The Supplementation of Branched-Chain Amino Acids, Arginine, and Citrulline Improves Endurance Exercise Performance in Two Consecutive Days.

The central nervous system plays a crucial role in fatigue during endurance exercise. Branched-chain amino acids (BCAA) could reduce cerebral serotonin synthesis by competing with its precursor tryptophan for crossing the blood brain barrier. Arginine and citrulline could prevent excess hyperammonemia accompanied by BCAA supplementation. This study investigated the combination of BCAA, arginine, and citrulline on endurance performance in two consecutive days. Seven male and three female endurance runners ingested 0.17 g·kg-1 BCAA, 0.05 g·kg-1 arginine and 0.05 g·kg-1 citrulline (AA trial) or placebo (PL trial) in a randomized cross-over design. Each trial contained a 5000 m time trial on the first day, and a 10000 m time trial on the second day. The AA trial had significantly better performance in 5000 m (AA: 1065.7 ± 33.9 s; PL: 1100.5 ± 40.4 s) and 10000 m (AA: 2292.0 ± 211.3 s; PL: 2375.6 ± 244.2 s). The two trials reported similar ratings of perceived exertion. After exercise, the AA trial had significantly lower tryptophan/BCAA ratio, similar NH3, and significantly higher urea concentrations. In conclusion, the supplementation could enhance time-trial performance in two consecutive days in endurance runners, possibly through the inhibition of cerebral serotonin synthesis by BCAA and the prevention of excess hyperammonemia by increased urea genesis.

Salivary Immuno Factors, Cortisol and Testosterone Responses in Athletes of a Competitive 5,000 m Race.

The exercise-stress model can be a model of temporary immunosuppression that occurs after severe physical and psychological stress. It also allows for the study of interactions between the endocrine and the immune systems. This study examined changes in salivary hormonal and immune factors in athletes in response to physical and psychological stress in a 5,000 m running competition. Eighteen endurance-trained runners (9 males and 9 females) participated in this study. All participants completed a competitive 5,000 m race. Saliva samples were collected 10 min before (PRE) and 10 min after (POST) the competition. Saliva was analyzed for α-amylase activity, concentrations of salivary immunoglobulin A (SIgA), lactoferrin, cortisol, testosterone and total protein. Although the concentrations of salivary TP, SIgA, lactoferrin, cortisol and α-amylase activity were significantly increased immediately after a competitive 5,000 m race, the secretion rates of these factors were not significantly altered in both male and female groups. Additionally, basal levels of SIgA and α-amylase activity were significantly higher in female runners than in male runners. This gender difference still existed after the race. The secretion rates of testosterone decreased significantly after the race in the male, but not in the female group. Moreover, testosterone-to-cortisol (T/C) ratios were significantly lower post-competition compared to pre-competition in both male and female athletes. The T/C ratio had been used as a performance index for athletes. Whether there are correlations between these changes of their physiological characteristics and better running performance need further investigations.