Menstrual Cycle Phases Influence on Cardiorespiratory Response to Exercise in Endurance-Trained Females

The aim of this study was to analyse the impact sex hormone fluctuations throughout menstrual cycle on cardiorespiratory response high-intensity interval exercise in athletes. Twenty-one eumenorrheic endurance-trained females performed an running protocol three phases: early-follicular phase (EFP), late-follicular (LFP) and mid-luteal (MLP). It consisted 8 × 3-min bouts at 85% their maximal aerobic speed with 90-s recovery 30% speed. To verify phase, we applied a three-step method: calendar-based counting, urinary luteinizing measurement serum analysis. Mixed-linear model for repeated measures showed ventilatory (EFP: 78.61 ± 11.09; LFP: 76.45 11.37; MLP: 78.59 13.43) heart rate 167.29 11.44; 169.89 10.62; 11.35) (F2.59 = 4.300; p 0.018 F2.61 4.648; 0.013, respectively). Oxygen consumption, carbon dioxide production, respiratory exchange ratio, breathing frequency, energy expenditure, relative perceived exertion readiness were unaltered by phase. Most variables measured appear be impassive phases seems that are not high enough disrupt tissues’ adjustments caused exercise. Nevertheless, HR based training programs should consider