With only a single event, it could be something as boring as what music you listened to during a workout. That can actually have a pretty strong influence, where maturation at best has a small influence, if any. If that weren't the case, the Olympics wouldn't be full of athletes fucking, because releasing their sperm somehow has a negative effect on performance. (If you believe it's only masturbation, not sex, I'm going to need you to consider what mechanism could possibly effect this, because I can't think of any.)