According to a recent study by Ozcan Esena, L-arginine supplementation could enhance 200-meter freestyle swimming performance in trained/developmental (regularly preparing three times per week for competition) male swimmers.

The Study

The effects of L-arginine supplementation on exercise performance remain inconsistent, and it has not been examined how it affects swimming performance in single bouts. Therefore, this study aimed to determine whether one week of L-arginine supplementation would enhance 200-meter freestyle swimming performance among trained/developmental male swimmers who train three times a week to compete.

They used a cross-over, randomized, double-blind design to study 8 trained or developing male swimmers who completed a 200-meter freestyle swim time trial on three different occasions: a controlled trial and two separate seven-day supplementation periods with either eight g/d L-arginine or a placebo.

Following time-trial swimming, blood lactate concentrations were measured immediately post-trial. There was no significant difference in the completion time of the 200-m freestyle swimming time trial between control (149.40 ± 9.88 s), L-arginine (146.02 ± 10.34 s), and placebo trials (147.58 ± 10.86 s).

A comparison of blood lactate concentration after time trials was not statistically significant. For trained/developing male swimmers, one week of supplementation with eight g/d of L-arginine did not have a significant ergogenic effect on freestyle middle-distance swimming (200 meters). 

Effect of L-Arginine supplementation
Effect of L-Arginine supplementation

Purpose For Testing Swimmers With L-arginine

Several ergogenic aids, including those containing nitric oxide precursors, have emerged over the past two decades to improve exercise performance. By oxidizing the semi-essential amino acid L-arginine into NO and L-citrulline by the NO synthase (NOS) enzyme, NO is generated as a signaling molecule. Blood flow (BF) is regulated during exercise by NO, which enhances oxygen (O2) and nutrient delivery to contracting muscles.

As a result of an increase in NO bioavailability via exogenous L-arginine supplementation, muscle force production has been shown to be reduced, blood lactate and ammonium accumulation are reduced, and exercise performance is improved.

There is extensive research demonstrating the energizing properties of L-arginine as a NO precursor, and regular supplementation occurs. However, the results of these studies are often inconsistent.

According to some studies, supplementation with L-arginine improved moderately trained individuals’ tolerance to high-intensity exercise, sprint performance, and muscle strength and power, but others found no effect on moderate- or high-intensity exercise or fatigue resistance.

Conflicting findings may be due to several factors, including (I) L-arginine has been found to enhance performance following high dose supplementation but not following low doses.

L-Arginine doses administered in different studies may explain the variation in ergogenic effects. It has been reported that after ingestion of six grams of L-arginine, the plasma concentration of L-arginine reaches its maximum concentration.

The impact of L-arginine supplementation on exercise performance at the appropriate dose is essential to improve our understanding of L-arginine supplementation in terms of ergogenic effects.

(II) In some studies, L-arginine was combined with 2 g glycine and 3.2 g α-ketoisocaproic acid rather than alpha-ketoglutarate, and one study administered the supplement without any other compounds.

The differences observed in the studies are therefore determined by the interaction between these other compounds and the L-arginine in the supplement.

Different exercise protocols and different training levels of individuals may have contributed to the inconsistent findings since some variables diverged among the studies. As a result, it is difficult to determine if L-arginine supplementation improves exercise performance in an ergogenic manner.

Despite inconsistent findings following acute supplements, L-arginine supplementation has improved exercise performance following short-term and chronic supplements. As a result, it may be possible to provide ergogenic effects and improve performance by short-term supplementation of six grams per day.

Among trained and developmental male swimmers, 8 g of L-arginine supplementation per day did not have a significant ergogenic effect on middle-distance (200 m) and freestyle swimming performance.

Therefore, it is premature to recommend L-arginine supplementation as an ergogenic aid for improving freestyle swimming performance in trained/developing male swimmers.

It is necessary to conduct more research to determine if L-arginine supplementation affects swimmers of various training levels (e.g., recreational and master athletes) and other swimming distances (>200 meters) before making any recommendations about its use as an ergogenic aid.

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