Abstract
Dietary nitrate supplementation has positive effects on mitochondrial and muscle contractile efficiency during large muscle mass exercise in humans and on skeletal muscle blood flow (Q ) in rats. However, concurrent measurement of these effects has not been performed in humans. Therefore, we assessed the influence of nitrate supplementation on Q and muscle oxygenation characteristics during moderate- (40 %peak) and severe-intensity(85% peak) handgrip exercise in a randomized, double-blind, crossover design. Nine healthy men (age: 25 2 yr) completed four constant-power exercise tests (2/intensity) randomly assigned to condition [nitrate-rich (nitrate) or nitrate-poor (placebo) beetroot supplementation] and intensity (40 or 85% peak). Resting mean arterial pressure was lower after nitrate compared with placebo (84 4 vs. 89 4 mmHg, P 0.01). All subjects were able to sustain 10 min of exercise at 40% peak in both conditions. Nitrate had no effect on exercise tolerance during 85% peak (nitrate: 358 29; placebo: 341 34 s; P 0.3). Brachial artery Q was not different after nitrate at rest or any time during exercise. Deoxygenated [hemoglobin myoglobin] was not different for 40% peak (P 0.05) but was elevated throughout 85% peak (P 0.05) after nitrate. The metabolic cost (V O2) was not different at the end of exercise; however, the V O2 primary amplitude at the onset of exercise was elevated after nitrate for the 85% peak work rate (96 20 vs. 72 12 ml/min, P 0.05) and had a faster response. These findings suggest that an acute dose of nitrate reduces resting blood pressure and speeds V O2 kinetics in young adults but does not augment Q or reduce steady-state V O2 during small muscle mass handgrip exercise. NEW & NOTEWORTHY We show that acute dietary nitrate supplementation via beetroot juice increases the amplitude and speed of local muscle V O2 on kinetics parameters during severe- but not moderate-intensity handgrip exercise. These changes were found in the absence of an increased blood flow response, suggesting that the increased V O2 was attained via improvements in fractional O2 extraction and/or spatial distribution of blood flow within the exercising muscle.
Original language | English (US) |
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Pages (from-to) | 254-262 |
Number of pages | 9 |
Journal | Journal of applied physiology |
Volume | 125 |
Issue number | 2 |
DOIs | |
State | Published - Aug 2018 |
Keywords
- Beetroot juice
- Dynamic exercise
- Kinetics
- Near infrared spectroscopy
ASJC Scopus subject areas
- Physiology
- Physiology (medical)