Ergogenic effects of beetroot juice supplementation during severe-intensity exercise in obese adolescents

Am J Physiol Regul Integr Comp Physiol. 2018 Sep 1;315(3):R453-R460. doi: 10.1152/ajpregu.00017.2018. Epub 2018 Apr 25.

Abstract

Previous studies showed a higher O2 cost of exercise, and therefore, a reduced exercise tolerance in patients with obesity during constant work rate (CWR) exercise compared with healthy subjects. Among the ergogenic effects of dietary nitrate ([Formula: see text]) supplementation in sedentary healthy subjects, a reduced O2 cost and enhanced exercise tolerance have often been demonstrated. The aim of this study was to evaluate the effects of beetroot juice (BR) supplementation, rich in [Formula: see text], on physiological variables associated with exercise tolerance in adolescents with obesity. In a double-blind, randomized crossover study, 10 adolescents with obesity (8 girls, 2 boys; age = 16 ± 1 yr; body mass index = 35.2 ± 5.0 kg/m2) were tested after 6 days of supplementation with BR (5 mmol [Formula: see text] per day) or placebo (PLA). Following each supplementation period, patients carried out two repetitions of 6-min moderate-intensity CWR exercise and one severe-intensity CWR exercise until exhaustion. Plasma [Formula: see text] concentration was significantly higher in BR versus PLA (108 ± 37 vs. 15 ± 5 μM, P < 0.0001). The O2 cost of moderate-intensity exercise was not different in BR versus PLA (13.3 ± 1.7 vs. 12.9 ± 1.1 ml·min-1·W-1, P = 0.517). During severe-intensity exercise, signs of a reduced amplitude of the O2 uptake slow component were observed in BR, in association with a significantly longer time to exhaustion (561 ± 198 s in BR vs. 457 ± 101 s in PLA, P = 0.0143). In obese adolescents, short-term dietary [Formula: see text] supplementation is effective in improving exercise tolerance during severe-intensity exercise. This may prove to be useful in counteracting early fatigue and reduced physical activity in this at-risk population.

Keywords: O2 uptake kinetics; endurance exercise; nitric oxide; obesity; oxidative metabolism.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Beta vulgaris* / adverse effects
  • Body Mass Index
  • Cross-Over Studies
  • Double-Blind Method
  • Exercise Test
  • Exercise Therapy / adverse effects
  • Exercise Therapy / methods*
  • Exercise Tolerance / drug effects*
  • Fruit and Vegetable Juices* / adverse effects
  • Humans
  • Italy
  • Male
  • Muscle Fatigue / drug effects
  • Nitrates / administration & dosage*
  • Nitrates / adverse effects
  • Nitrates / blood
  • Pediatric Obesity / blood
  • Pediatric Obesity / diagnosis
  • Pediatric Obesity / physiopathology
  • Pediatric Obesity / therapy*
  • Performance-Enhancing Substances / administration & dosage*
  • Performance-Enhancing Substances / adverse effects
  • Performance-Enhancing Substances / blood
  • Plant Roots* / adverse effects
  • Time Factors
  • Treatment Outcome

Substances

  • Nitrates
  • Performance-Enhancing Substances