Tjingg
2013-12-24, 08:29
Oral L-Arginine Prior To Resistance Exercise Blunts Growth Hormone in Strength Trained Males
Abstract:
Acute resistance exercise and L-arginine have both been shown to independently elevate plasma growth hormone (GH) concentrations; however, their combined effect is controversial. The purpose was to investigate the combined effects of resistance exercise and L-arginine supplementation on plasma L-arginine, GH, GH secretagogues, and IGF-1 in strength trained participants.
Fourteen strength trained males [age: 25±4 y; body mass: 81.4±9.0 kg; height: 179.4±6.9 cm; and training experience: 6.3±3.4 y] participated in a randomized double blind crossover design (separated by ~7 days). Subjects reported to the laboratory at 08:00 in a fasted state, consumed L-arginine (ARG; 0.075 g·kg-1 body mass) or a placebo (PLA) prior to performing an acute bout of resistance exercise (3 sets of 8 exercises, 10 repetitions at ~75% 1RM). Blood samples were collected at rest, before exercise, and at 0, 15, 30, 60 min of rest-recovery.
The ARG condition significantly increased plasma L-arginine concentrations (~120%) while no change was detected in the PLA condition. There were no differences between conditions for GH, GH-releasing hormone, ghrelin, or IGF-1 at any time point. GH-inhibiting hormone was significantly lower in the ARG condition.
However; integrated area under the curve for GH was blunted in the ARG condition (L-arginine = 288.4±368.7 vs. placebo = 487.9±482.0 min·ng·mL-1, p<0.05). L-arginine ingested prior to resistance exercise significantly elevated plasma L-arginine concentration but attenuated plasma GH in strength trained individuals despite a lower GHIH. Furthermore our data shows that the GH suppression was not due to a GH or IGF-1 induced autonegative feedback loop.
Int J Sport Nutr Exerc Metab. 2013 Nov 13.
http://www.ncbi.nlm.nih.gov/pubmed/24225560
Abstract:
Acute resistance exercise and L-arginine have both been shown to independently elevate plasma growth hormone (GH) concentrations; however, their combined effect is controversial. The purpose was to investigate the combined effects of resistance exercise and L-arginine supplementation on plasma L-arginine, GH, GH secretagogues, and IGF-1 in strength trained participants.
Fourteen strength trained males [age: 25±4 y; body mass: 81.4±9.0 kg; height: 179.4±6.9 cm; and training experience: 6.3±3.4 y] participated in a randomized double blind crossover design (separated by ~7 days). Subjects reported to the laboratory at 08:00 in a fasted state, consumed L-arginine (ARG; 0.075 g·kg-1 body mass) or a placebo (PLA) prior to performing an acute bout of resistance exercise (3 sets of 8 exercises, 10 repetitions at ~75% 1RM). Blood samples were collected at rest, before exercise, and at 0, 15, 30, 60 min of rest-recovery.
The ARG condition significantly increased plasma L-arginine concentrations (~120%) while no change was detected in the PLA condition. There were no differences between conditions for GH, GH-releasing hormone, ghrelin, or IGF-1 at any time point. GH-inhibiting hormone was significantly lower in the ARG condition.
However; integrated area under the curve for GH was blunted in the ARG condition (L-arginine = 288.4±368.7 vs. placebo = 487.9±482.0 min·ng·mL-1, p<0.05). L-arginine ingested prior to resistance exercise significantly elevated plasma L-arginine concentration but attenuated plasma GH in strength trained individuals despite a lower GHIH. Furthermore our data shows that the GH suppression was not due to a GH or IGF-1 induced autonegative feedback loop.
Int J Sport Nutr Exerc Metab. 2013 Nov 13.
http://www.ncbi.nlm.nih.gov/pubmed/24225560