Biceps

Biceps: what are they?

Two heads start on the scapula: the long head from just above the shoulder socket, the short head from the coracoid process. They join into one belly and attach on the radius, the forearm bone that rotates. Two things follow. First, because the tendon attaches to the rotating bone, the biceps is a strong supinator, turning the palm upwards, which is why a supinated curl loads it more than a neutral or pronated one. Second, because the long head crosses the shoulder, an arm positioned behind the body puts it on stretch. Those two facts explain the differences between every curl variation a client will ever be shown.

What the biceps do

Elbow flexion is the obvious action, but the biceps is not alone: brachialis sits underneath it and is often the stronger elbow flexor, and brachioradialis in the forearm contributes heavily in a neutral or pronated grip. Any curl trains all three in different proportions.

Supination is what makes the biceps distinctive. Turning the palm upwards against resistance loads it specifically, which is why a dumbbell curl that finishes with the palm turned up trains it differently from a hammer curl held neutral throughout.

The long head also helps flex the shoulder and contributes to shoulder stability. That is why curls performed with the elbow behind the torso, as on an incline bench, load it in a longer position than curls with the elbow in front, as on a preacher bench.

How curl variations differ

Elbow position relative to the torso and grip orientation are the two variables. Combining a stretched-position exercise with a shortened-position one covers the strength curve better than doing three versions of the same thing.

Programming biceps sensibly

The biceps already work in every pulling exercise, so the direct volume needed is lower than clients assume. For most people, six to twelve hard sets a week across two sessions produces as much as anything more. Adding sets past that usually just interferes with pulling performance, since the biceps recover between sessions more slowly than the volume suggests.

Rep ranges of 8 to 15 suit them well. Very heavy low-rep curls tend to become swinging, and very high reps become a burn without much tension. The tempo matters more than the number: a controlled two to three second lowering on every rep is what most clients are missing.

• Keep the elbow still; if it drifts forward, the front delt is helping.
• Straighten the arm fully at the bottom of every rep.
• Do one stretched-position variation and one shortened-position variation per week.
• Train biceps after back work, not before, unless the arms are the session priority.

What goes wrong in practice

The first pattern is a curl with a swing. Momentum from the hips and a forward-drifting elbow lets the client use more weight while reducing the work the biceps do. Standing against a wall or using an incline bench removes the option entirely.

The second is a partial range at the bottom. Stopping short of a straight arm cuts out the stretched position, which is the part that responds best. Reduce the load until the arm can straighten fully under control.

The third is a client with elbow discomfort during heavy barbell curls. A straight bar fixes the forearm in full supination, which some people do not tolerate. An EZ bar or dumbbells that allow a slight rotation usually solves it without changing anything else about the program.