May 30, 2023
Cyclists doing a time trial dealt with fatigue better when using a formula featuring branched chain amino acids (BCAAs), a new study has found.
The new research was published in the Journal of the International Society of Sports Nutrition (JISSN). It was the work of a researcher associated with North Carolina State University.
Fatigue in the legs, and in the brain
The paper notes that fatigue in an aerobic event like a cycling time trial has two facets. One, referred to as “peripheral fatigue,” concerns chemical changes in the muscle tissue that includes accumulation of metabolites, protein breakdown, carbohydrate consumption, and depletion of glycogen stores. The second, denoted as “central fatigue,” involves the buildup of serotonin in the brain that is thought to be associated with the subjective feeling of fatigue.
To tackle both aspects of fatigue, the researcher, Renee Nicole Harrington, MS, chose a multi-ingredient intervention for her double-blind, placebo-controlled trial that features BCAAs along with the amino acid l-citrulline and alpha-glycerylphosphorylcholine, commonly abbreviated as Alpha-GPC, which is a natural choline compound found in the brain.
Attacking fatigue from multiple directions
BCAAs have been mainstay sports nutrition ingredients and topics of research for decades. There are three BCAAs: leucine, isoleucine and valine.
These have been shown to have multiple effects when applied to sports nutrition endpoints. According to an ISSN protein position paper, BCAAs have been shown to slow the depletion of glycogen stores during longer-term aerobic exercise.
Also, via a complicated reaction that involves the balance of tryptophan, BCAAs have also been shown to slow the rate of serotonin accumulation, according to the ISSN paper.
The trouble with using BCAAs alone, Harrington stated, is “the excess levels of ammonia that results from increased BCAA metabolism during exercise. Research has shown that ammonia contributes to both central and peripheral fatigue, and thus would nullify the potential benefit of BCAA supplementation.”
However, l-citrulline has been shown to reduce ammonia buildup by promoting nitric oxide synthesis (arginine has a similar effect). In addition, Alpha-GPC, according to Harrington, “may be effective in increasing peak power and delaying neuromuscular fatigue in athletes.”
For her research cohort Harrington recruited 30 male high level recreational cyclists, 30 to 60 years of age, who were all training at least five hours a week. The subjects were told to maintain their regular training regimen, but to refrain from heavy efforts for 72 hours before test day, and not to exercise for 24 hours prior to the test.
The subjects took the test formula (8 g of BCAAs in a 2:1:1 ratio of leucine, isoleucine, valine, 6 g of l-citrulline, and 300 mg of A-GPC) or a placebo (15 g of maltodextrin) for seven days prior to the test.
High intensity, long duration tests done together
The test itself was done on a cycling ergometer and consisted of several phases. The first was a high intensity test to exhaustion in which the resistance was steadily ramped up to get baseline values. That was followed by a 20 km time trial, followed by another high intensity test. The test subjects were instructed to perform all portions of the test while seated to take the effect of body weight out of the equation.
Like much of the research into the effects of BCAAs, Harrington’s results present a mix bag.
She found a significant increase in peak power generated during the time trial by the supplement group versus placebo.
More power, less fatigue, but not more speed
The supplement group’s peak power output averaged 354 watts compared to 322 watts for the placebo group. That might not sound like much, but an almost 30-watt margin on this measure could be a winning difference in an actual race.
However, though the supplemented group could generate higher peaks, the average power output was similar between both groups.
The supplement intervention also significantly increased the time to fatigue during the high intensity portion of the test. The test group lasted an average of almost 20 minutes before having to quit, compared to less than 15 minutes in the placebo group.
Once again, not a huge difference in and of itself, but it could mean a supplemented athlete might be able to get over a climb at a speed that would make the non-supplemented athlete back off.
But, in the measure most readers of the study will be most interested in, the supplement group of cyclists did not go noticeably faster during their time trials than did the cyclists in the placebo group.
“The combination of BCAAs, L-citrulline, and A-GPC used in this study improves cycling performance and may be useful for individuals seeking to improve athletic performance, particularly in disciplines requiring lower body muscular strength and endurance,” Harrington concluded.
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