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CHAPTER 3:PART 1
MUSCULOSKELETAL SYSTEM:
THE MUSCULATURE
KINESIOLOGY
Scientific Basis of Human Motion, 12th edition
Hamilton, Weimar & Luttgens
Presentation Created by
TK Koesterer, Ph.D., ATC
Humboldt State University
Revised by Hamilton & Weimar
McGraw-Hill/Irwin
Copyright © 2012 by The McGraw-Hill Companies, Inc. All rights reserved.
OBJECTIVES
1. Describe the structure and properties of the whole muscle,
fast and slow twitch muscle fibers, and the myofibril.
2. Explain how the relationship of the muscle line of pull to the
joint axis affects the movement produced by the muscle.
3. Describe the relationship between skeletal muscle fiber
arrangement and function.
4. Define the roles a muscle may play and explain the
cooperative action of muscles in controlling joint actions by
naming and explaining the muscle roles in a specified
movement.
5. Define the types of muscular contraction, name, and
demonstrate each type of action.
6. Demonstrate an understanding of the influence of gravity
and other external forces on muscular action.
7. Describe various methods of studying muscle action.
8. State force-velocity and length-tension relationship and
explain the significance to static & dynamic movements.
9. Identify muscle groups active in a variety of motor skills.
3-2
SKELTAL MUSCLE STRUCTURE:
PROPERTIES OF MUSCULAR TISSUE

Extensibility and Elasticity: enable the
muscle to be stretched and return to normal
length.
 Tendons
are continuations of muscle’s
connective tissue and also possess these
properties.

Contractility: is the ability to shorten and
produce tension.
3-3
THE MUSCLE FIBER

Consists of myofibrils
held together by
sarcolemma (cell
membrane) that can
propagate nerve
impulses.
Fig 3.1
3-4
THE MUSCLE FIBER:
MYOFIBRILS



Are arranged in parallel
formation.
Made up of alternating
dark & light bands that
give muscle fiber their
striated appearance.
Each fiber enclosed by
endomysium.
3-5
THE MUSCLE FIBER:
MYOFILAMENTS
Actin: when stimulated
slides over myosin.
 Cross-bridges:
projections (heads) of
myosin attach to actin.
Fig 3.2
3-6
THE MUSCLE FIBER:
SARCOMERES
Myofibril between two Z
lines.
 Functional contractile
unit of skeletal muscle.

Fig 3.2
3-7
THE MUSCLE FIBER:
WHOLE MUSCLE
Fasiculus (bundle of
fibers) enclosed by
perimysium.
 Group of bundles
encased within
epimysium.

Fig 3.1
3-8
SLOW AND FAST TWITCH FIBERS





These are the two major categories pertinent for kinesiology.
Most limb muscles contain a relatively equal distribution of
each fiber type.
Postural muscles contain more slow twitch fibers.
Fast twitch fibers are large, pale, and have less blood supply
than slow twitch fibers.
 Two primary types are IIa (fast oxidative glycolitic) and IIb
(fast glycolitic).
 Suitable for intense responses over a short period of time
Slow twitch fibers are small, red, and have a rich blood
supply, and greater myoglobin.
 Highly efficient, do not fatigue easily.
 Suitable for long duration, posture and endurance
events.
3-9
MUSCULAR ATTACHMENTS



Muscles attach to bone by connective tissue,
which continues beyond the muscle belly to
form a tendon.
Origin: usually more proximal
Insertion: usually more distal



Contraction produces equal force on the two
attachments.
Origin usually stabilized by other muscles.
Reverse Muscle Action: occurs when the distal
bone is stabilized and the proximal bone moves.
3-10
STRUCTURAL CLASSIFICATION OF
MUSCLES BY FIBER ARRANGEMENT

Longitudinal: long, strap
like muscle with fibers in
parallel to its long axis.
 Sartorius
Fig 7.15
3-11
STRUCTURAL CLASSIFICATION OF
MUSCLES BY FIBER ARRANGEMENT
Quadrate or Quadrilateral:
four sided and usually flat.
 Consist of parallel fibers.

 Rhomboids
Fig 3.10b
3-12
STRUCTURAL CLASSIFICATION OF
MUSCLES BY FIBER ARRANGEMENT

Triangular: fibers radiate
from a narrow
attachment at one end to
a broad attachment at
the other.
 Pectoralis
major
Fig 5.11
3-13
STRUCTURAL CLASSIFICATION OF
MUSCLES BY FIBER ARRANGEMENT

Fusiform or Spindle-Shaped:
rounded muscle that tapers at
either end.
 Brachioradialis
Fig 6.8
3-14
STRUCTURAL CLASSIFICATION OF
MUSCLES BY FIBER ARRANGEMENT

Pennate: a series of short,
parallel, feather like fibers
extends diagonally from the
side of a long tendon.
 Tibialis
posterior
Fig 8.25
3-15
STRUCTURAL CLASSIFICATION OF
MUSCLES BY FIBER ARRANGEMENT

Bipennate: A long central
tendon with fibers
extending diagonally in
pairs from either side of the
tendon.
 Rectus
femoris
Fig 7.15
3-16
STRUCTURAL CLASSIFICATION OF
MUSCLES BY FIBER ARRANGEMENT

Multipennate: Several
tendons are present,
with fibers running
diagonally between
them.
 Middle
deltoid
Fig 5.11
3-17
EFFECT OF MUSCLE STRUCTURE ON
FORCE
 Force a muscle can exert is proportional to
its physiological cross section (PCS).
 A broad, thick, longitudinal muscle exerts
more force than a thin one.
 A pennate muscle of the same thickness as
a longitudinal muscle can exert greater
force.
 The
oblique arrangement of fiber allows for a
larger number of fibers than in comparable sizes
of other classifications.
3-18
EFFECT OF MUSCLE STRUCTURE ON
ROM
Muscle can shorten to approximately half its’
resting length.
 Long muscles with fibers longitudinally
arranged along the long axis can exert force
over a longer distance.
 Pennate muscles with their oblique fiber
arrangement and short fibers, can exert
superior force through only a short range.

3-19
SKELETAL MUSCLE FUNCTION:
LINE OF PULL



Movement that the contracting muscle
produces is determined by two factors:
 Type of joint that is spans
 The relation of the muscle’s line of
pull to the joint
Pectoralis major (clavicular) is primarily
a flexor, but it also adducts the
humerus.
When arm is abducted, line of pull
moves above axis of rotation and Fig 3.4
contributes to abduction of humerus.
3-20
ANGLE OF ATTACHMENT

If very shallow, most of the tension will produce a
force pulling along the bone.




Will tend to stabilize joint.
If fairly large, will have a much larger rotary
component of force.
In many muscles the angle changes throughout
ROM.
When muscle generates tension at a 900 angle to
the bone, it is the most efficient at producing joint
motion.
3-21
TYPES OF CONTRACTION
Contract literally means to “draw together”.
 Muscle contraction occurs whenever
muscle fibers generate tension which may
occur while the muscle is actually
shortening, remaining the same length, or
lengthening.

3-22
CONCENTRIC OR SHORTENING
CONTRACTION




When tension by the muscle is
sufficient to overcome a
resistance and move the body
segment.
The muscle shortens.
When a muscle slowly
lengthens as it gives in to an
external force that is greater
than the contractile force it is
exerting.
Muscle is acting as a “brake”.
Fig 3.5c
Fig 3.5a
3-23
ISOMETRIC OR STATIC
CONTRACTION
 Isometric means “equal length”.




Tension is developed in the muscle without any
appreciable change in length.
Occurs under two conditions:
1. Antagonistic muscles contract with equal strength.
2. Muscle is held against another force.
Isotonic means “equal tension” - the tension remains
constant while muscle shortens or lengthens.
Isokinetic means “equal or same motion”.
 Maximum muscle effort at the same speed.
 “Accommodating resistance”.
3-24
INFLUENCE OF GRAVITY

Movements may be in the direction as
gravitational forces (downward), opposing
gravity (upward), or perpendicular to
gravity (horizontal).

Horizontal motion is not affected by gravity.

Lifting against gravity requires a concentric
contraction of the agonist.

Slowly lowering with gravity requires an
eccentric contraction of the same muscle.

A forceful downward motion uses agonist
muscles in a concentric contraction, since
gravitational pull is being exceeded.
Fig 3.6
3-25
LENGTH-TENSION RELATIONSHIP

Optimum length is the length at which
a muscle can exert maximum tension.
 Slightly
greater than resting length.
1. Passively stretched
2. Total tension
3. Developed tension
2
3
1
Fig 3.7
3-26
FORCE-VELOCITY RELATIONSHIP
As the speed of
contraction increases,
the force it is able to
exert decreases.
 At maximum velocity of
contraction the load is
zero.

Fig 3.8
3-27
STRETCH-SHORTENING CYCLE



Both muscle and tendon possess elastic
properties.
When concentric contraction is preceded by a
phase of active stretching, elastic energy
stored in the stretch phase is available for
use in the contractile phase.
This enhanced potential for work is attributed
to a combination of the series elastic
components (tendon) and the parallel elastic
components (cross bridge and fascicle
elasticity; stretch reflex).
3-28
COORDINATION OF THE MUSCULAR
SYSTEM
Movements of the body use considerable
activity in muscles in addition to those
directly responsible for the movement.
 Muscles causing the movement must have
a stable base.
 Bones not engaged in the movement must
be stabilized by other muscles.

3-29
ROLES OF MUSCLES

Movers, or Agonists: directly responsible
for producing a movement.
 Prime
movers: large impact on movement
 Assistant movers: only help when needed

This distinction between the various
muscles that contribute to a movement is
not always clearly defined.
3-30
ROLES OF MUSCLES

Synergists: cooperative
muscle function
 Stabilizing,
Fixator, &
Support Muscles
Fig 3.9
The
rhomboids
stabilize the
scapula
against the
pull of the
teres major.
Fig 3.10
–
prevent undesired
action
 Neutralizers
3-31
ROLES OF MUSCLES

Antagonists: have an effect opposite to
that of movers, or agonists.
 Check
ballistic movements
First: Antagonists must relax to permit
movement.
 Second: Acts as a brake at completion
of movement.

3-32
COCONTRACTION
The simultaneous contraction of movers
and antagonists.
 Neutralizers and stabilizers may need to
cocontract to counteract the additional
function of a mover.

3-33
ACTION OF BI-ARTICULAR MUSCLES
Muscles that pass over and act on two
joints
 Whether muscles flex joints in the same
direction or opposite directions, they are
not long enough to permit complete
movement in both joints at the same time.
 Resulting tension in one muscle is
transmitted to the other.
 Bi-articular muscles can continue to exert
tension without shortening.

3-34
ACTION OF BI-ARTICULAR MUSCLES


Concurrent Actions:
Simultaneous flexion or
extension of the hip and
knee joints.
No net change in length
of either muscle.
Fig. 3.11a

Fig. 3.11b
Countercurrent Action: one
muscle shortens at both
joints as the antagonist
lengthens correspondingly
and thereby gains tension
at both ends.
3-35
TYPES OF BODILY MOVEMENTS


Passive: no effort on the part of the subject
involved, motion due to outside force.
Active: movement is produced by the subject’s own
muscular activity.


In slow movements muscular tension is maintained
throughout ROM.
In rapid movements, tension could be maintained
throughout ROM, but this is an inefficient way of
performing.
3-36
BALLISTIC MOVEMENT

Movements that are initiated by vigorous
contraction and completed by momentum.



Throwing, striking, & kicking
In the early stages of learning concentrate on
form rather that accuracy.
Termination of ballistic action:
1. By contracting antagonist muscles.
 Forehand drive in tennis
2. By passive resistance of ligaments or other tissues at limits of
motion.
 Throwing motion
3. By the interference of an obstacle
 Chopping wood
3-37
METHODS OF STUDYING THE ACTION OF
MUSCLES






Conjecture & Reasoning:
Using knowledge of location
and attachments, and nature of
joints, one can deduce a
muscle’s action.
Muscle attachments & line of
pull determine possible
movements.
Fig 3.12
Dissection: meaningful basis for the visualization of
muscle’s potential movements.
Inspection & Palpation: valuable method for superficial
muscles.
Models: used for demonstration.
Muscle Stimulation: contraction of individual muscles.
3-38
METHODS OF STUDYING THE ACTION OF
MUSCLES



Electromyography (EMG): based on the fact that
contracting muscles generate electrical impulses.
Reveals both intensity
& duration of muscle
activity.
Cannot indicate
nature of contraction
or muscle action.
Fig. 3.13
3-39
MUSCULAR ANALYSIS
Description of muscular involvement is
added to previously completed analysis of
joint and segment involvement.
 Muscular action is identified for each joint
movement and recorded next to the joint
action on the chart (Table 1.2).

 Main
Muscle Groups Active
 Kind of Contraction
3-40
ANATOMICAL ANALYSIS OF THE STANDING
LONG JUMP:(PREPARATION PHASE)
Joint
Joint
Action
Segment
moved
Plane &
Axis
Force
Contraction
type
Prime movers
Ankle
Dorsiflexion
Shank
Sag/bilat
Gravity
Eccentric
Gastrocnemius,
soleus, peroneus
longus
Knee
Flexion
Thigh
Sag/bilat
Gravity
Eccentric
Quadriceps
femoris
Hip
Flexion
Trunk
Sag/bilat
Gravity
Eccentric
hamstrings
Shoulder
HyperExtension
Upper arm
Sag/bilat
Muscle
Concentric
Latissimus dorsi,
teres major,
post.deltoid
Elbow
Extension
Lower arm Sag/bilat
Muscle
Concentric
Triceps brachii,
anconeus
3-41
ANATOMICAL ANALYSIS OF THE STANDING
LONG JUMP: (POWER PHASE)
Joint
Joint
Action
Segment
moved
Plane &
Axis
Force
Contraction
type
Prime movers
Ankle
PlantarFlexion
Shank
Sag/bilat
Muscle
Concentric
Gastrocnemius,
soleus, peroneus
longus
Knee
Extension
Thigh
Sag/bilat
Muscle
Concentric
Quadriceps femoris
Hip
Extension
Trunk
Sag/bilat
Muscle
Concentric
Hamstrings
Shoulder
Flexion
Upper
arm
Sag/bilat
Muscle
Concentric
Pectoralis major,
anterior deltoid
Elbow
Extension
Lower
arm
Sag/bilat
Muscle
Concentric
Triceps brachii,
anconeus
3-42