Physiol Rep. 2026 Jun;14(12):e70893. doi: 10.14814/phy2.70893.
ABSTRACT
Brief inhalation of carbon dioxide (CO) has been proposed to counteract transient hypocapnia by enhancing oxygen unloading, vasodilation, and sympathetic modulation. Despite these potential ergogenic mechanisms, CO has rarely been investigated in the exercise context. The present study investigated whether brief CO inhalation (iCO) influences performance and recovery during high-intensity interval exercise. Nine healthy adults completed two randomized, single-blinded crossover trials of repeated cycling intervals at 85% peak work rate until volitional exhaustion or cadence dropped below 60 rpm, with a minimum 2-min interval duration required and 3-min active recovery between bouts. Participants inhaled 5% CO or room air (15 breaths) before and after each exercise bout. Gas exchange, cardiovascular responses, and perceived exertion were assessed. Total exercise time was similar between trials; however, participants completed more intervals with iCO. During the first interval, iCO increased exercise duration and VO. At matched exercise time, perceived exertion and dyspnea were lower with iCO. During recovery, systolic blood pressure was lower and heart rate was higher following iCO. Brief iCO improved first-interval performance, altered cardiovascular recovery, and reduced perceptual strain but did not extend overall exercise duration. These findings suggest iCO may transiently modulate tolerance and autonomic-vascular responses during high-intensity interval exercise.
PMID:42322004 | DOI:10.14814/phy2.70893