L-carnitine is used in sports and bodybuilding not only as a fat burner but also as a means for gaining muscle mass, energy, endurance, and recovery – practically the entire arsenal of everything one can imagine.
We have figured out how beneficial L-carnitine is for athletes, particularly for increasing endurance and gaining muscle mass. The results are as disappointing as in the question of its benefits for weight loss…
Main thoughts:
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The fact that carnitine is involved in important mechanisms of energy production in the body from fats has become the basis for a huge number of speculations about the benefits for athletes from its additional intake.
The arguments used by sellers to confirm the effectiveness of L-carnitine are as follows:
- stimulates the use of fats for energy;
- reduces the rate of glycogen use in muscles;
- stimulates the use of glucose in muscles as energy;
- reduces muscle fatigue, increasing endurance;
- prevents the loss of carnitine by muscles during training.
The well-known foreign online store bodybuilding.com emphasizes the incredible benefits of L-carnitine as follows:
“Some of the most interesting recent scientific studies on L-carnitine have focused on examining its benefits for improving athletic performance.
In one of them, researchers found that during low-intensity cycling, those who took L-carnitine burned 55% less muscle glycogen and burned 55% more fat.
Additionally, those who took L-carnitine showed a lower level of lactic acid and a higher level of creatine phosphate, one of the main building blocks of the energy molecules ATP.
It was also found that athletes taking L-carnitine were more enduring, covering 25% more distance before feeling fatigued.”
Not bad.
Here is an alternative viewpoint from the scientific portal Examine.com, whose mission is to provide an objective, scientifically-based perspective on the benefits and effectiveness of various sports supplements:
“20 years of research DO NOT confirm the effectiveness of L-carnitine in improving any athletic performance (endurance, energy, fatigue) in healthy athletes 4-6.
Many scientists are convinced that athletes are generally NOT at risk of carnitine deficiency and there is no need for additional intake 3, as it does not improve the body’s use of oxygen or other metabolic functions and does not necessarily lead to an increase in carnitine concentration in the muscles themselves 5.”
20 years of research do not confirm the effectiveness of L-carnitine in sports, and there is no scientific justification for its additional use by athletes.
In this material, we will examine experimental evidence, if not of complete uselessness, then of the questionable benefits of additional L-carnitine intake for athletes.
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The Benefits of L-Carnitine in Bodybuilding for Muscle Mass Gain
Gaining muscle mass under the influence of a particular drug or sports nutrition supplement can be stimulated in several ways:
- increased concentration of building material for muscles (as in the case of protein and amino acids);
- increased effectiveness of the workouts themselves by reducing feelings of fatigue or providing more energy: more repetitions with heavier weights (creatine, energy drinks, etc.);
- the concentration of substances that enhance the anabolic effect (steroids, hormones, etc.) increases.
Carnitine for mass gain may work through a second mechanism: as an energy booster or an anti-fatigue agent.
The basis for the hypothesis that L-carnitine may be beneficial in sports is the important role it plays in fat oxidation within cells for energy production.
Scientists have suggested that if L-carnitine is taken additionally, it may lead to energy stimulation and an increase in physical performance 22. The effect is similar to that produced by energy drinks.
The primary use of fat cells for energy instead of glycogen will allow to delay the onset of fatigue 23.
Additionally, animal studies indicate that the intake of carnitine may prevent the accumulation of lactic acid in muscles, which directly affects the feeling of fatigue 24.
This is the theory.
Overall, research on the impact of additional L-carnitine intake on strength performance is very contradictory.
They state 7,8 that:
L-carnitine in any form does NOT lead to an increase in muscle strength and is useless for mass gain in bodybuilding
Moreover, it is interesting that studies do not confirm the existence of a relationship between L-carnitine intake and its content in muscles 21,35,36,43, despite the fact that its concentrations in the blood increase 30,35,36,40.
This means that if carnitine does lead to changes in any parameters important for athletes, it is not through the mechanism of accumulation in muscles, which is often argued as the importance of its intake.
Scientists state that the content of carnitine in muscles does not increase with additional intake
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The benefits of L-carnitine in sports for endurance and recovery
The effectiveness of L-carnitine for endurance and recovery has theoretical justification but very weak practical confirmation. Just like in the question of its benefits for weight loss.
First, let’s clarify what endurance is from a chemical perspective.
During exercise, certain substances – markers of fatigue – accumulate in the blood and muscles over time, which are metabolic products that act on various organs and systems, including the brain, leading to the feeling of fatigue.
The effectiveness of L-carnitine for endurance can be assessed as follows:
- to observe how the concentration of fatigue markers changes with its intake: their decrease should theoretically indicate an increase in endurance
- to ask the athlete “how do you feel” to assess the degree of perceived fatigue
A positive result in both points – with a high probability confirms effectiveness.
The paradox, however, is that some experiments indicate that the intake of L-carnitine does indeed lead to a decrease in the concentration of fatigue markers, while others show that the fatigue perceived by the athletes themselves and their endurance do not change.
Several examples.
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Scientific research on the benefits of L-carnitine for endurance
In one experiment, scientists aimed to determine how the consumption of carnitine affects endurance and recovery speed in athletes, hypothesizing that both indicators should significantly increase due to improved blood supply to the muscles 15.
12 subjects received L-carnitine or a placebo. After 3 hours – continuous cycling exercise to exhaustion at the threshold of capability. Another 3 hours later – the same thing. After 4-14 days, each participant took the other substance (those who were on carnitine switched to placebo, and vice versa).
Result: the duration of the ride to exhaustion for all subjects did not differ. Also, heart rate, oxygen consumption, and blood lactate concentration remained unchanged. When subjects took 2 grams of carnitine 2 hours before the first ride, it had no effect on the result of the second ride compared to those who took the placebo.
Conclusion: the intake of carnitine for endurance and recovery in athletes has no effect.
In other experiments here11 and here12, scientists note that the intake of 2 g of L-carnitine-L-tartrate over 3 weeks by trained athletes led to a decrease in fatigue markers. This effect was also confirmed with the use of L-carnitine.
That is, from a chemical perspective, this should have been accompanied by a delay in the onset of fatigue.
A possible explanation is the improvement of oxygen delivery to the muscles 13, and consequently, an improvement in endurance and recovery after performing anaerobic physical exercises (anaerobic, as in bodybuilding: short physical activity followed by rest).
This may occur due to an increase in the level of nitric oxide in the blood 1,2, which is known to have a vasodilatory effect.
In another experiment, the intake of carnitine at a dosage of 3 g daily for seven days, according to the subjective assessment of the athletes themselves, did not lead to an increase in endurance and a delay in the feeling of fatigue, as well as an increase in fat burning speed 16.
In yet another study on humans, it was demonstrated that the intake of large doses (15 grams) of L-carnitine may contribute to improved endurance during aerobic exercises 18, while smaller doses (2 g) are ineffective 8.
The overall conclusion is – controversy.
The consumption of carnitine leads to a decrease in the concentration of muscle damage and fatigue markers, but subjective feelings of fatigue do not always improve, nor do sports performance metrics
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Results of scientific research on the effectiveness of L-carnitine in sports
The results of the analysis of all scientific works regarding the effectiveness of L-carnitine for increasing sports performance (mass gain, endurance, fatigue) are presented in the table.
All studies were conducted on healthy individuals. Note the last column: it clearly shows the controversy of the results and the predominance of negative outcomes among them.
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| L-carnitine in sports: scientific studies | |||||
|---|---|---|---|---|---|
| Scientific study | On whom it was tested | L-carnitine dosage | Duration of the experiment | What parameters were measured | Effect of L-carnitine intake |
| Marconi et al, 1985 23 | 6 professional athletes | 4 g (oral) | 2 weeks | Aerobic capacity V̇O2max, lactic acid, respiratory quotient RQ | Increase in aerobic capacity V̇O2max and respiratory quotient RQ without changes |
| Greig et al, 1987 28 | 9 untrained individuals | 2 g (oral) | 14 days | Maximum load, lactic acid | No changes in aerobic capacity V̇O2max and lactic acid |
| Greig et al, 1987 28 | 10 untrained individuals | 2 g (oral) | 28 days | Maximum load, lactic acid | No changes in aerobic capacity V̇O2max and lactic acid |
| Dragan et al, 1987 39 | 40 professional athletes | 3 g (oral) | 21 days | Aerobic capacity V̇O2max | Increase in aerobic capacity V̇O2max |
| Oyono-Enguelle et al, 1988 32 | 10 untrained men | 2 g (oral) | 28 days | Oxygen uptake V̇O2, carbon dioxide output V̇CO2, respiratory quotient RQ, lactic acid, maximum load | No effect from L-carnitine intake |
| Soop et al, 1988 33 | 7 moderately trained men | 5 g (oral) | 5 days | Oxygen uptake V̇O2 at fixed load | No effect from L-carnitine intake |
| Gorostiaga et al, 1989 22 | 10 trained athletes | 2 g (oral) | 28 days | Respiratory quotient RQ, oxygen uptake V̇O2, pulse, lactic acid, blood glucose levels | Respiratory quotient RQ, oxygen uptake V̇O2, pulse, lactic acid, blood glucose levels |
| Siliprandi et al, 1990 37 | 10 moderately trained men | 2 g (oral) | 1 dose 1 hour before training | Blood lactic acid | Blood lactic acid concentration decreased after training |
| Vecchiet et al, 1990 38 | 10 moderately trained men | 2 g (oral) | 1 dose 1 hour before training | Aerobic capacity V̇O2max, blood lactic acid | Aerobic capacity increased V̇O2max, lactic acid concentration decreased |
| Wyss et al, 1990 29 | 7 healthy men | 3 g (oral) | 7 days | Aerobic capacity V̇O2max and respiratory quotient RQ | No effect from L-carnitine intake |
| Decombaz et al, 1993 34 | 9 healthy men | 3 g (oral) | 7 days | Fat burning, respiratory quotient RQ, perceived fatigue | No effect from L-carnitine intake |
| Natali et al, 1993 40 | 12 physically active men | 3 g (intravenous) | 1 dose 40 min before training | Oxygen uptake V̇O2 and carbon dioxide output V̇CO2 | No changes during training, but increased fat burning during recovery |
| Trappe et al, 1994 30 | 20 male athletes | 2 g (oral) | 7 days | Load tolerance during swimming, lactic acid concentration | No effect from L-carnitine intake |
| Brass et al, 1994 21 | 14 healthy men | 92.5 mmol/kg or 18.5 mmol/kg (intravenous) | 1 dose at the beginning of training | Respiratory quotient RQ, oxygen uptake during breathing V̇O2, lactic acid and glycogen in muscles at fixed load | No effect from L-carnitine intake |
| Vukovich et al, 1994 35 | 8 healthy men | 6 g (oral) | 7–14 days | Respiratory coefficient RQ, glucose utilization, oxygen uptake during breathing V̇O2 at fixed load | No effect from L-carnitine intake |
| Barnett et al, 1994 36 | 8 healthy men | 4 g (oral) | 14 days | Lactic acid concentration during exercise, carnitine content in muscles | No effect from L-carnitine intake |
| Colombani et al, 1996 31 | 7 male athletes | 4 g (oral) | On the day of competition | Marathon running time, lactic acid concentration after the marathon | No effect from L-carnitine intake |
| Arenas et al, 1991 25 | 24 athletes | 2 g (oral) | 6 months of training | Carnitine content in muscles | Prevents loss of carnitine by muscles during training |
| Huertas et al, 1992 41 | 14 athletes | 4 g (oral) | 4 weeks of training | Activity of enzymes in the mitochondrial electron transport chain | Increased enzyme activity |
| Arenas et al, 1994 42 | 16 long-distance runners | 2 g (oral) | 4 weeks of training | Activity of muscle pyruvate dehydrogenase and carnitine palmitoyltransferase | Increased activity of pyruvate dehydrogenase but no changes in carnitine palmitoyltransferase |
| Patrick L Jacobs et al, 2009 19 | 24 strength athletes | 4.5 g (oral) Glycine-Propionyl-L-Carnitine 90 minutes before sprinting | 6 months | Muscle strength | Slight increase in sprinting power |
| Jacobs PL et al, 2010 20 | 45 strength athletes | 1.5 g, 3 g, and 4.5 g (oral) Glycine-Propionyl-L-Carnitine 90 minutes before sprinting | 28 days | Muscle strength | Greater increase in sprinting power and less lactic acid accumulation at the dose of 1.5 g compared to doses of 3 g and 4.5 g |
RQ – respiratory quotient – is a parameter used to assess internal metabolism by measuring the carbon dioxide content in exhaled air. It is one of the types of indirect measurement of the number of calories burned (along with measuring the amount of oxygen consumed V̇O2max during breathing)
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VO2 max – maximum oxygen consumption, maximum absorption of oxygen, maximum uptake of oxygen, or maximum aerobic capacity – is the maximum rate of oxygen consumption measured during incremental exercise, most often on a motorized treadmill. Maximum oxygen consumption reflects the level of fitness or aerobic physical condition of a person and determines endurance during prolonged exertion.
The conclusion is obvious:
Based on the analysis of all available scientific data, it can be concluded that the benefits of additional L-carnitine intake in sports are very questionable
Individual positive results are more of an exception than a rule.
Scientists state that additional intake of carnitine may indeed be beneficial during training in the presence of certain diseases: there is evidence that patients with chronic kidney disease 44 and peripheral vascular diseases 45 tolerate physical loads better during training when consuming carnitine.
Carnitine may be beneficial during training in the presence of certain diseases, particularly chronic kidney disease and peripheral vascular diseases
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Conclusion
Research on the benefits of carnitine in sports is ambiguous.
There is no unanimous agreement among scientists that moderate and high doses of L-carnitine improve athletic performance, endurance, muscle strength, or recovery speed 5,6, although there is a theoretical basis for its improvement 17.
There is a small likelihood that the use of carnitine leads to improved recovery speed and endurance.
It is likely that a dose of 1.5-2 g of carnitine daily is optimal for increasing endurance, but further research is needed.
Research on the benefits of carnitine in sports for increasing endurance and muscle strength is ambiguous. There is a small likelihood that doses of 1.5-2 g of carnitine daily increase endurance, but further research is needed
