Stand facing the machine with the arms next the body and elbows bent and grasp the handle with an underhand grip:
• Inhale and extend the forearms by straightening the elbows, keeping them tucked into the body.
• Exhale at the end of the movement.
The underhand grip isolates the medial head of the triceps brachii and precludes working with heavy weights.
When extending the forearms, the anconeus and wrist extensors also contract.
The extensor carpi ulnaris, extensor digitorum, extensor digiti minimi, and extensors carpi radialis longus and brevis keep the wrist straight with isometric contraction during the exercise.