Bodybuilders have been doing preacher curls for decades to build a bigger biceps peak.
PROSECUTION
The incline dumbbell curl is a much better exercise for building the biceps peak than the preacher curl.
EVIDENCE
The biceps are composed of two heads — the long head, which makes up the outer head of the biceps and composes the majority of the biceps peak, and the short head, which makes up the inner biceps.
When you perform the incline dumbbell curl, your arms move behind your body. This stretches the long head of the biceps, which runs over the shoulder joint. When you stretch a muscle before you contract it, that muscle is able to contract with more force (i.e., it is stronger), and so it takes on the majority of the load during an exercise. Since the long head of the biceps makes up the mass of the biceps peak, the incline curl is an effective exercise for building the biceps peak.
When you perform the preacher curl, your arms move in front of your body. This causes slack on the long head of the biceps, which makes it the weaker biceps head during this exercise. Therefore, the short head of the biceps takes the majority of the load during the preacher curl. This makes the preacher curl a poor exercise for building the biceps peak, but a good exercise for building the inner biceps.
VERDICT: INCLINE DUMBBELL CURL
Since the long head of the biceps makes up the majority of the biceps peak and the incline dumbbell curl better targets the long head, the incline dumbbell curl is the better exercise for maximizing the biceps peak.
SENTENCING
Although the shape of your biceps peak is somewhat determined by your genetics, you build more mass on your biceps peak to make it more impressive. To focus more on the biceps peak, include incline dumbbell curls in your training.
Do them early in your workout, such as at the very beginning or following the major biceps mass builder — barbell curls. Of course, you should also include preacher curls in your training to work the short head of the biceps for better balanced biceps development.
