Manual of Structural Kinesiology

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Skeletal Muscles

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Skeletal Muscles
Over 600 skeletal muscles comprise approximately 40 to 50% of body weight
215 pairs of skeletal muscles usually work in cooperation with each other to perform opposite actions at the joints which they cross
Aggregate muscle action - muscles work in groups rather than independently to achieve a given joint motion

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Muscle Nomenclature
Muscles are usually named due to
visual appearance
anatomical location
function
Shape – deltoid, rhomboid
Size – gluteus maximus, teres minor
Number of divisions – triceps brachii
Direction of its fibers – external oblique

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Muscle Nomenclature
Action & size – adductor magnus
Shape & location – serratus anterior
Location & attachment – brachioradialis
Location & number of divisions – biceps femoris

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Muscle Tissue Properties
Skeletal muscle tissue has 4 properties related to its ability to produce force & movement about joints
Irritability
Contractility
Extensibility
Elasticity

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Muscle Tissue Properties
Irritability - property of muscle being sensitive or responsive to chemical, electrical, or mechanical stimuli
Contractility - ability of muscle to contract & develop tension or internal force against resistance when stimulated

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Muscle Tissue Properties
Extensibility - ability of muscle to be stretched back to its original length following contraction
Elasticity - ability of muscle to return to its original length following stretching

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
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Muscle Terminology
Origin - proximal attachment, generally considered the least movable part or the part that attaches closest to the midline or center of the body
Insertion - distal attachment, generally considered the most movable part or the part that attaches farthest from the midline or center of the body

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Types of muscle contraction
All muscle contractions are either isometric or isotonic
Isometric contraction
tension is developed within muscle but joint angles remain constant
static contractions
significant amount of tension may be developed in muscle to maintain joint angle in relatively static or stable position

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Types of muscle contraction
Muscle Contraction
(under tension)

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Types of muscle contraction
Isotonic contractions involve muscle developing tension to either cause or control joint movement
dynamic contractions
the varying degrees of tension in muscles are causing joint angles to change
Isotonic contractions are either concentric or eccentric on basis of whether shortening or lengthening occurs

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Types of muscle contraction
Concentric contractions involve muscle developing tension as it shortens
Eccentric contractions involve the muscle lengthening under tension
Contraction is contradictory regarding eccentric muscle activity, since the muscle is really lengthening while maintaining considerable tension
Eccentric muscle action is perhaps more correct

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Types of muscle contraction
Concentric contraction
muscle develops tension as it shortens
occurs when muscle develops enough force to overcome applied resistance
causes movement against gravity or resistance
described as being a positive contraction

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Types of muscle contraction
Concentric contraction
force developed by the muscle is greater than that of the resistance
results in joint angle changing in the direction of the applied muscle force
causes body part to move against gravity or external forces

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Types of muscle contraction
Eccentric contraction (muscle action)
muscle lengthens under tension
occurs when muscle gradually lessens in tension to control the descent of resistance
weight or resistance overcomes muscle contraction but not to the point that muscle cannot control descending movement

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Types of muscle contraction
Eccentric contraction (muscle action)
controls movement with gravity or resistance
described as a negative contraction
force developed by the muscle is less than that of the resistance
results in the joint angle changing in the direction of the resistance or external force
causes body part to move with gravity or external forces (resistance)

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Types of muscle contraction
Eccentric contraction (muscle action)
Some refer to this as a muscle action 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

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Types of muscle contraction
Isokinetics - a type of dynamic exercise using concentric and/or eccentric muscle contractions
the speed (or velocity) of movement is constant
muscular contraction (ideally maximum contraction) occurs throughout movement
not another type of contraction, as some have described
Ex. Biodex, Cybex, Lido

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Role of Muscles
Agonist muscles
cause joint motion through a specified plane of motion when contracting concentrically
known as primary or prime movers, or muscles most involved

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
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Role of Muscles
Antagonist muscles
located on opposite side of joint from agonist
have the opposite concentric action
known as contralateral muscles
work in cooperation with agonist muscles by relaxing & allowing movement
when contracting concentrically perform the opposite joint motion of agonist

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Role of Muscles
Stabilizers
surround joint or body part
contract to fixate or stabilize the area to enable another limb or body segment to exert force & move
known as fixators
essential in establishing a relatively firm base for the more distal joints to work from when carrying out movements

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Role of Muscles
Synergist
assist in action of agonists
not necessarily prime movers for the action
known as guiding muscles
assist in refined movement & rule out undesired motions

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Role of Muscles
Neutralizers
Counteract or neutralize the action of another muscle to prevent undesirable movements such as inappropriate muscle substitutions
referred to as neutralizing
contract to resist specific actions of other muscles

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Tying Roles of Muscles All Together
Muscles with multiple agonist actions
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 motor units activated
joint position
muscle length
relative contraction or relaxation of other muscles acting on the joint

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Tying Roles of Muscles All Together
Two muscles may work in synergy by counteracting their opposing actions to accomplish a common action

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Tying Roles of Muscles All Together
Example of muscle roles in kicking a ball
Muscles primarily responsible for hip flexion & knee extension are agonists
Hamstrings are antagonistic & relax to allow the kick to occur
Preciseness of the kick depends upon the involvement of many other muscles

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Tying Roles of Muscles All Together
Example of muscle roles in kicking a ball
The lower extremity route & subsequent angle at the point of contact (during the forward swing) depend upon a certain amount of relative contraction or relaxation in the hip abductors, adductors, internal rotators & external rotators (acting in a synergistic fashion to guide lower extremity precisely)

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Tying Roles of Muscles All Together
Example of muscle roles in kicking a ball
These synergistic muscles are not primarily responsible for knee extension & hip flexion but contribute to accuracy of the total movement
They assist in refining the kick & preventing extraneous motions

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Tying Roles of Muscles All Together
Example of muscle roles in kicking a ball
These synergistic muscles in contralateral hip & pelvic area must be under relative tension to help fixate or stabilize 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 adductors and abductors, respectively, in addition to flexors

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Tying Roles of Muscles All Together
Example of muscle roles in kicking a ball
Abduction & adduction actions are neutralized by each other
Common action of the two muscles results in hip flexion

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Tying Roles of Muscles All Together
Antagonistic muscles produce actions opposite those of the agonist
Ex. elbow extensors are antagonistic to elbow flexors
Elbow movement in returning to hanging position after chinning is extension, but triceps & anconeus are not being strengthened
Elbow joint flexors contract concentrically followed by eccentric contraction of same muscles

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Tying Roles of Muscles All Together
Antagonistic muscles produce actions opposite those of the agonist
Specific exercises are needed for each antagonistic muscle group

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Reversal of Muscle Function
A muscle group described to perform a given function can contract to control the exact opposite motion

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Neural control of voluntary movement
Muscle contraction result from stimulation by the nervous system
Every muscle fiber is innervated by a somatic motor neuron which, when an appropriate stimulus is provided, results in a muscle contraction

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Neural control of voluntary movement
Sensory neurons transmit impulses to spinal cord & brain from all parts of body
Motor neurons transmit impulses away from the brain & spinal cord to muscle & glandular tissue
Interneurons are central or connecting neurons that conduct impulses from sensory neurons to motor neurons

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Proprioception & Kinesthesis
Activity performance is significantly dependent upon neurological feedback from the body
We use various senses to determine a response to our environment
Seeing when to lift our hand to catch a fly ball

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Proprioception & Kinesthesis
Taken for granted are sensations associated with neuromuscular activity through proprioception
Proprioceptors - internal receptors located in skin, joints, muscles, & tendons which provide feedback relative to tension, length, & contraction state of muscle, position of body & limbs, and movements of joints

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Proprioception & Kinesthesis
Proprioceptors work in combination with other sense organs to accomplish kinesthesis
Kinesthesis - awareness of position & movement of the body in space
Proprioceptors specific to muscles
Muscles spindles
Golgi tendon organs (GTO)

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Proprioception & Kinesthesis
Muscle spindles
concentrated primarily in muscle belly between the fibers
sensitive to stretch & rate of stretch
Muscle stretch occurs
Impulse is sent to the CNS
CNS activates motor neurons of muscle and causes it to contract

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
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Proprioception & Kinesthesis
Ex. Knee jerk or patella tendon reflex
Reflex hammer strikes patella tendon
Causes a quick stretch to musculotendonis unit of quadriceps
In response quadriceps fires & the knee extends
More sudden the tap, the more significant the reflexive contraction

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Proprioception & Kinesthesis
Stretch reflex may be utilized to facilitate a greater response
Ex. Quick short squat before attempting a jump
Quick stretch placed on muscles in the squat enables the same muscles to generate more force in subsequently jumping off the floor

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Proprioception & Kinesthesis
Golgi tendon organ
found in the tendon close to muscle tendon junction
sensitive to both muscle tension & active contraction
much less sensitive to stretch than muscles spindles
require a greater stretch to be activated

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Proprioception & Kinesthesis
Tension in tendons & GTO increases as muscle contract, which activates the GTO
GTO stretch threshold is reached
Impulse is sent to the CNS
CNS causes the muscle to relax
facilitates activation of the antagonists as a protective mechanism
GTO protects us from an excessive contraction by causing it to relax

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
All or None Principle
All or None Principle - regardless of number, individual muscle fibers within a given motor unit will either fire & contract maximally or not at all
difference between lifting a minimal vs. maximal resistance is the number of muscle fibers recruited

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
All or None Principle
The number of muscle fibers recruited may be increased by
activating those motor units containing a greater number of muscle fibers
activating more motor units
increasing the frequency of motor unit activation

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Muscle Length - Tension Relationship
Maximal ability of a muscle to develop tension & exert force varies depends upon the length of the muscle during contraction

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Muscle Length - Tension Relationship
Generally, depending upon muscle involved
Greatest amount of tension can be developed when a muscle is stretched between 100% to 130% of its resting length
Stretch beyond 100% to 130% of resting length significantly decreases the amount of force muscle can exert

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Muscle Length - Tension Relationship
Generally, depending upon muscle involved
A proportional decrease in ability to develop tension occurs as a muscle is shortened
When shortened to around 50% to 60% of resting length ability to develop contractile tension is essentially reduced to zero

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
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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

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Muscle Force – Velocity Relationship
When muscle is contracting (concentrically or eccentrically) the rate of length change is significantly related to the amount of force potential
When contracting concentrically against a light resistance muscle is able to contract at a high velocity

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Muscle Force – Velocity Relationship
As resistance increases, the maximal velocity at which muscle is able to contract decreases
Eventually, as load increases, the velocity decreases to zero resulting in an isometric contraction
As load increases beyond muscle’s ability to maintain an isometric contraction, the muscle begins to lengthen resulting in an eccentric contraction

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Muscle Force – Velocity Relationship
Slight increases in load results in relatively low velocity of lengthening
As load increases further the velocity of lengthening will increase as well
Eventually, load may increase to point where muscle can no longer resist, resulting in uncontrollable lengthening or dropping of load
Inverse relationship between concentric velocity and force production

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Muscle Force – Velocity Relationship
As force needed to cause movement of an object increases the velocity of concentric contraction decreases
Somewhat proportional relationship between eccentric velocity and force production
As force needed to control an object’s movement increases, the velocity of eccentric lengthening increases, at least until when control is lost

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
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 changes
Joint movements & insertion angles involve mostly small angles of pull

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
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Angle of pull
Angle of pull decreases as bone moves away from its anatomical position through local muscle group’s contraction
Range of movement depends on type of joint & bony structure
Most muscles work at angles of pull less than 50 degrees
Amount of muscular force needed to cause joint movement is affected by angle of pull

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
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Angle of pull
Rotary component (vertical component) - component of muscular force that acts perpendicular to long axis of bone (lever)
When the line of muscular force is at 90 degrees to bone on which it attaches, all of the muscular force is rotary force (100% of force is contributing to movement)
All of force is being used to rotate the lever about its axis
The closer the angle of pull to 90 degrees, the greater the rotary component

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Angle of pull
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 less force, to rotate the lever about its axis
Second force component is the horizontal, or nonrotary component and is either a stabilizing component or a dislocating component, depending on whether the angle of pull is less than or greater than 90 degrees

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Angle of pull
If angle is less than 90 degrees, the force is a stabilizing force because its pull directs the bone toward the joint axis
If angle is greater than 90 degrees, the force is dislocating due to its pull directing the bone away from the joint axis

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Angle of pull
Sometimes desirable to begin with the angle of pull is at 90 degrees
chin-up (pull-up)
angle makes the chin-up easier because of more advantageous angle of pull
compensate for lack of sufficient strength

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
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Biarticular or Multiarticular Muscles
Biarticular muscles – cross & act on two different joints
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 more than one joint
are able to maintain a relatively constant length due to "shortening" at one joint and "lengthening" at another joint

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Biarticular or Multiarticular Muscles
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

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Biarticular or Multiarticular Muscles
Ex.1 Hip & knee biarticular muscles
Concurrent 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

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
Biarticular or Multiarticular Muscles
Ex. 2 Hip & knee biarticular muscles
Countercurrent 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

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
2-
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

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
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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

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
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Reciprocal Inhibition or Innervation
Ex. Compare the ease of
stretching hamstrings when simultaneously contracting the quadriceps
vs.
stretching hamstrings without contracting quadriceps

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
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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

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
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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

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
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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

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
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Web Sites
Neurologic Exam: An anatomical approach
http://medlib.med.utah.edu/neurologicexam/home_exam.html
A very thorough site regarding neurological exam including numerous movies with both normal & pathological results
Cranial Nerves: Review info
www.gwc.maricopa.edu/class/bio201/cn/cranial.htm
A good resource on the cranial nerves
University of Arkansas Medical School Nerve tables http://anatomy.uams.edu/htmlpages/anatomyhtml/nerves.html
Numerous tables of all nerves throughout the body
A Cyberanatomy Tutorial of the Brachial Plexus and its Associated Injuries
http://anatome.ncl.ac.uk/tutorials/brachial1/test/
A hands on guide to the Brachial Plexus.

Manual of
Structural Kinesiology
Neuromuscular Fundamentals
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Web Sites
Dermatomes
www.meddean.luc.edu/lumen/MedEd/GrossAnatomy/learnem/dermat/main_der.htm
An interactive review of the body’s dermatomes.
Loyola University Medical Education Network Master Muscle List
www.meddean.luc.edu/lumen/MedEd/GrossAnatomy/dissector/mml/
An interactive and graphical review of the muscles indexed alphabetically and by region.
Spinal Cord and Nervous System
www.driesen.com/spine_and_cord.htm
A review of the spinal cord and nervous system
Proprioception Exercises Can Improve Balance
http://sportsmedicine.about.com/library/weekly/aa062200.htm
Proprioception