Background and Aim: Results of previous studies about the effects of L-carnitine supplementation on lactic acid production and improve physical performance during exercise are conflicting. This study was carried out to determine the effect of a single dose of L-carnitine supplement (2 grams in the form of pills), 2 hours before exercise, on blood lactate levels during and after exercise and the distance run by athletes at anaerobic threshold.
Materials and Methods: During a single-blind crossover clinical trial, 12 elite Iranian male Taekwondo players with mean values (±SD) for age, weight, height, body mass index of 19.9±2.0, 71.3±6.4, of 179±4.5, and of 22.0±1.2 respectively were studied. Subjects were randomly assigned to either L-carnitine (n=6) or placebo groups (n=6). The washout period was 72 hours. L-carnitine group received 2 grams of L-carnitine pills dissolved in 200 ml of a sore solution (water containing 6 drops of lemon juice), while the placebo group received 200 ml water flavored with 6 drops of lemon juice. Three blood samples were obtained at 2 hours before, at the end of, and 30 minutes after the end of exercise tests. The exercise tests were carried out according to Conconi protocol on treadmill.
Results: Blood lactate levels per meter of distance, from the start to either the end of the exercise or to 30 minutes after the exercise were lower in L-carnitine group (p<0.05), but it did not significantly change in the time interval of 30 minutes after finishing the exercise. The distance run by athletes on treadmill was greater in the L-Carnitine group than the placebo group (1230.8±408.5 and 1045.8±421.9 m) (p<0.01). A significant negative correlation was seen between BMI and the distance run by the athletes, in both groups (r=-0.732, p<0.01 and r=-0.634, p<0.05 in placebo and L-carnitine group, respectively).
Conclusion: We concluded that a single dose of L-carnitine supplement, 2 hours before exercise on treadmill, can impede the blood lactate elevation during exercise and thereby improve the physical performance of Taekwondo players.
Key words: lactic acid level, L-carnitine, Acute supplementation, Distance covered