The JM press primarily targets the long head and medial head of the triceps, with the lateral head contributing during the hardest part of the lift. It’s one of the few pressing movements that meaningfully loads all three triceps heads in a single exercise, which is why powerlifters have used it for decades to build bench press lockout strength.
Which Triceps Heads Get the Most Work
Your triceps has three distinct sections: the long head (the large inner portion running along the back of your arm), the medial head (the smaller, deeper muscle closest to your elbow), and the lateral head (the outer portion that creates the “horseshoe” shape). The JM press hits them in a specific sequence as you move through the rep.
At the top of the movement, when you’re holding the bar at lockout, the lateral head is doing most of the work to keep your elbows straight. As you lower the bar and your elbows bend deeply, the extension phase at the bottom hammers the long head and medial head. This is the portion of the rep where the JM press really distinguishes itself from other triceps exercises. The lateral head then kicks back in as you push through the sticking point on the way up, making the exercise effective for building pushing power through the full range.
The medial head, in particular, is hard to isolate with most exercises. It sits deep beneath the other two heads and tends to be underdeveloped in lifters who rely solely on close-grip bench presses or pushdowns. The JM press loads it effectively because the movement emphasizes elbow flexion while keeping shoulder involvement minimal. This also makes it a strong choice for building the lower portion of the triceps near the elbow joint, an area that contributes to both arm size and pressing strength.
Why the Bar Path Matters
The JM press is a hybrid between a close-grip bench press and a skull crusher, and the bar path is what determines how much triceps work you actually get. A close-grip bench press brings the bar to your lower chest. A skull crusher brings it to your forehead. The JM press splits the difference: you lower the bar to roughly your chin or throat area, depending on your arm proportions. Many coaches cue the throat as the target.
This middle landing zone is what shifts stress away from your shoulders and chest and onto the triceps. Your elbows tuck about 45 degrees from your sides and point toward your feet, staying in front of the bar throughout the entire rep. That forward elbow position is critical. If your elbows drift back under the bar, the movement turns into a standard bench press variation and you lose the triceps emphasis. If they drift too far forward, you’re doing a skull crusher with more joint stress than necessary.
The original version of the exercise, developed by powerlifter JM Blakley, was specifically designed to work the triceps through the exact range of motion used during the last few inches of a bench press lockout. That’s why it remains one of the most popular bench press accessories in strength training.
How It Compares to Other Triceps Exercises
Most triceps exercises lean heavily on one or two heads. Overhead extensions stretch and load the long head. Pushdowns with a rope tend to favor the lateral head. Cable kickbacks can hit the medial head but with relatively light loads. The JM press is unusual because it sequences through all three heads within a single rep, and it lets you use substantially more weight than isolation movements.
The trade-off is complexity. The bar path takes practice to groove, and the movement feels awkward for the first few sessions. It’s not a beginner exercise. But once you have the pattern down, it’s one of the most efficient ways to build triceps mass and pressing strength simultaneously.
Sets, Reps, and Loading
For building triceps size, the moderate rep range of 10 to 20 reps per set tends to offer the best balance of muscle stimulus, joint-friendliness, and mind-muscle connection. This applies to the JM press as well, though its hybrid nature also makes it effective in the 5 to 10 rep range for strength work. If you’re using it primarily as a bench press accessory, heavier sets of 5 to 8 reps make sense. For pure hypertrophy, sets of 10 to 15 at a controlled tempo will keep tension on the triceps longer.
Most people benefit from triceps training spread across 2 to 3 sessions per week, with total weekly volume somewhere between 6 and 16 working sets depending on training experience. The JM press can serve as your primary triceps movement on one of those days, paired with a lighter isolation exercise like pushdowns on another day to cover the full loading spectrum.
Protecting Your Elbows
The JM press places significant demand on the elbow joint, particularly the tendons on the outer side. These tendons have relatively poor blood supply compared to muscle tissue, which makes them slower to adapt to new stress and more vulnerable to overuse. If you jump into heavy JM presses without a gradual ramp-up period, elbow tendon irritation is a real risk.
Start lighter than you think you need to. Spend the first two to three weeks learning the bar path with a weight you could comfortably do for 15 or more reps. This gives your tendons time to adapt while you dial in technique. If you feel a sharp or burning pain on the outside of your elbow during or after the exercise, reduce the weight or frequency before it becomes a chronic issue. Elbow tendon problems are far easier to prevent than to fix once they’ve taken hold.
Keeping your wrists neutral (not bent back) and maintaining that 45-degree elbow tuck throughout the movement also reduces shearing forces at the elbow. Flaring your elbows wide shifts stress onto structures that aren’t built to handle heavy pressing loads in that position.