Abstract
This study investigated the influence of dietary inorganic nitrate (NO3(-)) supplementation on pulmonary O2 uptake (V˙O2) and muscle deoxyhemoglobin/myoglobin (i.e. deoxy [Hb + Mb]) kinetics during submaximal cycling exercise. In a randomized, placebo-controlled, cross-over study, eight healthy and physically active male subjects completed two step cycle tests at a work rate equivalent to 50% of the difference between the gas exchange threshold and peak V˙O2 over separate 4-day supplementation periods with NO3(-)-rich (BR; providing 8.4 mmol NO3(-)∙day(-1)) and NO3(-)-depleted (placebo; PLA) beetroot juice. Pulmonary V˙O2 was measured breath-by-breath and time-resolved near-infrared spectroscopy was utilized to quantify absolute deoxy [Hb + Mb] and total [Hb + Mb] within the rectus femoris, vastus lateralis, and vastus medialis There were no significant differences (P > 0.05) in the primary deoxy [Hb + Mb] mean response time or amplitude between the PLA and BR trials at each muscle site. BR significantly increased the mean (three-site) end-exercise deoxy [Hb + Mb] (PLA: 91 ± 9 vs. BR: 95 ± 12 μmol/L, P < 0.05), with a tendency to increase the mean (three-site) area under the curve for total [Hb + Mb] responses (PLA: 3650 ± 1188 vs. BR: 4467 ± 1315 μmol/L sec(-1), P = 0.08). The V˙O2 slow component reduction after BR supplementation (PLA: 0.27 ± 0.07 vs. BR: 0.23 ± 0.08 L min(-1), P = 0.07) correlated inversely with the mean increases in deoxy [Hb + Mb] and total [Hb + Mb] across the three muscle regions (r(2) = 0.62 and 0.66, P < 0.05). Dietary NO3(-) supplementation increased O2 diffusive conductance across locomotor muscles in association with improved V˙O2 dynamics during heavy-intensity cycling transitions.
DOI
10.14814/phy2.13340
Publication Date
2017-07-25
Publication Title
Physiol Rep
Volume
5
Issue
14
Embargo Period
2018-06-15
Organisational Unit
School of Biomedical Sciences
Keywords
Heterogeneity, nitrate supplementation, oxygen delivery, oxygen utilization, time resolved near‐infrared spectroscopy
Recommended Citation
Breese, B., Poole, D., Okushima, D., Bailey, S., Jones, A., Kondo, N., Amano, T., & Koga, S. (2017) 'The effect of dietary nitrate supplementation on the spatial heterogeneity of quadriceps deoxygenation during heavy-intensity cycling.', Physiol Rep, 5(14). Available at: https://doi.org/10.14814/phy2.13340
