Decreased energy availability during training overload is associated with non-functional overreaching and suppressed ovarian function in female runners

Low energy availability (EA) suppresses many physiological processes, including ovarian function in female athletes. Low EA could also predispose athletes to develop a state of overreaching. This study compared the changes in ad libitum energy intake (EI), exercise energy expenditure (ExEE), and EA among runners completing a training overload (TO) phase. We tested the hypothesis that runners becoming overreached would show decreased EA, suppressed ovarian function and plasma leptin, compared to well-adapted (WA) runners. After 1 menstrual cycle (baseline), 16 eumenorrheic runners performed 4 weeks of TO followed by a 2-week recovery (131±3% and 63±6% of baseline running volume respectively). Seven-day ExEE, EI, running performance (RUNPERF) and plasma [leptin] were assessed for each phase. Salivary [estradiol] was measured daily. Urinary [luteinizing hormone] tests confirmed ovulation. Nine runners adapted positively to TO (WA,ΔRUNPERF: +4±2%); seven were non-functionally overreached (NFOR, ΔRUNPERF -9±2%) as RUNPERF remained suppressed after the recovery period. WA increased EI during TO, maintaining their baseline EA despite a large increase in ExEE (ΔEA=+1.9±1.3 kcal.kgFFM-1.d-1, P=0.17). By contrast, NFOR showed no change in EI, leading to decreased EA (ΔEA=-5.6±2.1 kcal.kgFFM-1.d-1, P=0.04). [Leptin]b, mid-cycle and luteal [estradiol]s decreased in NFOR only. Contrasting with WA, NFOR failed to maintain baseline EA during TO, resulting in poor performance outcomes and suppressed ovarian function.NCT02224976. NOVELTY BULLETS: -Runners adapting positively to training overload (TO) increased ad libitum energy intake, maintaining baseline EA and ovarian function through TO. -By contrast, NFOR runners failed to increase energy intake, showing suppressed EA and ovarian function during TO.