Dietary nitrate supplementation does not improve cycling time trial performance in the heat
ABSTRACT This investigation examined the effect of beetroot juice (BR) supplementation, a source of dietary nitrate (NO3 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, VO2peak 65.8 5.5 mL.kg 1.min 1) completed four cycling TTs (14 kJ.kg 1) in hot (35degC, 48% relative humidity) and euthermic (21degC, 52% conditions, following 3 days supplementation with BR (6.5 mmol NO3 for 2 days and 13 mmol NO3 on the final day) or NO3 depleted placebo (PLA) Salivary NO3 and nitrite, core (Tc) and mean skin temperature (Tsk) were measured. Salivary NO3 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 Tc (p 0.001) and Tsk (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.
Journal of sports sciences