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- Title
l-Arginine but not l-glutamine likely increases exogenous carbohydrate oxidation during endurance exercise.
- Authors
Rowlands, David; Clarke, Jim; Green, Jackson; Shi, Xiaocai
- Abstract
The addition of l-arginine or l-glutamine to glucose-electrolyte solutions can increase intestinal water, glucose, and sodium absorption in rats and humans. We evaluated the utility of l-arginine and l-glutamine in energy-rehydration beverages through assessment of exogenous glucose oxidation and perceptions of exertion and gastrointestinal distress during endurance exercise. Eight cyclists rode 150 min at 50% of peak power on four occasions while ingesting solutions at a rate of 150 mL 15 min that contained C-enriched glucose (266 mmol L) and sodium citrate ([Na] 60 mmol L), and either: 4.25 mmol L l-arginine or 45 mmol L l-glutamine, and as controls glucose only or no glucose. Relative to glucose only, l-arginine invoked a likely 12% increase in exogenous glucose oxidation (90% confidence limits: ±8%); however, the effect of l-glutamine was possibly trivial (4.5 ± 7.3%). l-Arginine also led to very likely small reductions in endogenous fat oxidation rate relative to glucose (12 ± 4%) and l-glutamine (14 ± 4%), and relative to no glucose, likely reductions in exercise oxygen consumption (2.6 ± 1.5%) and plasma lactate concentration (0.20 ± 0.16 mmol L). Effects on endogenous and total carbohydrate oxidation were inconsequential. Compared with glucose only, l-arginine and l-glutamine caused likely small-moderate effect size increases in perceptions of stomach fullness, abdominal cramp, exertion, and muscle tiredness during exercise. Addition of l-arginine to a glucose and electrolyte solution increases the oxidation of exogenous glucose and decreases the oxygen cost of exercise, although the mechanisms responsible and impact on endurance performance require further investigation. However, l-arginine also increases subjective feelings of gastrointestinal distress, which may attenuate its other benefits.
- Subjects
ARGININE; GLUTAMINE; CARBOHYDRATES; OXIDATION; ENDURANCE sports; GLUCOSE
- Publication
European Journal of Applied Physiology, 2012, Vol 112, Issue 7, p2443
- ISSN
1439-6319
- Publication type
Article
- DOI
10.1007/s00421-011-2225-4