[ effects of acute L-carnitine supplementation on anaerobic threshold and lactate accumulation during an incremental exercise]

ABSTRACT

Appropriate nutrition is an essential prerequisite for effective improvement of athletic performance, conditioning, recovery from fatigue after exercise, and avoidance of injury. Nutritional supplements containing carbohydrates, proteins, vitamins, and minerals have been widely used in various sporting fields to provide a boost to the recommended daily allowance. The aim of this study was to investigate the effects of acute L-carnitine supplementation on anaerobic threshold and lactate accumulation during incremental exercise. The study was double-blind, randomized and crossover in design. The subjects were 12 randomly selected active male physical education students, 21.75 +/- 0.64 years old, with a mean body mass index [BMI] of 23.7 +/- 0.94, divided into 2 groups. They received orally either 2g of L-carnitine dissolved in 200 ml water plus 6 drops of lemon juice or a placebo [6 ml lemon juice dissolved in 200 ml water] 90 minutes before they began exercise on treadmill. They performed a modified protocol of Conconi test to exhaustion. Plasma lactate concentrations were recorded at rest and immediately after the test. One-way analysis of variance with repeated measurements was used for data analysis. The results showed that lactate accumulation immediately after exercise in the L-carnitine group [3.870 +/- 0.19] was significantly lower [p=0.000] than in the placebo [6.080 +/- 0.58] group. In addition, the intervention led to a higher increase [p=0.000] in the maximum oxygen consumption [50.54 +/- 1.48], as compared to the placebo group [45.16 +/- 1.51]. The data also showed that the length of time required to reach the anaerobic threshold was higher in the L-carnitin group [19.14 +/- 0.65, vs 16.00 +/- 0.28 for the placebo group]. There was no statistically significant difference between the 2 groups with regard to the respiratory exchange ratio. L-carnitine supplementation seems to cause a reduction in the blood lactate accumulation and delay anaerobic threshold in an incremental exercise, resulting in improved performance