Upper Arm Muscles

Main muscles: About 3 major muscles primarily control upper arm movement.

• Biceps brachii:
  • Function: Flexion (pulling the forearm up, like bending the elbow) and supination (rotating the forearm so the palm faces up).
  • Role in push/pull: Primarily a pulling muscle.
• Triceps brachii:
  • Function: Extension of the elbow (straightening the arm).
  • Role in push/pull: Primarily a pushing muscle.
• Brachialis:
  • Function: Flexes the elbow, underneath the biceps, adds pulling strength.

Shoulder Muscles and Movement

The shoulder is a complex joint with around 9 major muscles controlling it — allowing a large range of motion:

• Deltoid (3 parts: anterior, lateral, posterior) — lifts the arm in various directions.
• Rotator cuff muscles (4 muscles): supraspinatus, infraspinatus, teres minor, subscapularis — stabilize and rotate the shoulder.
• Pectoralis major — brings the arm forward (flexion) and across the body (adduction).
• Latissimus dorsi — pulls the arm down and backward (extension, adduction).
• Teres major, Coracobrachialis — assist with rotation and flexion.

Shoulder movements: flexion, extension, abduction, adduction, internal/external rotation, and circumduction (circular movement).

Muscle coordination among these allows the shoulder’s huge range.

Forearm Muscles & Rotation

The forearm has about 20 muscles, many of which control wrist, hand, and finger movements. They are divided into: