Ehlers, G., Boehm, S., Brown, J., Gadeken, R., Keller, S., Mueller, M., Schmerber, S., Uffenbeck, D., & Nelson, R. (2012). Effect of an L-Arginine/L-Citrulline supplement on muscle oxygen saturation and maximal exercise performance. Presentation 1843 at the 59th Annual Meeting of the American College of Sports Medicine, San Francisco, California; May 29-June 2, 2012.

"L-Arginine (LA) is a semi-essential amino acid that is commonly used as a supplement to enhance blood flow and improve performance in resistance and aerobic exercise. LA exerts its primary effect by conversion to nitric oxide (NO), increasing vasodilation potential in the vasculature of the body. The addition of L-citrulline (LC) to LA has been shown to enhance the potential ergogenic effects of LA. "

This study examined the effects of an acute dose of L-Arginine/L-Citrulline supplementation on skeletal muscle oxygen saturation and maximal cycle exercise performance in college-aged Ss (M = 9; F = 3). Ss completed two maximal cycle ergometer exercise tests after ingesting either an L-Arginine/L-Citrulline (LA 5000mg, LC 1500mg) supplement in 0.5 liters of water or a placebo approximately 90 minutes before testing. Respiratory gases were collected for the determination of maximal oxygen consumption (VO2max) and ventilatory threshold. Heart rate, blood pressure, and rating of perceived exertion were measured throughout the exercise. Near infrared spectroscopy was used to assess skeletal muscle oxygen saturation in the vastus lateralis by analyzing the skeletal muscle oxygen utilization slope measured from the first significant reduction during exercise to the point of the ventilatory threshold.

No significant difference was found between the supplement and placebo for time to exhaustion, maximal workload, VO2max, skeletal muscle oxygen saturation slope, and time to ventilatory threshold. All Ss showed consistency in maximal effort based on a respiratory exchange ratio of greater than 1.10 for all tests for both supplement and placebo trials.

Implication. An L-Arginine/L-Citrulline supplement does not significantly affect maximal exercise test results or the onset of the ventilatory threshold. In addition, skeletal muscle oxygen utilization from the beginning of exercise up to the ventilatory threshold was not affected by the supplement when compared to a placebo.

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