The effect ofl-citrulline and watermelon juice supplementation on anaerobic and aerobic exercise performance

Abstract

Citrulline has been proposed as an ergogenic aid, leading to an interest in watermelon given its high citrulline concentration. The aim of this study was to determine the effects of a single, pre-exercise dose of l-citrulline, watermelon juice, or a placebo on the total maximum number of repetitions completed over 5 sets, time to exhaustion, maximal oxygen consumption (VO2max), anaerobic threshold, and flow-mediated vasodilation. A randomised double-blind within-participants study design was used to examine these effects among 22 participants (n = 11 males). Supplementation included either a 7.5% sucrose drink containing 6 g of l-citrulline, 710 mL of watermelon juice (~1.0 g citrulline), or a 7.5% sucrose placebo drink. Supplementation was administered 1 or 2 h before exercise testing to investigate a timing effect. There was no significant effect between the three supplements for the total number of repetitions, time to exhaustion, VO2max, anaerobic threshold, or flow-mediated vasodilation. There was also no interaction observed relative to gender or supplement timing (P > 0.05). A single dose of l-citrulline or watermelon juice as a pre-exercise supplement appears to be ineffective in improving exercise performance; however, greater doses of l-citrulline have been shown to be safe and are currently left unexamined.

Two weeks of watermelon juice supplementation improves nitric oxide bioavailability but not endurance exercise performance in humans

“…Two other recent studies have also observed no improvement in exercise performance indices after watermelon juice supplementation [28,42]. In our previous study where L-citrulline was ergogenic, we observed improved muscle oxygenation and faster O 2 kinetics and attributed the ergogenic effects of L-citrulline to an increase in proportional energy contribution from oxidative metabolism [22].…”

“…The effect of watermelon juice consumption on exercise performance, on the other hand, is unclear. The acute ingestion of 500 mL watermelon juice, which provided a L-citrulline dose of 1.17 g, did not improve performance during 8 × 30 s cycle efforts [28], while the acute ingestion of 710 mL watermelon juice, which provided a Lcitrulline dose of ~ 1 g, did not increase the number of repetitions completed during 5 sets of bench press at 80% of the 1 repetition maximum, or increase time-to-exhaustion, the gas exchange threshold or maximal oxygen uptake during an incremental treadmill test to exhaustion [42]. Since neither of these studies [28,42] …”

“…Supplementation with watermelon juice has been reported to enhance aspects of vascular health in hypertensive individuals [38][39][40][41], but not in normotensive individuals [42]. It has also been reported that watermelon juice ingestion can attenuate muscle soreness after completing intense exercise [28].…”

Comparison of Watermelon and Carbohydrate Beverage on Exercise-Induced Alterations in Systemic Inflammation, Immune Dysfunction, and Plasma Antioxidant Capacity

“…Tarazona-Diaz et al [32] found that acute WM supplementation did not enhance anaerobic cycle ergometer work capacity. Cutrufello et al [33] recently reported that a single acute dose of WM did not enhance strength, anaerobic threshold, time to exhaustion or VO 2max . These two WM studies utilized short-duration, high-intensity exercise bouts that are not limited by blood glucose or glycogen levels.…”

“…Acute WM consumption providing ~1.2 g of l -citrulline attenuated moderate muscle soreness in untrained healthy subjects participating in high-intensity exercise intervals, but did not improve performance [32]. Similarly, time to exhaustion during a graded exercise test was not improved following acute consumption of watermelon juice containing ~1 g l -cirulline [33]. …”