The medial head of your tricep helps stabilize your elbow and fills out your upper arm for a proportional look. While you can't entirely separate it from the other heads of your triceps muscle, you can choose exercises that emphasize its involvement.
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Three Heads, No Monster
Why all the fuss about which head of your triceps you're working? If you're not bodybuilding, it usually doesn't matter — all you have to do is choose triceps exercises that work your arms from a variety of angles, and include them in the full-body workouts prescribed by the U.S. Department of Health and Human Services to maintain optimal health.
But if you've been bodybuilding or want to get started, and if you think you need some more volume on the medial side (inner-arm side) of your triceps, it pays to focus on the medial head of the triceps. That's the side that's closest to your body, and it tends to be particularly active when your arm is flexed at the shoulder. The other heads of the triceps are the long head (which crosses both your elbow and shoulder joints) and the lateral head, which is easily visible from the side.
Testing Tricep Activity
The information about your medial triceps and shoulder angle isn't guesswork. Most EMG studies of the triceps track activity in the long and lateral heads, but one of the few studies that also tracked activity in the medial head was published in the May 2018 issue of Acta Orthopaedica et Traumatologica Turcica.
In that study, researchers used electromyography (EMG) to evaluate how different degrees of shoulder flexion affected the activity of the three triceps heads. The key takeaways are: While you can't completely isolate one head of the triceps from the others, you can strategically select exercises that emphasize the head you most want to develop.
In the case of the medial head tricep, that means getting your elbows out in front of you. The study showed that the medial head showed the most activation at 90, 135 and 180 degrees of shoulder flexion. The lateral head of your triceps kicks in more strongly as your arm is raised too, but the medial head generates more force.
Medial Head Tricep Exercises
So how can you shift the most emphasis possible to your triceps? With limited exceptions, the best approach is to get your elbows up and away from your body, but still keep them tucked close together (not splayed out) to minimize the involvement of other muscles. And when in doubt, opt for an underhand or neutral hand position.
1. Overhead Triceps Press
According to the Acta Orthopaedica study, working your arm at (or near) 180 degrees of shoulder flexion — with your upper arm pointing straight up — increases involvement of the medial head tricep. So although the overhead triceps press is often reckoned as an exercise for the long head of your triceps, there's a strong argument for using it to develop your medial triceps too.
- Hold one dumbbell in your right hand and press it straight up over your shoulder. Your thumb should point back behind you. Squeeze your core to keep your torso stable — this is your starting position.
- Bend your arm, keeping your elbow close to your ear as you lower the weight behind your head; your thumb should point down.
- Straighten your arm, pressing the weight back up to the starting position to complete the repetition.
2. JM Press
Any variation of the close-grip bench press is acknowledged as an excellent workout for your entire triceps. However, the JM press — sometimes called the Blakely press — is considered especially useful for building mass in your medial triceps.
- Adjust a barbell to light weight, and rack it over a flat bench.
- Lie on your back. Grasp the bar with hands shoulder-width apart or slightly narrower, and lift it off the rack.
- Keep the bar under control as you lower it down toward your neck. In order for this to happen, you must let your elbows "fold" out of the way, pointing down toward your feet. According to ExRx.net, the bar can come down anywhere between your chin and your upper chest.
- "Unfold" your arms by pressing the bar back up in a straight line.
This exercise takes some getting used to, and because it de-emphasizes involvement of your pectoral muscles, you're going to lift a lot less weight than you're used to putting on the bar for bench presses. Always prioritize technique over weight — it's the best way to make sure you're actually targeting the medial tricep head.
3. Triceps Push-Downs
There are many different theories about which hand position makes for the best medial head tricep development during triceps push-downs, and little to no clinical evidence to support them. But at least everybody agrees that this exercise is good for both the medial and lateral heads of your triceps — and it's generally accepted that using an underhand grip on a straight handle will emphasize your medial head tricep development.
- Attach a straight bar handle to the high pulley on a cable machine.
- Stand facing the pulley and take the bar in an underhand (palms up) grip, keeping your elbows tucked close to your body.
- Squeeze your core to stabilize your torso as you straighten your arms, pressing the handle down as far as you can.
- Bend your arms, and let the handle rise back up to the starting position.
4. Diamond/Triangle Push-Ups
According to a study sponsored and published by the American Council on Exercise, the triangle push-up — sometimes called a diamond push-up — is one of the best workouts for both the long and lateral heads of your triceps. So what's it doing in a list of exercises for the medial tricep head?
Two reasons: One, the ACE study didn't test activity in the medial triceps, but this exercise is generally accepted as being excellent for the medial head of your triceps too. And two, because you don't need any equipment for this exercise, you can drop and crank out a set of these any time, anywhere.
- Assume the standard push-up position, but place your hands together so that your thumbs and pointer fingers touch, creating the shape of a triangle or diamond.
- Bend your arms, lowering your chest toward the ground.
- Straighten your arms to return to the starting position.
Body position is important for any variation on the push-up — but especially this one, because it's very challenging compared to a normal push-up. Use a mirror or a friend's help to check your positioning throughout the motion: Your body should stay flat like a board. If your hips pike up or sag down past the line of your body, focus on maintaining a tight core — and if that doesn't work, consider bending your knees to assume a modified push-up position.
If a full set of triangle push-ups genuinely doesn't challenge you, you might consider upgrading to handstand push-ups. These aren't a beginner exercise, but they do put your arm in the perfect position to maximize involvement of the medial head triceps. Go ahead and use a study wall for support and remember the No. 1 rule of ice climbing, tightrope walking and handstand push-ups everywhere: Don't fall.
- Health.gov: "Dietary Guidelines for Americans, 2015-2010: Appendix 1. Physical Activity Guidelines for Americans"
- Acta Orthopaedica et Traumatologica Turcica: "The Different Role of Each Head of the Triceps Brachii Muscle in Elbow Extension"
- ExRx.net: "Barbell JM Bench Press"
- American Council on Exercise: "ACE-Sponsored Research: Best Triceps Exercises"