I don't know any fics, but... I originally read your request as looking for a J2 work-out video. And I started laughing, but then I started thinking...and then I started drooling...and then I thought, damn, that might actually get my ass off the couch! Or even if it was a vid of them working out, like one of those Rocky montages where they're sweating, and carrying a huge log while running through snow, and then sweating some more (the songtrack in my mind, obviously, was 'Eye of the Tiger').

Needless to say, when I clicked your link and saw a fic, I was disappointed.

Stupid brain, learn to read more carefully!

Stupid

Try http://blynnk.livejournal.com/18641.html, which is another fic with Jensen as a (rather aggressive) personal trainer.