Synergists: Biceps Brachii (especially the short head), Brachioradialis
Hold a dumbbell in each hand and sit on an inclined bench.
Let your arms hang straight down by your sides, with your palms facing away from the body.
Keeping your upper arms still, exhale as you slowly curl the dumbbells up towards your shoulders.
Hold for a count of two and squeeze your biceps.
Inhale as you slowly lower the dumbbells and return to the starting position.
Repeat for the desired number of repetitions.
Comments and tips
Use the incline dumbbell inner-biceps curl to develop the inner/short head of the biceps brachii, which gives the biceps brachii width.
Sitting in an inclined position, turning the palms away from the body and externally rotating the shoulders stretches the inner/short head of the biceps brachii, forcing it to contribute more to the exercise than the outer/long head of the biceps brachii. However, the brachialis is the target muscle in this exercise.
Only your forearms should move.
Instead of performing the dumbbell curl with both arms simultaneously, you can alternate curling the dumbbell up per repetition. You can also perform all repetitions on one arm first, followed by the opposite side.