Effects of Four Weeks L-Carnitine L-tartrate Ingestion on Substrate Utilization during Prolonged Exercise
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In a randomized, placebo-controlled, double-blind crossover design, 15 trained males undertook exercise trials during two 4 wk supplementation periods, with either 3 g L-Carnitine L-tartrate (LCLT) or 3 g placebo (P) daily. Total carbohydrate and fat oxidation during 90 min steady state cycling were not different between 0 or 4 wk within LCLT or P trials (mean ± standard deviation: carbohydrate oxidation P0 99 ± 36, P4W 111 ± 27, LCLT0 107 ± 33, LCLT4W 112 ± 32 g, respectively; fat oxidation P0 99 ± 28, P4W 92 ± 21, LCLT0 94 ± 18, LCLT4W 90 ± 22 g, respectively). Subsequent 20 km time trial duration was shorter after P (P0 31:29 ± 3:50, P4W 29:55 ± 2:58 min:s, P < 0.01), with no significant change over LCLT (LCLT0 31:46 ± 4:06, LCLT4W 31.19 ± 4.08 min:s). Four weeks LCLT supplementation had no effect on substrate utilization or endurance performance.
Broad and Galloway are with the Dept of Sports Studies, University of Stirling, Stirling, FK9 4LA, Scotland, U.K. Maughan is with Loughborough University, Loughborough, Leicestershire, LE11 3TU, U.K.
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