Final (Lectures 11-13; 30 Comprehensive Questions) Flashcards
The mechanics of materials of human connective tissue
Tissue mechanics
Components of tissue mechanics
Bones
Ligaments
Cartilage
Tendons
An externally applied force
Load
An objects response to load is determined by 7 things
- Magnitude
- Location
- Direction
- Duration
- Frequency
- Variability
- Rate
A load that squeezes the parts of the body together
Compression
A load that pulls the parts of a body apart
Tension
A load applied perpendicular to the longitudinal axis of a body causing it to curve
Bending
Three-point bending
Three forces applied which create two moments
Four-point bending
Four forces applied
The three factors determining the effect of bending on a body
- Cross-section area
- Distribution of the material around a neutral axis
- Length of the body
A measure of a body’s resistance to bending
Area moment of inertia
A combination of the cross-sectional area and the distribution of material around a neutral axis
Area moment of inertia
A load that causes one part of a body to move parallel past another part
Shear loading
Forces are directed towards each other; just not along the same line
Shear loading
An example of shear loading
Cutting paper
The type of loading that exists when there is a twist around the neutral axis
Torsion
In this type of loading, a body is twisted around an axis
Torsion
In this type of loading, the body is subjected to two or more types of loading
Torsion
This type of loading depends on the distribution of the material
Torsion
This tells you how the material that makes up the body will respond to loading
Material properties
This tells you how the body as a whole responds to loading
Mechanical properties
The 4 Components of mechanical properties
Strength
Deformation
Stiffness
Toughness
The amount of loading an object can withstand before failure
Strength
A change in dimensions of a body
Deformation
Determined as a change in length
Axial load
A characterization of an object that can undergo very small deformations
Brittle
A characterization of an object that can undergo very large deformations
Ductile
Example of a brittle object
Glass
Example of a ductile object
Gum
A deformation in which the object returns to its original dimensions
Elastic deformation
A deformation in which the object does not return to its original dimensions after deformation
Plastic deformation
Example of an elastic deformation
Rubber bands
Example of a plastic deformation
Plastic holding a six-pack of soda together
The amount of deformation that marks the transition from elastic to plastic deformations
Yield point
A deformation beyond this point results in permanent damage and microtearing
Yield point
The ratio of change in load to change in deformation
Change in load/change in deformation
Stiffness
The ratio of the change in deformation over the change in load
Change in deformation/change in load
Compliance
The amount of energy absorbed by the body as a result of deformation
Strain energy
The amount of energy that can be absorbed by a body before failure
Toughness
The way a force is distributed within a body
Stress
The change in dimension normalized to the original dimension
Strain
The ratio of stress to strain, or Young’s Modulus
Elastic modulus
Relative amount of energy stored by the material
Strain energy density
A decrease in stress when the strain is held constant for a given period of time
Stress relaxation
An increase in strain when stress is held constant for a period of time
Creep
A fluid is both absorbed by the articulating surfaces and placed between them
Lubrication
The lubricating fluid prevents direct surface-to-surface contact
Boundary lubrication
Movement increases the amount of fluid between articulating surfaces, thus increasing their separation
Fluid film lubrication
3 types of fluid film lubrication
Squeeze film lubrication
Hydrodynamic lubrication
Elastohydrodynamic lubrication
Surface material is deformed and removed by frictional forces
Wear
Wear that occurs when two surfaces come in direct contact
Interfacial wear
Types of interfacial wear
Adhesion wear
Abrasion wear
Wear that is the result of microdamage
Fatigue wear
A breaking apart of material
Material failure
Maximum stress exceeds the ultimate stress
Material failure
Strain exceeds the maximum strain
Material failure
When energy is entering more quickly than it is leaving,
It forms or propagates a crack in the material
Components of the model of injury
Failure tolerance
Actual stress
Margin of safety
The stress level above which failure will occur
Failure tolerance
How much stress the body is subjected to
Actual stress
The difference between the failure tolerance and the actual stress applied to a body
Margin of safety
An injury that happens immediately
Acute injury
An injury that develops over time
Chronic injury
A single external load creates enough stress that it exceeds the failure tolerance of the tissue
Acute injury
Outer layer of bone
Solid and dense
“Compact”
Cortical bone
Inner layer of bone
Less organized and random
“Spongy” “Cancellous”
Trabecular bone
The total amount of mineral in bone
Bone mineral content
The mineral content in an area or volume of bone
Bone mineral density
The overall strength of bone is not only determined by an increase in bone density, but also by where that bone is placed
Wolfe’s Law
Exhibits different properties when measured in different directions
Allows for stiffness and brittleness
Anisotropic
The breaking of a bone
Fracture
Lower than normal bone mineral density
Osteopenia
Severe decrease in bone mineral density
Osteoporosis
Bone health has an inverse relationship with
Age and disuse
Bone health has a direct relationship with
Weight bearing exercise
3 types of cartilage
Articulate (hyaline) cartilage
Fibrocartilage
Elastic cartilage
Covers the articular surface of bones
Articular (hyaline) cartilage
Has a specialized role
Fibrocartilage
Found in external ear, parts of the nose, and other places
Elastic cartilage
Function of articular cartilage
Distributes load transmitted across the joint, which decreases the stress on joint surfaces.
Allows for relative movement of two opposing joints surfaces with minimal wear and tear by decreasing friction.
Mechanics of articular cartilage
Primarily loaded under compression
Lubricates the joints
Is permeable
2 components of articular cartilage that allow it to be loaded under compression
Solid
Liquid
The progressive degeneration of the articular cartilage and the bone deep to it
Osteoarthritis
Cartilage decreases in thickness and becomes more rough
Osteoarthritis
Cause of osteoarthritis
Unknown
Risk factors of osteoarthritis (5)
- Aging
- Weakness
- Obesity
- Malalignment
- Injury
Function and structure of ligaments
Connect bone to bone
Restrict certain movements
Guide certain movements
Generally resist tensile loads in one direction, but offer little resistance to compressive loads
Ligaments
An injury to a ligament that occurs when it is stretched beyond its capacity
Usually occurs when a ligament is forcibly wrapped around a part of a bone
Sprain
Less is known about the mechanics of these tissues in comparison to other tissues
Ligaments
Muscles can only control movement by transmitting force through
Passive components (tendons) to the skeletal segments
The only action muscles can perform
Muscles can only pull
How does force work in the muscle-tendon complex?
Force works to bring two insertion points closer together.
Muscles can act as
A motor, brake, spring, or strut
An action in which the muscle-tendon complex develops greater torque than the external torque acting on it and shortens.
Concentric action
Torque and displacement are in the same direction; MTC is doing positive work and increasing the energy of the skeletal system
Concentric action
An action in which the MTC develops less torque than the external torque acting on it and lengthens
Eccentric action
Torque and displacement are in the opposite direction; MTC is doing negative work and decreasing the energy of the skeletal system
Eccentric action
A concentric action immediately after an eccentric action
Stretch-shortening cycle
Energy stored during the eccentric action contributed to the movement during the concentric action
Stretch-shortening cycle
An action in which the MTC develops less torque than the external torque acting on it and lengthens
Eccentric action
Torque and displacement are in the opposite direction; MTC is doing negative work and decreasing the energy of the skeletal system
Eccentric action
A concentric action immediately after an eccentric action
Stretch-shortening cycle
Energy stored during the eccentric action contributed to the movement during the concentric action
Stretch-shortening cycle
An action in which the MTC develops a torque that is equal to the external torque acting on it and does not change length
Isometric action
There is no displacement; the MTC is doing no work; the energy of the skeletal system remains unchanged
Isometric action
Determines both the force producing capabilities and operating range of a muscle
Muscle architecture
Refers to his fibers are arranged relative to the vector of force generalization
Can be parallel or penate
Muscle architecture
One of the passive elements in the MTC
Tendons
Are not straight; have a natural crimp or waviness
Type 1 Collagen
Arrange more like sheets
Converge at ends of the muscle bellies to form tendons
Fascia
Have both elastic and viscous properties
Viscoelastic
The primary components of tendon structure
Type 1 collagen
Fascia
Structural property of tendons
Viscoelastic
Tendons act similar to
Rubber bands
A resistance to change in deformation
Stiffness
The opposite of stiffness
Compliance
Stiffer materials require more ____ to achieve the same amount if deformation
Force
The total force produced in a tendon
Sum of the viscous and elastic properties
Energy is being stored when the tendon is
Lengthening
Energy is being released when the tendon is
Shortening
Equals the anatomical cross-sectional area for a parallel muscle arrangement
Physiological cross-sectional area
An increase in the number of muscle fibers
Hyperplasia
An increase in the size of muscle fibers
Hypertrophy
The action of the MTC determines
the amount of force it produces
___ produces more force than ___.
Eccentric, concentric
Why does eccentric action produce more force?
Muscle fibers are attempting to act isometrically as the tendons lengthen.
The amount of force that can be produced per cross-sectional area
Specific tension
A motor neuron and all the fibers it innervates
Motor unit
Muscle recruitment is governed by two principles
All or none principle
Size principle
An action potential does not directly excite muscle fibers, but does so through chemical processes.
If the action potential is strong enough, all the fibers innervated by that nerve will contract.
All or none principle
The all or none principle is similar to
firing a gun
Motor units are recruited in an orderly process from the smallest to largest.
Size principle
Which type of muscle is recruited first?
Type I
Type II muscle fibers are recruited as
more force is needed.
Force output is changed by either
Increasing the firing frequency, or
Activating more motor units
The time between onset of electrical activity at the muscle and production of measurable force
Electrochemical delay
Why does the electrochemical delay happen?
It provides:
Time needed for chemical processes
Time needed for cross-bridge formation, and
Time needed to take up the slack in the tendon.
Many activities occur in ___ time than it takes to develop the ___ amount of force.
less, maximum
The stretch shortening cycle
A well timed pre-activation of the muscle prior to the eccentric action
A short rapid eccentric action
An immediate transition from the eccentric action to the concentric action
Any reduction in force-generating capacity of the total neuromuscular system, regardless of the force required in any given situation.
Fatigue
The inability to continue or complete a desired action
Task failure
Occurs because one or several of the physiological processes involved in force production of the contractile proteins become impaired
Fatigue
Can occur in many potential sites within the neuromuscular system
Fatigue
The force-producing capabilities of the MTC decrease with
aging and disuse
A decrease in the physiological cross-sectional area
Atrophy
Age-related decrease in muscle mass
Sarcopenia
How is the tendon affected by aging and disuse?
Rapid decrease in stiffness and elastic modulus
Decrease in cross-sectional area
How does heavy resistance training alter all the factors in the MTC?
Increases physiological cross-sectional area
Increases number of sarcomeres in a series
Increases force production (by improving recruitment and changing specific tension)
Injury to a muscle
Strain
Injury to a ligament
Sprain
The mechanics that result in an injury
Mechanopathology
The mechanics that are a result of an injury
Pathomechanics
It is accepted that strains are a result of
both a stretch and load placed on the muscle.
Strains occur during
eccentric muscle actions due to both excessive stress and mechanical strain.
The mechanopathology of this tissue is very poorly understood.
Tendon mechanopathology
Which undergoes greater strain: muscles or tendons?
Tendons
Repetitive straining can lead to
degenerative changes, which can lead to rupture
Has the ability to regenerate
Muscle
When muscle regenerates, it is sometimes replaced with scar tissue. What does scar tissue do in muscle?
It decreases optimal length, decreases range of motion, and leads to high incidence of reinjury.
Alters both mechanical and material properties
Tendon
How does tendon alter mechanical and material properties?
Tendon increases cross-sectional area by decreasing stiffness and Young’s Modulus.
Occurs in a plane about an axis that is perpendicular to that plane.
Rotations
The plane of movement will not be coincident with any of the cardinal planes if
the axis is oblique.
Reference frames are attached locally to bone so that
problems with a global reference frame are avoided.
Rotations of bones
Osteokinematic Motion
Motions at the joint
Arthrokinematic Motion
The amount of rotation, measured in degrees available at a joint.
Range of motion
An angle between the long axis of the bone and some reference line
Segment angle
The angle between the long axis of the bone and some reference line in the global reference frame
Absolute
The orientation of one bone is measured relative to the orientation of another bone
Relative
The number of movements available
Degrees of freedom
1 degree of freedom
A movement in two directions (i.e.: flexion and extension)
Gliding joints
0 rotational degrees of freedom
No axis of rotation
Hinge joints
1 rotation degree of freedom
1 axis of rotation
Pivot joints
1 rotational degree of freedom
1 axis of rotation
Condyloid joints
2 degrees of freedom
2 axis of rotation
Saddle joints
2 degrees of freedom
2 axis of rotation
Spherical (ball and socket) joints
3 degrees of freedom
0 Axis of rotation
Examples of hinge joints
Ankle
Elbow
Interphalangeal joints
Examples of pivot joints
Proximal radioulnar joint
Examples of condyloid joints
Wrist (radialcarpal joint)
Examples of saddle joints
First carpometacarpal joint
Examples of spherical (ball and socket) joints
Hip (glenohumeral joint)
What is the purpose of manual therapy?
Breaks up adhesions and scar tissue to improve movement and range of motion at the joint.
3 types of arthrokinematic motion
- Gliding (sliding) - pure translation
- Spinning - pure rotation
- Rolling - combo of gliding and spinning
3 effects of the force produced by the MTC
- Compression or distraction of the joint
- Shear across the joint
- Rotation of the joint
This component causes rotation or shear
Perpendicular component
This component causes compression and distraction
Parallel component
This determines the amount of torque produced by an MTC
- The amount of force produced
2. Moment arm
The MTC moment arm is determined by
- The length from the axis of rotation to the insertion point.
- The direction of the line of pull.
2 factors that determine the direction of the line of pull
- The sense
2. The angle of pull from the long axis of the bone
The sense
Direction of pull
Which part of the moment arm has a more profound effect: the length or the angle?
The length
Newton’s First Law
A body will remain at rest or continue to move with a constant speed in a straight line unless acted upon by an outside force.
Newton’s Second Law
Acceleration is caused by a net force and is proportional to the magnitude of the force, and in the direction of the force.
Newton’s Third Law
For every force, there is an equal and opposite reaction force.
Formula for Newton’s Second Law
Force = (mass)(acceleration)
Formula for Impulse
Impulse = (force)(time)
Impulse is basically the same as
Momentum
The product of average force and the time that force is applied.
Equal to the change in momentum
Impulse
A resistance to change in motion, specifically resistance to change in a body’s velocity.
Inertia
A resistance to change in velocity of a moving body
Momentum
Formula for Momentum
Momentum = (mass)(linear velocity)
The amount of matter in an object
Mass
The angular equivalent of mass
Moment of inertia
Gives an indication of how difficult it will be to rotate an object
Moment of inertia
Formula for moment of inertia
Moment of inertia = (mass)(distance from the COM to the axis of rotation)^2
I=MK^2
Formula for angular momentum
Angular momentum = MK^2 x angular velocity
A push or pull by one body on another
Force
The turning effect of a force
Torque
Moment of force
Torque
Formula for torque
Torque = (lever arm)(perpendicular force)
Formula for work
Work = (force)(distance)
4 functions of a lever
- Balance 2 or more forces
- Change direction of the applied force
- Favor speed and range of motion
- Favor force production
A rigid body that is used in conjunction with a pivot point to multiply the force or speed applied to another body
Lever
5 components of a lever
- Applied force
- Force moment arm
- Axis of rotation
- Resistance force
- Resistance moment arm
Levers are classified by
the force, the axis, and the resistance.
First class lever
F-A-R
First class lever favors
All four functions of a machine
Example of first class lever
Neck extension
Elbow extension
Second class lever
A-R-F
Second class lever favors
force production
Examples of second class levers
Push ups
Toe raise
Third class lever
A-F-R
Third class levers favor
resistance and speed and ROM
Examples of third class levers
Elbow flexion
The state of matter that makes things change, or has the potential to make things change
Energy
The 5 types of energy
- Nuclear
- Chemical
- Electromagnetic
- Acoustic
- Mechanical
Energy due to motion
Kinetic energy
Energy due to position or deformation
Potential energy
Energy due to deformation
Strain potential energy
Potential energy due to position
Gravitational potential energy
The process of changing the amount of energy in a system.
Can only occur if there is displacement
Work
The time rate of doing work.
How quickly energy is entering or leaving a system.
Power
Formula for power
Power = work/change in time
How far a body has traveled
Distance
A change in position
Displacement
How fast a body is moving in a particular direction
Velocity
The time rate of change in position
Velocity
Change in velocity/change in time
Acceleration
Formula for kinetic energy
KE = 1/2(m)(v^2)
