limbering for timbering 

(v.) doing exercises, often crunches or push ups, before sex in order to look marginally more fit; to do a warm up routine in preparation for raucous sex.

Girl 1- "Isn't Mike coming over?"
Girl 2- "Yeah!"
Girl 1- "Then why are you doing crunches?"
Girl 2- "I'm just limbering for timbering. It's gonna get rough tonight, plus I want to burn some flab."

limbering for timbering by Da Sperminator March 31, 2011