Yeah, it is intense, but if you want to get fit it's probably one of the best ways - would sweat buckets, feel like collapsing and be on an adrenalin surge (not in a bad way) for an hour or two after. I don't know if you smoke, but if you do you might want to cut back a bit or quit, because you will feel the effects of every shit habit (as well as drinking, junk food, etc) during training. And it might just be me, but there's this great bit when you get 'in the zone' and don't think about what you're doing and it all comes together naturally...(I was never great at it though).