The purpose of this study was to evaluate the effect of glycine propionyl-Lcarnitine (GPLC) supplementation and endurance training for 8 wk on aerobicand anaerobic-exercise performance in healthy men and women (age 18–44 yr). Participants were randomly assigned to 1 of 3 groups: placebo (n = 9), 1 g/d GPLC (n = 11), or 3 g/d GPLC (n = 12), in a double-blind fashion. Muscle carnitine (vastus lateralis), VO2peak, exercise time to fatigue, anaerobic threshold, anaerobic power, and total work were measured at baseline and after an 8-wk aerobic-training program. There were no statistical differences (p > .05) between or within the 3 groups for any performance-related variable or muscle carnitine concentrations after 8 wk of supplementation and training. These results suggest that up to 3 g/d GPLC for 8 wk in conjunction with aerobic-exercise training is ineffective for increasing muscle carnitine content and has no significant effects on aerobic- or anaerobic-exercise performance.
The authors are with the Dept. of Health and Sport Sciences, University of Memphis, Memphis, TN 38152.