AUTHOR=Castellanos-Mendoza M. Carolina , Galloway Stuart D. R. , Witard Oliver C. 

TITLE=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

JOURNAL=Frontiers in Sports and Active Living

VOLUME=5

YEAR=2023

URL=https://www.frontiersin.org/journals/sports-and-active-living/articles/10.3389/fspor.2023.1279534

DOI=10.3389/fspor.2023.1279534

ISSN=2624-9367

ABSTRACT=<sec><title>Introduction</title><p>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.</p></sec><sec><title>Methods</title><p>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 (<italic>n </italic>= 8) and runners (<italic>n </italic>= 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.</p></sec><sec><title>Results</title><p>Participants that reported an EA of &lt;35 kcal·kg FFM<sup>−1</sup>·day<sup>−1</sup> (<italic>n </italic>= 7) exhibited ovulatory disturbances (Pk-PRG ≤9.40 ng·mL<sup>−1</sup>). Athletes with EA ≥36 kcal·kg FFM<sup>−1</sup>·day<sup>−1</sup> (<italic>n </italic>= 8) recorded “normal”/“potentially fertile” cycles (Pk-PRG &gt;9.40 ng·mL<sup>−1</sup>), except for a single racewalker with the lowest reported protein intake (1.1 g·kg body mass<sup>−1</sup>·day<sup>−1</sup>). EA was positively associated with Pk-PRG [<italic>r</italic>(9) = 0.79, 95% confidence interval (CI): 0.37–0.94; <italic>p </italic>= 0.003; 1 − <italic>β</italic> = 0.99] after excluding participants (<italic>n </italic>= 4) that likely under-reported/reduced their dietary intake.</p></sec><sec><title>Conclusions</title><p>The result from the linear regression analysis suggests that an EA ≥ 36 kcal·kg FFM<sup>−1</sup>·day<sup>−1</sup> 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.</p></sec>