I have been doing various bicep exercises to help rebuild and strengthen my left bicep after the tear it experienced back in November. So far I can say without a doubt spider curls, both inner and outer grip, are working the best. I superset them and I can't use a lot of weight but they seem to be the only exercise that minimizes brachioradialis involvment and gives my left bicep a pump.
With other traditional curling exercises, I am finding that my body is recruiting the brachioradialis muscle more since both bicep heads tore back on the tendon but the short head tore the most. I thus have a severe leverage problem with the short head when trying to curl since it is higher on the tendon and has less muscle fibers now. The body instinctively recruits additional fibers to compensate for the imbalance. Since the brachioradialis is involved in elbow flexion, it was getting used. By doing spider curls, it forces my body to primarily use only the long and short bicep heads. I really don't care about the amount of weight I curl anymore and I know my days of strict heavy curling (outside of cheat curls) are over but I can tell you super setting outer and inner grip with just 45 Lbs hits my biceps harder than when I was doing 135Lb olympic bar curls :-)
John