Chronic supplementation of L-carnitine (LC) and carbohydrate (CHO) has been reported to increase the content of LC in skeletal muscle and have positive influences on exercise parameters. CHO is thought to increase the uptake of LC into skeletal muscle against a significant concentration gradient via the action of insulin. Insulin stimulates the activity of the sodium potassium exchange pump, increasing extracellular sodium levels. The transport of LC into skeletal muscle is sodium dependent. The acute effect of supplementation on exercise parameters has yet to be investigated. PURPOSE: To determine if acute supplementation of LC when coupled with CHO influences exercise parameters during a bout of cycling. METHODS: A total of 10 males (27.0 ± 4 yrs) completed two exercise sessions consisting of 40 min of cycling at 65% of VO2peak (peak oxygen consumption), immediately followed by cycling to exhaustion at 85% of VO2peak. Supplementation of either LC and CHO or a placebo and CHO occurred prior to the exercise sessions. LC or placebo was consumed 3 hr prior to exercise, and beverages consisting of 94 g of CHO were consumed at both 2 hr, and 30 min prior to exercise. Repeated measures ANOVAs were used to compare respiratory exchange ratio (RER), blood lactate (BL), and power output (PO) across experimental trials and time. A repeated measures t-test was used to analyze differences between conditions and time to exhaustion (TTE) at 85% of VO2peak. RESULTS: RER was significantly lower (p < .05) prior to exercise with LC ingestion (.83 ± .05) compared to the placebo ingestion (.86 ± .06). BL was significantly lower (p < .05) after 10 min of cycling at 65% of VO2peak with ingestion of LC (35% change from baseline) compared to placebo ingestion (53% change from baseline). No significant differences were found for PO at any time point, and TTE at 85% of VO2peak did not differ between conditions. CONCLUSION: Despite lower BL levels after 10 min of cycling a VO2peak, no other differences existed between exercise conditions. Acute supplementation of LC and CHO did not influence exercise parameters, most likely due to a lack of sufficient change in the content of LC in skeletal muscle.

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