Muscular System
• Back muscles
• Abdominal muscles
• Proprioceptors
• Lever system
• Fast / slow twitch muscles
Trapezius: Origin:
occipital bone and
vertebrae. Insertion:
scapula
Action: moves scapula -adduction, elevation &
rotation. Also rotates
head of humerus
Latissimus dorsi: Origin:
vertebrae
Insertion: humerus
Action: adducts and
medially rotates arm
Levator Scapulae
Origin: transverse process of
C1 – 4
Insertion: scapula – superior
medial border
Action: elevate scapula
Rhomboids: minor / major
Origin: spinous process of
cervical & thoracic
vertebrae
Insertion: medial border of
scapula
Action: adduct & downward
rotation of scapula
Deltoids – anterior/
middle/posterior Origin:
clavicle & scapula
Insertion: Humerus
Action: abducts the arm
Errector Spinae
Origin: transverse &
spinous processes of
thoracic & lumbar
Insertion: spinous &
thoracic process of
thoracic & cervical, ribs
Action: extends & lateral
flexion of neck &
vertebral column
Obliques: Internal & External
Action – compress abdomen
Internal – origin: Iliac crest & fascia
insertion: lower ribs & fascia
External – origin: rib cage
insertion: iliac crest & fascia
Transversus abdominis: action – compress abdomen
origin: lower ribs & fascia
insertion: linea alba & pubis
Rectus Abdominis: flex vertebral column & compress
abdomen
origin: pubic bone
insertion: ribs & sternum
Proprioceptors
• Proprioceptors are sensory nerve endings found
in all joints, muscles, and tendons. that sense (ception) a change in body position (proprio-).
• detect any changes in physical displacement
(movement or position) and any changes in
tension, or force, within the body
• can cause an immediate reaction or its memory
can be stored in the brain for minutes or years
and then used to determine a bodily reaction at
a future date.
• The proprioceptors related to stretching are
located in the tendons and in the muscle fibers
• There are two kinds of muscle fibers: "intrafusal
muscle fibers" and "extrafusal muscle fibers".
Extrafusil fibers -contain myofibrils and are what
is usually meant when we talk about muscle
fibers.
• Intrafusal fibers -called "muscle spindles" and lie
parallel to the extrafusal fibers. Muscle spindles,
or "stretch receptors", are the primary
proprioceptors in the muscle.
• Another proprioceptor, called the "golgi tendon
organ” is located in the tendon near the end of
the muscle fiber, is associated with stretching
• A third type of proprioceptor, called a "pacinian
corpuscle", is located close to the golgi tendon
organ and is responsible for detecting changes
in movement and pressure within the body.
• When the extrafusal fibers of a muscle
lengthen, so do the intrafusal fibers
(muscle spindles). The muscle spindle
contains two different types of fibers (or
stretch receptors) which are sensitive to
the change in muscle length and the rate
of change in muscle length. When
muscles contract it places tension on the
tendons where the golgi tendon organ is
located. The golgi tendon organ is
sensitive to the change in tension and the
rate of change of the tension.
Levers
• Each muscle is attached to at least 2
bones & cross at the joint [ exception –
sphincters]
• Each lever has components:
Rod = bone
Pivot = joint
Weight that is moved = muscle +
Force = energy for movement
Lever Types
• 1st class :
weight ----pivot---force
• 2nd class:
pivot—weight---force
• 3rd class:
pivot—force—weight
This is the most common type in the body
** not every muscle will operate within a lever system
Fast Twitch/Slow Twitch Fibers
Skeletal muscle consists of three types of fiber.
Type I fibers (also called slow-twitch) cope better
with repeated muscle contractions, partly because
they have higher numbers of mitochondria than
type II (fast-twitch) fibers. Slow muscle fibers
contract slower and are used mostly in endurance
exercises. Fast muscle fibers contract quickly and
are involved in quick movements. Most top sprinters
are 80% fast twitch while top marathoners are 80%
slow.
The average person has a ratio of fast:slow twitch
fibers that falls between 60:40 and 40:60.
• Type I cells = Slow Oxidative. Have alot of mitochondria
(containing oxidative enzymes) and capillaries.
• Type II cells = Fast fibers are divided into two sub-categories:
Fast Glycolytic (FG) or Fast Oxidative Glycolytic (FOG).
• The FG fibers store lots of glycogen and have high levels of
enzymes necessary for producing energy without oxygen, but
contained few mitochondria. The FOG fibers have the best of
both worlds, high speed and glycolytic capacity, plus high levels
of oxidative enzymes.
These INTERMEDIATE fibers [FOG] were termed type IIA fibers
by Brooke & Kaiser, 1970.
The pure fast fibers (FG) were termed Type IIb.
It does appear that pure fast (Type IIb) fibers can transition to
"hybrid" (Type IIa) fibers with chronic endurance training.
Biopsies of elite endurance athletes reveal that after years of
training, they have almost no IIb fibers, but often have a
significant percentage of the intermediate, IIa fibers. BUT, the
majority of the available research suggests that Type IIa fibers
do not transition to Type I.
TYPE of FIBER
Characteristic
Slow Oxidative
(I)
Fast Oxidative
( IIa)
Fast Glycolytic
(IIb)
Myosin ATPase activity
LOW
HIGH
HIGH
Speed of Contraction
SLOW
FAST
FAST
Fatigue Resistance
HIGH
Intermediate
LOW
Oxidative Capacity
HIGH
HIGH
LOW
Anaerobic Enzyme
Content
LOW
Intermediate
HIGH
Mitochondria
MANY
MANY
FEW
Capillaries
MANY
MANY
FEW
Myoglobin Content
HIGH
HIGH
LOW
Color of Fiber
RED
RED
WHITE
Glycogen Content
LOW
Intermediate
HIGH
Myoglobin Content
HIGH
HIGH
LOW
Fiber Diameter
SMALL
Intermediate
LARGE
Type I is darkest
Type IIb is lightest
Type IIa is medium color
Energy Use & Muscular Activity
• Resting Muscle tissue – low energy need.
Tissue reserves of ATP and CP [creatine
phosophate ] are made [ fatty acids]
• Moderate levels of activity – energy needs
increase, mitochondria able to meet
demands with available oxygen and body
fuel [glucose/ fatty acids]
• High Intensity level of activity –
mitochondrial ATP production at maximum
said to be about 1/3 of needed amount
[glucose]
Muscle Fatigue
• When you can no longer sustain a certain
level of activity –it is said to be fatigued
• Depletion of ATP / CP reserves, calcium
levels
• Damage to the tissue
• Effects of energy, pain