The Key Amino Acids For Endurance Athletes

Glutamine

Glutamine is the most abundant amino acid in the body, accounting for greater than 60% of the total intramuscular free amino acid pool. Virtually every cell in the body uses this non-essential amino acid.

Glutamine is synthesized in both skeletal muscle and in adipose tissue in addition to the lungs, liver and brain. Because the body has the ability to produce glutamine it has long been considered a non-essential amino acid, which simply means the body has a mechanism to produce this powerful amino acid. However, there is evidence that, during times of stress, the body cannot produce enough glutamine to keep up with demand which in turn can reduce performance, immune function and mood. As a result, glutamine has recently been classified as a conditional non-essential amino acid. Glutamine offers a significant benefit to exercising individuals and those looking to increase lean muscle mass and decrease body fat. Supplemental glutamine can help promote cell volumization, the phenomenon of drawing of water INSIDE muscle cells which can help increase muscle “fullness”, increase protein synthesis (the making of proteins), and decrease proteolysis (the breakdown of protein).

Glutamine and overtraining

Intense physical exercise drains glutamine stores faster than the body can replenish them. When this occurs, the body breaks down muscles and becomes catabolic. There is evidence that supports glutamine supplementation for recovery, glycogen storage, synthesis of other amino acids and reduction of the catabolic effects of over-training. With reduced glutamine levels, performance and recovery are also compromised. It’s been proven that glutamine levels in the serum are dramatically reduced following exhaustive exercise. Glutamine has also been shown to aid in recovery and recuperation in addition to boosting immune function. It accomplishes this as one of the building blocks for the body’s most powerful anti-oxidant, glutathione, and may possibly cause extra growth hormone release with just a 4 gram oral dosage.

A strict and strenuous training program, which does not allow for enough recovery time, may cause an athlete to experience over-training syndrome (OTS). Researchers have effectively correlated OTS to amino acid imbalances. Decreased performance, decreased mood, and increased incidence of infections characterize these amino acid imbalances caused by OTS. Athletes who exercise extensively and are suffering from OTS may become immuno-suppressed. This can lead to increased infection and upper respiratory illness. In addition, recent clinical trials have shown that over-trained endurance athletes suffer from chronic low plasma glutamine levels. Maintaining normal levels of intramuscular glutamine is critical in preventing the breakdown of skeletal muscle and catabolism (the breakdown of muscle). There is also strong evidence that glutamine acts as an immuno-stimulant, which reduces the incidence of infection during training and racing. The best time to take a glutamine or glutamine peptide supplement is right after a hard exercise session since glutamine stores in muscle can be depleted up to 40% after exhaustive exercise.

Branched Chain Amino Acids (BCAAs)

Low levels of branched chain amino acids (BCAAs) may contribute to fatigue so BCAAs should be replaced within two hours or less following exercise. These include the essential amino acids leucine, isoleucine, and valine. They are very popular among athletes and there is some research validating their use. Numerous research studies have shown these three key amino acids are extremely important to consume, especially during dieting and exercising (and according to one study, BCAAs are even more important when exercising in the heat). During exercise, the body uses a mix of glucose, fats, and even protein as a fuel source. When diet and carbohydrate intake is lower than normal, the percentage of protein the body uses for fuel (specifically Leucine, Isoleucine, and Valine) dramatically increases. The body will pull those needed amino acids from the continuously circulating pool of amino acids in the bloodstream.

And if not replenished from an outside source, i.e. specific amino acid ingestion in the form of BCAAs, the body will breakdown other areas of the body in order to supply this pool. Studies have shown that subjects who consume an effective dose of BCAAs while endurance training have greater levels of lean muscle mass retention than control subjects who ingest a placebo (and typically lose muscle during the same dieting period). Additionally, BCAAs form antibodies that combat invading bacteria and viruses. The body cannot manufacture its own BCAAs, so they must be supplied through diet and supplementation. BCAAs have also been studied for their ability to improve exercise capacity in heat. In a 1998 study, subjects supplementing with BCAAs significantly improved moderate exercise performance in the heat.

BCAAs and Central Fatigue

Branched Chain Amino Acids are also associated with a syndrome termed central fatigue. Following exhaustive exercise, BCAAs are depleted from the working muscle and from the circulating pool of amino acids. This depleted state causes an imbalance of the BCAA to Tryptophan (another amino acid) ratio..

When BCAAs are low, Tryptophan (a precursor to serotonin) is more readily available and can cause increases in serotonin. Low levels of BCAAs cause an increase in serotonin, which causes a feeling of sleepiness and lethargy It is this imbalance that can cause an athlete to become lethargic and almost sleepy.

Supplementing with higher levels of BCAAs will help stop the Tryptophan/serotonin mechanism. All whey protein supplements contain Tryptophan, however only some will actually disclose an amount on the label. An effective supplement should contain at least three grams of BCAAs and minimal levels of tryptophan.

If you are interested in learning more about endurance and proteins, make sure to read our free form amino acids article.

Glutamine References

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BCAAs References

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Castell LM, Yamamoto T, Phoenix J, Newsholme EA. The role of tryptophan in fatigue in different conditions of stress. Adv Exp Med Biol. 1999;467:697-704.

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Davis JM, Bailey SP, Woods JA, Galiano FJ, Hamilton MT, Bartoli WP. Effects of carbohydrate feedings on plasma free tryptophan and branched-chain amino acids during prolonged cycling. Eur J Appl Physiol Occup Physiol. 1992;65(6):513-9.

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Newsholme EA, Blomstrand E. Tryptophan, 5-hydroxytryptamine and a possible explanation for central fatigue. Adv Exp Med Biol. 1995;384:315-20.

Raguso, C.A., Pereira, P., Young, V.R., 1999. “A tracer investigation of obligatory oxidative amino acid losses in healthy young adults.” American Journal of Clinical Nutrition, October, 70(4):474-483.

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Schena, F., Guerrini, F., Tregnaghi, P., and Kayser, B., 1992. “Branched-chain amino acid supplementation during trekking at high altitude.” European Journal of Applied Physiology, 65:394-398.

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Yamamoto T, Castell LM, Botella J, Powell H, Hall GM, Young A, Newsholme EA. Changes in the albumin binding of tryptophan during postoperative recovery: a possible link with central fatigue? Brain Res Bull. 1997;43(1):43-6.

Yamamoto T, Newsholme EA. Diminished central fatigue by inhibition of the L-system transporter for the uptake of tryptophan. Brain Res Bull. 2000 May 1;52(1):35-8.

Raguso, C.A., Pereira, P., Young, V.R., 1999. “A tracer investigation of obligatory oxidative amino acid losses in healthy young adults.” American Journal of Clinical Nutrition, October, 70(4):474-483.

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Raguso, C.A., Pereira, P., Young, V.R., 1999. “A tracer investigation of obligatory oxidative amino acid losses in healthy young adults.” American Journal of Clinical Nutrition, October, 70(4):474-483.

 

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