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Citation

Castellanos-Mendoza MC, Galloway SDR & Witard OC (2023) Free-living competitive racewalkers and runners with energy availability estimates of <35 kcal·kg fat-free mass?1·day?1 exhibit peak serum progesterone concentrations indicative of ovulatory disturbances: a pilot study. Frontiers in Sports and Active Living, 5, Art. No.: 1279534. https://doi.org/10.3389/fspor.2023.1279534

Abstract
Introduction: The release of luteinising hormone (LH) before ovulation is disrupted during a state of low energy availability (EA). However, it remains unknown whether a threshold EA exists in athletic populations to trigger ovulatory disturbances (anovulation and luteal phase deficiency) as indicated by peak/mid-luteal serum progesterone concentration (Pk-PRG) during the menstrual cycle. Methods: We assessed EA and Pk-PRG in 15 menstrual cycles to investigate the relationship between EA and Pk-PRG in free-living, competitive (trained-elite) Guatemalan racewalkers (n?=?8) and runners (n?=?7) [aged: 20 (14–41) years; post-menarche: 5 (2–26) years; height: 1.53?±?0.09?m; mass: 49?±?6?kg (41?±?5?kg fat-free mass “FFM”)]. EA was estimated over 7 consecutive days within the follicular phase using food, training, and physical activity diaries. A fasted blood sample was collected during the Pk-PRG period, 6–8 days after the LH peak, but before the final 2 days of each cycle. Serum progesterone concentration was quantified using electrochemiluminescence immunoassay. Results: Participants that reported an EA of <35?kcal·kg FFM?1·day?1 (n?=?7) exhibited ovulatory disturbances (Pk-PRG ≤9.40?ng·mL?1). Athletes with EA ≥36?kcal·kg FFM?1·day?1 (n?=?8) recorded “normal”/“potentially fertile” cycles (Pk-PRG?>9.40?ng·mL?1), except for a single racewalker with the lowest reported protein intake (1.1?g·kg body mass?1·day?1). EA was positively associated with Pk-PRG [r(9)?=?0.79, 95% confidence interval (CI): 0.37–0.94; p?=?0.003; 1???β?=?0.99] after excluding participants (n?=?4) that likely under-reported/reduced their dietary intake. Conclusions: The result from the linear regression analysis suggests that an EA?≥?36?kcal·kg FFM?1·day?1 is required to achieve “normal ovulation.” The threshold EA associated with ovulatory disturbances in athletes and non-invasive means of monitoring the ovulatory status warrant further research

Keywords
anovulation; luteal phase deficiency; short luteal phase; female athletes; endurance sports; menstrual cycle; exercise; energy availability

Journal
Frontiers in Sports and Active Living: Volume 5

• Published version