Exercise-induced dehydration does not impair cognitive performance in naturally menstruating women

Despite increased female workforce engagement, research into physiological responses to thermally challenging environments has primarily focused on males. This study examined the combined impact of exercise-induced elevated core temperature and progressive dehydration on cognitive performance in naturally menstruating females. It was hypothesized that progressive increases in dehydration, heat and associated physiological responses would detrimentally affect cognitive performance. Twelve recreationally trained, naturally menstruating participants completed two experimental conditions - dehydrated (DEHY), and hydrated (HYD) - during the mid-luteal phase of their menstrual cycle. Participants cycled in a controlled environment (40°C, 20% humidity) for three 45-minute bouts at progressively reducing work intensity. Cognitive performance was assessed using the Parametric Go/No-Go (PGNG), Corsi Block Tapping (CBT), and Classic Stroop tasks, selected to represent the three key domains of executive function - cognitive inhibition, working memory, and cognitive flexibility. In DEHY, no fluid was permitted; in HYD, fluid was administered based on body mass loss. Body mass loss and serum osmolality was significantly higher in DEHY (-3.57[0.99] kg; 299[6] mOsm·kg^-1), compared to HYD (-0.48[0.30] kg; 283[5] mOsm·kg^-1) (p < .05). Contrary to the hypothesis, cognitive performance remained largely unaffected by exercise-induced dehydration and thermal strain. Only PGNG reaction time was significantly affected, with slower responses in the HYD condition. Despite physiological markers indicating significant dehydration, cognitive performance appeared to be largely preserved against the stressors of prolonged exercise and heat. Emphasizing the resilience of cognitive performance under these conditions strengthens understanding of sex-specific responses to environmental and physiological stress.