Instructions:

1. Sit on a preacher curl bench and hold a dumbbell in one hand with an underhand grip.
2. Rest your upper arm on the preacher bench pad, allowing your arm to fully extend.
3. Curl the dumbbell up towards your shoulder, keeping your upper arm stationary.
4. At the top of the curl, rotate your wrist so that your palm faces up.
5. Slowly lower the dumbbell back down to the starting position, rotating your wrist back to the starting position.
6. Repeat for the desired number of repetitions, then switch arms.