L-Ornithine gives faster sprint during endurance activity

The amino acid L-ornithine [structure below] improves stamina and reduces fatigue during periods of extended physical exercise. Japanese researchers discovered that L-ornithine supplementation helps give you more energy for short sprints during endurance activities.

Ornithine is released in the urea cycle. This is a chain of reactions by which the body rids itself of ammonia and used up proteins. Extra ornithine speeds up these reactions, enabling the body to eliminate ammonia and other nitrogen compounds more quickly from the blood. This in turn reduces fatigue caused by exertion.

The researchers got their test subjects to cycle for four hours at 80% of the heart rate at the anaerobic threshold. Half an hour after starting to cycle and half an hour before the end of the period, the researchers got their tests subjects to cycle as fast as they could for ten seconds.


The supplement resulted in less decrease in speed during the sprint. The effect was also accompanied by a lower accumulation of ammonia in the blood.


“It is difficult to obtain sufficient amounts of L-ornithine from ordinary meals for antifatigue”, the researchers write. “In this study, we used L-ornithine synthesized by the fermentation method. We recommend L-ornithine intake as a nutritional supplement in cases of fatigue.”

The research was financed by Kyowa Hakko Kogyo, a manufacturer of L-ornithine.

L-ornithine supplementation attenuates physical fatigue in healthy volunteers by modulating lipid and amino acid metabolism.


We examined the effects of L-ornithine administration on physical fatigue. In a double-blind, placebo-controlled, 2-way crossover study, 17 healthy volunteers were randomized to L-ornithine (2000 mg/d for 7 days and 6000 mg/d for 1 day as L-ornithine hydrochloride) or placebo for 8 days. The fatigue-inducing physical task consisted of workload trials on a cycle ergometer at fixed workloads for 2 hours on 2 occasions. We found that oral L-ornithine administration promoted lipid metabolism and activated the urea cycle from serum triacylglycerol, ketone bodies, free fatty acids, and blood ammonia level changing. L-ornithine significantly attenuated the subjective feeling of fatigue (measured by visual analog scale at postrecovery) compared with postload (P < .01). Moreover, in female subjects, the subjective feeling of fatigue was significantly lower compared with the placebo group (P < .05). In the physical performance test in female subjects, the decrease in mean speed for 10 seconds maximum pedaling from 0.5- to 3.5-hour trials in the group receiving L-ornithine was smaller than that in the group receiving placebo (P < .05). These results suggest that L-ornithine has an antifatigue effect by increasing the efficiency of energy consumption and promoting the excretion of ammonia. L-ornithine is a free amino acid and is not rich in meats or fish, so it is difficult to obtain amounts of L-ornithine from ordinary meals that would be sufficient to promote the antifatigue effect. We recommend L-ornithine intake as a nutritional supplement in cases of physical fatigue. PMID: 19083482 [PubMed - indexed for MEDLINE] Source: http://www.ncbi.nlm.nih.gov/pubmed/19083482

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