The Effect of Body Mass Index on Prefrontal Cortex Hemodynamic and Cognitive Functions In Exercise-Induced Hypohydration in Male Athletes

Objectives: This study examines the impact of exercise-induced hypohydration on prefrontal hemodynamic and cognitive functions within high and low body mass index athletes. Methods: A total of twelve athletes well adapted to the bicycle ergometer were included in the study (LBMIG (24.64 kg/m²) and HBMIG (32.45 kg/m²)). Participants attended two visits to the laboratory. At their first visit, their body weight and hemocrit values were assembled, and they completed the practice 2-back test. At their second visit, participants' body weights and hematocrit values were measured, followed by recording their 2-back performance and prefrontal hemodynamic responses during performance. This session was followed by submaximal exercise and then 4x20 seconds of sprint intervals. Afterward, 2-back test performance was measured with their prefrontal hemodynamic responses. Results: Hematocrit levels increased in both groups compared to pre-exercise levels (p< 0.05), with a higher increase in the HBMIG (p=0.045). On the other hand, pre-post exercise responses in prefrontal hemodynamic activity during the 2-back test showed different patterns for each group: an increase in oxyhemoglobin for the LBMIG (p=0.002), an increase in deoxyhemoglobin for the HBMIG (p=0.033), and an increase in total hemoglobin for the HBMIG (p=0.050). Furthermore, the number of missing answers in the post-exercise 2-back test results was significantly higher in the HBMI group compared to the LBMI group. Conclusions: Exercise-induced hypohydration may negatively affects prefrontal hemodynamics and cognitive function in high-BMI athletes. This effect may cause cognitive decline in athletes with high BMI values, negatively affecting their sport or match performance under physical fatigue.