I've wondered that myself. Lisfranc sounds like a connective tissue problem; back in the steroid era I seem to recall hearing that while you can strengthen muscles, including artificially (not saying THill did that at all), but the surrounding tissue doesn't necessarily strengthen, and can actually weaken. He sure does seem to push himself, and there are only so many protein molecules in his system; is the rest of his body breaking down to feed the growing muscles?