Branched-chain amino acid (bcaa)
Branched chain amino acids prevent muscle protein breakdown but they don't boost performance.
Branched-chain amino acid (BCAA) supplements are all the rage with endurance athletes these days. One popular idea is that the three BCMs - valine, leucine, and isoleucine - can move through the blood to the brain and decrease the production of serotonin in the brain's interior, thereby lowering mental fatigue (serotonin can create a sense of tiredness - see previous story). A fairly limited amount of scientific research supports this hypothesis.
Ingestion of tryptophan boosted blood levels of the chemical by 500 per cent, and consumption of ample amounts of BCAAs quintupled BCM-blood concentrations, but neither supplement had any effect on performance; time to exhaustion averaged about 120 minutes on all four trials. The researchers concluded that supplementation with BCAAs does not improve endurance during exertions lasting about two hours.
A second study confirmed the idea that BCAAs have little impact on endurance. At the University of Cape Town, eight endurance-trained cyclists pedaled away for four hours in the laboratory at 55% V02max (70 per cent of maximal heart rate) and then tried to cover a 40-kilometre distance as quickly as possible. On separate occasions, the cyclists sipped a 10-per cent carbohydrate sports drink, a 10-per cent drink with BCMs, or a beverage with BCMs alone as they exercised.
Use of the BCAAs didn't help the athletes at all; time for the 40-K trial averaged about 68 minutes, regardless of whether BCMs were ingested, and perceived exertion (how the effort actually felt) was the same in all three trials. The South African researchers concluded that BCAAs might be slightly helpful but that physical fatigue overrode any possible mental relief provided by the BCAA supplementation.
However, a final study carried out at the University of Guelph in Canada detected a possibly positive role for BCAAs. At Guelph, subjects completed two trials in which they exercised their quadriceps muscles continuously for 60 minutes. Prior to only one of the trials, the athletes ingested 77 mg of BCAAs per kilogram of body weight (about a five-gram dose for a 154-pound individual).
As a result of the pre-workout BCAA supplementation, degradation of proteins inside the quadriceps muscles was considerably reduced during exercise. This is a potentially positive effect, since proteins broken down during exercise must be replaced before subsequent workouts so that an athlete can continue training at a high level. In other words, BCM intake before exercise may lead to a lower requirement for muscle repair after a workout - and a quicker recovery from a strenuous exertion.
In previous studies carried out over the last year or so, BCAA supplementation has been linked with better immune-system functioning and superior preservation of muscle mass in athletes undergoing heavy training. Therefore, although an acute dose of BCAAs probably won't directly boost endurance during a competitive event, it's tempting to speculate that taking in three to five grams of BCAAs before and after strenuous workouts might produce some beneficial long-term effects in serious endurance athletes.
('Branched Chain Amino Acid Supplementation Attenuates Net Muscle Protein Degradation during Exercise, ' Biochemistry of Exercise Ninth International Conference, p.51, 1994, 'The Effect of Carbohydrate and Branch-Chain Amino Acid Supplementation on Cycling Performance and Mental Fatigue,' Biochemistry of Exercise Ninth International Conference, p. 53, 1994, and 'Supplementation with Branched-Chain Amino Acids (BCAA) and Tryptophan Has No Effect on Performance during Prolonged Exercise, n Biochemistry of Exercise Ninth International Conference, p. 52, 1994)
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