The brachialis and biceps muscles both contribute to flexing the arm at the elbow, but they also have key functional differences.
Comparing Brachialis and Biceps Functions
| Muscle | Primary Function | Secondary Functions |
|---|---|---|
| Brachialis | Flexion of the forearm at the elbow | None |
| Biceps | Flexion of the forearm at the elbow | Supination of the forearm, Flexion of the humerus at the shoulder |
Detailed Breakdown
Brachialis Muscle
- The brachialis is located in the upper arm and its sole purpose is to flex the forearm at the elbow joint. This muscle is the prime mover for elbow flexion, meaning it's the main muscle responsible for this action.
- It doesn’t contribute to any other movements, focusing all its power on this single joint action.
Biceps Muscle
- The biceps also flexes the arm at the elbow, working alongside the brachialis.
- However, it also has additional functions that the brachialis lacks.
- Supination of the forearm: This means turning the palm upwards, like when you're turning a doorknob.
- Flexion of the humerus at the shoulder: The biceps assists in lifting the arm at the shoulder joint.
Practical Implications
- When performing a bicep curl, you're engaging both the brachialis and biceps. The brachialis is always active during elbow flexion, whereas the biceps will have more activation during elbow flexion with supination.
- Exercises that target forearm supination, like turning a screwdriver, primarily engage the biceps.
- When just focusing on elbow flexion without supination, the brachialis is more active.
