Neuromuscular Fundamentals
Chapter 2
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.
Size
Shape
Number of Division
Direction
Location
Point of Attachment
Action
Action & Shape
Action & Size
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. .
• Cross-sectional
• Ability to shorten
2. .
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
Shape
Fiber Arrangements
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 shortensMuscular force > Resistive forceBody part moves against (_____) gravity or external forceAcceleration effectMuscle(s) involved and movement are the ______
Eccentric (negative contraction or “action”)Muscle lengthensMuscular force < Resistive ForceBody part moves with (_____) gravity or external forceDeceleration effectMuscle(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 contractContinuation 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
Crunch/Curl up
Straight leg raise lying supine
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. The Common action of muscles
2. 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
Kicking a football
Biceps curl (dumbbell)
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
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Neuromuscular Concepts
Muscular Length- Tension RelationshipThe 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 PullThe angle between the 1) line of pull of the
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
• When angle of pull is 90° =____% rotary forceNote: 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 ComponentIf angle of pull is <90° =___________
Why?
If angle of pull is >90° =___________
Why?
Angle of pull >90°
Angle of pull <90°
Angle of pull = 90°
Neuromuscular ConceptsAngle of ResistanceThe angle between the:1) direction of resistance and the2)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: • ___________________ element• ___________________ element• There is no force causing movement of the bone/lever around its axis
90º
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
1. Test both sides – comparison
2. “Isolate” the muscle
3. Stabilize the proximal segment
4. Apply a 90º angle of resistance
5. Apply resistance to the distal end of distal segment
6. To overcome a deformity• Stretch tight muscle groups• Strengthen the weak muscle groups• Maintain ______ _________ (24-7)• External force is usually required
Questions1. 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:
B. Bone tissue:
C. Corrective treatment:
•Second Degree (improvable by exercise)
A. Soft tissue:B. Bone tissue:C. Corrective treatment:
•Third Degree (little if any change achieved with exercise)
A. Bone tissue:
Changes in muscle tone and habitual posture
No bony change
The patient can himself correct the position of the affected part
Contracture of soft tissue structuresSlight degree of bony change
Patient cannot himself correct the deformity, but can be corrected to some extent by another person (external source)
Serious bony change
Posture
Anterior Line of GravityLateral Line of Gravity
The relationship of body segments to one another