Dumbbell one arm wrist curl

Sit on a bench or chair with your feet flat on the ground. Hold a dumbbell in one hand with an underhand grip, resting your forearm on your thigh. Allow your wrist to extend, letting the dumbbell roll down towards your fingers. Slowly curl your wrist back up, bringing the dumbbell towards your forearm. Repeat for the desired number of repetitions, then switch to the other hand.