Yesterday I setup a slip rope in my shop, I must have done hundreds of rolls. My legs were on fire. The last time I felt like that was when I was in the Army, I remember the ruck marches that would go for ten miles and all the squats we would do every day. You try and walk but your legs would give out.
I got through it, then did 100 crunches.
I read somewhere that Mike Tyson would do 2500 crunches per day. That is my goal too. I want to be doing thousands of reps of each exercise (crunches, squats, punches, jump rope skips, etc).
I will get there soon.