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Chapter 2
Neuromuscular Fundamentals
Muscular System
• Over 600 muscles (215 pair) approximately 40% to
50% of body weight
• Functions
–
–
–
–
Movement
Protection
Support and Posture
Heat Production
Muscular Nomenclature
•Usually named because of one or more distinctive
characteristics. Often there is a crossover among
the various nomenclature.
Shape
Size
Number of Division
Location
Direction
Action
Action & Shape
Action & Size
Point of Attachment
Location & Attachment
Location & Number of Divisions
Muscular Shape and Fiber Arrangements
•
Muscle shape and fiber arrangement play a role in the muscle’s ability to exert force and the
ROM through which it can effectively exert force onto the bones to which it is attached.
1.
2.
. Shape
•
Cross-sectional
•
Ability to shorten
. Fiber Arrangements
Parallel arrangement (Fibers arranged parallel to
length of muscles)
=  ROM )
•
Flat
•
Fusiform
•
Strap
•
Radiate
•
Sphincter
Pennate Arrangement (Shorter fibers
arranged obliquely to their tendons)
=  Force )
•
Unipennate
•
Bipennate
•
Multipennate
Muscle Tissue Properties
• Irritability — ability to respond to a stimulus
• Contractility — ability to contract and develop tension
• Extensibility — ability to be stretched beyond resting
length
• Elasticity — ability to return to original length following
stretching
• Tonicity — state of
firmness of a muscle due to
nerve stimulation and motor
unit contraction
Muscle Terminology
• Intrinsic- muscles within or belonging solely to a body part it acts upon
• Extrinsic- muscles that originate outside a body part on which it acts
• Action- specific movement of a joint resulting from a concentric contraction
– Why do Muscles perform their particular actions?
• Line of pull
• Planes of motion of a joint
• Innervation- nerve responsible to provide stimulus to muscle fibers
• Amplitude- range of fiber length between maximal and minimal lengthening
• Gaster (belly)- portion of muscle that increases in diameter as muscle
contracts
• Origin- proximal attachment, usually least moveable part
• Insertion- distal attachment, usually most moveable part
– Exceptions
Muscle Contractions
•Isometric – (Static): muscle contraction in which:
–Tension develops, no change in length of muscle
–Muscular Force = Resistive Force
–Stabilization effect
•Isotonic – (Dynamic): muscle contraction in which:
–Tension develops, “causing” or “controlling” joint movement
Concentric (positive contraction)
Muscle shortens
Muscular force > Resistive force
Body part moves against (_____)
gravity or external force
Acceleration effect
Muscle(s) involved and movement
are the ______
Eccentric (negative contraction or
“action”)
Muscle lengthens
Muscular force < Resistive Force
Body part moves with (_____) gravity
or external force
Deceleration effect
Muscle(s) involved and movements
are ______
Muscle Force – Velocity Relationship
Concentric contraction against a
light resistance = ______ velocity
Increasing resistance = _______ in
the maximal velocity the muscle can
contract
Continuation of increasing
resistance eventually = _________
contraction if equal to muscular force
If resistance increases beyond
muscular force = _____ contraction
Role of Muscles
Agonist (prime mover): muscle that when
contracting concentrically causes joint motion
How do you determine which muscle groups are
involved?
Step #1: Identify what movement the resistance is
tending to cause
Step #2: The opposite muscle group is involved
If contracting = ______
If relaxing = _______
Antagonist: opposite side of the joint from the agonist
Role of Muscles
Stabilizer (fixator): a muscle(s) that contracts to fix or stabilize
a bone so that a muscle can do its intended work/movement
Straight leg raise lying supine
Crunch/Curl up
Neck flexion
Bench press
Role of Muscles
Static Stabilization
vs
Dynamic Stabilization
Role of Muscles
Neutralizer: Muscle that contracts to counteract or neutralize
the action of another muscle to prevent undesirable motions
Resulting from the combination of:
1.
2.
The Common action of muscles
The antagonistic action of muscles
Movement/ Action:
– Muscles:
– Common Actions:
– Neutralizing Actions:
Role of Muscles
Synergist: A muscle(s) that works with an agonist, is partial
antagonist, and contracts to prevent an undesired movement
Agonist(s)
Synergist(s)
Undesired
Movement
Making a fist
Biceps curl
(dumbbell)
Kicking a
football
Note: A muscle tends to perform all its actions when it contracts
unless something prevents those movements from occurring.
Role of Muscles
If the stabilizer muscle is a non-antagonistic muscle  it is called a
“____________”
If the stabilizer muscle is an antagonistic muscle  it is called a
“____________”
If the stabilizer muscle is an antagonistic muscle + a common
action it is called a “____________”
Central Nervous System
Peripheral Nervous System
Myotome
Dermatome
Stretching
Myotatic Reflex (Stretch Reflex)
Inverse Myotatic Reflex
Neuromuscular Concepts
• Motor Unit
• All or none principle
• Increasing Fiber Recruitment
Click
here
Neuromuscular Concepts
Muscular Length- Tension Relationship
The greatest muscle tension can be developed when a muscle is
stretched. Why?
• Greatest tension: Between 100% and 130% of resting length
• Least tension: Muscle shortened to approx. 50 – 60% of resting
length
• Seated leg extension
• Prone hamstring curl
• Vertical jump
Active & Passive Insufficiency
• Active Insufficiency:
– When a muscle becomes shortened to
the point at which it cannot generate or
maintain active tension
• Passive Insufficiency:
– When the opposing
muscle becomes
stretched to the point
at which it can no
longer lengthen and
allow movement
Neuromuscular Concepts
Angle of Pull
of
The angle between the 1) line of pullAngle
of
the
pull >90°
muscle and the 2) bone on which it inserts
Rotary components– that muscular force that acts
perpendicular to the long axis of the bone/lever
Angle of
•
pull <90°
When angle of pull is 90° =____% rotary force
Note: at all other degrees of angle of pull one or two of the other components
of force (non-rotary) is operating “in addition to” the rotary component.
Non-Rotary Component
Angle of pull
90° =___________
If angle of pull is <90° =___________ If angle of pull is=>90°
Why?
Why?
Neuromuscular Concepts
Angle of Resistance
The angle between the:
1) direction of resistance and the
2)lever to which the resistance is attached or applied
•
•
Differentiate between applied and attached
The angle of resistance is zero if the center of gravity at the segment
lies on a line between the _________ and the ___________
Rotary Component
•
At a 90° angle of resistance 100% of the energy of resistance is
causing the lever to __________________________________
•
At a 0° angle of resistance 100% the energy of resistance is
causing either:
•
•
•
___________________90º
element
___________________ element
There is no force causing movement of the bone/lever around its axis
Biarticular Muscles & Movement Patterns
•Concurrent Movement Pattern – Muscle movement pattern that
allows the muscles to maintain a relatively constant length and tension
at both joints as go through a range of motion.
•Parallel Squat
–Rectus Femoris Contraction = __________
•Hamstrings = ___________
–Biceps Femoris Contraction = __________
•Quadriceps = ___________
•Lombard’s Paradox?
–Involves comparison between two
antagonistic muscles
–Both muscles must be biarticular
Parallel Squat:
–Rectus Femoris
–Biceps Femoris
Knee
Hip
MFA
Rectus Femoris
4.4
3.9
Longer @ Knee
Biceps Femoris
3.4
6.7
Longer @ Hip
• Countercurrent Movement Pattern
– Muscle movement pattern that results from the concentric contraction
of a biarticular muscle that produces its intended movements. Results
in increased tension and stretch of the antagonist muscle.
Guidelines for Muscle Testing and Exercise
Test both sides – comparison
“Isolate” the muscle
Stabilize the proximal segment
Apply a 90º angle of resistance
Apply resistance to the distal end of distal
segment
6. To overcome a deformity
1.
2.
3.
4.
5.
•
•
•
•
Stretch tight muscle groups
Strengthen the weak muscle groups
Maintain ______ _________ (24-7)
External force is usually required
Questions
1.
Person has a weak right biceps.
Question
To strengthen, would you perform biceps curl with a barbell?
2.
Person has a weak left triceps.
Question
Would push-ups be a good exercise to strengthen the left
triceps?
3.
Person has weak right rhomboids.
Question
How would you strengthen?
4.
How would you isolate the soleus to stretch/strengthen?
5.
How would you isolate the gluteus maximus?
Stages of Development of Acquired
Musculoskeletal Deformities
•First Degree (curable by exercise – strengthening the
weak, stretching the tight)
A. Soft tissue: Changes in muscle tone and habitual posture
B. Bone tissue: No bony change
C. Corrective treatment: The patient can himself correct the
position of the affected part
•Second Degree (improvable by exercise)
A. Soft tissue: Contracture of soft tissue structures
B. Bone tissue: Slight degree of bony change
C. Corrective treatment: Patient cannot himself correct the
deformity, but can be corrected to some extent by
another person (external source)
•Third Degree (little if any change achieved with
exercise)
A. Bone tissue: Serious bony change
Posture
The relationship of body segments to one another
Lateral Line of Gravity
Anterior Line of Gravity