Exercise Cycling

This study investigated the influence of dietary inorganic nitrate (NO) supplementation on pulmonary Ouptake (V˙O) 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˙Oover separate 4-day supplementation periods with NO-rich (BR; providing 8.4 mmol NO∙day) and NO-depleted (placebo; PLA) beetroot juice. Pulmonary V˙Owas measured breath-by-breath and time-resolved near-infrared spectroscopy was utilized to quantify absolute deoxy [Hb + Mb] and total [Hb + Mb] within the,, andThere were no significant differences (>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 mol/L,<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 mol/L sec,=0.08). The V˙Oslow component reduction after BR supplementation (PLA: 0.27 ± 0.07 vs. BR: 0.23 ± 0.08 L min,=0.07) correlated inversely with the mean increases in deoxy [Hb + Mb] and total [Hb + Mb] across the three muscle regions ( = 0.62 and 0.66,<0.05). Dietary NOsupplementation increased Odiffusive conductance across locomotor muscles in association with improved V˙Odynamics during heavy-intensity cycling transitions.