The effects of L-citrulline supplementation on physical performance
Stordahl, Peter Lawrence
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INTRODUCTION. Recent studies have investigated l-citrulline (CIT) as a possible ergogenic aid. A small number of studies have explored the performance question, with varying methodologies and results. The purpose of this study was to examine CIT influence on cycling time to exhaustion, cardiovascular function, and muscle activity. METHODS. Thirteen healthy subjects volunteered for this study. The first visit was to obtain a maximal power output, where 80% and 50% of maximal power were calculated for the following two visits. Subjects were then randomly assigned into either treatment or placebo groups for the second visit and the opposite treatment for the third visit. Subjects were instructed to drink their treatment 1 hour prior to coming into the laboratory. The treatment drink contained 10g of CIT while the placebo (PBO) was formulated to look and taste like the CIT drink. The second and third visits to the laboratory consisted of EMG from the rectus femoris, vastus medialis, and medial gastrocnemius of the right leg, along with HR monitor and BP. Subjects completed a 40-minute interval ride, consisting of 8 5-minute intervals of 3 minutes at 50% maximal power and 2-minutes at 80% maximal power. After the interval ride, subjects received a second dose of either treatment, 5g of CIT or PBO and were allowed 1-hour rest before the ramped time to exhaustion (TTE) test. RESULTS. There was no significant difference in TTE by treatment (CIT, 20.79 + or - 4.48 and PBO, 20.86 + or - 3.99). There was no significant main effect of treatment on percent of maximum heart rate (p = 0.084), mean arterial pressure (p = 0.714), or muscle activity of the rectus femoris (p =0.300), vastus medialis (p = 0.641), or medial gastrocnemius (p = 0.133) during the TTE test. CONCLUSIONS. There were no differences in cycling TTE between treatments. Further research should investigate the metabolism of CIT under different physiological conditions.