The Effect on Carbon Dioxide Production During Maximal Exercise with Distinct Breathing Mechanisms
Nasal breathing (NB) may lead to lower maximal oxygen uptake (VO2max) compared to oral breathing (OB) or nasal/oral combined breathing (CB) due to a transient increase in the systemic concentration of carbon dioxide (CO2) that can replicate the effects of a hypoxic environment. The exercise intensity at which NB can elicit this response is poorly understood. PURPOSE: To examine the increase in the fractional rate of exhaled CO2 (FECO2) and FEO2 with different breathing conditions during a graded maximal aerobic exercise test (GXT). METHODS: Eight healthy males (21.88 ± 0.46 years) completed 3 GXTs (separated by 48+ hours of recovery) using a different randomly assigned breathing condition (NB, OB, and CB). Participants exercised on a semi-recumbent bicycle at a pedaling speed of 70 rpm, increasing resistance every 2 minutes until volitional fatigue. Following the GXT, participants had a 2-minute recovery. Expired respiratory gases were collected via a metabolic cart. Six time points (40%, 55%, 70%, 85%, 100% VO2max, and recovery) were compared between NB, OB, and CB. Data are presented as mean ± SD. RESULTS: FECO2 was significantly higher during NB than OB at 70% [4.52 ± 0.37 vs. 4.07 ± 0.26%, p = 0.031 and 85% (4.49 ± 0.43% vs. 3.80 ± 0.32%, p = 0.009) of VO2max. Additionally, FECO2 at 100% of VO2max was significantly higher (p = 0.001) during NB (4.33 ± 0.69%) than OB (3.47 ± 0.29%) and CB (3.55 ± 0.19%). The transient change in FECO2 during exercise rapidly changed after the 2-minute recovery, where NB = 3.75 ± 0.71%, OB = 3.38 ± 0.17%, and CB = 3.30 ± 0.27%. FEO2 was significantly lower during NB than OB at 70% (16.34 ± 0.45% vs. 17.04 ± 0.3%, p = 0.011) and 85% (16.50 ± 0.53% vs. 17.32 ± 0.38%, p = 0.009) of VO2max. FEO2 was significantly lower (p = 0.003) during NB (16.66 ± 0.91%) compared to OB (17.67 ± 0.33%) and CB (17.61 ± 0.26%) at 100% VO2max. The transient change in FEO2 during exercise rapidly changed after the 2-minute recovery, where NB = 17.67 ± 1.00%, OB = 18.03 ± 0.23%, and CB = 18.20 ± 0.17%. CONCLUSION: NB elicits an exercised-induced increase in FECO2 that is analogous to a decrease in FEO2 starting at 70% of VO2max. Given the transient increase in FECO2, NB should be considered as a potential breathing method and further explored to replicate a temporary hypoxic environment that could promote a greater exercise adaptation than CB or OB might do.
Paidisetty, Vineet K.; Moris, Jose M.; Blades, Alexandra; Curtis, Ryan; Chang, Christian J.; Petty, Garret; and Koh, Yunsuk
"The Effect on Carbon Dioxide Production During Maximal Exercise with Distinct Breathing Mechanisms,"
International Journal of Exercise Science: Conference Proceedings: Vol. 2:
15, Article 111.
Available at: https://digitalcommons.wku.edu/ijesab/vol2/iss15/111