Unless you make your home in the land of the never-ending sun, you should be packing up your heavy pullovers and buying a few good T-shirts and maybe a couple of tank tops. The best kinds hug your body and show the effort that you invested all last winter in the gym. Sure, your arms may not be 20 inches in circumference, but then you don’t need 20-inch arms to belt a home run, lay up a winning basket, or serve an ace on through your opponent’s forehand. Nevertheless, there is no doubt that a more powerful arm hanging below your shirtsleeve is more capable of contributing to a win or two on any field or court. Therefore, if the question is: How can I obtain a little more strength and shape in my biceps without adding another 45 minutes to my workout? Your answer lies in accentuating the natural shape of the biceps by challenging it to contract in the optimal positions in which it was designed to work.
Biceps Structure and Function
The biceps brachii muscle has two (“bi”) heads (“ceps”). The short head of the biceps brachii attaches to the anterior part of the scapula (shoulder blade) near the shoulder joint and runs down the medial (inner) part of the humerus bone of the arm. It joins with the long head of the biceps brachii to form the thick bicipital tendon. This tendon crosses the elbow and attaches on the radius bone near the elbow. The long head of the biceps brachii begins on the scapula just above the shoulder joint. It has a very long tendon that crosses the shoulder joint, and therefore, the shoulder position will affect the function of the long head.
Most people will not realize that the biceps’ function is affected by shoulder position. This is because the long head of the biceps crosses the shoulder where it contributes to shoulder flexion (i.e., bringing the arm forward). However, the long head of the biceps is mechanically advantaged when stretched, as when doing a curl with the shoulders in slight extension (arms and elbows held slightly back). The long head of the biceps sits on the lateral part of the arm, and its fibers mesh with the short head as it approaches the elbow and attaches to the radius bone of the forearm. Because the muscle belly of the long head is actually rather short (it has a long tendon), thickening the muscle belly long head of the biceps will improve your arm’s muscle shape more rapidly than thickening the longer-bellied short head of the biceps.
Strengthening the long head will also improve your ability to throw a ball (or any other object) because it will contribute to the forward movement of the arm at the shoulder joint. The enhanced power from enhancing the long head of the biceps will therefore contribute more than an improved silhouette in your new shirt, but that is not such a bad thing either.
Both heads of the biceps muscle are strong flexors of the forearm. However, because the biciptial tendon attaches on the radius bone, which is the most lateral forearm bone, the biceps (both heads) is a very strong supinator of the hand (turns the palm toward the ceiling), if the forearm begins in a pronated position. This is because when the hand is pronated, the radial bone of the forearm sits on top of the ulna bone. When the biceps muscle contracts, it pulls on the radius bone, and pulls it back into a position where the radius lies beside, and not on top of, the ulna. This moves the hand from a pronated to a supinated position. Thus, to fully activate both heads of the biceps, there must be a supination component as well as flexion of the elbow joint, with the arms pulled into extension. The one-arm cable curl fulfills all of these requirements.