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Seated Alternate Dumbbell Curls |
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Written by Stephen E. Alway, PhD, FACSM
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Monday, 23 April 2007 |
Introduction. The siren-like call that resonates from the biceps muscles has largely captured the hearts of almost all that dare to pick up a weight for the purposes of training their bodies for health or fitness. While certainly not the strongest, nor the largest muscle in the body, the biceps has assumed a prominent role as a symbol of human power and strength. It is with this acknowledgement that we will re-explore the components of the arm and a relatively simple exercise for uniformly the building and strengthening and thickening the biceps muscles. This exercise is the seated alternate dumbbell curl. It is especially well-suited for its assigned task because it activates the entire biceps muscle and the deeper and very strong brachialis muscle.
Arm structure. The arm is divided into anterior and posterior compartments by a strong sheet of connective tissue. The anterior compartment contains the biceps and brachialis muscles of the arm and the nerves and the blood vessels associated with these muscles. These muscles function primarily at the elbow joint although parts of these muscles also can function at the shoulder joint.
Biceps Brachii. As the name "biceps" suggests, this muscle has two ("bi") heads ("ceps"). The short-head of the biceps attaches to the coracoid process (a beak-like projection on the anterior part of the scapula bone or "shoulder blade"), near the shoulder. It runs 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 thick bicipital tendon. This tendon crosses the elbow anteriorly, and it inserts into the radius bone near the anterior part of the elbow joint. The bicipital tendon protects important arteries and nerves running through this area to the forearm and hand. Both heads of the biceps work as strong flexors of 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 towards the ceiling), if the hand begins in a pronated position.
When the biceps muscle contracts it pulls on the radius, and pulls it back into a position where the radius lies beside and not on top of the ulna. Although the short-head does not cross the shoulder joint per se, it can have some minor functions at the shoulder because it is attached to the anterior part of the scapula. Its secondary function is most noticeable during arm adduction (bringing the arm towards the center of the body).
The long-head of the biceps brachii muscle has its medial attachment on a bump called the glenoid tubercle, which is directly over the shoulder joint. The long head of the biceps brachii muscle crosses the shoulder joint and therefore, it has a function at this joint. Likely, the early anatomists must have decided that the muscle spanning the greatest distance (tendon plus muscle belly) from one end to the other was to be called the long-head of the biceps brachii muscle. However, by comparison, the muscle belly of the long head of the biceps brachii is not as long as the short-head of the biceps. The long-head of the biceps sits on the lateral (outer) part of the arm, and its fibers intertwine with the short-head as it approaches the elbow and attaches to the bicipital tendon. Because the long-head also crosses the shoulder, it becomes involved during shoulder flexion (i.e., bringing the arm forward).
Brachialis Muscle. This muscle is largely forgotten when most people think about the arm, however, it 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 prevents the brachialis from having any role in supination, but it does not reduce its ability to be a very strong elbow (forearm) flexor. Some studies suggest that 60-70% of forearm flexion is due to the strength of the brachialis muscle. Because this muscle is not affected by the hand position, it is an effective flexor, whether the hand is supinated or pronated.
Seated alternate dumbbell curls. This exercise utilizes a shoulder position that will effectively activate both heads of the biceps, and it also incorporates supination of the hand to ensure that the muscle heads are fully contracted. The brachialis muscle is active throughout the exercise.
1. Move one dumbbell to either side of a bench with a short vertical backrest. If possible, you should position the bench in front of a mirror so that you can closely monitor your exercise form. Usually it is most convenient to first sit on the bench then to lift the dumbbells from off of the floor one at a time. However, if you have a weak or injured lower back or intervertebral disc, you should avoid flexing your torso to pick the weight from off of the floor. Instead, you may wish to have a partner hand the weights to you when you are seated with your lower back pressed firmly against the backrest of the bench. Turn the dumbbells so that the hands are semipronated (i.e., with palms facing the side of the things).
2. Begin by flexing the elbow joint of one arm so that the dumbbell moves closer to your face. After the dumbbell has cleared the thigh, begin to turn the palm towards the ceiling by supinating the hand. Keep the upper arm perpendicular to the floor as you are curling the weight upwards. Try to keep the arm in close to the side of the ribs, but you do not have to be particularly rigid about this. On the other hand, do not swing the weight upward by using body movement and momentum, but make sure that the effort is generated by the arm muscles.
3. Continue to curl the weight upward towards your face as far as possible without letting the elbow travel forward more than a few inches at the top. Hold the weight at the top position, with the arm fully contracted, for a count of two. If you want to really experience an overwhelming but painful contraction, isometrically squeeze the biceps muscle while it is fully contracted and the hand supinated. This muscle "burn" will encompass both heads of the biceps almost equally, as well as the brachialis. The supination of the hand will activate the biceps even more strongly than if you kept the palms facing forward throughout the curl, so be ready for a difficult set if you have not trained it this way before.
4. Slowly lower the weight towards the floor as you simultaneously pronate your hand. Be careful that you do not hit the thigh with the dumbbell on the descent of the weight. It is not necessary to fully pronate your hand so the palm is facing behind you, but rather you can stop when your hand is in a semi pronated position.
5. Alternate contractions between arms until your set is completed. Replace the weight on the floor or rack after the set is finished. You might need to swing your arms backwards and forwards to get the blood back to the hands and forearms quickly before the next set starts. This will help to reduce the accumulation of metabolic byproducts that will increase fatigue in your forearms that are important to maintain a strong grip on the dumbbell. If you find your grip failing early in the set, you might want to attempt to use wrist straps to help keep the grip tight and the set moving for a few more repetitions.
You can add a couple of "forced" repetitions to the last two sets of the exercise if you have your partner help you lift the dumbbell with some slight pressure upwards on the back of your hands (this way you will be keeping the balance of the dumbbell, rather than your partner affecting the balancing by pressing directly on the dumbbell). You should, however, control the weight during the decent. If you think you need your partner to help slow the weight on the downward part of the lift, then you are using too much resistance in your set at this point.
It is easy to see that this is not a particularly complex exercise, but then we are not dealing with 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 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. Nothing can replace hard work and plenty of sweat for creating success, but then, large biceps always look better when they are glistening with sweat and reflecting the gut-busting effort of a warrior lost in the pursuit of success.
References
Basmajian, J.V and C.J. DeLuca. Muscles Alive, 5th Ed. Baltimore, Williams & Wilkins, 1985, pp. 285-286.
Clemente, C.D. "Anatomy, A regional atlas of the human body."2nd edition, Baltimore, Urban & Schwarzenberg Pub. Co. p.43-55, 1981.
Guevel, A., J. Y. Hogrel, and J. F. Marini. Fatigue of elbow flexors during repeated flexion-extension cycles: effect of movement strategy. Int.J.Sports Med. 21: 492-498, 2000.
Kulig, K., C. M. Powers, F. G. 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, G. P., E. W. Olcott, and J. E. Drace. Imaging of skeletal muscle function using (18)FDG PET: force production, activation, and metabolism. J.Appl.Physiol 90: 329-337, 2001.
Rasch, P.J. "Kinesiology and Applied Anatomy" Seventh edition. Philadelphia, London. Lea & Febiger, 136-150, 1989.
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Word count (without references): 1563
Word count (with references): 1734
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