Muscle Actions: Flexion and Extension Overview

Knee Flexion

Hamstrings (Biceps femoris, Semitendinosus, Semimembranosus)

Knee Extension

Quadriceps (Rectus femoris, Vastus lateralis, Vastus medialis, Vastus intermedius)

Hip Flexion

Iliopsoas, Rectus femoris

Hip Extension

Gluteus maximus, Hamstrings

Hip Abduction

Gluteus medius, Gluteus minimus

Hip Internal Rotation

Gluteus medius, Gluteus minimus, Tensor fasciae latae

Hip External Rotation

Gluteus maximus, Deep external rotators (e.g., Piriformis)

Shoulder Flexion

Anterior deltoid, Pectoralis major (clavicular head), Coracobrachialis

Shoulder Extension

Posterior deltoid, Latissimus dorsi, Teres major

Shoulder Internal Rotation

Subscapularis, Pectoralis major, Latissimus dorsi, Teres major

Shoulder External Rotation

Infraspinatus, Teres minor

Elbow Flexion

Biceps brachii, Brachialis, Brachioradialis

Elbow Extension

Triceps brachii

Wrist Flexion

Flexor carpi radialis, Flexor carpi ulnaris, Palmaris longus

Wrist Extension

Extensor carpi radialis longus and brevis, Extensor carpi ulnaris