['Oral L-arginine supplementation has been shown to improve treadmill time to exhaustion and resting insulin sensitivity in individuals with peripheral vascular disease and type 2 diabetes, respectively. Furthermore, L-citrulline supplementation increases plasma L-arginine concentration to a level higher than that achieved by oral L-arginine supplementation. The purpose of this investigation was therefore to determine whether time to exhaustion during a graded treadmill test, as well as plasma insulin and glucose profiles, could be improved with oral L-citrulline supplementation in healthy individuals.', 'Seventeen young (18-34 yr), healthy male and female volunteers performed incremental treadmill tests to exhaustion following either placebo or citrulline ingestion (3 g 3 h before test, or 9 g over 24 h prior to testing).', 'Steady-state submaximal respiratory exchange ratio and VO2max were not significantly different between placebo and citrulline trials. Treadmill time to exhaustion was lower following citrulline ingestion than during placebo trials (888.2 +/- 17.7 vs 895.4 +/- 17.9 s; P < 0.05; N = 17), which was accompanied by a higher rating of perceived exertion during exercise in the L-citrulline compared with the placebo condition. There was also an increase in plasma insulin in response to this high-intensity exercise in the placebo, but not in the L-citrulline, condition (P < 0.05).'] Does l-citrulline reduce time to exhaustion and insulin response to a graded exercise test?