Branched-chain amino acids, arginine, citrulline alleviate central fatigue after 3 simulated matches in taekwondo athletes: a randomized controlled trial

Chen et al. Journal of the International Society of Sports Nutrition Branched-chain amino acids, arginine, citrulline alleviate central fatigue after 3 simulated matches in taekwondo athletes: a randomized controlled trial I-Fan Chen 0 4 Huey-June Wu 0 4 Chung-Yu Chen 3 Kuei-Ming Chou 2 Chen-Kang Chang 1 5 0 , Shuan-Shih Rd, Taichung 404 , Taiwan 1 Sport Science Research Center, National Taiwan University of Sport , 16, Sec 2 Department of Combat Sport, National Taiwan University of Sport , 16, Sec 1, Shuan-Shih Rd, Taichung 404 , Taiwan 3 Department of Physical Education, National Taiwan University of Sport , 16, Sec 1, Shuan-Shih Rd, Taichung 404 , Taiwan 4 Graduate Institute of Sport Coaching Science, Chinese Culture University , 55, Huagang RdShilin District, Taipei 111 , Taiwan 5 Sport Science Research Center, National Taiwan University of Sport , 16, Sec 1, Shuan-Shih Rd, Taichung 404 , Taiwan Background: The decline in cognitive performance has been shown after fatiguing exercise. Branched-chain amino acids (BCAA) have been suggested to alleviate exercise-induced central fatigue. Arginine and citrulline could remove the excess NH3 accumulation accompanied with BCAA supplementation by increasing nitric oxide biosynthesis and/or urea cycle. The purpose of this study is to investigate the effect of the combined supplementation of BCAA, arginine, and citrulline on central fatigue after three simulated matches in well-trained taekwondo athletes. Methods: In a double-blind randomized cross-over design, 12 male taekwondo athletes performed two trials containing three simulated matches each. Each match contained three 2-min rounds of high-intensity intermittent exercise. At the end of the second match, two different supplementations were consumed. In the AA trial, the subjects ingested 0.17 g/kg BCAA, 0.05 g/kg arginine and 0.05 g/kg citrulline, while placebo was consumed in the PL trial. A validated taekwondo-specific reaction test battery was used to measure the cognitive performance after each match. Results: The premotor reaction time in the three single-task tests and the reaction time in the secondary task in the dual-task test were maintained in the AA trial after three matches, while they were impaired in the PL trial, resulting in significantly better performance in the AA trial. These improvements in the AA trial coincided with significantly lower plasma free tryptophan/BCAA ratio, increased NOx concentrations, and similar NH3 concentrations. Conclusions: This study suggested that the combined supplementation could alleviate the exercise-induced central fatigue in elite athletes. Abbreviations: BCAA, branched-chain amino acids; CI, confidence interval; EMG, Electromyography; NEFA, nonesterified fatty acids; NO, nitric oxide; PRT, premotor reaction time Premotor reaction time; Dual task; Tryptophan; Taekwondo Background The central nervous system plays an important role in development of exercise-induced fatigue [ 1 ]. The increased cerebral serotonin (5-hydroxytryptamine) concentration during exercise may be one of the factors responsible for central fatigue. Cerebral serotonin could result in the feeling of lethargy and tiredness, and the loss of central drive and motivation [ 2 ]. To support this hypothesis, endurance capacity was significantly decreased by the administration of serotonin agonists, while it was increased by serotonin antagonists in humans and rats [ 3–5 ]. In addition to the decreases in muscle output, it has been known that cognitive and skill performance was also impaired as exercise progresses. The studies using functional magnetic resonance imaging have shown that the brain regions involved in high-order motor tasks, such as prefrontal cortex and supplementary motor areas, were affected during fatiguing exercise [ 6, 7 ]. As the result, cognitive performance, measured by an auditory choice reaction task and reaction time to visual stimulus, were progressively impaired after exhausting exercise [ 8, 9 ]. The performance in a color-word test was also decreased after a 30-km crosscountry race [ 10 ]. Furthermore, several studies reported impairments in sport-specific skill performance after strenuous exercise [ 11–13 ]. Branched-chain amino acids (BCAA), including leucine, isoleucine, and valine, have been suggested to alleviate exercise-induced central fatigue. Plasma BCAA could compete with tryptophan, the precursor for cerebral serotonin synthesis, for the L-system transporter to cross the blood brain barrier [ 14 ]. Animal studies have shown that BCAA could increase running time to exhaustion by reducing exercise-induced cerebral synthesis and release of serotonin [ 15, 16 ]. However, humans studies have failed to find ergogenic effect of BCAA supplementation [ 17, 18 ]. One possible drawback for BCAA supplementation in humans is the excess hyperammonemia due to increased BCAA metabolism during exercise [ 18–20 ]. Elevated cerebral uptake and ac (...truncated)