This movement is excellent for working the strong mid-range of the bicep. It also removes much of the shoulder action from the lift. This exercise should not be the soul movement done for bicep work as it will shorten the muscle. You should also be careful not to fully extend you arms when using extremely heavy weights. This can cause you to hyper-extend your elbows.
How to do:
1. Find a comfortable position seated behind a preacher bench holding a pair of dumbbells.
2. Use an underhand grip slightly wider than your shoulders.
3. Lean into the preacher stand, firmly pressing the upper chest muscles against it..
4. Lift the dumbbells slowly upward in an arc until they almost touche the biceps
5. Make sure to keep your upper arms on the pad and don't let your elbows spread apart.