I did day 2 of the 30 day shred yesterday. It took me 3 days to do the two workouts though... because I got sore after Day One and had to take some time to recover!
I looked it up and it's apparently called DOMS:
http://en.wikipedia.org/wiki/Delayed_onset_muscle_soreness
Wikipedia said that stretching does not prevent soreness but just in case, I did some extra stretching yesterday. I think maybe it helped? We'll find out tomorrow, I guess ha.
Do you get sore after you work out? What do you do to prevent soreness?