Barbell Wrist Curl:

Set up a barbell with weights or get a pre-weighted bar. Place the bar on one side of the bench. Kneel in front of the other side of the bench. Reach over and grab the bar with an underhand grip, shoulder width apart. Place the tops of your arms on the bench, with your wrists hanging over the edge of the bench. Start out with your wrists aligned with your arms, or slightly lower. Inhale.
Keeping your arms stationary, raise your wrists up as high as you can. Pause, squeeze your forearms and exhale. Then lower your wrists back to the starting point. Repeat for reps.