Those certain summer muscles...

Summer has come early to Chicago, it seems. We usually have until June, but it looks like we will have to begin our obsession for the not-so-major muscle that everyone is most concerned with come tank top weather. The Bicep.

Kinematics

The biceps brachii control several movements and they generate flexion about two joints, the shoulder and the elbow. Primarily the bicep flexes the elbow joint, and this flexion is so well visualized by people that most people think of it when they imagine the very sense of the verb. However, the bicep has another very important function, which is the suppination of the forearm. (Palm up) This became quite clear to me after I fractured my radial head; it was impossible to suppinate my forearm, thus it was impossible to contract my biceps. (My sudden inability to recruit that not-so-major muscle suddenly became an obsession.) When the forearm is fully suppinated, the biceps brachii tendon is at full stretch, when you turn the wrist into pronation, the tendon rotates the radius over the ulna and the forearm is pronated. (Palm down)

Kinetics

What does this mean for bicep curls? There are several ways to perform curls, and they all recruit the biceps to a different extent.

When the forearm is fully suppinated as in a flat barbell curl, the biceps and their tendons are under maximum tension, and they will contribute the most force to the curl. As soon as the forearm leaves full suppination and starts to rotate towards a neutral grip, tension is taken off the biceps, and other muscles are engaged, primarily the brachialis and the brachioradialis. So as the forearm pronates, the work by the biceps is reduced.

Lets look at some pictures of my left arm, (Sadly, the right one is still lagging because of the above mentioned fracture) and it becomes quite clear how the muscles of the arm are recruited differently.

1. Neutral grip. Note how when the arm is flexed the bicep remains long.
2. 50% suppinated, as with an E-Z Bar. The bicep is somewhat more contracted.
3. Full suppination. Note both the shortness and fullness of the bicep, it is fully contracted.

Training

What does this mean?

1. Well, for full bicep engagement and maximum recruitment of that muscle, stick with flat barbell curls or suppinated dumbell curls. This will fully engage both heads of the biceps. (Changing hand width on the barbell will alter the recruitment of either the long head or the short head.)

2. The E-Z bar curl is just that, easy; on the wrists. Unless you are recovering from an injury, you should skip E-Z bar curls if the biceps are your primary goal. If you find that your wrist flexibility is holding you back, work on making your wrists more flexible. The flat barbell curl is unbeatable for building thick biceps.
3. When the grip is neutral, you are primarily recruiting the brachialis and the brachioradialis, the biceps are only assisting. This is still a great exercise to use, by all means you want to develop those muscles as much as your biceps, but be sure to understand which exercise recruits which muscles.

E-Z Bar curls and Barbell Curls