Cardio is really hard and intense out of all, abs and legs in my opinion. I like this video by Caroline Girvan for one reason. The fact that it made me sweat without having to jump up or down or anything like that. I was looking at it and it was like easy to be until I tried it out for myself. I think it would be a good try for those who wish to have a cardio day. YouTube, Caroline Girvan is her channel name.