Content area
Full text
In recent years, many supplements with ergogenic properties have been developed to optimize gains in muscular strength and hypertrophy during resistance training. Supplements containing L-arginine are the latest ergogenic supplements to become commercially available. The semi-essential amino acid, L-arginine, is the only substrate for endogenous synthesis of nitric oxide (NO). The acute effects of L-arginine supplementation supposedly promote vasodilation due to enhanced NO synthesis in the active muscle during exercise.
In animals, L-arginine supplementation has demonstrated positive effects on aerobic exercise performance and skeletal muscle adaptations. Maxwell et al.[1] observed that mice supplemented with L-arginine showed increases in post-exercise urinary nitrate excretion (an indicator of NO production) and aerobic capacity (measured by maximal oxygen consumption [[OV0312]O2max]). Long et al.[2] reported increases in myotube density, total nuclei number and nuclear fusion index after L-arginine supplementation. The authors of both studies conclude that enhanced exercise performance and skeletal muscle adaptations might be explained in part by the augmented NO production from L-arginine supplementation.
In humans, L-arginine administration has been claimed to promote an increase in blood perfusion in the active muscle,[3] increasing substrates necessary for improving muscular recovery and protein synthesis during and/or after exercise. It also promotes greater removal of metabolites, such as lactate and ammonia,[4] which are related to muscle fatigue during intense physical exercise.
In a recent survey, Malinauskas et al.[5] observed that 17% (out of 89 males) and 7% (out of 56 females) of the athletes of the National Collegiate Athletic Association (NCAA) at a southeastern state university in the US were interested in taking supplements for increasing circulation. Among these athletes, 8% and 5% of males and females, respectively, were taking L-arginine.
It appears that there is an increasing interest in L-arginine-based supplements, and, therefore, more knowledge about its effects in healthy physically active subjects is needed.
In 2007, McConell[6] published a review analysing the effect of both oral and intravenous L-arginine administration on metabolism at rest and during exercise. The author concluded that L-arginine supplementation appears to improve exercise capacity in individuals with cardiovascular disease, but had little impact on aerobic exercise capacity in healthy individuals. Although the author had cited other types of exercise such as resistance and anaerobic power exercise, the conclusion of the review was limited...