Length-Tension Relationship

Sit-ups

Muscles that produce flexion at the hip

• Iliopsoas (Iliacus and Psoas major)• Sartorius*• Rectus femoris*• Tensor fasciae latae*• Pectinius (assists)

• *These muscles are two-joint muscles, also acting at the knee

Iliopsoas: Iliacus and Psoas Major

• Origin:– Iliacus: Illium– Psoas major: Lumbar

vertebrae and sacrum• Insertion:– Lesser trochanter of the

femur and just below• Actions:– Flexion at the hip– External or lateral rotation at

the hip

Iliacus muscle

Psoas major

Sartorius

• Origin:– Anterior superior iliac

spine• Insertion:– Anterior-medial aspect

of the tibia• Actions:– Flexion at the hip– External (lateral)

rotation at the hip– Flexion at the knee

Rectus Femoris

• Origin:– Anterior inferior iliac

spine (ilium)

• Insertion:– Patella, patellar tendon, tibial

tuberosity

• Actions:– Flexion at the hip– Extension at the knee

Rectus Femoris

Tensor fascia latae

• Origin:– Iliac crest (Illium)

• Insertion:– Iliotibial tract

• Actions:– Flexion of the hip– Abduction of the hip– Slight internal rotation at

the hip

Tensor Fascia Latae

Muscles of the abdomen

• Rectus abdominis• External oblique• Internal oblique• Transverse abdominis

Rectus Abdominis:

• Origin: pubis (pubic crest, symphysis pubis)

• Insertion: sternum and ribs (xiphoid process, cartilage)

• Actions: – Both=flexion,

compression– Single= lateral flexion

External Obliques:

• Origin: ribs (lower 8)

• Insertion: Iliac crest, pubis, inguinal ligament, linea alba

• Actions: – Both: flexion– Single: lateral flexion,

rotation

• External Oblique

• External oblique

Internal Obliques:

• Origin: Iliac crest, inguinal ligament

• Insertion: ribs, linea alba• Actions:

– Both: flexion– Single: lateral flexion,

rotation

Internal Oblique

Internal oblique

Transverse Abdominis:

• Origin:– Iliac crest, cartilage of

ribs

• Insertion:– Pubis, linea alba

• Action:– Compression, forced

expiration

Transverse Abdominis

Transverse abdominis