“Why don’t boxers have sex the night before a fight?”/“They don’t fancy each other.”

A boxing riddle is:
     
Q: Why don’t boxers have sex the night before a fight?\
A: They don’t fancy each other.

   
The question sounds like one asking how a boxer prepares for a fight. Abstaining from sex the night before a fight could be a way to conserve energy. However, the answer assumes that the question was being asked about why boxers don’t have sex with each other—not about abstinence from sex.
   
“Why don’t boxers have sex before a fight? Because they don’t fancy each other” was posted on the newsgroup microsoft.public.dotnet.framework.aspnet on July 4, 2006. “Q: Why don’t boxers have sex the night before a fight? A: Because they don’t fancy each other. (not mine, Jimmy Carr’s)” was posted on Twitter by The Fairsley Difference on May 30, 2009. “A classic from @jimmycarr: Why don’t boxers have sex before a fight? Because they don’t fancy each other…” was posted on Twitter by Jay on September 25, 2009.  British-Irish comedian, presenter, writer and actor Jimmy Carr probably originated the joke.
     
   
9 February 1997, Chicago (IL) Tribune, “A funny search for love and a serious look at aggression” book reviews by Carolyn Alessio, sec. 14, pg. 6, col. 2:
Sandoval awkwardly informs Denfeld that no boxer should have sex for two weeks before a fight; when male boxers have sex, they end up losing power in their legs. Denfeld thinks this is a superstition, but as she does with many of her experiences in the gym, she ponders it long afterward.
 
Google Groups: microsoft.public.dotnet.framework.aspnet
Deleting row from GridView causes ArgumentOutOfRangeException during System.Web.UI.WebControls.Grid­View.set_SelectedIndex(Int32 value)
Jan Hyde
Jul 4, 2006, 9:04:04 AM
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Why don’t boxers have sex before a fight?
Because they don’t fancy each other.
 
Twitter
The Fairsley Difference
@ColonelDeDecker
@serafinowicz Q: Why don’t boxers have sex the night before a fight? A: Because they don’t fancy each other. (not mine, Jimmy Carr’s)
2:30 PM · May 30, 2009
   
Twitter
Jay
@litotist
A classic from @jimmycarr: Why don’t boxers have sex before a fight? Because they don’t fancy each other…
7:07 AM · Sep 25, 2009
   
Twitter
Derren Brown
@DerrenBrown
Great but can’t ALL be Jimmy Carr RT @AnnekaHansen why don’t boxers have sex before a fight?  Because they don’t fancy each other.
7:08 AM · Jan 12, 2010
 
Reddit—Jokes
Posted by u/[deleted] January 12, 2014
Why won’t boxers have sex before a fight?
The don’t fancy each other.
 
Reddit—Jokes
Posted by u/MangoMandarin April 17, 2015
Why don’t boxers have sex before a fight?
They don’t fancy each other.
     
Reddit—Jokes 
Posted by u/dead4seven May 13, 2015
Why don’t Boxers have sex before a fight?
They don’t like eachother
 
Reddit—Jokes
Posted by u/ontheroadtofindout August 4, 2016
Why don’t boxers have sex the night before a fight?
Cos they don’t fancy each other.
   
Reddit—Jokes
Posted by u/spoilingattac April 27, 2019
Why don’t boxers have sex before a big match?
They’re just friends.
 
Reddit—Jokes
Posted by u/Kyle______ July 28, 2020
Why don’t professional boxers have sex before a fight?
They probably don’t like each other.
   
Reddit—Jokes
Posted by u/castle_03 May 27, 2023
Why don’t boxers have sex the night before a fight
They just don’t really like each other