I just got done doing the no-equipment required routine, and damn. I'm kinda shaky. I also noticed that when I was doing some of the ab exercises my ab muscles started to...spasm (not sure if that's the right term for it, but oh well) after I held them for 10 or so seconds. This has happened to me all my life whenever I'm in any position that relies heavily on my ab muscles. Perhaps this is a result of my weak muscles....or maybe I'm just not doing the exercise properly.
In any case, I substituted a different tricep pushup than what the workout page recommended, and I skipped the regular pushups and the silly "swing dance" thing on the end. I'll add the regular pushups back in when I feel I'm strong enough to do them properly.
W00t for feeling the buuuuurrrrnn!