2.1. Study Design and Participants
RECRUITMENT, DISEASES
The present study was a randomized, double-blind, placebo-controlled, crossover study. A total of 15 healthy active males were recruited in the present study. Fourteen participants completed all experiments (means ± standard errors; age 22.3 ± 0.3 years, height 172.1 ± 1.7 cm, weight 65.4 ± 2.2 kg), while a participant was excluded because he could not complete all the experiments. We recruited individuals who (1) were aged between 20 and 29 years, (2) were healthy Japanese males, (3) had exercise habits, and (4) were capable of independent decision-making and the provision of written informed consent. The exclusion criteria were as follows: the participants who (1) were considered to have difficulty in exercising due to medical or surgical diseases, (2) were participating in other research or participated in a study requiring the chronic intake of medicines or specific foods within the preceding month, and (3) had undergone blood tests or given blood, with a collection of more than 200 mL of blood, within 12 weeks of this study. All participants were non-smokers and were asked to avoid intense exercise, caffeine, alcohol, and supplements for 24 h before each experiment. They were not accustomed to the repeated-sprint exercise with maximal effort on the cycle ergometer, so the familiarization was conducted before the main experimental trials. The diet pattern on the day before experimental trials was not controlled, but the participants were asked to maintain regular dietary habits throughout the study. Participant recruitment into the study began in June 2019 and ended in July 2019. The last participants completed a cross-over trial in August 2019. This study was conducted in accordance with the Declaration of Helsinki. All participants were given an overview, potential risks, and benefits of the present study and provided written informed consent. The study was approved by the Research Ethics Committees of Ritsumeikan University, Japan (BKC-IRB-2018-071), and Ajinomoto Co. Inc. (2018-013). It was registered in the University Hospital Medical Information Network Clinical Trials Registry (UMIN000037306).