The Effect of Acute L-Carnitine Supplementation on Anaerobic Threshold during Maximum Activity in Middle-Distance Runners

Increasing the anaerobic threshold reduces lactate accumulation, postpones fatigue and improves exercise performance. Therefore, the aim of this study was to investigate the effect of acute L-carnitine supplementation on the anaerobic threshold during maximum activity in collegiate runners. For this purpose, 12 trained collegiate runners participated voluntarily in this study (exercise experience: at least 3 years, mean age: 23.33 ± 2.93 years, weight: 66.00 ± 7.21 kg, height: 176.00 ± 6.49 cm, body mass index 21.27 ± 1.35 kg/m2). The subjects were divided randomly into two groups: placebo and supplement. The study design was crossover and double-blind. Subjects in supplement group received 2g of L-carnitine while the control group received placebo 90 minutes before the exercise protocol. Blood samples were collected before and after the CONCONI protocol to measure blood lactate changes. The gas analyzer was used to estimate the respiratory exchange ratio (RER) and heart rate deflection point. After a 7-day period, the position of the two groups changed, and the previous steps were repeated again. One-way ANOVA and LSD post hoc test were used to analyze the data at a significance level less than 0.05. The results of this study showed that L-carnitine supplementation significantly improved the running time (P=0.001), the distance traveled until the anaerobic threshold (P=0.001), respiratory exchange ratio (P=0.001), and lactate accumulation (P=0.001) compared with the placebo group. But, it had no significant effect on delaying the heart rate deflection point at higher speeds (P=0.173). According to these results, it can be concluded that acute L-carnitine supplementation delays fatigue and improves the performance of runners.