Influence of oral contraceptive phase on cardiorespiratory response to exercise in endurance-trained athletes

Objective The aim of the study was to analyse the cardiorespiratory response to exercise during an oral contraceptive (OC) cycle in endurance-trained women. Methods Sixteen low-dose monophasic OC pill (OCP) users performed an interval-running protocol. The protocol consisted of eight 3 min bouts at 85% of participants' maximal aerobic speed (vV?o(2peak)) with a 90s recovery at 30% vV?o(2peak) in two OC phases: a withdrawal phase (WP) and an active pill phase (APP). The non-parametric Wilcoxon test was applied to analyse differences (p < 0.05) in performance variables between OC cycle phases. Results Throughout the high-intensity intervals, higher ventilation (WP 80.90 +/- 11.49 L/min, APP 83.10 +/- 13.33 L/min; p < 0.001) and relative perceived exertion (WP 14.51 +/- 2.58, APP 15.11 +/- 3.11; p = 0.001) during the APP were found, whereas carbon dioxide production (WP 2040.92 +/- 262.93 mL/min, APP 2010.25 +/- 305.68 mL/min; p = 0.003) was higher in the WP. During the active recovery intervals, ventilation (WP 65.78 +/- 9.90 L/min, APP 67.88 +/- 12.66 L/min; p < 0.001) was higher in the APP, while heart rate (WP 159.93 +/- 10.26 bpm, APP 159.74 +/- 12.83 bpm; p = 0.029) was higher in the WP. Conclusion An increase in ventilation occurs during the APP, which is accompanied by higher perceived exertion. Therefore, coaches and athletes should be aware of these variations, especially perceived exertion, in regard to women's training programmes, in order to improve their performance, wellness and adherence to physical activity.