L -Carnitine and the recovery from exhaustive endurance exercise: a randomised, double-blind, placebo-controlled trial

Abstract

We hypothesised that L: -carnitine could accelerate recovery from exhaustive exercise since increased blood L: -carnitine concentrations elicit a vasodilation in isolated animal vessels as well as in patients with peripheral vascular or coronary artery disease during exercise. Twelve subjects received either 2 g L: -carnitine or a placebo in a study which was double-blind and crossover in design. Two hours after administration, the subjects performed a constant-load exercise test (CET(1)) cycling at their individual anaerobic threshold to exhaustion. Three hours later this test was repeated (CET(2)). After 4-14 days, each subject performed the same cycling tests after having taken the other substance. Exercise times of the 12 subjects were identical with L: -carnitine (CET(1): 21.3+/-5.7 min; CET(2): 21.4+/-5.3 min) and placebo (CET(1): 21.9+/-6.2 min; CET(2): 20.4+/-4.8 min). Also, heart rate, oxygen consumption, respiratory exchange ratio, and blood lactate concentration were identical. In conclusion, 2 g of L-carnitine taken 2 h before a first of two constant-load exercise tests had no influence on the second tests performed 3 h after the first test compared with placebo.