Starting Strength

injury frequency. Your abs and back muscles will remain strong from doing their primary jobs under the bar, and you’ll stop having injury problems that interfere with your training.
    Curls
     
    Since you’re going to do them anyway, we might as well discuss the right way to do curls. Curls are performed to train the biceps, a muscle that commands an inordinate amount of attention from far too many people. But that is the nature of things, and who are we to question so fundamental a matter? Effective curls require an awareness of the biceps anatomy and a willingness to diverge from the conventional wisdom regarding technique.
    The biceps muscle is one of the many muscles of the body that crosses two joints. (Technically, this muscle is the biceps brachii , or “arm” biceps, which is distinct from the biceps femoris , one of the hamstring muscles.) Like its partner the triceps, the biceps crosses both the elbow and shoulder joints, and therefore causes movement to occur around both joints. The chin-up uses a combination of elbow flexion and shoulder extension. But so does the pull-up, the difference being the prone versus supine grip. The elbow flexion during the pull-up is performed without much biceps involvement, while the biceps are heavily involved in the chin-up.

    Figure 7-54. Both the biceps (A) and the triceps (B) muscles cross the elbow and shoulder joints, causing movement around both.

    This difference is due to the anatomy of the elbow. The distal end of the biceps attaches to the radius – the shorter of the two forearm bones – at a point called the radial tuberosity , located on the posterior and medial aspects of the radius when the forearm is pronated (the palm is facing back). “Supination” is the term given to the position in which the hand is rotated forward and the palm is up, and the palm-up position of the hand is referred to as “supine.” The forearm supinates when the biceps attachment on the radius rotates inward and upward as the muscle shortens. In fact, if the biceps are in full contraction, the hand is supine. The pull-up, performed with a prone grip, utilizes very little biceps – and therefore proportionately more triceps and lats – while the chin-up uses lots of biceps. The elbow-flexion part of the pull-up is accomplished by the other elbow flexors: the brachialis, the brachioradialis, and some of the smaller forearm muscles.
    The biceps also performs the movement known as shoulder flexion. Anatomical movement descriptions can sometimes be arbitrary, and flexion in the shoulder joint is defined as the forward and upward movement of the humerus. The biceps contributes to this movement because the proximal attachments (yes, there are two, thus the name bi ceps) are located on the anterior (forward) side of the scapula, the main bone of the shoulder joint. Because the tendon attachments cross the joint, the muscle moves the joint, and shoulder flexion is therefore a biceps function.
    Elbow flexion, along with shoulder extension, is used whenever anything is grasped and pulled in toward the body. This is why chin-ups and pull-ups are such functional exercises: they duplicate this very normal motion under a load ( Figure 7-55 ).

    Figure 7-55. Chin-ups are an example of an exercise involving elbow flexion (a function of the distal biceps and forearm) and shoulder extension (a function of the lats and proximal triceps).

In fact, elbow flexion is normally accompanied by shoulder extension; this is the way the arm is designed to work. And this is why elbow flexion with an immobile shoulder requires special equipment: the preacher curl was invented for the purpose of providing a way to work the biceps in isolation. The isolation of a single muscle group that moves a single joint seldom contributes significantly to other, more complex movements which include that muscle group. Remember that our definition of “functional exercise” is a normal human movement that can be performed under a scalable, increasable load. By this definition, no exercise that requires a machine or specific device to perform it can be a functional exercise (we’re not including the barbell or power rack in the “specific device” category here, since we can’t limit our training to the use of sticks and rocks). And if a muscle is isolated in an exercise, its tendon attachments are, too; this fact has a bearing on the injury-causing potential of these types of exercises.
    Examples of shoulder