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.