Wrist curls flex/ext
with elbows flexed to 90 degrees and arms resting at your side.
With palms facing up, flex your wrist toward your body for 8-12 repetitions. This will work your wrist flexors on the palmar aspect of your forearms. For wrist extensor muscles, simply pronate your forearms so that your palms face toward the ground, perform 8-12 extension repetitions. Do 3 sets for both muscle groups.