Sex-flex

A personality trait formed of boasting about sex/sexual activities usually done by a person who has recently begun having sex after a long dry spell. The change in subject to sex in the group is also likely to have been brought up by the same person, making tenuous links to otherwise non-sexual discourse.
(Flexing about sex)

Person 1: Jake wouldn’t stop going on about how many times he has sex last week
Person 2: yeah he’s got sex-flex at the moment