How to Build Rock-Hard Arms

One-Arm Preacher Curls for Bigger Biceps

The biceps is symbolic of upper arm strength and power. I doubt that there’s a serious trainer alive who at some point hasn’t looked in the mirror and wished that he had larger, thicker, stronger and harder upper arms. Of course, you might be the one guy out of 10 million who has biceps genes that seem to grow and strengthen just by walking past a weight stack. But more than likely, you’re like the rest of us mortals, who must sweat blood to develop a strong, rock-hard upper arm. Certainly you get some indirect work for the arms when you do your back work (chins, pull-ups, rows, etc.), but that’s not enough to develop a quality upper extremity. However, by shifting your exercise training orders around and prioritizing the biceps, you can make major improvements in your arm strength and contours in only a few months. Although part of the answer to improving your arm size and power is to increase the amount of resistance you lift for each exercise, shear pounds alone won’t get the job done if each repetition isn’t executed in a proper fashion that recruits all of the muscle fibers possible. With one-arm preacher curls, you don’t need a ton of weight to improve your upper arm, but you’ll have to be prepared to put in some serious effort to force your arms into a new dimension.

Arm Structure

The anterior compartment of the arm contains the biceps and brachialis muscles. The primary function of these muscles is at the elbow joint, although parts of these muscles can also function at the shoulder joint. The biceps brachii is a two-headed muscle. The long head of the biceps brachii muscle has its upper attachment on a bump over the shoulder joint called the glenoid tubercle. It sits on the lateral (outer) part of the arm, and its fibers intertwine with the short head of the biceps as it approaches the elbow. Because the long head of the biceps brachii crosses the shoulder, it becomes involved during shoulder flexion (i.e., bringing the arm forward). This anatomical positioning also means that the arms and elbows need to be back to stretch the long head (such as in barbell curls) to maximize the stretch and activation of this muscle belly during elbow flexion.

The short head of the biceps lives along the inside (medial side) of the arm. At the top, it attaches to the coracoid process just below the shoulder joint. This is a beak-like projection on the anterior (front) part of the scapula bone or “shoulder blade.” The muscle stretches along the medial (inner) part of the humerus bone of the arm and it comes together with the long head of the biceps brachii muscle to form the strong bicipital tendon. The bicipital tendon crosses the front part of the elbow joint and it attaches on the radius bone of the forearm near the elbow joint. Contraction of the biceps muscle can pivot the radius bone at the elbow joint and this supinates the hand (turns the palm toward the ceiling) if the hand begins in a pronated position. Because the short head of the biceps brachii doesn’t cross the shoulder joint, it’s activated just as strongly whether the shoulder and arm are forward (arm flexion) or pulled backward (arm extension) during elbow flexion (e.g., curls).

Brachialis Muscle

This muscle is a very important flexor of the elbow joint. It attaches along the anterior side of the humerus bone throughout its journey down the arm. It crosses the elbow joint anteriorly and attaches to the anterior side of the non-pivoting ulna bone of the forearm near the elbow joint. The attachment to the ulna prevents the brachialis from having any role in supination. As much as 60 percent to 70 percent of forearm flexion is thought to be due to the strength of the brachialis muscle.

Single-Arm Preacher Curls

The preacher bench is also called the Scott bench by some, because it was used extensively by the bodybuilder Larry Scott, who was first to be named Mr. Olympia. Largely with this exercise and bench, he turned pretty average arms into one of the fullest biceps of his day – or any other day. The angle of the preacher bench puts the arm forward with respect to the shoulder (arm flexion), and this puts emphasis on the medially placed short head biceps brachii muscle. The bench angle should be quite steep (about 70° to 80°, not 30° to 45°), otherwise, the arm will be too far forward and activation of the long head of the biceps brachii will be severely diminished. The brachialis muscle is active throughout the exercise. Although the exercise can be used with dumbbells or a barbell, the one-arm dumbbell version is described below.

Exercises done with one limb generally require greater neural and muscle activity than if the same exercise is done with two limbs. In addition, one-arm training prevents the weaker of your two arms from riding along on the shirttails of the stronger arm, as is the case if you were to do two-arm exercises. In the case of the one-arm preacher curl, each arm has to pull its full load on every repetition. Furthermore, it’s difficult to cheat on this exercise, so the muscles of the upper arm get fully activated.

1. If possible, position the preacher bench in front of a mirror so you can monitor your exercise form. Bring the dumbbell up to the shoulder. Turn the hand holding the dumbbell to a supinated position (palms up).

2. Sit on the seat (or stand if your bench doesn’t have a seat) while keeping the dumbbell at the shoulder. Position your armpit (axilla) above the edge of the bench and your triceps comfortably on the bench. Don’t jam your axilla into the top edge of the bench because it’s too easy to cheat from this position. If you have a weak or injured lower back or intervertebral disc, you should first position yourself on the bench and invoke the help of a training partner to lift the dumbbell to your shoulder. This will help to avoid flexing your torso and re-injuring your back as you pick the weight up and get into position.

3. Hold on to the edge of the seat or bench with the free hand. Slowly lower the dumbbell in the working arm toward the floor. It’s important to make this a slow descent and control the lowering of the weight. At best, a fast descent will reduce the effectiveness of the exercise, but at worse, it will result in injury to your elbow joint and bicipital tendon, particularly as it’s straightened.

4. Stop just before the elbow is straight and begin flexing the elbow joint (i.e., curling the weight) so the dumbbell moves closer to your face and shoulder. The bench will prevent you from pulling the elbows posteriorly into arm flexion; this concentrates the efforts to the short head of the biceps.

5. Continue to curl the weight upward toward your face or nose as far as possible. Because the hands are supinated throughout the exercise, the biceps will be strongly activated throughout the range of motion.

6. Stop the downward descent just before your elbow joint becomes completely straight. Then begin the curl back toward your face. This will maintain the tension on the biceps throughout the full range of motion.

7. After eight good repetitions, your biceps should be screaming. You might want to do a couple of partial repetitions once you can’t complete the full range of motion. Alternatively, you can use your nonworking arm to give your fatiguing arm just enough help on the way up to get another two to three repetitions before calling it a set with that arm. However, you’re not done. Move the weight to the opposite arm and repeat the set.

If you can’t control the weight during the dumbell’s descent, then you need to lower the resistance or stop the set to reduce the risk of becoming injured.

The preacher bench is much harder to complete than standing curls. There’s no way to pull the arms into extension to gain additional assistance from the long head of the biceps or to do any “cheating” to swing the weight up with your torso body movement in the one-arm preacher curl, as is often the case with barbell curls. That doesn’t mean that you should be using pencil weights to do the preacher curls or haphazardly thinking about the next thing on your calendar. It will take extreme concentration and dedicated, gut-busting efforts to get the most out of this exercise. Nothing can replace hard work and gallons of sweat for creating quality biceps. Nevertheless, choosing to invest sweat-laden sets in the preacher curl will almost assuredly bring you closer to acquiring strong, thick, rock-hard arms from top to bottom.


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