The original 1 has two challenges (six sprints and then three hill climbs). The revised 1 has three challenges (six hill climbs, three sprints, and a long/fast paced hill climb). You can get the specifics on the CC site. And of course, the music is different in the revised 1 and 2. Volume 1 and 2 revised has music by Todd Washburn instead of the other dude who did the original 1 and 2 (can't remember his name). I think the revised 2 is the same as far as challenges go in the original 2, just different music.