I mean the highest level I've been to is college camp and it's pretty tough. It's not that it's physically demanding it's that there's a lot going on at once. Weightlifting workouts, position drills, live scrimmages. In between you'll have to learn the playbook and attend position meetings. Now, at the college level the coaches are just trying to push you and develop you into the best player you can be. In the NFL, the coaches already know what they are looking for and are ultimately trying to put together the best 53 man roster they possibly can. So I would imagine that NFL training camp is probably way more demanding because there's very little room for error. If you screw something up, you will probably get cut pretty quickly.
