The effect of oral supplementation with L-carnitine on maximum and submaximum exercise capacity.
Two trials were conducted to investigate the effects of L-carnitine supplementation upon maximum and submaximum exercise capacity. Two groups of healthy, untrained subjects were studied in double-blind cross-over trails. Oral supplementation of 2 g per day L-carnitine was used for 2 weeks in the first trial and the same dose but for 4 weeks in the second trial. Maximum and submaximum exercise capacity were assessed during a continuous progressive cycle ergometer exercise test performed at 70 rpm. In trial 1, plasma concentrations of lactate and beta-hydroxybutyrate were measured pre- and post-exercise. In trial 2, pre- and post-exercise plasma lactate were measured. The results of treatment with L-carnitine demonstrated no significant changes in maximum oxygen uptake (VO2max) or in maximum heart rate. In trial 1, there was a small improvement in submaximal performance as evidenced by a decrease in the heart-rate response to a work-load requiring 50% of VO2max. The more extensive trial 2 did not reproduce the significant result obtained in trial 1, that is, there was no significant decrease in heart rate at any given submaximal exercise intensity, under carnitine-supplemented conditions. Plasma metabolic concentrations were unchanged following L-carnitine, in both trials. It is concluded, that in contrast to other reports, carnitine supplementation may be of little benefit to exercise performance since the observed effects were small and inconsistent.
Greig
C
C
Finch
K M
KM
Jones
D A
DA
Cooper
M
M
Sargeant
A J
AJ
Forte
C A
CA
D020155:3-Hydroxybutyric Acid; D000328:Adult; D002331:Carnitine / Q000494:pharmacology*; D002986:Clinical Trials as Topic; D004311:Double-Blind Method; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D006885:Hydroxybutyrates / Q000097:blood; D007773:Lactates / Q000097:blood; D019344:Lactic Acid; D008297:Male; D010101:Oxygen Consumption / Q000187:drug effects; D010807:Physical Endurance / Q000187:drug effects*; D005082:Physical Exertion; D011659:Pulmonary Gas Exchange / Q000187:drug effects
D006885:Hydroxybutyrates; D007773:Lactates; D019344:Lactic Acid; D002331:Carnitine; D020155:3-Hydroxybutyric Acid