4. Discussion
reduction in blood pH
In the present study, we examined the effects of aspartate supplementation on performance and blood pH during repeated-sprint exercise in healthy males. Consequently, the ASP trial evidenced a smaller reduction in blood pH and increased peak cadence during the second exercise set than the PLA trial. To the best of our knowledge, this is the first study to indicate the effect of aspartate supplementation on RSA with concomitant data on acid-base balance.Aspartate supplementation has previously been shown to decrease blood lactate concentration and increase fat oxidation during submaximal cycling at 100 and 150 W [The high-intensity repeated exercise induces a fall in both blood and skeletal muscle pH [Another potential factor of the positive impact is the involvement of metabolites of aspartate. Our results showed that the plasma levels of aspartate metabolic pathway members (glutamate, alanine, citrulline, and phenylalanine) [Given that evidence, the improved peak cadence during the second exercise set in the ASP trial may be associated, at least in part, with the mitigation of blood pH reduction, probably attributable to the acceleration of the TCA cycle, as supported by a study demonstrating the facilitated TCA cycle flux and fatty acid oxidation by aspartate supplementation [At 60 min after exercise completion, the ASP trial evidenced a significantly higher blood pH, HCOThe present study had some limitations. Firstly, we did not control the physical activity level and diet pattern on the day before experimental trials, although participants were asked to avoid intense exercise, caffeine, alcohol, and supplements. In addition, we evaluated the acute effect of aspartate supplementation (2 × 4 g aspartate) or placebo supplementation on the trial days. Therefore, the impact of daily aspartate supplementation on exercise performance during consecutive days of training (e.g., multiple days of competition, training camp) remains unclear. Also, we utilized a relatively small dose of aspartate. Although there is evidence that smaller doses of aspartate show positive effects [