Build Denser Biceps / With Machine Preacher Curls

 

By Stephen E. Alway, Ph.D., FACSM

Although exercises like barbell and dumbbell curls should form the base of your upper-arm training, they do have their limits. These exercises activate the upper two-thirds of the arm quite well, but the lower part of the biceps does not get quite as much direct stimulation. Fortunately, the 21st century has provided us with training tools like machine preacher curls that although rooted in the past, can efficiently result in indestructibly hard, dense and symmetrical upper arms by targeting the lowest part of your biceps.

The preacher bench is a much harder exercise than standing curls. It places stress on the biceps throughout the entire range of motion, and it allows the tension to drop off at the top of the lift like free weights. The preacher bench also prevents you from pulling your arms posteriorly to gain assistance from the long head of the biceps, or from ‘cheating’ to swing the weight up with torso movement, as is often the case with standing barbell or dumbbell curls.

ANATOMY LESSON

The biceps brachii has two heads. The upper attachment of the long head of the biceps brachii muscle attaches just over the shoulder joint on the glenoid tubercle of the scapula bone (shoulder blade). It runs along the lateral side of the humerus bone of the upper arm. The short head of the biceps brachii attaches to the coracoid on the anterior (front) part of the scapula bone below the shoulder joint. The muscle stretches along the medial (inner) part of the humerus bone of the arm and it comes together with the fibers of the long head of the biceps brachii, to anchor on 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 flexes the elbow joint. It can also 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 does not cross the shoulder joint, it is activated just as strongly whether the shoulder and arm are placed forward (arm flexion, as in the case of preacher curls). In contrast, the long head is somewhat unloaded in this position.

THE EXERCISE: Machine Preacher Curls

The preacher bench angle helps to provide an isolated activation of the elbow flexors, which stresses the lower one-third with an emphasis on the short head of the biceps brachii. The angle of the preacher bench puts the arm position forward (arm flexion), and this slackens the long head of the biceps, so it is not emphasized in this exercise. The preacher bench angle should be 60 to 80 degrees, and not less than 45 degrees.

1. Sit on the bench’s seat and place your triceps along the top one-third of the bench. Do not jam your armpits (axillas) into the top edge of the bench, because it is too easy to cheat from this position. Rather, your axillas should be above the edge of the bench and only your triceps should contact the bench.

2. Take a supinated (palms-up) grip on the bar with your hands 12-15 inches apart. Pull the bar so your hands move closer to your face. Take about 1 second to do the contraction phase of the lift.

3. Slowly lower the weight (2-3 seconds) as you extend (straighten) your elbows. If you cannot control the handle when it is being lowered or if it is too heavy to make the descent of the bar last 3 full seconds, reduce the weight of the bar. A fast descent of the bar will at best reduce the effectiveness of the exercise, but at worst, will result in injury to the elbow joint and bicipital tendons.

4. Stop the descent of the handle before your elbows become straight. This will maintain tension on the biceps throughout the full range of motion.

5. Immediately begin to curl the weight upward toward your face as far as possible.

RX TIP

If you want to turn up the heat, try to isometrically squeeze the biceps muscle at the top of the movement. This voluntary isometric contraction will ensure that all of the fibers in the biceps are activated in each repetition, and that none of them get an opportunity to relax at the top of the movement. Because your hands are supinated throughout the exercise, both the short head of the biceps and brachialis muscles will be strongly activated throughout the range of motion.

References:
Gauche E, Couturier A, Lepers R, Michaut A, Rabita G and Hausswirth C. Neuromuscular fatigue following high versus low-intensity eccentric exercise of biceps brachii muscle. J Electromyogr Kinesiol, 2009.
Humburg H, Baars H, Schroder J, Reer R and Braumann KM. 1-Set vs. 3-set resistance training: a crossover study. J Strength Cond Res, 21: 578-582, 2007.
Moore KL and AF Dalley. Clinically Orientated Anatomy. 4th Edition. Lippincott Williams & Wilkins, PJ Kelly, Editor. Baltimore, Philadelphia. pp. 720-723, 1999.
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.
Oliveira AS and Goncalves M. Positioning during resistance elbow flexor exercise affects electromyographic activity, heart rate, and perceived exertion. J Strength Cond Res, 23: 854-862, 2009.
Oliveira AS and Goncalves M. EMG amplitude and frequency parameters of muscular activity: effect of resistance training based on electromyographic fatigue threshold. J Electromyogr Kinesiol, 19: 295-303, 2009.
Semmler JG, Tucker KJ, Allen TJ and Proske U. Eccentric exercise increases EMG amplitude and force fluctuations during submaximal contractions of elbow flexor muscles. J Appl Physiol, 103: 979-989, 2007.

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