Defecation enhances cerebral perfusion and delays fatigue in elite triathletes

Background Rectal distension increases regulatory burden to autonomic nervous system in the brain. Purpose To determine the effect of rectal defecation on endurance performance and blood supply to the prefrontal brain and sub-navel regions of elite triathletes. Methods Thirteen elite triathletes completed a cycling time trial (80% VO2max) under defecated and non-defecated conditions, using a counterbalanced crossover design. Oxygenation and blood distribution in prefrontal brain and sub-navel regions were monitored by near-infrared spectroscopy (NIRS) during cycling. Results Defecation moderately decreased systolic blood pressure (−4 mmHg, p