Written by Stephen E. Alway, PhD, FACSM
24 April 2007
Workers who make their living from intense and prolonged manual labor, often possess outstanding forearm strength. This comes from lifting, twisting and rotating heavy objects, not just lifting a weight up and down in the same plane. As bodybuilders, we don't typically rely on our jobs to develop the muscles that will win competitions. Nevertheless, even among bodybuilders who should know better, "automation" in equipment has led to reduced indirect activation of the forearm muscles. For example, instead of lifting a barbell to a shoulder press station, then loading the bar with weights (requiring forearm activation to lift and position the plates on a bar), we sit under a weight stack and adjust a pin. The same thing happens for seated incline, decline or flat bench presses.

Don't get me wrong; I am not against such machines or automation. However, the downside is that these machines tend to minimize the work required by the forearms, and this weak link is never allowed to get stronger unless you intentionally put some serious effort into improving them. One way to improve forearm strength and mass, while adding mass to the upper arms, is by stepping back through time and shaking the dust off an era that has hidden Zottman's curls. The Zottman curl is an unusual exercise that incorporates all the elements needed to activate the forearm musculature and because it removes much of the mechanical advantage of the biceps, it also strongly activates the fibers of the brachialis muscle of the arm.

Muscles Activated  
Although the brachialis muscle is covered by the biceps and is not easily visible, it's a very important flexor of the elbow joint. This muscle attaches from along the anterior side of the humerus bone to the ulna bone near the elbow joint. The attachment to the ulna prevents the brachialis from having any role in supination, but it is a very strong elbow (forearm) flexor. Some studies suggest that 60-70 percent of forearm flexion is due to the strength of the brachialis muscle. To strongly activate this muscle, the hand should be semi-pronated (or fully pronated) during elbow flexion.

The brachioradialis muscle begins at the humerus bone just above the lateral epicondyle of the elbow (a  'bump' on the outside of the humerus bone just above the elbow joint). It attaches distally by a long tendon along the lateral side of the radius bone near the wrist. This forearm muscle assists the biceps and brachialis in elbow flexion.

The extensor carpi radialis longus muscle is partly covered by the brachioradialis. The muscle bellies are separate and provide a clear delineation when you reduce your body fat stores. This muscle arises above the lateral epicondyle of the humerus, but just below the proximal attachment of the brachioradialis. It attaches distally on the back (dorsum) of the base of the second metacarpal bone of the hand. The hand is made up of five metacarpal bones, each of which connects to its respective phalange, or finger bones. The extensor carpi radialis longus extends the hand at the wrist joint.

The flexor carpi radialis longus muscle is a long narrow muscle located over the radius bone of the forearm. Its thick muscle belly becomes a round cord as it approaches the wrist. It runs from the medial epicondyle of the humerus to the base of the third finger. It flexes the wrist joint and moves the lateral (thumb) portion of the hand toward the shoulder (abduction of the wrist). The flexor carpi ulnaris muscle is attached to the medial epicondyle of the humerus and the ulna bone, near the elbow joint. It attaches to several small bones of the medial part of the hand and into the base of the little finger (fifth metacarpal bone). This muscle flexes the wrist and adducts the hand (moves the little finger on the medial side of the hand toward the midline of the body, when the palms are facing forward and away from the body).

The pronator teres muscle sits on the forearm just below the tendon of the biceps muscle. It has attachments on the medial epicondyle of the humerus bone and the ulna bone of the forearm. The muscle attaches to the radius and wraps around this bone when the hand is supinated. After the pronator teres is activated to contract, it unwraps around the radius, and in doing so, it pronates the forearm (turns the palm of the hand toward the floor). It also functions as a weak flexor of the elbow joint. The pronator quadratus muscle is a deep quadrangular-shaped muscle that arises from the ulna and inserts into the radius bone at the wrist. It pronates the hand; it has no function at the wrist or in the hand.

The flexor digitorum superficialis muscle begins on the medial epicondyle of the humerus, the ulna and the radius bones of the forearm and ends on the palmar side of fingers two to five, but not the thumb. This muscle flexes the wrist joint and the middle four fingers and is important in determining grip strength. The flexor digitorum profundus muscle is a long, thin and deep muscle. It's attached between the ulna bone and the distal bones (finger tip region) of the medial four fingers. It flexes all the fingers and every joint in the fingers of the hand.

Zottman Curls
This exercise has been given a variety of names over the years, but the Zottman curl under any name continues to be a good overall forearm exercise.

1.    This begins a bit like a standing dumbbell curl, except the curl is done in counterclockwise circular motion instead of lifting the weight straight up and down. You will face a mirror and grasp a dumbbell in each hand with your hands in a semi-pronated position; your hands should be beside your thighs.

2.    Flex both elbows simultaneously and lift the dumbbells upward. However, as you lift, move the dumbbell in your right hand so it moves across in front of your right thigh toward your left thigh. Your left forearm should swing away and to the left of your body's midline.

3.    Continue to curl upward, but move the dumbbells in a counterclockwise manner, so as you approach a position where your elbows are flexed, the right dumbbell should come up toward your left pectoralis muscle, then it should continue toward your right pectoralis muscle, with your left arm following the same path from left to right. Your upper arms and elbows should remain close to your rib cage.

4.    The right dumbbell will now be on the right side of your body and the left dumbbell in front of your right pectoralis major muscle. Slowly lower the dumbbells to the right side of your body.

5.    After reaching the bottom, continue the counterclockwise movement so the dumbbells move across to the left side of your body, over to the right and down.

6.    On the next set, begin with the dumbbells on the right side and make the movements in a clockwise curl from right to left. Your hands will remain in a semi-pronated position throughout each set.

Training Tips
The brachialis, brachioradialis, pronator and forearm muscles will be strongly activated during the exercise. The extensor carpi radialis longus muscle is critical for stabilizing the wrist during the exercise. You can activate the flexor carpi radialis more forcefully if you move the lateral (thumb) portion of your hand toward your shoulder (abduction of the wrist) when the dumbbell is at shoulder level and you begin to make the elbow adjustment for the downward part of the lift.

Once you are nearing the state of fatigue and the arm/forearm burn is getting intense, you can briefly put the dumbbell down (i.e., two to three seconds) and shake your hands and wrists to increase blood flow to the deprived muscles. However, quickly pick up the dumbbells and continue your set for several more repetitions. This will push your set well beyond the initial failure point.
    
Controlling the circular descent of the dumbbells is quite important. This is because some of the rotator cuff muscles will help stabilize your shoulder during the top part of the curl and sudden or uncontrolled jerky descents could place these stabilizing muscles at risk for injury. Therefore, explosive movements should not be used in this exercise, unless you are looking for a good reason for an injury-induced layoff.

Is this an unusual exercise? Yes, but don't discount its effectiveness. The direct effects of the exercise will be that your arm and forearm mass will begin to explode in an attempt to adapt to these new ranges of motion. Is it easy and painless? No! You will find that the forearm and arm burn is unbelievable.  The burn will be like a volcano erupting, first deep under your biceps where the brachialis muscle lives, then the burn will flow down your forearms to your hands. Zottman curls are not easy or pain free, but, is not a complete and powerful physique with huge forearms and arms worth a little extra effort and sacrifice?

References
Basmajian, J.V. and C.E. Slonecker. Grant's Method of Anatomy.  A clinical Problem Solving Approach. 11 th edition. Williams and Wilkins, Baltimore, 1989, pp.398-427.

Caruso, J. F., Skelly, W. A., Cook, T. D., Gibb, G. J., Mercado, D. R., Meier, M. L. (2001) An isokinetic investigation of contractile mode's effect on the elbow flexors. J Strength Cond Res, 15, 69-74

Hunter, S. K., Lepers, R., MacGillis, C. J., Enoka, R. M. (2003) Activation among the elbow flexor muscles differs when maintaining arm position during a fatiguing contraction. J Appl Physiol, 94, 2439-2447

Mahakkanukrauh, P., Somsarp, V. (2002) Dual innervation of the brachialis muscle. Clin Anat, 15, 206-209

Naito, A., Sun, Y. J., Yajima, M., Fukamachi, H., Ushikoshi, K. (1998) Electromyographic study of the elbow flexors and extensors in a motion of forearm pronation/supination while maintaining elbow flexion in humans. Tohoku J Exp Med, 186, 267-277

Rasch, P.J. Kinesiology and Applied Anatomy. 7th edition. Philadelphia, London. Lea & Febiger, 1989, pp. 138-167.

Spinner, R. J., Pichelmann, M. A., Birch, R. (2003) Radial nerve innervation to the inferolateral segment of the brachialis muscle: from anatomy to clinical reality. Clin Anat, 16, 368-369