All P < 0.05). COP was occurred during follicular and luteal at 200±72 and 230±67, respectively, and the difference between phases was significant (P < 0.05).

In sum, the results of the present study showed that different values of sexual hormones probably result in improvement in AT and seemingly do this due to change in substrate selection toward fat oxidation at intensities below the AT.