Failure of Glycine-Arginine-α-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 current study was to examine the effects of GAKIC supplementation on fatigue during high-intensity, repeated cycle sprints in trained cyclists. After at least 2 familiarization trials, 10 well-trained male cyclists completed 2 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 before the 2 experimental trials, administered in a randomized and double-blind fashion. Peak power declined from the 1st sprint (M +/- SD; P1 1,332 +/- 307 W, GAKIC 1,367 +/- 342W) to the 10th sprint (P1 1,091 +/- 229W, GAKIC 1,061 +/- 272W) and did not differ between conditions (p = .88). Mean power declined from the 1st sprint (P1 892 +/- 151 W, GAKIC 892 +/- 153 W) to the 10th sprint (P1 766 120 W, GAK1C 752 +/- 138 W) and did not differ between conditions (p = .96). The fatigue index remained at similar to 38% throughout the series of sprints and did not differ between conditions (p = .99). Heart rate and ratings of perceived exertion increased from the 1st sprint to the 10th sprint and did not differ between conditions (p = .11 and p = .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.