Fatigue Resistance Is Altered during the High-Hormone Phase of Eumenorrheic Females but Not Oral Contraceptive Users

Serene J.L. Lee, Marc P. Sim, Fleur E.C.A. Van Rens, Jeremiah J. Peiffer

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Purpose This study aimed to examine the effect of ovarian hormones and their synthetic equivalents on substrate utilization and fatigue resistance during a race-specific cycling protocol. Methods Seventeen well-trained female cyclists (nine eumenorrheic females, eight oral contraceptive users) completed two experimental trials, in a randomized order, in their low- (follicular/sugar pill) and high-hormone (luteal/active pill) phases. Each 91-min trial consisted of a 45-min moderate-intensity component (submaximal cycling, or SMC) followed by 6 min of high-intensity (HIT) and then a fatigue resistance test (FRT): 6 × 1-min all-out efforts with 1-min active recovery. Meals, comprising carbohydrate (CHO) intake of 8 g·kg-1 body mass, were standardized 24-h pretrial. An electrolyte-only solution was provided ad libitum during each trial. Results In eumenorrheic females, a large reduction in average power during FRT was observed in the luteal phase (277 ± 31 vs 287 ± 33 W; P = 0.032). Greater CHOox (∼ 4%, P = 0.020) during SMC and ventilatory inefficiencies during SMC and HIT (∼7%, P < 0.001) were also observed in the luteal phase. In contraceptive users, despite some phasal changes in cardiorespiratory and metabolic data in SMC (∼6% higher blood glucose and ∼2% higher minute ventilation in active pill phase), none of the performance parameters in the FRT were different. Conclusions Fatigue resistance was compromised only in high-hormone phase of the menstrual cycle, with eumenorrheic females likely susceptible because of increased CHO utilization during SMC. Hormone-induced ventilatory inefficiencies may also have increased metabolic demand. These findings emphasize the need to maintain CHO availability for power production, particularly in high-hormone phases.

Original languageEnglish
Pages (from-to)92-102
Number of pages11
JournalMedicine and Science in Sports and Exercise
Issue number1
Publication statusPublished - 1 Jan 2024

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