The term "bicep muscles" usually refers to the muscles on the front of your upper arm involved in elbow flexion. Let's break down all the relevant anatomy.
The Primary Players
Biceps Brachii
The main muscle people mean when they say "biceps":
• Latin for "two-headed muscle of the arm"
• Long head (outer) + Short head (inner)
• Functions: Elbow flexion, forearm supination, shoulder flexion
• Most visible muscle on front of arm
Brachialis
The often-forgotten muscle under the biceps:
• Single muscle, lies beneath biceps brachii
• Pure elbow flexor (no supination function)
• Stronger than biceps for pure flexion
• Visible on outer arm between biceps and triceps
Brachioradialis
Technically a forearm muscle but part of the curling team:
• Located on thumb-side of forearm
• Assists elbow flexion, especially in neutral grip
• Adds to forearm and arm appearance
Biceps Brachii: Deeper Look
Long head:
• Origin: Supraglenoid tubercle (top of shoulder socket)
• Travels through the bicipital groove of the humerus
• Creates the bicep "peak"
• Emphasized with arm-behind-body exercises
Short head:
• Origin: Coracoid process of scapula
• Creates bicep width/thickness
• Emphasized with arm-in-front-of-body exercises
Insertion:
Both heads join to form a single tendon attaching to the radial tuberosity (radius bone, just below elbow).
Functions Explained
Elbow flexion: Bending your elbow—the primary function trained with curls. All three muscles (biceps, brachialis, brachioradialis) contribute.
Forearm supination: Rotating your forearm so palm faces up. The biceps is actually the strongest supinator. Try this: hold your arm at 90 degrees and rotate your palm up against resistance—you'll feel your bicep contract hard.
Shoulder flexion: Raising your arm forward. A minor function, but the biceps does assist since it crosses the shoulder joint.
Grip Position and Muscle Activation
Supinated grip (palms up):
• Maximum biceps brachii activation
• Standard curls, preacher curls, incline curls
Neutral grip (palms facing each other):
• Increased brachialis and brachioradialis activation
• Reduced biceps brachii activation
• Hammer curls
Pronated grip (palms down):
• Maximum brachialis and brachioradialis activation
• Significantly reduced biceps activation
• Reverse curls
Training Recommendations
For complete "bicep muscle" development:
Volume: 10-20 sets per week for the bicep region (including all muscles)
Exercise selection:
• Include supinated grip work (standard curls) for biceps brachii
• Include neutral grip work (hammer curls) for brachialis
• Consider pronated grip work (reverse curls) for completeness
Sample weekly split:
• Session 1: Barbell curl (supinated), Hammer curl (neutral)
• Session 2: Incline curl (supinated), Reverse curl (pronated)
The Bottom Line
The "bicep muscles" include the biceps brachii (two heads), brachialis, and brachioradialis. Training all three with appropriate grip variations builds complete, well-developed arms. Don't just do supinated curls—include hammer curls and consider reverse curls for comprehensive development.