Could masturbation affect track runners?

Not unfavorably: This won't slow you down, any more than it will make you short, stupid, hairy, smooth, or an unfit husband / father. In fact, most teens who try not to enjoy their bodies every few days end up unable to sleep or focus on things they need to be doing. Stop worrying, and avoid people who try to frighten you about your own developing mind and body. Love responsibly ; good luck running.