Physiol Rep. 2026 Jun;14(12):e70893. doi: 10.14814/phy2.70893.
ABSTRACT
Brief inhalation of carbon dioxide (CO2) has been proposed to counteract transient hypocapnia by enhancing oxygen unloading, vasodilation, and sympathetic modulation. Despite these potential ergogenic mechanisms, CO2 has rarely been investigated in the exercise context. The present study investigated whether brief CO2 inhalation (iCO2) 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% CO2 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 iCO2. During the first interval, iCO2 increased exercise duration and VO2. At matched exercise time, perceived exertion and dyspnea were lower with iCO2. During recovery, systolic blood pressure was lower and heart rate was higher following iCO2. Brief iCO2 improved first-interval performance, altered cardiovascular recovery, and reduced perceptual strain but did not extend overall exercise duration. These findings suggest iCO2 may transiently modulate tolerance and autonomic-vascular responses during high-intensity interval exercise.
PMID:42322004 | DOI:10.14814/phy2.70893