Comparative Responses of Self-Regulated Exercise, Thermoregulation, and Neuromuscular Function to Monophasic Oral Contraceptives Across One Menstrual Cycle.

This study investigated the effect of monophasic oral contraceptive (OC) use on self-paced cycling performance, thermoregulation, and skeletal muscle strength and contractile properties in healthy women. Eight physically active women performed 30 min fixed intensity cycling at 50% Wmax, followed by a 30 min self-paced time trial (TT) with each section interspersed with a 30 s maximal sprint at 9, 19, and 29 min. The tests were conducted in different ambient conditions corresponding to either baseline day 1 (20°C, BASE), day 8 (20°C COOL), or day 18 (32°C WARM) of 1 month pill cycle. Core (Tc) and skin (Tsk) temperatures, heart rate, perceptual, neuromuscular responses, and serum cortisol (CORT) were measured multiple times throughout the trials and postexercise. Time trial performance remained unchanged across conditions (range 10.9-11.1 km) although Tc was elevated in WARM in the final 15 min of self-paced exercise, reaching 38.5°C (p < 0.05). CORT was increased from preexercise, whereas lactate increased in all conditions (p < 0.05). Peak force was significantly reduced from pre (439 ± 95 and 429 ± 121 N) to postexercise (345 ± 91 and 361 ± 94 N) for BASE and WARM, respectively, (p < 0.05). Twitch contractile duration declined (∼14%; p < 0.05) in all conditions along with time to peak force (∼17%, p < 0.05) in BASE and WARM. We conclude that OC use does not affect self-paced cycling performance across ambient conditions with no detrimental alteration in neuromuscular performance across the menstrual cycle.