By Stephen Always, Ph.D.
Upper arm development is seen as an important barometer of power and strength. As a result, there are many arm-training articles published each year— so you may be asking what possible new twist can there be that you haven’t already tried? Even old exercises that you have not done in quite a while can help your transformation to thick and dense upper arms. Seated alternate hammer curls are a perfect example. They are especially well suited for their assigned task because not only do they activate the biceps muscle, but also strongly activate the deeper, thicker and stronger brachialis muscle. The brachialis muscle is important because thickening this muscle will push the biceps out and up and increase your overall upper arm mass.
ARM ANATOMY
The well-recognized biceps brachii muscle has two heads. The short head of the biceps attaches on the anterior part of the scapula bone or “shoulder blade,” and it runs along the medial (inner) part of the humerus bone of the arm. The long head of the biceps attaches on the scapula just above the shoulder joint, and it runs down the lateral part of the humerus to the elbow. Near the elbow, it comes together with the long head of the biceps brachii muscle to form the thick bicipital tendon. This tendon crosses the elbow anteriorly, and inserts into the radius bone near the anterior part of the elbow joint. Both heads of the biceps flex the elbow at the forearm. However, the radius bone can pivot at the elbow joint— so because the bicipital tendon inserts on the radius bone, contraction of the biceps muscle can pivot the radius and supinate the hand (turn the palm toward the ceiling) if the hand begins in a pronated position. When the hand is semipronated, such as during hammer curls, the mechanical contribution of the biceps to elbow flexion is greatly reduced— and the other major muscle, the brachialis, is fully activated.
The brachialis 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, and it crosses the elbow joint anteriorly and attaches distally to the anterior side of the non-pivoting ulna near the elbow joint. The attachment to the ulna means that the brachialis is not affected by the hand position, and this makes it an effective flexor, whether the hand is supinated or pronated.
THE EXERCISE: SEATED HAMMER CURLS
This exercise utilizes a hand position that ensures that the brachialis muscle is maximally activated, while the biceps make modest contributions to the exercise
1. Sit on a seat with a vertical backrest and hold a pair of dumbbells at your sides with your hands in a semipronated position (i.e., palms facing toward each other ).
2. Flex the elbow joint of one arm so that the dumbbell moves closer to your face. Keep your hand in a semipronated position throughout the lift. Your upper arm should remain perpendicular to the floor as you are curling the weight upward. Try to keep your arm in close to the side of your ribs, but you do not have to be particularly rigid about this.
3. Continue to curl the weight upward toward your face as far as possible without letting your elbow travel forward more than a few inches at the top.
4. Slowly lower the weight toward the floor. Be careful that you do not hit your thigh with the dumbbell on the descent of the weight.
5. Alternate contractions between arms until your set is completed.
RX TIP
Completing a set of seated hammer curls does not turn out to be a particularly complex exercise, but then the brachialis and biceps are not particularly complex muscles. Because the exercise is done while you are seated, you should be able to hoist some hefty iron in a short time, without the worry of stabilizing your body during the lift or hurting your back. On the other hand, it is a little harder to cheat than with standing curls— but if you try hard enough, cheating can be accomplished. Nevertheless, if the cheating is designed to reduce your effort just to get through the set, then you will be short-circuiting your success.
References:
Basmajian, JV and CJ DeLuca. Muscles Alive, 5th Ed. Baltimore, Williams & Wilkins, 1985, pp. 285-286.
Clemente CD. Anatomy, A Regional Atlas of the Human Body, Second edition, Baltimore, Urban & Schwarzenberg Pub. Co. p.43-55, 1981.
Guevel A, JY Hogrel and JF Marini. Fatigue of elbow flexors during repeated flexion-extension cycles: effect of movement strategy. Int J Sports Med, 21: 492-498, 2000.
Kulig K, CM Powers, FG Shellock and M Terk. The effects of eccentric velocity on activation of elbow flexors: evaluation by magnetic resonance imaging. Med Sci Sports Exerc, 33: 196-200, 2001.
Nosaka K and K Sakamoto. Effect of elbow joint angle on the magnitude of muscle damage to the elbow flexors. Med Sci Sports Exerc, 33: 22-29, 2001.
Pappas GP, E W Olcott and JE Drace. Imaging of skeletal muscle function using (18)FDG PET: force production, activation, and metabolism. J Appl Physiol, 90: 329-337, 2001.
Rasch, PJ. Kinesiology and Applied Anatomy, Seventh edition. Philadelphia, London. Lea & Febiger, 136-150, 1989.
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