The authors examine the effect of an acute dose of beetroot juice on endurance running performance in “real-world” competitive settings. In total, 70 recreational runners (mean ± SD: age = 33.3 ± 12.3 years, training history = 11.9 ± 8.1 years, and hours per week training = 5.9 ± 3.5) completed a quasi-randomized, double-blind, placebo-controlled study of 5-km competitive time trials. Participants performed four trials separated by 1 week in the order of prebaseline, two experimental, and one postbaseline. Experimental trials consisted of the administration of 70-ml nitrate-rich beetroot juice (containing ∼4.1 mmol of nitrate, Beet It Sport^®) or nitrate-depleted placebo (containing ∼0.04 mmol of nitrate, Beet It Sport^®) 2.5 hr prior to time trials. Time to complete 5 km was recorded for each trial. No differences were shown between pre- and postbaseline (p = .128, coefficient variation = 2.66%). The average of these two trials is therefore used as baseline. Compared with baseline, participants ran faster with beetroot juice (mean differences = 22.2 ± 5.0 s, p < .001, d = 0.08) and placebo (22.9 ± 4.5 s, p < .001, d = 0.09). No differences in times were shown between beetroot juice and placebo (0.8 ± 5.7 s, p < .875, d = 0.00). These results indicate that an acute dose of beetroot juice does not improve competitive 5-km time-trial performance in recreational runners compared with placebo.

作者研究了急性剂量的甜菜根汁对“现实世界”竞争环境中耐力跑表现的影响。总共有 70 名休闲跑步者（平均值 ±  SD：年龄 = 33.3 ± 12.3 岁，训练历史 = 11.9 ± 8.1 岁，每周训练小时 = 5.9 ± 3.5）完成了一项准随机、双盲、安慰剂对照研究5公里的竞争性计时赛。参与者按照基线前、两项实验和一项基线后的顺序进行了四次间隔 1 周的试验。实验性试验包括给予 70 毫升富含硝酸盐的甜菜根汁（含有 ∼4.1 mmol 硝酸盐，Beet It Sport ^®）或不含硝酸盐的安慰剂（含有 ∼0.04 mmol 硝酸盐，Beet It Sport ^®) 计时赛前 2.5 小时。每次试验记录完成 5 公里的时间。基线前和基线后没有差异（p  = .128，系数变化 = 2.66%）。因此，这两个试验的平均值用作基线。与基线相比，使用甜菜根汁（平均差 = 22.2 ± 5.0 s，p  < .001，d  = 0.08）和安慰剂（22.9 ± 4.5 s，p  < .001，d  = 0.09）的参与者跑得更快。甜菜根汁和安慰剂在时间上没有差异 (0.8 ± 5.7 s, p  < .875, d = 0.00)。这些结果表明，与安慰剂相比，急性剂量的甜菜根汁并不能提高休闲跑步者的 5 公里计时赛成绩。