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