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Can L-arginine Influence the Acute Hormonal, Metabolic, and Physiological Responses at Rest and Prior to Exercise? Open Access


Other title
Growth Hormone
Nitric Oxide
Type of item
Degree grantor
University of Alberta
Author or creator
Forbes, Scott C
Supervisor and department
Bell, Gordon (Physical Education and Recreation)
Examining committee member and department
Vicki Harber (Physical Education and Recreation)
Peter Lemon (School of Kinesiology, University of Western)
Daniel Syrotuik (Physical Education and Recreation)
Normand Boule (Physical Education and Recreation)
Linda McCargar (Agricultural, Food & Nutritional Science)
Physical Education and Recreation

Date accepted
Graduation date
Doctor of Philosophy
Degree level
L-arginine is a conditionally essential amino acid and has recently been purported as ergogenic for both strength and aerobic athletes; however, the value of oral L-arginine supplementation in physically active participants is controversial. The purpose of this dissertation was threefold: first to examine the hormonal and metabolic responses of low vs. high relative doses of oral L-arginine at rest; second to determine the GH response when L-arginine was ingested prior to a bout of whole-body resistance exercise in strength trained men; and third to evaluate the hormonal and metabolic responses when L-arginine was consumed prior to a bout of submaximal aerobic exercise in trained cyclists. Study 1: fourteen physically active men (age: 25 ± 5 y; body mass: 78.0 ± 8.5 kg; height: 179.4 ± 4.7 cm) volunteered to be in a randomized, double-blind, repeated measures design. Each subject was provided three treatment conditions (placebo: flour, low dose: 0.075 g•kg-1 or high dose: 0.150 g•kg-1 body mass of L-arginine). L-arginine plasma concentrations significantly increased to a similar concentration at any time point in both the low and high dose conditions, while there was no change over time in the placebo condition. There was no significant difference between conditions for plasma growth hormone (GH), nitrate+nitrite (NOx), insulin-like growth factor-1 (IGF-1), or insulin. Study 2: fourteen strength trained men (age: 25 ± 4 y; body mass: 81.4 ± 9.0 kg; height: 179.4 ± 6.9 cm) participated in a randomized crossover design. L-arginine (0.075 g•kg-1 body mass) or a placebo was ingested 60 minutes prior to performing an acute bout of resistance exercise (3 sets of 8 exercises, 10 repetitions at ~75% 1RM). There were no differences between conditions for GH, GH-releasing hormone (GHRH), ghrelin, or IGF-1 at any time point. GH-inhibiting hormone (GHIH) was significantly lower in the L-arginine condition. However; integrated area under the curve (iAUC) for GH was significantly blunted in the L-arginine condition. Study 3: fifteen aerobically trained men (age: 28 ± 5 y; body mass: 77.4 ± 9.5 kg; height: 180.9 ± 7.9 cm; training experience: 5.9 ± 3.4 y, VO2 max: 59.6 ± 5.9 ml•kg-1•min-1) participated in a randomized crossover design. L-arginine (0.075 g•kg-1 body mass) or a placebo was ingested prior to performing an acute bout of submaximal aerobic exercise. There were no difference between conditions for GH, non esterified fatty acids (NEFA), lactate, glucose, VO2, VCO2, RER, and NOx. However, there was a small but significant elevation in plasma glycerol at the 45 minute time point after L-arginine consumption. In summary, L-arginine consumed orally at rest was effective at increasing plasma L-arginine. L-arginine prior to resistance exercise attenuated plasma GH compared to resistance exercise alone. Lastly, L-arginine before aerobic exercise did not enhance GH, glucose, lactate, NOx, or any cardio-respiratory parameters; however there was a small but significant increase in glycerol during exercise. In conclusion, L-arginine is effective at increasing L-arginine plasma concentrations; however the hormonal and metabolic responses are small and further research is required to examine the ergogenic potential.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
Forbes SC and Bell GJ. 2011. The acute effects of a low and high dose of oral L-arginine in young active males at rest. Appl Physiol Nutr Metab 36(3):405-411.

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