• The effects of acute arginine supplementation on 10 mile cycling time trial performance in young adult males

      Morris, Mike; Gill, Sam (University of Chester, 2012-09)
      L-arginine is one of the most metabolically versatile amino acids in the human body, most notably serving as the pre-cursor for the biosynthesis of nitric oxide (NO). The reported physiological effects of L-arginine have served as the rationale behind the development and marketing of a number of NO stimulating dietary supplements, which profess to augment NO production and improve blood flow to muscle during exercise. Supplementation with L-arginine and similar “NO boosters” has soared in popularity over the last decade, despite the fact that there is an overall lack of supportive data in healthy humans, as ergogenic potential remains inconclusive. The aim of this study was therefore to determine the effects of acute supplementation of commercially available L-arginine on exercise performance. Twelve recreationally trained, young adult males (22.3 ± 4.1 yr, 79.3 ± 7.9 kg, 180.9 ± 2.3 cm) consumed either: a placebo (PLA), an L-arginine beverage containing 8g L-arginine (ARG) or no beverage (CON) in a double-blind, repeated-measures design. 45 minutes following consumption, participants completed a 10 mile time trial on a cycle ergometer. There was no significant difference (p=0.643) in time-trial performance between the conditions (CON 29:49 ± 2:19 vs ARG 29:49 ± 3:18 vs PLA 29:30 ± 2:42 minutes). There was no significant difference (p=0.276) between conditions in volitional power output (W) (CON 119.3 ± 8.7 vs ARG 120.1 ± 7.7 vs PLA 121.2 ± 6.2 W), or in heart rate responses (p=0.129) (CON 169.2 ± 11.3 vs ARG 167.2 ± 10.8 vs PLA 166.3 ± 7.8 bpm). Significant differences (p=0.033) were observed between conditions (CON 15.6 ± 1.6 vs ARG 15.2 ± 2.0 vs PLA 15.0 ± 1.7) in RPE responses. With no ergogenic benefits observed in this study, the rationale for pre-exercise supplementation with arginine may be further brought into question.