Chapter 2

Neuromuscular Fundamentals

Manual of Structural Kinesiology

 

Skeletal Muscles

Responsible for movement:

Muscle contraction produces:

Muscles also provide

_________________

_________________

_______________________________

 

 

Over ___________ skeletal muscles comprise approximately 40 to 50% of body weight

_______ pairs of skeletal muscles usually work in cooperation with each other to perform opposite actions at the joints which they cross

Aggregate muscle action - _______________________________________

 

Muscle Nomenclature

Muscles are usually named due to

_______________________

_______________________

_______________________

Shape – _____________________

Size – _____________________

Number of divisions – ‚‚_____________________

Direction of its fibers – _____________________

 

Location - _____________________

Points of attachment - _____________________

Action - _____________________

Action & shape – _____________________

 

Action & size – _____________________

Shape & location – _____________________

Location & attachment – _____________________

Location & number of divisions – _____________________

 

Muscle grouping & naming

Shape – _____________________

Number of divisions – _____________________

Location – _____________________

Action – _____________________

Shape of Muscles & Fiber Arrangement

Muscles have different shapes & fiber arrangement

Shape & fiber arrangement affects

Cross section diameter

_____________________

greater cross section diameter = _____________________

Muscleís ability to shorten

_____________________

 

2 major types of fiber arrangements

_____________________

each is further subdivided according to shape

_____________________

 

Fiber Arrangement - Parallel

Categorized into following shapes

_____________________

_____________________

_____________________

_____________________

_____________________

Flat muscles

__________________________________________________

__________________________________________________

Ex. rectus abdominus & external oblique

Fiber Arrangement - Parallel

Fusiform muscles

__________________________________________________

__________________________________________________

Ex. brachialis, biceps brachii

Strap muscles

‚‚‚‚‚‚‚‚‚‚‚‚‚__________________________________________________

__________________________________________________

Ex. sartorius

Radiate muscles

_________________________________________________

_________________________________________________

_________________________________________________

Ex. pectoralis major, trapezius

Sphincter or circular muscles

_________________________________________________

_________________________________________________

Ex. orbicularis oris surrounding the mouth

 

Fiber Arrangement - Pennate

Pennate muscles

___________________________

_____________________________________________________________

_____________________________________________________________

 

Categorized based upon the exact arrangement between fibers & tendon

__________________

__________________

__________________

 

Unipennate muscles

__________________________________________________

Ex. biceps femoris, extensor digitorum longus, tibialis posterior

Fiber Arrangement - Pennate

Bipennate muscle

___________________________________________________

Ex. rectus femoris, flexor hallucis longus

 

Multipennate muscles

___________________________________________________

Ex. deltoid

Bipennate & unipennate produce _______________________

 

Muscle Tissue Properties

Skeletal muscle tissue has 4 properties related to its ability to produce force & movement about joints

_________________

_________________

_________________

_________________

Muscle Tissue Properties

________________- property of muscle being sensitive or responsive to chemical, electrical, or mechanical stimuli

________________ - ability of muscle to contract & develop tension or internal force against resistance when stimulated

Muscle Tissue Properties

________________ - ability of muscle to be stretched back to its original length following contraction

________________- ability of muscle to return to its original length following stretching

 

Muscle Terminology

Intrinsic - _________________________________________________________

Ex. small intrinsic muscles found entirely within the hand

Extrinsic - ________________________________________________________

Ex. forearm muscles that attach proximally on distal humerus and insert on fingers

Muscle Terminology

Action - __________________________________________________________

Ex. biceps brachii has the action of flexion at elbow

Actions are usually _________________________________________________

Any of the muscles in the group can be said to cause the action, even though it is usually an effort of the entire group

A muscle may cause more than one action either at the same joint or a different joint depending upon the characteristics of the joints crossed by the muscle

 

Origin - ____________________________________________________________

Insertion - ___________________________________________________________

 

When a particular muscle contracts

it tends to pull both ends toward the _____________

if neither of the bones to which a muscle is attached are stabilized then both bones move _________________________________________________

more commonly one bone is more stabilized by a variety of factors and the less stabilized bone usually moves toward the more stabilized bone upon contraction

Ex. biceps curl exercise

biceps brachii muscle in arm has its origin (least movable bone) on scapula and its insertion (most movable bone) on radius

In some movements this process can be reversed, Ex. pull-up

radius is relatively stable & scapula moves up

biceps brachii is an extrinsic muscle of elbow

brachialis is intrinsic to the elbow

Types of muscle contraction

All muscle contractions are either isometric or isotonic

Isometric contraction

_____________________________________________________________

_______________________________

____________________________________________

 

Isotonic contractions involve muscle developing tension to either cause or control joint movement

________________________________

________________________________________________________________

________________________________________________________

 

Movement may occur at any given joint without any muscle contraction whatsoever

________________________

solely due to external forces such as those applied by another person, object, or resistance or the force of gravity in the presence of muscle relaxation

 

Concentric contractions involve ________________________________

Eccentric contractions involve ________________________________________

Contraction is contradictory regarding _______________________, since the muscle is really lengthening while maintaining considerable tension

Eccentric muscle action is ________________________

 

Concentric contraction

‚‚‚‚‚‚‚‚‚____________________________________________

____________________________________________

causes movement _____________________________

described as being _____________________________

 

Concentric contraction

force developed by the muscle __________________________________

results in joint angle changing in the direction of ____________________

causes body part to move _______________________________________

 

Eccentric contraction (muscle action)

muscle lengthens __________________

occurs when muscle gradually ________________________________________

weight or resistance ____________________________but not to the point that muscle cannot control descending movement

 

Eccentric contraction (muscle action)

controls movement with _____________________________

described as a __________________________

force developed by the muscle is ________________________

results in the joint angle changing in the ______________________________

causes body part to move __________________________________

 

Eccentric contraction (muscle action)

Some refer to this as a ___________________ instead of a contraction since the muscle is lengthening as opposed to shortening

Various exercises may use any one or all of these contraction types for muscle development

Types of muscle contraction

____________________ - a type of dynamic exercise using concentric and/or eccentric muscle contractions

the speed (or velocity) of movement is ________________

muscular contraction (ideally maximum contraction) occurs _____________________

not another type of contraction, as some have described

Ex. Biodex, Cybex, Lido

 

Agonist muscles

cause joint motion through a specified plane of motion when contracting ____________

known as __________________________________

 

Antagonist muscles

located on _____________________________

have the ________________________________

known as ________________________ muscles

work in cooperation with agonist muscles by relaxing & allowing movement

when contracting concentrically perform the ________________________________

 

Stabilizers

surround _________________________

contract to _______________________ the area to enable another limb or body segment to exert force & move

known as ___________________

essential in establishing a relatively firm base for the more distal joints to work from when carrying out movements

 

Synergist

assist in ________________________

not necessarily _______________________for the action

known as ____________________________

assist in ____________________& rule out _____________________

 

Neutralizers

___________________________ the action of another muscle to prevent undesirable movements such as inappropriate muscle substitutions

referred to as _______________________

contract to ______________________________ of other muscles

 

Tying Roles of Muscles All Together

Muscles with __________________________

attempt to perform all of their actions when contracting

cannot determine which actions are appropriate for the task at hand

Actions actually performed depend upon several factors

the ___________________

______________________

______________________

___________________________________________________________________

Tying Roles of Muscles All Together

Two muscles may work in synergy by counteracting their opposing actions to accomplish a common action

 

Example of muscle roles in kicking a ball

Muscles primarily responsible for ____________________________are _________

Hamstrings are _________________________________

Preciseness of the kick depends upon _____________________________________

The lower extremity route & subsequent angle at the point of contact (during the forward swing) depend upon a certain amount of _________________ or ____________ in the hip abductors, adductors, internal rotators & external rotators (acting in a synergistic fashion to guide lower extremity precisely)

These synergistic muscles are not primarily responsible for knee extension & hip flexion but _______________________________________________

They assist in _____________________& _________________________

These synergistic muscles in contralateral hip & pelvic area must be under relative tension to help ____________ or ______________ the pelvis on that side to provide a relatively stable base for the hip flexors on the involved side to contract against

Pectineus & tensor fascia latae are _______________________, respectively, in addition to flexors

Abduction & adduction actions are _______________________________

Common action of the two muscles results in _________________________

 

Antagonistic muscles produce ______________________________________

Ex. elbow extensors are antagonistic to elbow flexors

Elbow movement in returning to hanging position after chinning is _________________________, but triceps & anconeus are not being strengthened

Elbow joint flexors contract ___________________________________________

 

Antagonistic muscles produce actions __________________________________

Specific exercises are needed for each antagonistic muscle group

 

Reversal of Muscle Function

A muscle group described to perform a given function can contract to control the exact opposite motion

 

Determination of Muscle Action

Variety of methods

____________________________________

____________________________________

____________________________________

________________

________________

________________

 

Determination of Muscle Action

Palpation

using to sense of touch to feel or examine a muscle as it is contracted

limited to superficial muscles

helpful in furthering oneís understanding of joint mechanics

Long rubber bands may be used as models to simulate muscle lengthening or shortening as joints move through ranges of motion

 

Electromyography (EMG)

utilizes either surface electrodes which are placed over muscle or fine wire/needle electrodes placed into muscle

as subject moves joint & contracts muscles, EMG unit detects action potentials of muscles and provides an electronic readout of contraction intensity & duration

most accurate way of detecting presence & extent of muscle activity

 

Electrical muscle stimulation

reverse approach of electromyography

use electricity to cause muscle activity

surface electrodes are placed over muscle & the stimulator causes muscle to contract

joint actions may then be observed to see the effect of the muscleís contraction

 

Lines of Pull

Consider the following

____________________________________________________________

____________________________________________________________

____________________________________________________________

 

As a joint moves the line of pull may ______________________________
_____________________________________________________________

Potential effect of other musclesí relative ___________ or _____________ on a particular muscleís ability to cause motion

Effect of a muscleís __________________ on its ability to ______________

Lines of Pull

Effect of the ________________________ on the ability of a biarticular or multiarticular muscle to generate force or allow lengthening

 

Proprioception & Kinesthesis

Activity performance is significantly dependent upon ________________ feedback from the body

We use various ______________________ to determine a response to our environment

___________________________________________

 

All or None Principle

When muscle contracts, contraction occurs at the muscle fiber level within a particular motor unit

The number of muscle fibers contracting within the muscle may vary significantly

from ________________________________

depending on the number of muscle fibers within each activated motor unit & the number of motor units activated

 

All or None Principle - regardless of number, individual muscle fibers within a given motor unit will either fire & contract ________________ or _________________

difference between lifting a minimal vs. maximal resistance is the number of _____________________________________

The number of muscle fibers recruited may be increased by

______________________________________________

______________________________________________

______________________________________________

______________________________________________

 

Muscle Length - Tension Relationship

 

Maximal ability of a muscle to develop tension & exert force varies depends upon __________________________________________

Generally, depending _________________________

Greatest amount of tension can be developed when a muscle is stretched between __________________________of its resting length

Stretch beyond ______________________ of resting length significantly _________________ the amount of force muscle can exert

 

Muscle Length - Tension Relationship

Generally, depending upon muscle involved

A proportional decrease in ability to develop tension occurs as a muscle is __________

When shortened to around ______________________of resting length ability to develop contractile tension is essentially reduced to ____________

 

Muscle Length - Tension Relationship

Ex. 1 Increasing ability to exert force

squat slightly to stretch the calf, hamstrings, & quadriceps before contracting same muscles concentrically to jump

Ex. 2. Reducing ability to exert force

isolate the gluteus maximus by maximally shortening the hamstrings with knee flexion

 

Muscle Force – Velocity Relationship

When muscle is contracting (concentrically or eccentrically) the rate of length change is __________________________________

When contracting concentrically against a light resistance muscle is able to contract at a ______________________

 

As resistance increases, _____________ at which muscle is able to contract __________

Eventually, as load increases, the velocity decreases to ____________ resulting in an _________________ contraction

As load increases beyond muscleís ability to maintain an isometric contraction, the muscle begins to ____________________ resulting in an ________________ contraction

Slight increases in load results in relatively _________velocity of lengthening

As load increases further the velocity of lengthening will ________________ as well

Eventually, load may increase to point where muscle can _________________, resulting in ____________________________________

__________________ relationship between concentric velocity and force production

 

As force needed to cause movement of an object increases the velocity of concentric contraction __________________

Somewhat proportional relationship between ________________ and ______________

As force needed to control an objectís movement increases, the velocity of eccentric lengthening __________________, at least until when control is lost

 

Angle of pull

Angle between the line of pull of the muscle & the bone on which it inserts (angle of attachment facing away from joint as opposed to angle on side of joint)

With every degree of joint motion, the angle of pull _______________

Joint movements & insertion angles involve mostly ____________ of pull

 

Angle of pull _____________ as bone moves away from its anatomical position through local muscle groupís contraction

Range of movement depends on _________________ & _______________

Most muscles work at angles of pull less than ________________ degrees

Amount of muscular force needed to cause joint movement is affected by ___________

 

Rotary component (vertical component) - component of muscular force that acts ________________________________ (lever)

When the line of muscular force is at _______degrees to bone on which it attaches, all of the muscular force is ______________ (100% of force is contributing to movement)

All of force is being used to _______________________________________

The closer the angle of pull to 90 degrees, the _______________ the rotary component

 

At all other degrees of the angle of pull, one of the other two components of force are operating in addition to rotary component

Rotary component continues with _____________, to rotate the lever about its axis

Second force component is the horizontal, or _____________________ and is either a _____________________ or a ___________________, depending on whether the angle of pull is less than or greater than _________degrees

 

If angle is less than 90 degrees, the force is a ____________________ force because its pull directs the bone toward the joint axis

If angle is greater than 90 degrees, the force is ___________________ due to its pull directing the bone away from the joint axis

 

Sometimes desirable to begin with the angle of pull is at ______________degrees

chin-up (pull-up)

angle makes the chin-up easier because of more advantageous angle of pull

compensate for lack of sufficient strength

 

Biarticular or Multiarticular Muscles

Biarticular muscles – _________________________

Depending, biarticular muscles may contract & cause motion at either one or both of its joints

Two advantages over uniarticular muscles

can cause and/or control motion at ___________________

are able to maintain a relatively constant length due to ___________________ and _____________________________

 

Muscle does not actually shorten at one joint & lengthen at other

The concentric shortening of the muscle to move one joint is offset by motion of the other joint which moves its attachment of muscle farther away

This maintenance of a relatively constant length results in the muscle being able to continue its exertion of force

 

Ex.1 Hip & knee biarticular muscles

______________________________movement pattern occurs when both the knee & hip extend at the same time

If only knee extension occurs, rectus femoris shortens & loses tension as do other quadriceps muscles, but its relative length & subsequent tension may be maintained due to its relative lengthening at the hip joint during extension

 

Ex. 2 Hip & knee biarticular muscles

________________________________movement pattern occurs in kicking

During the lower extremity forward movement phase the rectus femoris concentrically contracts to flex the hip & extend the knee

These two movements, when combined, increase the tension or stretch on the hamstring muscles both at the knee & hip

Biarticular or Multiarticular Muscles

Multiarticular muscles act on three or more joints due to the line of pull between their origin & insertion crossing multiple joints

Principles relative to biarticular muscles apply similarly to multiarticular muscles

Reciprocal Inhibition or Innervation

Antagonist muscles groups must relax & lengthen when the agonist muscle group contracts

This reciprocal innervation effect occurs through reciprocal inhibition of the antagonists

Activation of the motor units of the agonists causes a reciprocal neural inhibition of the motor units of the antagonists

This reduction in neural activity of the antagonists allows them to subsequently lengthen under less tension

Reciprocal Inhibition or Innervation

 

Ex. Compare the ease of

stretching hamstrings when simultaneously contracting the quadriceps

       vs.

stretching hamstrings without contracting quadriceps

Active & Passive Insufficiency

As muscle shortens its ability to exert force diminishes

Active insufficiency is reached when the muscle becomes shortened to the point that it can not generate or maintain active tension

Passively insufficiency is reached when the opposing muscle becomes stretched to the point where it can no longer lengthen & allow movement

Active & Passive Insufficiency

Easily observed in either biarticular or multiarticular muscles when full range of motion is attempted in all joints crossed by the muscle

Ex. Rectus femoris contracts concentrically to both flex the hip & extend the knee.

Can completely perform either action one at a time but actively insufficient to obtain full range at both joints simultaneously

Active & Passive Insufficiency

Similarly, hamstrings can not usually stretch enough to allow both maximal hip flexion & maximal knee extension due passive insufficiency

As a result, it is virtually impossible to actively extend the knee fully when beginning with the hip fully flexed or vice versa