Assaulting your Triceps with One-arm Dumbbell Extensions

By Stephen E. Alway, Ph.D. FACSM

Arms become key players in any great physique. Often the biceps become the focus of a lifter’s workout, but if you want to maximize your upper arm size and contours, you can’t afford to neglect the triceps brachii. This muscle group makes up almost two-thirds of the upper arm girth, with the biceps playing a much smaller role in determining overall arm size. The triceps is also critically important in sports like football, many track and field events and most activities that demand pushing.

Thus, you’ll have added benefits other than possessing a great-looking arm if you invest some time in working the triceps. Although all regions of the triceps must be developed to ensure optimal symmetry, the inner region of this muscle is the largest component and its development is crucial to possessing large arms that can be viewed from any angle. Thus, doing a specializing exercise for the inner triceps is important if your goal is to maximize your triceps development and strength.

Overview of Muscle Structure & Function

The triceps derived its name because it has three clear heads (tri=three; ceps=heads). Although there’s been a recent report suggesting that the triceps may have a fourth head, this idea hasn’t caused anyone to re-write the anatomy textbooks just yet.

The fibers of the triceps attach to a single triceps tendon that crosses the elbow joint posteriorly. The tendon anchors to the olecranon on the ulna bone (the olecranon makes up the point of the elbow). Contraction of the triceps brachii muscle primarily extends the forearm at the elbow (straightens the elbow joint). The long head of the triceps brachii (or the “inner head”) begins on the scapula (shoulder blade) just below the head of the humerus at the shoulder joint. This muscle belly crosses the shoulder joint posteriorly, so that the arm must be moved into shoulder flexion (i.e., arms and elbows lifted high over your head) if you want to fully activate the long head of the triceps. The lateral head of triceps brachii creates the outside (lateral) boundary of triceps. Its fibers run from a small section of bone on the posterior part of the humerus (upper arm bone), starting about one-third of the way down the humerus bone from the shoulder. The medial head of the triceps brachii is deeper and lies between the other two heads of the triceps. It attaches to two-thirds of the upper and posterior part of the humerus bone. The medial head is a rather thick muscle farther up the arm toward the shoulder. It provides enormous depth to the top part of the horseshoe-shaped muscle, which becomes apparent when the elbow joint is straightened.

Seated One-arm Dumbbell Extensions

The arm position of this exercise makes it great for hammering the long (inner) head of the triceps brachii. The shoulder joint is flexed with the arm and forearm directly above the shoulder. This stretches the long head of the triceps because it’s attached to the scapula of the shoulder joint. Because the long head is more fully activated in a stretched position, it provides a greater mechanical contribution to the exercise than either the lateral or medial heads of the triceps.

1. Although the exercise can be done standing, it’s preferable to sit on a chair that supports your lower back. This reduces the probability of obtaining back injury or losing your balance during the part of the exercise when the dumbbell is over your head. The seated version also allows you to direct more of your concentration to the long head of the triceps rather than working on maintaining body stability. If possible, position the chair in front of a mirror so you can see the triceps muscles working and you can monitor your exercise form during the exercise.

2. Sit comfortably on a bench that has a short, vertical back and press your lower back firmly into the back support. Grasp the dumbbell with a semi-pronated position (palm facing the side of the thigh). Lift the dumbbell over your head as if you were going to do a one-arm dumbbell press.

3. Move the upper arm close to the side of your head and keep it perpendicular to the floor. Bend (flex) the elbow and control the weight as it’s lowered behind your head and neck. The elbow should point forward and upward as the weight is lowered. Don’t let you upper arm and elbow swing out to the side or drop downward as you’re lowering the weight. The tension on the long head of the triceps brachii will be reduced if you don’t keep the upper arm in the proper position.

4. Continue to lower the dumbbell until one end either barely makes contact with the trapezius muscle of the upper back, or your arm or elbow flexibility prevents you from lowering the weight farther. Don’t use your trapezius or neck as a trampoline to get the weight moving again, as this could result in serious neck injury and pain. Because you’re working close to your head and with the weight over your head at least part of the time, you need to be very careful, especially as fatigue sets in. A spotter can be a valuable resource during the latter part of each heavy set.

5. Finally, extend your forearm (straighten your elbow) toward the starting position, but stop just short of being fully straight.

6. After several weeks you might want to add a few forced reps to the final 2 sets. Your spotter can help you get 2-3 repetitions after you fail on the way up. However, if you can’t control the weight during the descent toward your upper back, it’s time to stop and/or switch to a lower resistance, even if you’re using a spotter. Make sure you have a competent training partner who will prevent the dumbbell from hitting your neck or head as he helps it move upward. However, don’t go crazy with forced reps on this exercise; you don’t need them on every set.

You should avoid locking out your elbows after each repetition. Preventing the lockout will maintain the resistance on the triceps, rather than transmitting the load through the bones and unloading the triceps. Also, lockouts are rather nasty for the elbow joints, because if they’re done particularly forcefully, the elbows will “ram” the head of the ulna bone (olecranon process) into its fossa on the humerus, and this powerfully compresses the bursa protecting this joint. This may not immediately cause you any major problems, but continued lockouts, especially if they’re done explosively, will likely result in you having sore elbows and bursitis (swelling of the elbow bursa).

You can get a good stretch of the long head of the triceps muscle if you slowly lower the weight behind your head as far as possible. The activation of the long head of the triceps will be improved if the elbows are kept closer to the head, but it will also be a harder exercise than if the elbows move away from the side of the head. Thus, don’t let the elbows come forward (e.g., so your elbow is in front of your nose) or you’ll reduce the stretch on the long head and transfer much of the work to the medial or lateral heads of the triceps.

It’s important to use sufficient resistance in this exercise, and you should be able to work up to some pretty hefty loads, but do so safely. Keep your exercise form perfect, otherwise you may find the dumbbell crashing down on your head and neck. On the other hand, if you have a full stretch and proper arm position and a heavy enough weight, you’ll feel the fibers stretch and strain on each rep as if they’re about to explode. The heavy weights will ensure that the long head contributes substantially to building mass in the triceps brachii muscle. In contrast, light weights tend to recruit the medial and lateral heads to a greater degree than the long head. Therefore, if you’ve been training your triceps with only medium or light weights, chances are your long head will be underdeveloped. Heavier one-arm dumbbell extensions provide a great tool for overcoming this deficit. Nevertheless, warm up the elbows with a couple of light sets before hitting the heavy stuff. The one-arm dumbbell extension is simple enough to perform, but it’s definitely not easy.

Success will never reach those who only think of training hard. So, if you’re someone who’s determined to be successful and you’re persistent and consistent, you can have larger and stronger arms by spring. Your “inner” long head of the triceps will explode with new growth and strength if you faithfully assault your arms with one-arm dumbbell extensions for only few months. Imagine the possibilities of training after a few years!

References

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Illustrations by William P. Hamilton, CMI