Neither. It is best during the game. Proof; Kasparov 1985
Is it better to have sex before or after a game of chess?

The game of chess could be a metaphor for sex. There's nothing on the chess board that has not been part of some well-known sexual stereotype.

Must have read your advice that bumping is good for you and you recommend it... Well done. You have another follower :)

Madam Marfona likes it when Louis Lunchbox is in before the lock... Phner Phner Mrs (acknowledged source... Ladybird book of Carry On rejected jokes)
I know in some sports one is expected to refrain from sex before the game to conserve energy. Is it that way in chess? Is it generally better to have or be free of sexual tension before playing?