The lying single arm extension trains both functions of the triceps brachii (elbow extension and shoulder extension) by having you lower the dumbbell behind or to the side of your head rather than directly to your face.
This lifting motion necessitates some backward shoulder movement, which in turn places the long head of your triceps (the biggest head) under an enhanced eccentric stretch. As such, despite only requiring one weight, the single arm lying tricep extension is an effective exercise for building mass.
Related: Decline triceps extension
One arm lying tricep extension exercise details
- Also Known As: Single arm lying triceps extension, one arm dumbbell skull crushers
- Main Muscles: Triceps
- Exercise Type: Strength
- Exercise Mechanics: Isolation
- Difficulty Level: Intermediate
- Equipment Needed: Dumbbell, bench
How to do a one arm lying tricep extension
- Grab a dumbbell with a neutral grip and lie on a weight bench.
- Press the weight up so that your elbow is locked out.
- Lower the weight behind or to the side of your head.
- Descend until you feel an intense stretch in your triceps.
- Flex your triceps to reverse the motion and keep doing until your elbow reaches full extension.
- Repeat the movement with your other arm after doing all your reps for the first arm.
- Perform 3-5 sets of 10-20 reps per side.
Single arm lying tricep extension benefits
Like the side leaning triceps extension, the one arm lying dumbbell triceps extension enables you to train both of your arms completely separately. As you'll soon learn, this unilateral training style has some excellent benefits when it comes to muscle symmetry and triceps isolation.
Enhanced mind-muscle connection
When your brain only has to focus on moving one limb at a time, when it only has to focus on stretching and squeezing one triceps at a time, you can naturally evoke a stronger mind-muscle connection because your brain doesn't need to split its attention between two sides of your body.
This enhanced mind-muscle connection will carry over nicely to your other tricep exercises like the lying cable extension because you'll be better at activating your triceps in general and during lying movements in particular.
The one arm lying tricep extension is especially useful for improving the mind-muscle connection with your weaker triceps because the exercise really enables you to hone in on each of your arms.
Oftentimes, when you lift both weights together, your weaker side gets left behind, and, as a result, you don't feel the exercise as much in that arm. But when you train your triceps separately, you can dedicate 100% of your attention to each side of your body and enhance your muscle activation because of it.
Don't be fooled by the fact that you're only lifting one dumbbell; the one arm dumbbell lying triceps extension is capable of building just as much mass as the pronated triceps extension.
In addition to training all three tricep heads well, the lying single dumbbell extension gives additional emphasis to the most prominent of these heads—the long head—because of the shoulder movement.
Since you're lowering the dumbbells behind or to the sides of your head rather than directly to your forehead or nose, your shoulders naturally have to move backward slightly, which in turn puts the long head of your triceps under a superior eccentric stretch.
The eccentric portion of the rep is critical for hypertrophy because it's the part of the rep where most of the muscle fibers get broken down. So if you want to maximize the benefits of the lying one arm extension, make sure to bring the weights back and down rather than just straight down to your head.
Better triceps symmetry
While exercises like the decline cable triceps extension can certainly build size, they're not optimal for developing muscle symmetry because you're lifting the same weight with both hands.
Therefore, during bilateral exercises, your stronger triceps muscle can often dominate the movement and receive far more muscle-building tension as a result.
Conversely, when you perform a one arm dumbbell lying tricep extension, you're forced to lift each weight separately, which means that it's impossible for your stronger triceps to assist your weaker triceps.
So if you want to enhance your upper body aesthetics by sculpting a proportional pair of arms, then it's definitely worth your time (because your sets will take longer) to do a unilateral lying tricep extension or a single arm cross body tricep extension.
Single arm lying tricep extension drawbacks
Like the alternating dumbbell lying triceps extension, the one arm lying triceps extension also has a couple of drawbacks that you should consider before including it in your workout program.
There's no getting around the fact that your sets will take significantly longer when you do one arm lying tricep extensions (or any other unilateral exercise, for that matter).
This is simply because you're training your triceps one after the other rather than at the same time like you would during floor tricep extensions.
The question is: Is the extra workout time worth the enhanced muscle symmetry?
If you lack a solid foundation of triceps size, then the answer is most likely no. After all, you need enough muscle mass to make muscular symmetry apparent.
On the other hand, if you already have decent arm development and want to reduce any size asymmetries that you might have, then it's definitely worth your time to do a few sets of the single arm dumbbell lying tricep extension.
In summary, the more significant and noticeable your tricep muscle imbalances are, the more sets (and the earlier on in your workout) you should do unilateral exercises like one arm lying triceps extensions.
Barbell exercises are highly effective for building mass because they enable you to overload the target muscles with the heaviest possible resistance levels.
But given that dumbbells require more stabilization than barbells, you're going to need to lift lighter on single arm lying tricep extensions than you would on barbell-based movements.
Since the triceps are a very fast-twitch muscle group, you could argue that performing single arm lying triceps extensions is suboptimal for hypertrophy.
However, the fact that you can put forth a better mind-muscle connection when you only have to focus on training one triceps at a time could well make up for the reduced resistance.
As any bodybuilder can tell a powerlifter, the potential for overload is not the only measure of an exercise's effectiveness (though it's undeniably a major part of it). Often, the amount of tension that you can put your muscles under is more important than the number on the side of the dumbbell.
Read More: Incline triceps extension
If you want to develop triceps that are both symmetrical and muscular, then the one arm lying tricep extension is an excellent exercise for the job because it enables you to completely isolate both of your triceps via unilateral training.
While you'll need to reduce the resistance a bit to enjoy the exercise's best effects, you'll still be putting plenty of tension through your muscles, which is what counts the most when it comes to stimulating hypertrophy (muscles, as pieces of meat, can't see how many pounds or kilos you're lifting).