Lie prone on an incline bench with a pair of dumbbells hanging at arms’ length, and perform a curl, keeping the upper arm approximately vertical.
 
Purpose
The spider curl trains the biceps in a shortened position and eliminates any help from the rest of the body.
 
Programming
Generally sets of 6-15 reps are appropriate.
 
Variations
Dumbbell spider curls can be done with the hands in any position, from supinated, neutral and pronated, or done starting in one and rotating to another (eg starting neutral and supinating during extension).