School of Applied Sciences, Edinburgh Napier University, Sighthill Campus, Edinburgh, UK.
Institute of Cellular Medicine, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK.
Eur J Appl Physiol. 2019 Mar;119(3):723-733. doi: 10.1007/s00421-018-04063-9. Epub 2019 Jan 8.
Dietary nitrate (NO) has repeatedly been shown to improve endurance and intermittent, high-intensity events in temperate conditions. However, the ergogenic effects of dietary NO on intermittent exercise performance in hot conditions have yet to be investigated.
In a randomised, counterbalanced, double-blind crossover study, 12 recreationally trained males ingested a nitrate-rich beetroot juice shot (BRJ) (6.2 mmol NO) or a nitrate-depleted placebo (PLA) (< 0.004 mmol NO) 3 h prior to an intermittent sprint test (IST) in temperate (22 °C, 35% RH) and hot conditions (30 °C, 70% RH). The cycle ergometer IST consisted of twenty maximal 6 s sprints interspersed by 114 s of active recovery. Work done, power output, heart rate and RPE were measured throughout; tympanic temperature was measured prior to and upon completion.
There were no significant effects of supplement on sprint performance in either temperate or hot, humid conditions (p > 0.05). There was a reduced peak (BRJ: 659 ± 100W vs. PLA: 693 ± 139W; p = 0.056) and mean power (BRJ: 543 ± 29W vs. PLA: 575 ± 38W; p = 0.081) following BRJ compared to PLA in the hot and humid condition, but this was not statistically significant. There was no effect of supplement on total work done irrespective of environmental condition. However, ~ 75% of participants experienced performance decreases following BRJ in the hot and humid environment. No differences were observed between trials for tympanic temperature measured at the conclusion of the exercise trial.
In conclusion, an acute dose of inorganic dietary NO does not improve repeated-sprint performance in either temperate, or hot and humid conditions.
饮食硝酸盐（NO）已多次被证明可提高温带条件下的耐力和间歇性高强度运动表现。然而，饮食 NO 对热环境下间歇性运动表现的促进作用尚未得到研究。
在一项随机、对照、双盲交叉研究中，12 名有经验的男性在温带（22°C，35%相对湿度）和热环境（30°C，70%相对湿度）下进行间歇性冲刺测试（IST）前 3 小时摄入富含硝酸盐的甜菜根汁（BRJ）（6.2mmolNO）或硝酸盐耗尽的安慰剂（PLA）（<0.004mmolNO）。循环测力计 IST 由二十次最大 6 秒冲刺组成，间隔 114 秒主动恢复。在整个过程中测量做功、功率输出、心率和 RPE；在测试前和测试结束时测量鼓膜温度。
补充剂对温带或热、高湿度条件下的冲刺表现均无显著影响（p>0.05）。BRJ 后峰值（BRJ：659±100W vs. PLA：693±139W；p=0.056）和平均功率（BRJ：543±29W vs. PLA：575±38W；p=0.081）均低于 PLA，BRJ 后峰值和平均功率均低于 PLA，但这并不具有统计学意义。无论环境条件如何，补充剂对总做功均无影响。然而，在热、高湿度环境下，约 75%的参与者在服用 BRJ 后表现出下降。在运动试验结束时测量鼓膜温度，两次试验之间没有差异。
总之，急性摄入无机饮食硝酸盐不会提高温带或热、高湿度条件下的重复冲刺表现。
