Influence Of Inhaled Carbon Dioxide On Exercise Performance In Active Individuals

Jesse Schwartz, Dongwook Yeo, Soumya Vungarala, Chul-Ho Kim, Bruce Johnson Human Integrative and Environmental Physiology LaboratoryDepartment of Cardiovascular Disease, Mayo Clinic, Rochester, MN 55905 PURPOSE: Carbon dioxide (CO2) can modulate various physiological responses, such as ventilation, vasodilation, pH changes, and hemoglobin-oxygen unloading. This study investigated acute CO2 inhalation effects on exercise performance and recovery in aerobically trained people. METHODS: 1 screening and 2 experimental visits (CO2 vs. CON; 5% FICO2 vs. room air (RA), respectively) were completed, while experimental conditions were randomized and single-blinded. 9 participants (male/female: 4/5, age: 32.4 ± 8.7 years, Ht: 171.8 ± 10.2 cm, Wt: 68.2 ± 11.9 kg, and 126 ± 7.7% of age-predicted VO2max) underwent a VO2max test for eligibility and maximal workload. During experimental visits, exercise bouts (≤6) were completed until volitional fatigue on a cycle ergometer (60 ~ 80 rpm) at 85% (203.7 ± 44.3 W) of maximal workload after warm-up. 3-minute recovery between bouts was given. 15 breaths of CO2 or RA gas was applied before and after exercise. Exercise time, heart rate (HR), oxygen consumption (VO2), rate of perceived exertion (RPE), dyspnea scores (DYS), and blood pressure (BP) were assessed. 3-minute active (15 W) and 2-minute (at rest) passive recovery were completed after all exercise bouts. RESULTS: Number of bout that subjects completed (CO2 vs. CON) was the following: 4 bouts (n = 8 vs. 7), 5 bouts (n = 6 vs. 5), and 6 bouts (n = 3 vs. 2). CO2 had a greater number of intervals completed vs. CON (4.9 ± 1.05 vs. 4.6, respectively, p = 0.04). Exercise duration during the 1st bout was greater with CO2 vs. CON (11.31 ± 5.1 vs. 9.43 ± 4.1 min, p = 0.02), but not the total exercise time of all bouts (p > 0.05). There were no differences in peak HR or VO2 during exercise or recovery (p > 0.05). There was no difference in DYS during recovery, while RPE was lower in CO2 (p = 0.02) during recovery after 2nd bout. CO2 had a lower systolic BP than CON after active and passive recovery (p = 0.02 and p = 0.01, respectively). CONCLUSION. Our findings suggest that brief periods of CO2 inhalation can extend initial exercise duration, intervals completed and reduce post-exercise blood pressure. Future studies are needed to investigate underlying mechanisms.