Hydrogen gas supplementation prior to high-intensity training reduces attenuation of nitric oxide signaling

During the first training week, each group received the assigned supplement (H₂or placebo) for 20 min starting 1 h before training on each training day. The seventh day in each week was a rest day, with no training program scheduled and no H₂or placebo intervention given. During the second week, considered the washout period, no participant received a supplement but participated in low-intensity training. During the third week, each group received the supplement they had not received during the first week (crossover design) while participating in the same high-intensity training as in the first week. Blood samples were collected prior to training on D1, after training on D6, and on non-training D7, of the first and the third weeks.