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

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 (CET₁) cycling at their individual anaerobic threshold to exhaustion. Three hours later this test was repeated (CET₂). 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 (CET₁: 21.3±5.7 min; CET₂: 21.4±5.3 min) and placebo (CET₁: 21.9±6.2 min; CET₂: 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.