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Exercise ScienceThe Muscular System
Agonist and Antagonist• Agonist
– responsible formain movmenet• Antagonist
– Acts in opposition to specific movements generated by the agonist
– Returns the limb to initial position• Antagonistic pairs
– Needed in body because muscles can only exert a pulling force and can’t push themselves back in original position
Movement Agonist Antagonist
Knee Flexion Hamstrings Quadriceps
Medial Shoulder Rotation Pectoralis Major Infraspinatus
Shoulder Rotation & Elevation Trapezius Lattissimus Dorsi
Hip Extension Gluteus Maximus Iliopsoas
Trunk Extension Erector Spinae Rectus Abdominus
Plantar Flexion Gastrocnemius Tibialis Anterior
Wrist Flexion Wrist Flexors Wrist Extensors
Forearm Supination Supinator Pronator (teres/quadratus)
Dorsi Flexion Tibialis Anterior Gastrocnemius
Shoulder Abduction Anterior Deltoid Latissimus Dorsi
Shoulder Adduction/Rotation Latissimus Dorsi Deltoid/Trapezius
Thigh Flexion Iliacus Gluteus Maximus
Hip Extension & Adduction Adductor Magnus Gluetus Medius & Psoas
Trunk Rotation External Obliques Rectus Abdominus
Adducts/Lateral Rotation of Arm Infraspinatus Supraspinatus
Retracts Scapula Rhomboids Serratus Anterior
Neck Flexion Sternocleidomastoid Trapezius
Principles of Muscle Action
1. Muscle must cross a joint to act directly on that joint
2. How a muscle crosses a joint will affect the action
3. When muscles shorten, it exerts on equal pull on origin & insertion – whichever offers less resistance is the one which will move
• Origin = the end that stays fixed
• Insertion = the end that moves
Muscles of the Neck
• Sternocleidomastoid– Origin: clavicle & sternum– Insertion: mastoid process
(temporal bone behind ear)– Function: flex & rotate head
side to side
• Spinalis– Origin: cerical & thoracic
vertebrae– Insertion: cervical and
thoracic vertebrae above– Function: extend & laterally
flex spine
Muscles of the Abdomen
• Rectus Abdominus– Origin: pubic crest &
pubic symphysis– Insertion: xiphoid
process & inferior ribs– Function: trunk flexion;
also expiration, defecation & childbirth
• External Obliques/Transverse Abdominus– Origin: lower 8th rib– Insertion: iliac crest, linea
alba & pubis– Function: flex & rotate
vertebral column, compressabdomen during forced expiration
Muscles Acting on the Upper Limb
• Pectoralis Major– Origin: clavicle, sternum,
coastal cartilage of 1st to 6th rib, external oblique muscle
– Insertion: intertubercular groove
– Function: internal rotation, adduction & flexion of arm
• Latissimus Dorsi– Origin: lumbar & 7th thoracic
vertebrae, iliac crest, down to the sacrum
– Insertion: back of humerus at floor of interturbercular groove
– Function: adductor, extensor and internal rotator of the arm
Muscles of the Rotator Cuff• Supraspinatus
– Origin: posterior scapula – Insertion: greater tubercle of humerus– Function: stabilize shoulder joint,
abducts shoulder
• Infraspinatus– Origin: posterior scapula – Insertion: greater tubercle of humerus– Function: stabilize shoulder joint,
laterally rotates shoulder
• Teres Minor– Origin: Lateral border of scapula– Insertion: greater tubercle of
humerus– Function: stabilzes, laterally rotates
shoulder
• Subscapularis – Origin: anterior scapula– Insertion: lesser tubercle of humerus– Function: stabilize, rotates humerus
medialy
* S.I.T.S.
Muscles that Position the Scapula• Trapezius
– Origin: occipital bone down to the 12th vertebrae
– Insertion: spine of the scapula, acromion & clavicle
– Function: important lateral neck muscles
• Acting alone: tilt the head side to side• Together: neck extension
• Rhomboid Major and Minor– Origin: T2-T5 (major), C7-T1 (minor)– Insertion: scapula (major), scapular
spine (minor)– Function: adduction & retraction of
scapula, downward rotation of scapula
• Levator Scapulae– Origin: 4 upper cervical
vertebrae near base of skull– Insertion: scapula– Function: elevates & rotates
scapula
• Serratus Anterior– Origin: first 8-9 ribs– Insertion: scapula– Function: upward
rotation & abduction or protraction of scapula
• Pectoralis Minor– Origin: 3rd, 4th, 5th rib– Insertion: scapula– Function: elevates ribs, depress & protracts
scapula
Scapular Muscles that Move Humerus
• Deltoid– Origin: clavicle, acromion, spine
of of scapula– Insertion: humerus (deltoid
tuberocity)– Function: medially rotates
shoulder, abducts arm, extends & laterally rotates arm
• Teres Major– Origin: scapula– Insertion: intertubercular
groove of humerus– Function: medial rotator,
adductor, extends humerus at the arm
Elbow Flexors and Extensors
• Biceps Brachii– Origin: scapula (coracoid
process & supraglenoid tubercle)
– Insertion: radial tuberocity– Function: forearm supinator,
elbow flexion
• Brachialis– Origin: lower anterior surface of
humerus– Insertion: corocoid process of ulna– Function: elbow flexion
• Brachioradialis– Origin: lateral epicondyle of
humerus– Insertion: styloid process of radius– Function: elbow flexion
• Triceps Brachii– Origin: posterior humerus & infraglenoid tubercle
of scapula– Insertion: olceranon process of the ulna– Function: elbow extension
• Anconeus– Origin: lateral epicondyle of humerus– Insertion: olecranon & superior-posterior
ulna– Function: assists triceps in extending
forearm
Supination and Pronation
• Supinator– Origin: lateral epicondyle of humerus– Insertion: lateral radius– Function: supination of forearm
• Pronator Teres– Origin: medial epicondyle of humerus– Insertion: midshaft of radius– Function: pronation of forearm
• Pronator Quadratus– Origin: anterior surface of distal ulna– Insertion: anterior surface of distal radius– Function: pronation of forearm
Extrinsic Hand Muscles
ANTERIOR VIEW
POSTERIOR VIEW
Intrinsic Hand Muscle
• Thenar Eminence• Hypothenar Eminence
Muscles of the Hip (Posterior)
• Tensor Fasciae Latae– Origin: anterior iliac crest– Insertion: iliotibial tract (lateral
femur)– Function: flex, abduct & medially
rotate thigh
• Sartorius– Origin: anterior superior iliac spine– Insertion: medial tibia– Function: flexion & outward
rotation of hip, knee flexion
• Gluteus maximus– Origin: illium crest, sacrum, coccyx– Insertion: greater trochanter of femur,
iliotibial tract– Function: hip extension & external rotation
• Gluteus medius– Origin: lateral surface of ilium– Insertion: posterior greater trochanter– Function: hip abduction & internal rotation
• Gluteus minimus– Origin: lateral surface of ilum– Insertion: anterior greater trochanter– Function: hip abduction & internal rotation
Muscles of the Hip (Anterior)
• Iliopsoas (iliacus + psoas major)– Origin: inner ilium– Insertion: lesser trochanter of femur– Function: hip flexion
Hip Adductors
• Adductor Longus• Adductor Magnus• Adductor Brevis
• Pectineus– Origin: superior ramus of pubis– Insertion: lesser trochanter to
linea aspera– Function: hip adduction & flexion
• Gracilis– Origin: inferior ramus of pubis– Insertion: medial tibial condyle– Function: hip adduction, knee
flexion
Anterior Thigh (Quadriceps)• Rectus Femoris
– Origin: anterior inferior iliac spine– Insertion: tibial tuberosity– Function: knee extension & hip
flexion
• Vastus Lateralis– Origin: linea aspera & greater
trochanter– Insertion: tibial tuberosity– Function: knee extension
• Vastus Intermedius– Origin: anterior shaft of femur– Insertion: tibial tuberosity– Function: knee extension
• Vastus Medialis– Origin: medial aspect of linea
apsera– Insertion: tibial tuberosity– Function: knee extension
*Quadriceps = Rectus Femoris, Vastus Lateralis Vastus Intermedius & Vastus Medialis,
Posterior Thigh (Hamstring)
• Biceps Femoris– Origin: ischial tuberosity & linea
aspera– Insertion: head of fibula– Function: knee flexion,
hip extension
• Semimembranosus– Origin: ischial tuberosity– Insertion: medial tibial condyle– Function: knee flexion,
hip extension
• Semitendinosis– Origin: ischial tuberosity– Insertion: proximal part of tibia,
below medial condyle– Function: knee flexion, hip extension
*Hamstrings = Biceps Femoris, Semimembranosus & Semitendinosis
Extrinsic Foot Muscles
• Tibialis Anterior– Origin: anterior shaft of tibia– Insertion: 1st metatarsal (big toe)– Function: dorsi flexion, inversion
Anterior Compartment
Posterior Component
• Gastrocnemius– Origin: lateral & medial conyles
of femur– Insertion: calcaneus– Function: plantar flexion, knee
flexion
• Soleus– Origin: upper tibia & fibula– Insertion: calcaneus– Function: plantar flexion
*Calf Muscles = Gastrocnemius & Soleus
• Tibialis Posterior– Origin: posterior surface of tibia & fibula– Insertion: tuberosity of navicular bone– Function: plantar flexion, inversion
• Popliteus– Origin: lateral condyle of femur– Insertion: proximal shaft of tibia
on posterior side below medialcondyle
– Function: medially rotates leg
Posterior Compartment
• Extensor hallucus longus
• Extensor digitorum longus
• Flexor Digitorum Longus• Flexor Hallucis Longus
Intrinsic Foot Muscles
• Flexor Digitorum Brevis• Flexor Hallucis Brevis• Quadratus Plantae