Grasp the stirrup using a reverse (underhand) grip.
Tuck your elbow into your side.
Keeping your elbow fixed against your side, exhale as you extend your elbow and push the stirrup downward until your arm is almost fully extended.
Inhale as you flex your elbow and allow the stirrup to rise to the starting position in a controlled manner.
Repeat for the prescribed number of repetitions.
Repeat the exercise with your opposite arm.
Comments and tips
Position your body in such a way as to ensure resistance throughout the range of motion.
Keeping your elbow fixed against your side is important for isolating your triceps.
Your triceps has three heads: long head, lateral head, and medial head. It’s very common to hear instructors (including myself in the past) to say that the cable one-arm reverse-grip triceps push-down emphasizes the medial head. You might also hear some instructors say that it emphasizes the long head. However, according to Per A. Tesch’s classic book Target Bodybuilding, in which he assessed muscle activation using magnetic resonance imaging (MRI), the exercise elicits equal activation of all three heads of the triceps. The only problem with the exercise is that the relative weakness of your wrist extensors limits the amount of weight you can use to overload the muscle.
Other exercises that, according to Tesch’s book, activate all three heads of the triceps include the triceps dip, bench dip, decline French press, triceps rope push-down, triceps v-bar push-down, and dumbbell overhead neutral-grip triceps extension.
Cable one-arm reverse-grip triceps push-down video