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KIN 316 - Biomechanics of Tissue > Biomechanical Concepts > Flashcards

Biomechanical Concepts Flashcards

1
Q

How do we define the basic properties of standing balance?

A

Using
- Forces
- Moments
- Displacement

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2
Q

What are Tissue Mechanics?

A
  • The Foundation to understand tissue injury
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3
Q

What is movement essential for in life?

A

Life Processes
- Blood Circulations
- Respiration
- Muscle Contraction
Activities
- Walking
- Grasping
- Talking
- Stance

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4
Q

What are the two types of motion in mechanics?

A
  • Linear
  • Angular
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5
Q

What is human movement a combination of?

A
  • Linear and Angular Motion
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6
Q

What are the two perspectives human movement can be viewed from?

A
  • Internal Mechanics
  • External Mechanics
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7
Q

Describe the Internal Mechanics perspective of human movement. What are some examples?

A
  • Mechanical factors that produce and control movement from inside the body
    ex.
  • Muscle Action
  • Ligaments
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8
Q

Describe External Mechanics of the perspective of human movement. What are some examples?

A
  • Mechanical factors affecting the body from without
    ex.
  • Gravity
  • Brick falling on your head
  • Car Accident
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9
Q

What is an Idealized Force Vector?

A
  • Single force vector representing the NET effect of all other vectors
  • SImplifies Computation (Free Body Diagrams)
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10
Q

What is Injury Analysis?

A

Describes forces acting on the body such as:
- Gravity
- Impact of feet and hands
- Objects impacting body
- Musculotendinous Forces
- Ligament forces
- Compressive forces acting on long bones of lower extremities

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11
Q

What are Net Muscle Forces?

A
  • Clavicular and Sternal Components of the force added vectorially
  • Muscle force has antagonist and agonist effect on total force
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12
Q

Why is it useful to use an idealized force vector?

A
  • What is lost in information is gained in creating a simplified model for calculations
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13
Q

What is the Centre of Mass (CoM)?

A
  • Reducing the distributed mass of a body to a single point
  • Represents the entire body or point about which a body’s mass is equally distributed
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14
Q

What is the Centre of Mass equivalent to?

A
  • Idealized force vector
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15
Q

Is the Centre of Mass always located on the body?

A
  • NO
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16
Q

What is a Free Body Diagram? What is it useful for?

A

FBD
- Graphical representation of all forces acting on a system
Useful
- Biomechanical analysis of injury and modeling through idealized force vectors

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17
Q

What is the Moment of Force? when is it used?

A

Moment of Force
- Equivalent of force for angular motion
Used
- When net force is not applied perpendicular to segment

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18
Q

How is the Moment of Force calculated?

A
  • Using Trigonometric Function
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19
Q

What is the Equation for Moment of Force?

A

M = dxF (units = Nm)
F = Force
d = Moment arm (torque arm or lever arm)

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20
Q

How can you increase the moment of force?

A
  • Increase force
  • Increase moment arm
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21
Q

What happens when you apply force through the axis of rotation?

A
  • No moment of force is produced
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22
Q

What kind of forces can act on tissues with no moment of force created? What happens when that occurs?

A

Compressive forces on vertebrae
- no rotation induced
- High risk of compressive fractures

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23
Q

How many components of force are involved in producing a moment?

A
  • Usually only one component of the force
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24
Q

What is the system’s response based on?

A

NET moment
- Mnet = M1 + M2 +….

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25
Q

What is the Joint Reaction Force?

A

Forces experienced between segments of a free-body diagram
- Difficult to measure experimentally

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26
Q

Where is the Free body diagram usually broken? What must be shown?

A

Joints
- force acting across joints must be shown

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27
Q

What is Newton’s Third Law? How does it relate to the Free body diagram? ex.

A

There is an equal and opposite force acting on each joint
- Influenced by any effect included in the free body diagram
ex.
- Ground reaction force
- Muscle-ligament-joint capsule forces

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28
Q

When does Equilibrium exist?

A
  • When forces and moments are balanced
  • Exists for the body at rest or moving with constant linear and angular velocity
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29
Q

What happens to the sum of forces and moment of force at rest?

A
  • Equals 0
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30
Q

What is the equation of motion?

A
  • F = ma
  • M = la
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31
Q

What is pressure?

A

The total applied force divided by the total area over which the force is applied

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32
Q

What is the equation for Pressure?

A

p = F/A (units SI: Pa) (1PA = 1N.m^-2)

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33
Q

What is the Centre of Pressure (CoP)? what units?

A
  • Average location of all forces acting on a surface
    Units
  • m
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34
Q

When does pressure have an effect on injuries?

A
  • When one object impacts another
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35
Q

What is the general rule for pressure resulting in injury?

A
  • Force applied over a larger area decreases the likelihood of injuries
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36
Q

What is standing upright in relation to movement?

A
  • common form of active balance
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37
Q

What is the aim of balancing?

A
  • Keeping the position of the CoM above and within the base of support
38
Q

How can the base of support be modified?

A
  • changing the stance width
39
Q

What happens to the Centre of Mass while humans maintain balance?

A
  • Moves horizontally and vertically (sway)
40
Q

What is the difference between Centre of Mass and Centre of Pressure?

A

CoM
- Idealized point representing the mass of the whole body (vertical projection on the ground)
CoP
- Weighted average location of all downward forces acting on the ground (e.g. force platform)

41
Q

What does Centre of Pressure depend on? What does it not depend on?

A

Depends on:
- Foot placement on the force platform
- Neuromuscular response to maintain balance
Does not:
- Measure of the sway of the Centre of Mass

42
Q

What is the Centre of Pressure equations?

A
  • CoPx = -My/Fz
  • CoPy = Mx/Fz
43
Q

What are the Torso Movements influenced by?

A
  • changes in stance
44
Q

What are the 5 degrees of Freedom?

A
  • 2 hip joints
  • 2 ankle joints
  • motion of torso relative to lower body
45
Q

What happens as Stance width increases?

A
  • A change in ankle angle leads to a larger change in hip angle
  • Proprioceptors at the hip can detect motion
  • CoM excursion increases
46
Q

What happens to the dynamics with a larger stance width?

A
  • Same hip moment produces a greater total moment on the motion of the four-bar linkage (inertia also decreases)
47
Q

What are some difficulties of measuring Angular Kinematics?

A
  • Finite rotation cannot be treated as vectors in 3D
48
Q

What is the equation of Angular Kinematics?

A

Wnet = w1 + w2 + w3 +….
W = angular velocity

49
Q

What are the Material Mechanic terms?

A
  • Stress, strain
  • Compression, tension, shear, bending, torsion
  • Viscoelasticity
  • Material Fatigue and Failure
50
Q

What is a Load?

A
  • An externally applied force
51
Q

What is Deformation?

A
  • Change in shape of a body when a load is applied to it
52
Q

What is material mechanics?

A
  • Study of Internal Response of material to externally applied loads
53
Q

Describe Stress in Material Mechanics

A
  • Resistance Developed by tissue when externally loaded
  • Internal measure of force divided by cross-sectional area of the tissue
54
Q

What is the equation for stress?

A
  • σ = F/A (SI Units: Pa)
55
Q

What is Stress categorized as?

A
  • Compressive
  • Tensile
  • Shear
56
Q

Describe Strain relative to Material Mechanics

A
  • Deformation of Tissue subjected to the external load
57
Q

What kind of strain can we measure?

A
  • Absolute strain
58
Q

What is the equation for Relative Strain?

A
  • relative stain: e = l - lo / lo
  • l = length after deformation
  • lo: resting length
59
Q

What is Strain Categorized as?

A
  • Compressive
  • Tensile
  • Shear
60
Q

What does the slope of the load-deformation curve define?

A
  • Stiffness
61
Q

What is the opposite of stiffness?

A
  • Compliance
62
Q

What are stiff materials? what is their load-deformation curve profile?

A

Stiff materials
- Bones
Curve
- Steep slopped

63
Q

When do stress and strain operate according to Hooke’s Law?

A
  • When they are linearly related
64
Q

What is Hooke’s Law?

A
  • σ = E * ε ( E: Elastic Modulus or Y: Young’s Modulus)
65
Q

Why do human tissues not behave linearly?

A
  • Due to their fluid component
66
Q

When is Stiffness related to the slope of the torque-angle relationship?

A
  • for Standing Balance
67
Q

What is the load stiffness of the human body during standing balance? Why?

A

Load Stiffness = mgh
why?
- Small angles during standing balance (less than 6 degrees)

68
Q

What are the two major types of bone?

A
  • Cortical (compact)
  • Trabecular (cancellous bone)
69
Q

How much weight of the bone comes from cortical bone?

A
  • 80%
70
Q

Describe Trabecular Bone

A
  • Spongy
  • Makes up interior of bones
71
Q

What happens in the linear region of the bone?

A
  • where elastic modulus is calculated
72
Q

What leads to large bone deformation?

A
  • Small increases in force
73
Q

What happens when you release the load from a bone?

A
  • bone does not return to original configuration (remains deformed)
74
Q

What is the elastic modulus of Cortical bone?

A
  • 13-17GPa
75
Q

What is the elastic modulus of the Trabecular Bone?

A
  • 10-2000MPa
76
Q

Describe the composition relationship between the femur and phalanx bones

A

Femur
- Greater ability to carry load due to larger diaphysis
Phalanx
- Smaller diaphysis
Femur and Phalanx
- Similar composition of Compact Bone

77
Q

What happens to the difference in maximal stress of the femur and phalanx when normalized for cross-sectional area?

A
  • minimal difference
78
Q

What is the Stress Response a function of?

A
  • Strain and Strain Rate
79
Q

What is Strain Rate?

A
  • Speed at which deformation occurs
  • Units (SI: s^-1)
80
Q

What does biological tissue have?

A
  • Fluid component
81
Q

What happens when you increase strain rate?

A
  • increases slope of σ/ε relationships (and stiffness)
82
Q

What happens to purely elastic material when a load is removed?

A
  • Returns to original shape (or length)
83
Q

How do purely elastic materials deform?

A
  • according to their σ/ε relationship
84
Q

Describe Viscoelastic Tissue.

A
  • Loses energy during deformation
  • Return following unloading is retarded
  • Return path different from initial path during loading
85
Q

What are the 3 properties of viscoelastic tissue?

A
  • Hysteresis
  • Creep Response
  • Stress Relaxation
86
Q

Describe Hysteresis

A
  • Energy lost during loading-unloading cycle
87
Q

Describe Creep Response

A
  • Tissue Subjected to constant load continues to deform
88
Q

Describe Stress Relaxation

A
  • tissue stretch maintained at a given length will result in decreased stress
89
Q

What happens to materials subjected to repeated loads?

A
  • Experience Fatigue
90
Q

What is the difference between the mechanical response of the initial load vs subsequent ones?

A
  • They differ
91
Q

What happens to the continued loading of fatigued material?

A
  • May lead to failure
92
Q

What is the susceptibility to material failure determined by? Explain

A

Determined by:
- how the stress is distributed throughout the material
Explanation
- Stress concentrated in one area = greater likelihood of failure

KIN 316 - Biomechanics of Tissue (11 decks)

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