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