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How Amino Acids Improve Endurance

January 03, 2018 8 min read

How Amino Acids Improve Endurance

It is well known that amino acids are the building blocks of muscle.   They play very specific key roles in health and performance in human physiology and help athletes retain muscle and burn fat.   Proteins are made up of both essential and non-essential amino acids that can be used by the body for a plethora of benefits.   Some of these key benefits beyond muscle building include improved glycogen resynthesis, improved mineral absorption and improved focus during exercise.   The body must break the protein down into these free form amino acids in order for them to function.   Consuming amino acids in their free form is beneficial since these amino acids can address their function almost immediately.


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.


image credit: the balancedbeautyblog.

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, clinical evidence shows 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 mechanism of drawing of water INSIDE muscle cells which can help increase muscle hydration, 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. Glutamine levels in the serum are dramatically reduced following exhaustive exercise.When this occurs, the body breaks down muscles and becomes catabolic.  With reduced glutamine levels, performance and recovery are compromised. 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.   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, worsened 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 or the perception of fatigue through a process called ‘central fatigue’.  BCAA’s include the essential amino acids leucine, isoleucine, and valine. They are very popular among strength athletes yet there is strong evidence validating their use for endurance training and racing.   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.

If these amino acids not replenished from an outside source, 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.  Studies showed that 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. This increase in serotonin causes a feeling of sleepiness and lethargy.  This imbalance causes an athlete to become lethargic and almost sleepy even during exercise.

Using free form BCAAs during exercise will help stop the tryptophan/serotonin mechanism which helps athletes stay focused and have a sense of mental strength and energy.



EFS Contains 2g Glutamine & BCAA’s



EFSPRO Contains 2g Glutamine & BCAA’s



ultragen_new_flavors-600Ultragen contains 4.5g Glutamine & BCAA’s


Glutamine References

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BCAAs References

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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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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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