barbell palms up wrist curl over a bench

Sit on a bench with your feet flat on the ground and hold a barbell with an underhand grip, palms facing up. Rest your forearms on the bench, allowing your wrists to hang off the edge. Keeping your forearms stationary, exhale and curl your wrists upwards as far as possible. Hold the contracted position for a brief pause, then inhale and slowly lower the barbell back to the starting position. Repeat for the desired number of repetitions.