Qanon Anonymous has been doing a good patreon series about masculinity cults. This week it's about health perverts and they got to /r/nofap. Apparently the guy who created it was inspired by a post on /r/TodayIlearned about pseudoscientifically boosting your testosterone by not masturbating. I was friends with the guy who created r/TodayIlearned and he had me on as a comoderator in its early days. By not removing that post, I've directly altered the course of history and convinced a generation of reactionaries that they're the Harry Potter of cum.
I think what happens is your testosterone temporarily goes down after ejaculation due to prolactin release, but goes back to normal within 30 minutes. So reactionaries misread the studies and thought that it testosterone levels stay down much longer.
There is a hypothesis that being in the company of people you find attractive (so attractive women for straight guys) can temporarily boost testosterone. So that's why some coaches encourage getting laid. Other coaches discourage it because they fear it could make the athletes exhausted, so they say no sex the day before a game, or that the athletes must be on the bottom and/or put no effort in. (There's a meme about Antonio Conte saying that).
All in all I think it makes no difference and people are just weird about it, because society is weird about sex in general.
I know if I'm doing sports with someone I think of as attractive, I can go much longer. I feel it the next day though