Kent Georgina L, Dawson Brian, Cox Gregory R, Burke Louise M, Eastwood Annette, Croft Kevin D, Peeling Peter
a Sport Science, Exercise and Health, School of Human Sciences , The University of Western Australia , Crawley , Australia.
b Sports Nutrition , Australian Institute of Sport , Canberra , Australia.
J Sports Sci. 2018 Jun;36(11):1204-1211. doi: 10.1080/02640414.2017.1364404. Epub 2017 Aug 7.
This investigation examined the effect of beetroot juice (BR) supplementation, a source of dietary nitrate (NO), on cycling time-trial (TT) performance and thermoregulation in the heat. In a double-blind, repeated-measures design, 12 male cyclists (age 26.6 ± 4.4 years, VO 65.8 ± 5.5 mL.kg.min) completed four cycling TTs (14 kJ.kg) in hot (35°C, 48% relative humidity) and euthermic (21°C, 52%) conditions, following 3 days supplementation with BR (6.5 mmol NO for 2 days and 13 mmol NO on the final day), or NOdepleted placebo (PLA). Salivary NO and nitrite, core (T) and mean skin temperature (T) were measured. Salivary NO and nitrite increased significantly post-BR supplementation (p < 0.001). Average TT completion time (mm:ss) in hot conditions was 56:50 ± 05:08 with BR, compared with 58:30 ± 04:48 with PLA (p = 0.178). In euthermic conditions, average completion time was 53:09 ± 04:35 with BR, compared with 54:01 ± 04:05 with PLA (p = 0.380). The TT performance decreased (p < 0.001), and T (p < 0.001) and T (p < 0.001) were higher in hot compared with euthermic conditions. In summary, BR supplementation has no significant effect on cycling TT performance in the heat.
本研究调查了补充甜菜根汁（BR）（一种膳食硝酸盐（NO）来源）对热环境下自行车计时赛（TT）成绩和体温调节的影响。在一项双盲、重复测量设计中，12名男性自行车运动员（年龄26.6±4.4岁，VO₂ 65.8±5.5 mL·kg⁻¹·min⁻¹）在热环境（35°C，相对湿度48%）和常温环境（21°C，相对湿度52%）下，在补充BR（前两天补充6.5 mmol NO，最后一天补充13 mmol NO）或无硝酸盐安慰剂（PLA）3天后，完成了四次自行车TT（14 kJ·kg⁻¹）。测量了唾液中的NO和亚硝酸盐、核心体温（Tₑ）和平均皮肤温度（Tₛ）。补充BR后唾液中的NO和亚硝酸盐显著增加（p<0.001）。在热环境下，BR组的平均TT完成时间（分:秒）为56:50±05:08，PLA组为58:30±04:48（p = 0.178）。在常温环境下，BR组的平均完成时间为53:09±04:35，PLA组为54:01±04:05（p = 0.380）。与常温环境相比，热环境下TT成绩下降（p<0.001），Tₑ（p<0.001）和Tₛ（p<0.001）更高。总之，补充BR对热环境下自行车TT成绩无显著影响。
