Barbell Spider Curl

The spider curl is performed lying face down on an incline bench with the chest supported and the arms hanging vertically toward the floor. That position places the upper arm in front of the body, the opposite of an incline curl, and it means the short head of the biceps works in its most shortened position exactly where the contraction peaks. Supporting the chest against the bench removes momentum completely: there is no way to help with the hips or the shoulders, so the load you see on the bar is the load the biceps actually moves. It is one of the exercises where the peak contraction is felt most clearly. Lower the bar until the arms are fully straight, and avoid shrugging the shoulders to lift it, which is the most common fault here.