For novice lifters, the most challenging part of biceps curls is not cheating
by swinging the shoulders and using momentum from the legs. When you do
stability ball dumbbell biceps curls you will not have to worry about any of
these things. Since your elbows and part of your upper arms immobile and resting
on the stability ball you will be able to totally focus on the biceps (unless
you roll the stability ball forward).