Dietary Nitrate Fails to Improve 1 and 4 km Cycling Performance in Highly Trained Cyclists

作者：McQuillan Joseph A^*; Dulson Deborah K; Laursen Paul B; Kilding Andrew E

来源：International Journal of Sport Nutrition and Exercise Metabolism, 2017, 27(3): 255-263.

DOI：10.1123/ijsnem.2016-0212

• beetroot juice
• time-trial
• exercise economy
• nutrition

We aimed to compare the effects of two different dosing durations of dietary nitrate (NO3-) supplementation on 1 and 4 km cycling time-trial performance in highly trained cyclists. In a double-blind crossover-design, nine highly trained cyclists ingested 140ml of NO3--rich beetroot juice containing +/- 8.0mmol [NO3-], or placebo, for seven days. Participants completed a range of laboratory-based trials to quantify physiological and perceptual responses and cycling performance: time-trials on day 3 and 6 (4km) and on day 4 and 7 (1km) of the supplementation period. Relative to placebo, effects following 3-and 4-days of NO3- supplementation were unclear for 4 (-0.8; 95% CL, +/- 2.8%, p =.54) and likely harmful for 1km (-1.9; +/- 2.5% CL, p = .17) time-trial mean power. Effects following 6- and 7-days of NO3- supplementation resulted in unclear effects for 4 (0.1; +/- 2.2% CL, p = .93) and 1km (-0.9; +/- 2.6% CL, p = .51) time-trial mean power. Relative to placebo, effects for 40, 50, and 60% peak power output were unclear for economy at days 3 and 6 of NO(3)(-)supplementation (p > .05). Dietary NO3- supplementation appears to be detrimental to 1km time-trial performance in highly trained cyclists after 4-days. While, extending NO3- dosing to > 6-days reduced the magnitude of harm in both distances, overall performance in short duration cycling time-trials did not improve relative to placebo.

• 出版日期2017-6