Creatine Monohydrate » branched-chain http://www.creatine-monohydrate.org/blog A Blog all about fitness and bodybuilding supplements like creatine. Tue, 12 Jan 2010 05:19:49 +0000 en hourly 1 http://wordpress.org/?v=3.0 Carnitine and Some facts About it http://www.creatine-monohydrate.org/blog/creatine/carnitine-and-some-facts-about-it http://www.creatine-monohydrate.org/blog/creatine/carnitine-and-some-facts-about-it#comments Mon, 09 Feb 2009 08:09:32 +0000 editor http://www.creatine-monohydrate.org/blog/creatine/carnitine-and-some-facts-about-it L-carnitine is a creatine which contains a short-chain carboxylic acid and has a potential effect on endurance performance because it is a physiological carrier of activated long-chain fatty acids across the inner mitochondrial membrane. Once inside the mitochondria, the long-chain fatty acids are beta-oxidized and carnitine exports acylcoenzyme A compounds. The oxidation of fatty acids in the mitochondria is the main fuel source for skeletal muscle. Also, the carnitine shuttle of a muscle controls the efficiency of the use of fatty acids and the activation of branched-chain amino acid oxidation in the muscle.

The ingestion of carnitine has been speculated to enhance fatty acid oxidation and thus spare skeletal muscle glycogen, and this glycogen-sparing effect may aid endurance performance.

Human Studies

Marconi et al. were the first to investigate the use of carnitine supplementation on endurance performance. Six long distance competitive walkers ingested 4 g/day of L-carnitine for 2 weeks. After the 2-week training period, the subjects’ increased 6% . On the other hand, when the subjects walked 120 minutes at 65%, heart rate, pulmonary ventilation, oxygen consumption, and respiratory quotient remained unchanged. The authors concluded that the slight, but significant increase was probably due to an activation of substrate flow through the TCA cycle.

In a study by Greig et al. two groups of untrained individuals were used in a double-blind, crossover designed study. In the first trial, 2 g of L-carnitine were ingested per day for 2 weeks, and in the second trial, the same dose was given for 4 weeks. Maximal and sub maximal exercise capacity was assessed with a cycle ergometer at 70 rpm. The results showed no significant increase or maximum heart rate.

Gorostiaga et al. conducted a study on ten endurance­trained athletes . The subjects first performed a control test consisting of 45 minutes of cycling at 66% of followed by 60 minutes of seated rest. After 28 days of supplementation with 2 g/day of L-carnitine or a placebo (double-blind, crossover design), the subjects performed the same routine. The results showed a lower respiratory quotient in the treatment group, and there were also trends for an improvement in oxygen uptake and heart rate, but no significant improvements in performance were seen.

In a double-blind, crossover design field study, seven male subjects were given 2 g of L-carnitine 2 hours before the start of a marathon and 20 km into the run. The subjects’ respiratory exchange ratio (RER) was determined before and after the race, and a submaximal performance test was conducted on a treadmill the morning after the race. Supplementation with L-carnitine showed no significant change in marathon running time or RER. Moreover, there were no changes in the sub maximal treadmill test conducted the morning after the run.

One could reasonably conclude at this point that carnitine does not have any consistent effect on endurance performance.

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