Start out by placing a flat bench in front of a low pulley cable that has a straight bar attachment.
Use your arms to grab the cable bar with a narrow to shoulder width supinated grip (palms up) and bring them up so that your forearms are resting against the top of your thighs. Your wrists should be hanging just beyond your knees.
Start out by curling your wrist upwards and exhaling. Keep the contraction for a second.
Slowly lower your wrists back down to the starting position while inhaling.
Your forearms should be stationary as your wrist is the only movement needed to perform this exercise.
Repeat for the recommended amount of repetitions.
This exercise can also be performed sitting down by kneeling and using the bench as a resting position for your forearms. Your wrist can hang over the bench and the same movements as mentioned above can be performed.