We had Enya music for kickboxing last night. Enya with a techno beat.
D'you know how hard it is to actually kick and jab and bob and weave when you're laughing? Pretty hard.
Also, when you're doing sit-ups, and you let your mind wander, don't let it wander to anything funny, like, say, this blog, because I tell you what's even harder than kickboxing when you're laughing - doing sit-ups!