Purpose: To investigate the effect of the MC and endogenous sex hormone concentrations on performance-determining variables in three distinct MC phases in endurance-trained females.
Methods: Twenty-one eumenorrheic trained/highly trained endurance athletes completed a standardized test battery during the early follicular phase (EFP), ovulatory phase (OP), and mid-luteal phase (MLP) for either one (n = 7) or two test cycles (n = 14). MC phases were determined using calendar-based counting, urinary ovulation testing, and verified with serum hormone analysis. MCs were retrospectively classified as eumenorrheic or disturbed. Disturbed MCs were excluded from analysis. The test battery consisted of 4-6 x 5-min submaximal stages with stepwise speed increases, a 30-s all-out double-poling ski ergometer test, and a maximal incremental treadmill running test.
Results: At a group level, there was no effect of MC phase or the serum concentrations of estrogen and progesterone on peak oxygen uptake ( O 2peak ), oxygen uptake at 4 mmol·L -1 blood lactate concentration, time-to-exhaustion, running economy, or mean 30-s power output (MPO 30s ). Serum testosterone concentration was positively associated with MPO 30s (p = 0.016). Changes in O 2peak from EFP to MLP were inconsistent between individuals and across cycles.
Conclusions: None of the measured performance-determining variables were influenced by MC phase or serum estrogen or progesterone concentrations. While some individual patterns could be observed, there was no indication that any single MC phase is consistently associated with improved or impaired O 2peak on a group level.
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