An individual’s ability to use oxygen to sustain aerobic performance, as denoted by the oxygen uptake efficiency (OUE), is calculated by dividing oxygen uptake (VO2) by ventilation (VE). Whether nasal breathing (NB) during exercise would improve OUE more significantly compared to combined breathing (CB) remains uncertain. PURPOSE: To determine the effects of utilizing NB during exercise on OUE. METHODS: Fourteen males (age: 20.57 ± 1.22 yrs; BMI: 26.03 ± 3.16 kg/m2) were randomly assigned to the NB (n = 8) or CB (n = 6) group for a 4-week supervised aerobic exercise intervention conducted four times per week for 30 minutes at moderate intensity (70% maximal heart rate). VO2max tests were performed during the pre- (week 0) and post-study (week 4) periods on a recumbent bike to determine the change in OUE, VO2, and VE at varying intensities (40%, 55%, 70%, 85%, and 100% of VO2max). The OUE was calculated as VO2 (L) ÷ VE (L). A one-way ANCOVA, controlling for OUE, VO2, and VE at pre-study, was utilized to examine if NB elicited cardiorespiratory adaptations that were superior to the CB training at post-study. A paired-sample t-test examined changes in OUE, VO2, and VE throughout the GXT from week 0 to week 4. Data are presented as mean ± standard error. RESULTS: The NB group demonstrated significantly greater [F(1,11) = 7.213, p = 0.021] OUE (0.048 ± 0.002) at 85% of VO2max than the CB (0.037 ± 0.003) group. Similarly, the NB group had a significantly greater (p = 0.014) OUE (0.025 ± 0.001) at 100% of VO2max than the CB (0.021 ± 0.001) group. Only the NB group experienced significant improvements after exercise training in VO2 at 40% ( p = 0.003, 12.02 ± 0.50 to 13.72 ± 0.59 mL·kg·min-1], 55% (p = 0.006, 16.68 ± 0.71 to 18.87 ± 0.81 mL·kg·min-1), 70% (p = 0.005, 21.16 ± 0.93 to 24.00 ± 1.01 mL·kg·min-1), 85% (p = 0.004, 25.81 ± 1.11 to 29.03 ± 1.23 mL·kg·min-1), and 100% VO2max (p = 0.005, 30.31 ± 1.30 to 34.18 ± 1.48 mL·kg·min-1). While not statistically significant, the NB group displayed a trend of reduced VE compared to the CB group. CONCLUSION: The integration of NB during aerobic exercise enhanced the OUE, particularly at higher intensities, compared to CB. This adaptation is noteworthy, as the NB group achieved a comparable range of VO2 as the CB group while maintaining a lower VE after just 1-month of training. This denotes that NB could promote enhanced oxygen movement. Future studies are warranted to investigate additional health adaptations resulting from such training benefits.



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