Muscle Group: Forearms
Hold a dumbbell and sit on a bench. Place your forearm on your thigh so that your wrist and the weight extend out over the knee, with your palm and the inside of your forearm facing upward. Bend forward, use your free hand, and take hold of the elbow of the working arm to stabilize it. Bend your wrist and lower the weight as far as possible, opening your fingers slightly to let the dumbbell roll down out of your palm.
Close your fingers again and, keeping the effort in your wrist, rather than the biceps, curl the weight up as high as you can. Complete your reps, then repeat using the other wrist.