I really don't know what I did, if anything. I didn't do anything different that day then I normally do, other then doing pad work with a really really short guy (me:6'4 him: 5'4) I didn't even do that much. Just some skipping/jogging/pad work/shadow boxing. But didn't stick around for the mma class after because my legs were killing me. Now 2 days later I still can't walk properly, my calfs are on fire and very very very tight. Defiantely feels like more then just regular stiffness after a workout. I work out my legs on a regular basis, as well bike/rollerblade/jog/climb quite often, and have never had my legs do this before.