After the first H2 treatment, we further kept a sperm
suspension at 25°C in room air for 24 h and found that
its motility still remained a level approximately 36% of
that of the first treatment (Figure 4). However, it was
not significantly higher than that before treatment. We
then treated this sperm suspension with H2 for 30 min
(second treatment) and kept it at 25°C in room air for