How to Replicate Preacher Curls
The reason preacher curls target the short head of the bicep has to do with a few different biomechanical factors. Mainly, these factors include hand, forearm, and upper arm position.
Supination is when your palm faces up, and pronation is when your palm faces down. The more pronated your hand, the more you work the long head. While the more supinated your hand, the more you work the short head.
Preacher curls typically use an underhand or supinated grip, working the short head.
When your forearm is angled across your body, you accentuate the long head. And when your forearm is angled away from your body, you accentuate the short head.
Preacher curls generally place your forearms in a neutral position or straight ahead. However, grip width can change your forearm angle slightly.
Upper Arm Position
Lastly, keeping your elbows behind your body targets the long head. Whereas having your elbows in front of your body targets the short head.
One of the defining characteristics of preacher curls is that they angle your upper arms forward. So we should emulate this with alternative exercises to work the same muscles.