Written by Jessica Patella, ND. Performance was 35% greater in the carnitine group compared to the control group.
Recent research inThe Journal of Physiology was the first to show that L-carnitine plays a different role, depending on the intensity of the exercise and if it is taken with carbohydrates (1). L-carnitine is an amino acid that transports fats into the mitochondria (“power generator”) of the cell to be converted into energy (2).
The research included 14 healthy male recreational athletes aged 23.8 to 28 who trained 3-5 times per week in cycling, running or swimming (1). Two weeks before the trial began, a baseline VO2max on a stationary cycle was calculated for each participant (2). VO2max is the maximum amount of oxygen the participant could take in, despite an increase in exercise intensity or workload (1). Based on these results, the individual’s 50% VO2max and 80% VO2max were calculated.
The 14 athletes were randomly assigned to one of two groups. The control group was given an orange-flavored carbohydrate drink (700ml, 80g carbohydrates), while the carnitine group was given an orange-flavored carbohydrate plus L-carnitine drink (700ml, 80g carbohydrate, 2.0g L-carnitine tartrate). Both groups were instructed to drink the solution twice a day, once at breakfast time and again four hours later (1).
Over the 24-week study, participants underwent exercise and lab testing three times, each 12 weeks apart. The testing included 30 minutes on the stationary cycle at 50% VO2max, immediately followed by 30 minutes at 80% VO2max, which was immediately followed by 30 minutes of cycling at the participant’s own pace (1).
Performance (work output) was 35% greater in the carnitine group compared to the control group (p<0.05) and improved 11% from baseline in the carnitine group (p<0.05), after 24 weeks.
Perceived exertion between the two groups only differed after week 24. The group supplementing with carnitine perceived lower exertion compared to baseline (14.0 vs. 15.0; p<0.05) and a lower exertion compared to the control group (14.0 vs. 16.2; p<0.05).
At low intensity exercise (50% VO2max), muscle glycogen content was 35% greater in the carnitine group compared to control (p<0.05), which equated to 55% less glycogen being used during exercise. This means more fat was used for energy at lower intensity exercise.
At high intensity exercise (80% VO2max), muscle lactate content was 44% lower in the carnitine group compared to the control group after 24-weeks (p<0.05). This translates to a decrease in muscle fatigue at higher intensity exercise.
In conclusion, supplementation with L-carnitine with carbohydrate solution increases exercise performance and decreases perceived exertion (1). This is the first study to demonstrate that carnitine plays a different role in muscle energy production, depending on the intensity of exercise (1). This type of supplementation might be helpful to those lacking in energy. Further research with more participants need to be conducted to confirm the results.
Source: Wall, Benjamin T., et al. “Chronic oral ingestion of l‐carnitine and carbohydrate increases muscle carnitine content and alters muscle fuel metabolism during exercise in humans.” The Journal of physiology 589.4 (2011): 963-973.
© 2011 The Authors. Journal compilation © 2011 The Physiological Society
Posted August 4, 2011.
References:
- Wall B, et al. Chronic oral ingestion of L-carnitine and carbohydrate increases muscle carnitine content and alters muscle fuel metabolism during exercise in humans. 2011 J Physiol 589.4; 963-973. Doi: 10.1113/jphysiol.2010.201343.
- Steiber A, Kerner J, Hoppel C (2004). “Carnitine: a nutritional, biosynthetic, and functional perspective”.Mol. Aspects Med.25 (5-6): 455–73.
