This was something he hashed out with Paul Carter from Lift-Run-Bang, who has written about 100-rep curls for a while now. I've thrown them at the end of my workout week before, and you definitely feel it, even with a light weight. I had to use an empty EZ curl bar (15 lbs) to finish all 100 reps the first time. Seems like it'd be good for some hypertrophy.