Failure of Glycine-arginine-[alpha]-ketoisocaproic acid to improve high intensity exercise performance in trained cyclists

Oral supplementation with Glycine-arginine-[alpha]-ketoisocaproic acid (GAKIC) has previously been shown to improve exhaustive high intensity exercise performance. There are no controlled studies involving GAKIC supplementation in well-trained subjects. The aim of the present study was to examine the effects of GAKIC supplementation on fatigue during high intensity, repeated cycle sprints in trained cyclists. After at least two familiarisation trials, 10 well-trained male cyclists completed two supramaximal sprint tests each involving 10 sprints of 10 s separated by 50 s rest intervals on an electrically braked cycle ergometer. Subjects ingested 11.2 g of GAKIC or placebo (Pl) during a period of 45 min prior to the two experimental trials administered in a randomised and double blind fashion. Peak power declined from the 1st sprint (mean +- SD) (Pl: 1332 +- 307 W, GAKIC: 1367 +- 342 W) to the 10th sprint (Pl: 1091 +- 229 W, GAKIC: 1061 +- 272 W) and did not differ between conditions (P=0.88). Mean power declined from the 1st sprint (Pl: 892 +- 151 W, GAKIC: 892 +- 153 W) to the 10th sprint (Pl: 766 +- 120 W, GAKIC: 752 +- 138 W) and did not differ between conditions (P=0.96). The fatigue index remained at ~38% throughout the series of sprints and did not differ between conditions (P=0.99). Heart rate and ratings of perceived exertion increased from the 1st sprint to the 10th sprint and did not differ between conditions (P=0.11 and P=0.83, respectively). In contrast to previous studies in untrained individuals, these results suggest that GAKIC has no ergogenic effect on repeated bouts of high intensity exercise in trained individuals.