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Exam 1 Flashcards

1
Q

Definition of Biomechanics

A

The study of forces and their effects on living systems

*Bio = Life

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2
Q

Definition of Mechanics

A

The branch of physics specifically concerned with the effect of forces and energy on the motion of bodies

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3
Q

Definition of Static Mechanics

A

The study of systems in a state of equilibrium

  • At rest or in a constant state of motion
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4
Q

Definition of Dynamic Mechanics

A

The study of systems in a state of accelerated/changing motion

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5
Q

Definition of Kinetics

A

Study of forces that inhibit, cause, facilitate or modify motion of a body

  • e.g. Friction, gravity, and pressure
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6
Q

Definition of Kinematics

A

Study or description of the spatial and temporal characteristics of motion without regard to the causative forces

  • e.g. Displacement and velocity
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7
Q

Steps of a Qualititative Biomechanical Analysis

A
  1. Description
  2. Observation
  3. Evaluation
  4. Instruction
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8
Q

Goals of Biomechanical Analysis

A
  • Technique Improvement
  • Equipment Improvement
  • Training Improvement
  • Injury Prevention and Rehabilitation
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9
Q

Biomechanics and Ergonomics

A

Analyzing the work environment and human-machine interaction.

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10
Q

Qualitative Biomechanical Analysis

A

Pertaining to quality (without the use of numbers)

  • Example: Strong, skillful, agile, flexible, fast
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11
Q

Quantitative Biomechanical Analysis

A

Involving numbers

  • Example:
    • Running speed = 5 m/s
    • Height = 1.75 m
    • Mass = 68.2 kg
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12
Q

Definition of a System

A

Any structure or organization of related structures whose state of motion is of analytical interest

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13
Q

Anthropometry

A
  • Describes the shape of the system
    • Studies the measurements of the body and segments in terms of:
      • Height, weight, volume, breadth, proportion, and other properties related to shape, mass and mass distribution
    • Varying body shape and limb proportions affect motion
      • e.g. competitive swimmers tend to have long torsos and short legs
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14
Q

Basic anthropometric measures

A
  • Height and weight
  • BMI
  • Somatotype (endo-, ecto-, meso-morph)
  • Waist-to-hip ratio
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15
Q

Anatomical position

A

—Refers to a person standing erect with all joints extended, feet parallel, palms facing forward, and fingers together.

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16
Q

Superior

A

Closer to the head

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17
Q

Inferior

A

Closer to the feet

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18
Q

Anterior

A

Toward the front of the body

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19
Q

Posterior

A

Toward the back of the body

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20
Q

Medial

A

Position or movement toward the midline of the body

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21
Q

Lateral

A

Position or movement away from the midline of the body

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22
Q

Proximal

A

Closer to the attachment or midline of a limb to the body

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23
Q

Distal

A

Having a position further from the attachment of the limb to the body

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24
Q

Superficial

A

Closer to the surface of the body

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25
Q

Deep

A

Further from the surface of the body

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26
Q

Cardinal plane

A
  • A plane that passes directly through the midline of the body
  • Divides the mass of the body in half
  • 3 cardinal planes:
    • Sagittal - right/left halves
    • Frontal - anterior/posterior
    • Transverse/Horizontal - superior/inferior
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27
Q

Circumduction

A

Involves flexion, extention, abduction and adduction

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28
Q

Axes of rotation

A
  • Imaginary line positioned perpendicular to a plane
  • All movement occurs around an axis
  • Axis is at the center of mass for whole body movements
    • imaginary line about which a joint or structure revolves
  • Axis is usually a joint for segmental movements
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29
Q

Longitudinal axis

A

Directed vertically

Rotational movements in the transverse plane occur

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30
Q

Anteroposterior axis

A

Directed along the sagittal plane

Rotations in the frontal plane occur

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31
Q

Mediolateral axis

A

Directed along the frontal plane

Rotations in the sagittal plane occur

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32
Q

Translation

A
  • Motion along one axis in which all points of the system move at the same time, in the same direction, with respect to the defined reference frame
    • Path may be represented by one point traveling along a line from one place to the other
  • Also called Linear motion
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33
Q

Linear motion

A
  • Path of a system can be straight or curved
    • Rectilinear translation: path of the system is a straight line
    • Curvilinear translation: path of the system is a curved line
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34
Q

Rotation

A
  • Occurs when the system is restricted to move around a fixed axis - therefore in a circular path
    • Also called angular motion
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35
Q

General Motion

A
  • Combination of tranlation and rotation
    • most human motion is general
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36
Q

Closed skills

A
  • A skill performed under standard environment conditions
    • e.g. basketball free throw
      • Goal is always the same height
      • Free throw line is the same distance from the goal
      • Ball is standard size and weight
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37
Q

Open skills

A
  • A skill that must be altered because of the changing dynamics of the activity, environment, or object of interest
    • e.g. passing and dribbling during a soccer game
      • During a game, no two passes are identical
      • Dribbling is a dynamic skill that changes contantly depending on defensive pressure, open spaces, position of teammates and velocity of player with the ball
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38
Q

Motion

A
  • Change in position with respect to spatial and temporal frames of reference
    • No motion occurs without force
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39
Q

Discrete skills

A
  • Movement with a definite beginning and end-point
    • e.g. broad jump
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40
Q

Continuous skills

A
  • Cycles of motion performed repeatedly with no well-defined beginning or end-points
    • e.g. walking
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41
Q

Serial skills

A
  • Movements that appear to be continuous but are really a combination of discrete motions
    • e.g. rowing
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42
Q

Kinetic Chain

A
  • System of linked rigid bodies subject for force application
    • Simple kinetic chain: each segment participates in no more than two linkages
      • e.g. arm
    • Complex kinetic chain: a segment is linked to more than two other segments
      • e.g. torso
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43
Q

Open vs. Closed Kinetic Chains

A
  • Open kinetic chain
    • the most distal segment is free to move
      • e.g. barbell curl
  • Closed kinetic chain
    • the most distal segment is stationary
      • e.g. push up
      • Total chain has less mobility than open kinetic chain
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44
Q

Force

A
  • Strength or energy as an attribute of physical action or movement
    • A push or a pull
    • Characterized by magnitude, direction, and point of application
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45
Q

Types of force

A
  • External/Internal
  • Contact/Non Contact
  • Action/Reaction
  • Motive/Resistive
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46
Q

Unit for Force

A

Newtons (N)

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47
Q

1 Newton of force = how many lbs of force?

A
  • 1 N = 0.225 lbs. of force

or

  • 1 lb. of force = 4.448N
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48
Q

Internal forces

A
  • Act within the defined system
    • Internal forces can change only the shape of the system
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49
Q

External forces

A
  • Forces that act on an object as a result of its interaction with the environment surrounding it
    • Only external forces can cause a change in the motion of a system
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50
Q

Tensile forces

A

Pulling forces which act on the ends of the internal structure

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51
Q

Compressive forces

A
  • Pushing forces that act on the ends of an internal structure
  • Internal forces hold things together when the structure is under tension or compression
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52
Q

Non contact force

A
  • Forces that occur without contact
    • Gravity
    • Magnetic forces
    • Electrical forces
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53
Q

The only non contact force is…

A
  • Gravity
    • 9.81 m/s2
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54
Q

What is weight?

A
  • The amount of gravitational force exerted on a body
  • W = mg (product of mass and the acceleration of gravity)
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55
Q

What is mass?

A
  • Quantity of matter composing a body (dog, tree, desk, swimming pool, you)
  • Represented by m
  • Units are in kg
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56
Q

Contact forces

A

The result of physical contact between two bodies

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57
Q

Action force

A
  • The initially applied force
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58
Q

Reaction force

A
  • The “opposite force”
    • The simultaneous equal counterforce acting in the opposite direction to the action force
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59
Q

Motive Force

A
  • Increases the speed of an object
  • Changes direction of an object
  • Usually concentric
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60
Q

Resistive Force

A
  • Resists motion
  • Decreases speed
  • Usually eccentric
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61
Q

Properties of a force

A
  • Direction: way the force is applied
  • Magnitude: size of the applied force
  • Point of application: point at which the system receives the applied force
  • Line of action: imaginary line extending indefinitely along the vector through the tip and tail
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62
Q

Net force

A
  • The single resultant force derived from the vector composition of all the acting forces
  • The force that determines the net effect of all acting forces on a body
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63
Q

Pressure

A
  • Force per unit of area over which the force acts
  • Commonly used to describe force distribution within a fluid (blood pressure, water pressure)
  • P = F/A
  • Measured in N/cm2 & in Pascals (Pa)
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64
Q

Stress

A
  • Distribution of force within a body, quantified as force divided by the force over which the force acts
  • Commonly used to describe force distribution within a solid
  • Measured in N/cm2
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65
Q

Friction

A
  • Force acting over an area of contact between two surfaces in the direction opposite that of motion or motion tendency
  • Quantified in units of force (N) because friction is a force
  • Starting friction is greater than moving friction
  • It takes more force to start moving an object than it does to keep it moving
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66
Q

Maximum static friction

A
  • (Fm)
  • As magnitude of applied force becomes greater and greater, magnitude of opposing friction force increase to a critical point
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67
Q

What determines the difficulty of motion for two objects in contact?

A

Magnitude of friction

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68
Q

Mechanical behavior of bodies in contact friction

A
  • Static bodies: friction is equal to the applied force
  • Dynamic bodies: friction is constant and less than maximum static friction
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69
Q

Definition of a Vector

A

Force quantities described by magnitude and direction

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70
Q

Definition of Scalar

A

Quantities that have magnitude but no specific direction

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71
Q

Scalar Quantities

A

Mass, volume, length, and speed

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72
Q

Colinear Forces

A
  • The composition of vectors with the same direction requires adding their magnitudes
  • Forces that have the same line of action
  • The forces may act in the same direction or opposite direction on the same line
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73
Q

Vector Composition

A

Process of determining a single vector from two or more vectors by vector addition

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74
Q

Segments and Forces

A
  • Segments are represented with lines connecting points
  • Forces are represented by vectors or arrows
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75
Q

Vector Equality

A
  • Two vectors are considered equal if they possess the same magnitude and direction

A = B

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76
Q

Vector Algebra

A

The composition of vectors with the opposite directions requires subtracting their magnitudes

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77
Q

Resultant

A

A vector that represents the sum of all forces (net force) acting upon a system

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78
Q

Vector Resolution

A

Operation that replaces a single vector with two perpendicular vectors such that the vector composition of the two perpendicular vectors yields the original vector

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79
Q

Concurrent Forces

A
  • Do not act along the same line
  • All forces pass through a common point
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80
Q

Pythagorean Theorem

A
  • A2 + B2 = C2
  • sin = O/H
  • cos = A/H
  • tan = O/A
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81
Q

Movement kinematics is also referred to as _____ or ______

A

Form or technique

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82
Q

Linear Displacement

A
  • Change in location
  • The directed distance from initial to final location
  • The vector equivalent of linear distance
  • Measured in units of cm, m, km
  • Vector quantity: initial to the final position
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83
Q

Linear Distance

A
  • The total length of the path traveled by the system of interest
  • Scalar in nature; only tells magnitude
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84
Q

Linear Speed

A
  • Distance covered over the time taken
  • Speed = Distance/Time
  • A scalar quantity
  • Measured in units of m/s
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85
Q

Running speed is the product of stride ______ and stride _______

A

Stride Length & Stride Frequency

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86
Q

What’s the Spatial Reference System useful for?

A
  • Standardizing descriptions of human motion
  • Most commonly used is the Cartesian coordinate system
  • Human body joint centers are labeled with numerical x and y coordinates for 2D
  • x, y, and z for 3D
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87
Q

Position

A
  • Defined as location in space
  • Where is an object in space:
    • At the beginning of it’s movement?
    • End of the movement?
    • Some time during its movement?
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88
Q

Linear Velocity

A
  • The rate of change in location
  • Velocity = Displacement/Time
  • The vector equivalent of linear speed
  • Measured in units of m/s
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89
Q

Speed vs. Velocity

A
  • Speed = rate of motion
    • Rate of distance traveled
  • Velocity = rate of motion in a specific direction
    • Rate of displacement
      • Displacement = vector quantity = so is velocity
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90
Q

Human systems usually do not have the same ____ __ ______ throughout the position change

A
  • Same rate of motion
    • Periods of speeding up and slowing down
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91
Q

Peak rate of motion

A

Maximum rate of motion achieved

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92
Q

Average speed/velocity vs. Instantaneous speed/velocity

A
  • Average: Velocity or speed over whole time interval
  • Instantaneous: Rate of motion at one given instant in time
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93
Q

Acceleration

A
  • Change in velocity divided by the time it took for the change in velocity to take place
  • The rate of change in linear velocity
  • Acceleration = change in velocity/time
    • a = V2 - V1 / t
  • Measured in units of m/s2
    • ​Can be 0, negative or positive
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94
Q

Projectile

A

A body in free fall that is subject only to the forces of gravity and air resistance

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95
Q

Why do we analyze the horizontal and vertical components of projectile motion separately?

A

The vertical component is influenced by gravity and the horizontal component is not

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96
Q

Kinematics of projectile motion (two balls)

A
  • Two balls - one dropped and one projected horizontally from the height
    • Both land at the same time since gravity affects their vertical velocities equally
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97
Q

What is the effect of gravity?

A

The force of gravity produces a constant acceleration of -9.81m/s2 on bodies near the surface of the earth

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98
Q

The pattern of change in the vertical velocity of a projectile is ……

A

Symmetrical about the apex

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99
Q

Vertical velocity _____ as the ball ______ ……

A

Vertical velocity decreases as the ball rises and increases as the ball falls due to the influence of gravitational force

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100
Q

3 factors influencing the trajectory (flight path) of a projectile

A
  1. The angle of projection
  2. The projection speed
  3. The relative height of projection
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101
Q

Projection angle

A

The direction of projection with respect to the horizontal

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102
Q

Projection speed

A

The magnitude of projection velocity

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103
Q

Inital velocity

A
  • Incorporates both the intial speed (magnitude) and the angle of projection (direction) into a single quantity
  • When initial velocity is resolved the horizontal and vertical components will have separate speeds
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104
Q

Relative projection height

A

The difference between projection height and landing height

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105
Q

Newton’s law of inertia

A

A body will maintain a state of rest or constant velocity unless acted on by an external force that changes its state

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106
Q

Linear momentum

A
  • Product of an object’s mass and its linear velocity
  • Linear momentum = M
    • M = mv
    • Units: (kg)(m/s)
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107
Q

Elastic Collisions

A

When two objects collide head-on, their combined momentum is conserved

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108
Q

Inelastic Collisions

A
  • Objects in collision stay together and move together with the same velocity
  • Also called plastic collision
  • Most collisions are not perfectly inelastic or elastic, they are usually somewhere in between
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109
Q

Coefficient of restitution

A

When two bodies undergo a direct collision the difference in their velocities immediately after impact is proportional to the difference in their velocities immediately before impact

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110
Q

Factors affecting coefficient of restitution

A
  1. Velocities
  2. Temperature
  3. Material
  4. Spin
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111
Q

Application of Newton’s 2nd Law

A
  • Assuming mass remains constant, the greater the force, the greater the acceleration
  • Acceleration is inversely proportional to mass
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112
Q

Summation of Forces

A
  • The combination of forces produced by different parts of the human body
    • When a person is moving or attempting to move an object, several different parts of the body act together to maximize the force
  • Sequential and simultaneous force
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113
Q

Newton’s law of acceleration

A
  • A force (F) applied to a body causes an acceleration (a) of that body of a magnitude proportional to the force, in the direction of the force, and inversely proportional to the body’s mass (m)
  • F = ma
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114
Q

Impulse

A

Product of force and time interval the force acts

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115
Q

Newton’s 3rd Law (action-reaction)

A
  • For every action, there is an equal and opposite reaction
  • F1 = F2
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116
Q

Work

A
  • Product of force and the amount of displacement in the direction of that force
    • Means by which energy is transferred from one object or system to another
  • U = F(d)
  • Units = J = 1 J = 1 Nm
117
Q

Energy

A
  • Capacity to do work
    • Biomechanics = concerned with mechanical energy
  • Mechanical energy comes in 2 forms
    • Kinetic
    • Potential
118
Q

Kinetic Energy

A
  • Moving object has the capacity to do work due to its motion
  • Affected by the mass and the velocity of the object
119
Q

Potential Energy

A

The energy that an object has due to its position

120
Q

2 types of potential energy

A

Gravitational potential energy

Strain energy

121
Q

GPE

A
  • Potential energy due to an objects position relative to the earth
  • GPE of an object is related to the object’s weight and its elevation or height above the ground or some reference
  • PE = Wh
122
Q

Strain Energy

A

Energy due to the deformation of an object

123
Q

Power

A
  • Rate of work production
  • Can be thought of as how quickly or slowly work is done
  • P = U/T
  • Measured in Watts
    • 1W = 1 J/s
124
Q

Shear Stress

A
  • Compression and tension are axial stresses
  • Shear stress is a transverse stress that acts parallel
  • Shear Stress = F/A
125
Q

Bending

A
  • Asymmetric loading that produces tension on one side of a body’s longitudinal axis and compression on the other side
  • Multiple stresses along the analysis plane
126
Q

Torque

A
  • The rotary effect of a force
  • The angular equivalent of force
  • AKA as moment of force
127
Q

Torsion

A

Load producing twisting of a body around its longitudinal axis

128
Q

Repetitive

A
  • Repeated application of a subacute load that is usually of relatively low magnitude
    • Microtrauma
129
Q

Acute

A
  • Application of a single force of sufficient magnitude to cause injury to a biological tissue
    • Macrotrauma
130
Q

Strain

A

Quantification of the deformation of a material

131
Q

2 types of strain

A
  1. Linear strain
  2. Shear strain
132
Q

Linear strain

A

Occurs as a result of a change in the objects length

133
Q

Shear strain

A

Occurs with a change in orientation of adjacent molecules as a result of these molecules slipping past each other

134
Q

Poisson’s Ratio

A
  • When an object is stretched, it becomes narrower; if the object is compressed, it becomes wider in the lateral direction
  • Ratio between strain in the axial direction to strain in the transverse direction
    • Most materials = between 0.25 and 0.35
  • Example: intervertebral discs
135
Q

Explain the change of height that occurs in intervertebral discs throughout the day

A

Decrease their height by an average of 2cm throughout the day, with approximately 54% of the loss occuring in the first 30 minutes

136
Q

Stiffness

A

Stress/strain in a loaded material; stress divided by the relative amount of change in shape

137
Q

Deformation

A
  • Change in shape
  • Force applied on object = acceleration and deformation
138
Q

Elastic Behavior (Graph)

A

An object facing a load will reach a yield point at which deformation occurs until the ultimate failure point is reached, in which permanent damage is done

139
Q

How does the structure of bone affect its strength?

A

Bone is anisotropic, it has different srength and stiffness depending on the direction of the load

140
Q

Cortical vs Trabecular (cancellous) bone

A
  • Cortical bone = higher mineral content = stiffer = withstand greater stress
  • Trabecular bone = less compact minerals = more porous = withstand more strain
141
Q

What contributes to stiffness and compressive strength in bone?

A

Calcium carbonate and calcium phosphate make contribute to 60-70% of bone stiffness and strength

142
Q

What contributes to flexibility and tensile strength in bone?

143
Q

How do bones respond to stress?

A
  • LIke muscle, bones respond to certain kinds of training through hypertrophy
144
Q

Wolff”s law

A

The densities and to a lesser extent, the sizes and shapes of bones are determined by the magnitude and direction of the acting forces

145
Q

How is Wolff’s law carried out?

A
  • Osteoblasts and osteoclasts are continually building and resorbing bone, respectively.
  • Increased or decreased mechanical stress leads to a predominance of osteoblast or osteoclast activity, respectively.
146
Q

Functions of articular cartilage

A
  • Spreads load over wide area, reducing contact stress
  • Provides a protective lubrication that minimizes friction and mechanical wear at the joint
  • AKA hyaline cartilage
  • 10-30% collagen
147
Q

Articular Cartilage

A
  • Soft, porous and permeable material
  • Consists of chondrocytes
  • Under load = exudes synovial fluid = creep
148
Q

Chondrocytes

A

Maintain and restore cartilage from wear

149
Q

Articular Fibrocartilage

A

Soft-tissue discs or menisci that intervene between articulating bones, as exemplified by the menisci of the knee

150
Q

Functions of articular fibrocartilage

A
  • Distributing loads over joint surfaces
  • Improving the fit of articulations
  • Limiting slip between articulating bones
  • Protecting the joint periphery
  • Lubricating the joint
  • Absorbing shock at the joint
151
Q

Tendons and ligaments

A
  • Similar in composition and structure
  • By weight, tendons and ligaments consist of approximately:
    • 70% water
    • 25% collagen
    • 5% ground substance and elastin
  • Ligaments have more elastin than tendons
152
Q

Tendons

A
  • Attach muscles to bone
  • Consist of groups of collagen fibers, which are bound together in parallel
    • Parallel arrangement produces a material very stiff and high in tensile strength
    • Parallel arrangement has little resistance to compession or shear forces
153
Q

Ligaments

A
  • Fibrous CT which attaches bone to bone and serves to hold structures together and keep them stable
  • Different arrangement than collagen fibers and a slightly larger elastin component than tendons - making them less stiff and slightly weaker than tendons
  • Non parallel collagen alignment = withstand uniaxial loads
154
Q

Muscle

A
  • Unlike connective tissue, muscle tissue is capable of actively contracting to produce tension within itself and the structures to which it attaches
  • The active contractile components of muscle thus determine the stiffness of the muscle at any instant
    • Muscle stiffness varies as a function of the number of active contractile elements
155
Q

Muscle force

A
  • The force of muscle action varies from slight to maximal in one of two mechanisms:
    • Increasing the number of motor units recruited
    • Increasing the frequency of motor unit discharge
156
Q

Muscle Spindles

A
  • Provide mechano-sensory information about changes in muscle fiber length and tension
  • Primarily respond to muscle stretch through reflex action by initiating a stronger muscle action to counteract the stretch
  • More spindles exist in muscles that routinely perform complex movements
157
Q

Stretch Reflex

A
  • The stretch reflex consists of three main components:
    • Muscle spindle that responds to stretch
    • Affarent nerve fiber that carries the sensory impulse from the spindle to the spinal cord
    • Efferent spinal cord motor neruon that activates the stretched muscle fibers
158
Q

GTOs

A
  • Connect in series to skeletal muscle fibers and also located in ligaments of joints to primarily detect differences in muscle tension
  • When activated by excessive muscle tension or stretch, GTOs immediately transmit signals to cause reflex inhibition of the muscles they supply
  • Protect muscles and its CT fom injury by sudden, excessive load or stretch
159
Q

Forces acting on the spine

A
  • Body weight
  • Tension in the spinal ligaments
  • Tension in the surrounding muscles
  • Intraabdominal pressure
160
Q

The major form of loading on the spine is

161
Q

Spinal compression

A
  • Resulting from:
    • Body weight + weight held by arms and hands
162
Q

When standing upright

A
  • Total body center of gravity is anterior to the spinal column
  • Spine is placed under constant forward bending movement
163
Q

Movements of the spine

A
  • Flexion
  • Extension
  • Hyperextension
  • Lateral Flexion
  • Rotation
164
Q

Structure of the spine

A
  • Vertebral column
  • Motion segment
  • Vertebrae
  • Intervertebral Discs
    • Annulus fibrosus
    • Nucleus pulposus
165
Q

Motion Segment

A
  • AKA functional spinal unit (FSU)
  • Smallest physiological motion unit of the spine to exhibit biomechanical characteristics similar to those of the entire spine
  • A motion segment consists of two adjacent vertebrae, the intervertebral disc and all adjoining ligaments between them
166
Q

Intervertebral discs

A
  • Annulus fibrosus consists of 90 concentric bands of collagenous tissue
  • Collagen fibers crisscross vertically at a 30° angle to make the structure able to withstand rotational strain
167
Q

Spinal Curves

A
  • Influenced by heredity, pathological conditions, individual’s mental state, and forces to which the spine is habitually subjected
    • Prestress
    • Primary spinal curve
    • Secondary spinal curve
    • Lordosis
    • Kyphosis
    • Scoliosis
168
Q

Prestress

A
  • The ligamentum flavum is in tension even when the spine is in anatomical position, enhancing spinal stability
  • The tension = constant compression in in the intervertebral discs, referred to as prestress
169
Q

Primary spinal curves

A

Present at birth = c-shape for babies

170
Q

Secondary Spinal Curves

A

Begin to develop when children start to sit up and stand

171
Q

Lordosis

A
  • Refers to the normal inward curvature of the limbar and cervical regions of the spine
  • Cause = Congenital spinal deformity, weakness of the abdominal muscles, poor postural habits
172
Q

Kyphosis

A
  • Also called roundback, a condition of over curvature of the thoracic vertebrae
  • Cause = degenerative diseases, developmental problems (Scheuermann’s disease) osteoporosis with copression fractures of the vertebrae, or trauma
173
Q

Scheuermann’s disease

A
  • Vertebrae grow unevenly
  • One or more wedge shaped vertebrae develop because of abnormal epiphyseal plate behavior
174
Q

Scoliosis

A
  • Condition in which a person’s spine is curved laterally
  • Classified as either congenital, carrying heavy objects, leg length discrepancies and unknown
175
Q

Why should we lift with the legs?

A

Back muscles, with a moment arm of approximately 6cm, must counter the torque produced by the weights of the body plus any external loads

176
Q

Stress fractures

A
  • Most common type of vertebral fracture is in pars interarticularis
    • Spondylolysis
    • Spondylolisthesis
  • Spondylolysis and spondylolisthesis dont tend to heal with time
  • Common with sports involving repeated hyperextension of the limbar spine
177
Q

Classifications of Joints

A
  • Synarthroses
  • Syndesmoses
  • Amphiarthroses
  • Synchondroses
  • Symphyses
  • Diarthroses or synovial
178
Q

Is Synarthroses movable or immovable?

179
Q

Syndesmosis

A

Where fibrous tissue binds bones together

180
Q

Examples of Syndesmoses Joints

A
  • Coracoacromial
  • Mid-tibiofibular
  • Inferior tibiofibular
181
Q

Is amphiarthroses movable or immovable?

A

They are slighly moveable

182
Q

Synchondroses

A

The articulating bones are jointed by a thin layer of hyaline cartilage

183
Q

Example of synchondroses joints

A

Epiphyseal plate before ossification

184
Q

Example of symphasys joints

A

Vertebral joints

185
Q

Diarthroses (or synovial) are characterized by:

A
  • Articular cartilage
  • Articular capsule
  • Synovial membrane
  • Synovial fluid
  • Associated bursae
186
Q

Articular Capsule

A

A double layered membrane that surrounds the joint (ligamentous sleeve)

187
Q

Synovial Membrane

A

Membrane that lines the interior of the articular capsule

188
Q

Synovial fluid

A

A clear, slightly yellow liquid that provides lubrication inside the articular capsule

189
Q

Associated bursae

A

Small capsules filled with synovial fluid that cushion the structures they separate

190
Q

Bursa

A
  • 160 in the body
  • Decreases friction between two joints
191
Q

Bursitis

A

Loses its gliding capabilities and becomes irritated during movement

192
Q

Darthroses or Synovial classes

A
  • Gliding
  • Hinge
  • Pivot
  • Condyloid
  • Saddle
  • Ball & socket
193
Q

Gliding Joints

A
  • Articulating bone surfaces are nearly flat
  • Movement = nonaxial gliding
  • Examples:
    • Intermetatarsal
    • Intercarpal
    • Intertarsal
    • Facet joints
194
Q

Hinge Joints

A
  • One articulating bone surface in convex and the other is concave
  • Strong collateral ligaments restrict movement in a planar hinge-like motion
  • Examples:
    • Ulnahumoral
    • Interphalangeal
    • Tibiafemoral joints
195
Q

Pivot Joints (Screw, Trochoid)

A
  • Rotation is permitted around one axis
  • Examples:
    • Atlantoaxial joint and the radioulnar joint
196
Q

Condyloid (Ovoid, Ellipsoidal)

A
  • One articulating bone surface is an ovular convex shape, and the other is a reciprocally shaped concave surface
  • Movement: Flexion, extension, abduction, adduction and circumduction
  • Examples:
    • 2nd-5th metacarpalpholangeal joints and the radiocarpal joints
    • Radiocarpal joints
197
Q

Saddle (Sellar) joints

A
  • Both sides shaped like a riding saddle
  • Movement: Same as the condyloid joint
  • Example:
    • Carpometacarpal joint of the thumb
198
Q

Ball and Socet (Spheroidal)

A
  • Surfaces of the articulating bones are reciprocally convex and concave
  • Movement: Same as condyloid, but greater range of motion
    • Movement in all 3 plans of motion are permitted
  • Examples:
    • Hip joint
    • Shoulder joint
199
Q

Joint stability

A
  • Refers to the joint’s resistance to movement of planes other than those defined y the degrees of freedom of movement for the joint
  • Ligaments and tendons help resist tensile forces acting at the joints
200
Q

Close-pack position

A
  • Articulating bones have their maximum area of contact with each other
  • Position that joint stability is greates
201
Q

The close-packed position for the knee, wrist, and interphalangeal joints is at ………..

A

Full extension

202
Q

Loose-packed position

A

Position in which the area of contact and joint stability is reduced

203
Q

Joint flexibility

A

A description of the relative ranges of motion allowed at a joint in different directions from anatomical position (0 degrees)

204
Q

Range of motion (ROM)

A

The angle through which a joint moves from anatomical posiiton to the extreme limit of segment motion in a particular direction

205
Q

Factors influencing joint flexibility

A
  • Intervening bony or muscle tissue or fat at the end of the ROM
  • Tightness/laxity in the muscle and collagenous tissue crossing a joint
  • Muscle fatigue
206
Q

What Sensory receptors influence the extensibility of the musculotendinous unit?

A
  • Golgi tendon organs: inhibit tension in muscle and initiates tension development in antagonists
  • Muscle spindles: provoke reflex contraction in stretched muscle & inhibit tension in antagonists
207
Q

What is PNF

A
  • Proprioceptive neuromuscular facilitation is a group of stretching procedures involving alternating contraction and relaxation of the muscles being stretched
208
Q

PNF stretching

A

Goal: Enhance both active and passive range of motion

  1. An active PNF stretch involves a shortening contraction of the opposing muscle to place the target muscle on stretch
  2. The passive stretch is then followed by an isometic contraction of the target muscle
  3. This is repeated 3-4 times with the assistance of a partner
209
Q

Muscle Tissue Characteristics

A
  • Contractility - produce force
  • Irritability - ability to be stimulated
  • Extensibility - ability to be stretched
  • Elasticity - ability to return to original shape if deformed (stretched)
210
Q

Components of Elasticity

A
  • Paralell elastic component - passive elasticity derived from muscle membranes
  • Series elastic component - passive elasticity derived from tendons when a tensed muscle is stretched
211
Q

What are some predictors of athletic success?

A
  • Cardiovascular function
  • Motivation
  • Training size
  • Muscle size
  • fiber type is not a sole predictor of success
212
Q

What are disadvantages associated with muscles that cross more than one joint?

A
  • Active Insufficiency: Failure to produce force when slack
    • Decreased ability to form a fist with the wrist in flexion
  • Passive Insufficiency: Restriction of joint range of motion when fully stretched
    • Decreased ROM for wrist extension with the fingers extended
213
Q

What factors effect Force Production

A
  • MU Recruitment
  • Preloading
  • Cross-Sectional area
  • Angle of pennation
  • Sarcomere and muscle length
  • Prestretching
  • Exercise induced muscle damage
  • Older muscle
  • Muscle fiber type
214
Q

A lever

A
  • A rigid object pivoted about a fulcrum
  • Used to transfer a force to a load
  • Provides a mechanical advantage
215
Q

Moment arm

A

MAF: Perpendicular distance from the line of action of the force to the fulcrum

216
Q

Describe muscle force relative to resistance force

A

Muscle force draws the opposite ends of a muscle towards each other while resistive force is the force generated by a source external to the body

217
Q

Mechanical advantage

A

The ratio of the output force produced by a system to the applied input force

218
Q

A First-class lever

A

Fulcrum placed between the applied force and the resistant force

219
Q

A second-class lever

A

A lever for which the muscle force and resistive force act on the same side of the fulcrum

220
Q

A third-class lever

A

Force is placed between the axis and resistance

221
Q

How do we measure muscular strength?

A

The amount of torque a muscle group can generate at a joint

222
Q

Centric and Eccentic Forces

A
  • Centric forces result in linear motion only
  • Eccentric (off center) forces always result in rotation
223
Q

Force couple

A

Pair of equal, oppositely directed forces that act on opposite sides of an axis of rotation to produce torque

Example: A dancer

224
Q

What factors affect muscular strength?

A
  • Tension-generating capacity of the muscle tissue, which is in turn affected by:
    • Muscle cross-sectional area
    • Training state of muscle
  • Moment arm ot the muscles crossing the joint (Mechanical advantage), in turn affected by:
    • Distance between muscle attachment to bone and joint center
    • Angle of the muscle’s attachment to bone
225
Q

Explain skeletal muscle function in terms of torque, rotation and muscle force

A

Torque produced by a muscle (Tm) at the joint center of rotation is the product of muscle force (Fm) and muscle moment arm

226
Q

Muscular strength, Power and endurance

A

The mechanical advantage of the biceps bracchi is maximum when the elbow is at approximately 90 degrees, because 100% of muscle force is acting to rotate the radius

227
Q

What is the center of gravity

A
  • Point at which a body’s weight is equally balanced in all directions
  • Point that serves as an index of total body motion
  • Same as the center of mass
228
Q

Why is the center of gravity of interest in the study of human biomechanics?

A
  • The body responds to external forces as though all mass were concentrated at the CG
  • This is consequently the point at which the weight vector is shown to act in a free body diagram
229
Q

Different ways of finding center of gravity

A
  • Reaction Board: Specially constructed board for determining the center of gravity location of a body positioned on top of it
  • Segmental Method: Procedure for determining total-body center of mass location based on the masses and center of mass locations of the individual body segment
230
Q

Why is it difficult to find center of gravity?

A

Bone, muscle and fat have different densities and are unequally distributed throughout the body

231
Q

What is stability?

A

Resistance to disruption of equilibrium

232
Q

What is balance?

A

Ability to control equilibrium

233
Q

Base of support

A

Area bound by the outermost regions of contact between a body and the support surface

234
Q

What can increase a bodys stability?

A
  • Increasing body mass
  • Increasing friction between between the body and the surfaces of contact
  • Increasing the base of support in the direction of an external force
  • Horizontally positioning the center of gravity near the edge of the base of support on the side of the external force
  • Vertically positioning the center of gravity as low as possible
    • The higher the CG, the greater amount of torque its motion creates about the support surface
235
Q

Differences and similarities between Linear and Angular kinematics

A
  • Angular kinematic values are described the same way as linear kinematic values
  1. Eccentric force is applied and therefore torque is present
  2. There is a specified axis of rotation
  3. A segment rotating around an axis may have the ability to travel completely in a circle
236
Q

What is a relative angle?

A
  • Angle at a joint formed between the longitudinal axes of adjacent body segments
  • The straight, fully extended position at a joint is regarded as zero degrees
    • The relative angle at the lead knee tends to be smaller during sprinting than during distance running
    • When joint ROM is quantified, it is the relative joint angle that is measured
237
Q

What is an absolute angle?

A
  • Angular orientation of a body segment with respect to a fixed line of reference
  • Reference lines are usually vertical or horizontal
  • The absolute angle of the trunk with respect to vertical is often a quantity of interest in studies of lifting as related to low back pain
238
Q

What is angular position?

A

The distance from the origin, and the angle between the chosen reference axis and the line formed by connecting the given point to the origin

239
Q

What is the instant center of rotation?

A

The center of rotation at a given joint angle, or at a given instant in time during a dynamic movement

240
Q

What happens after the angular position is established?

A

Once the angular position is established, we have a reference position from which to measure angles and changes in motion

241
Q

What is angular displacement?

A
  • Change in angular position of a segment or any point on the rotating segment
  • The directed angular distance from initial to final angular position
  • The vector equivalent of angular distance
242
Q

What is angular displacement measured in?

A

Degrees or radians

243
Q

What is a radian? What does 1 radian = ?

A
  • The size of the angle subtended at the center of a circle by an arc equal in length to the radius of the circle
  • Unit of angular measure used in angular-linear kinematic quantity conversions: 1 radian = 57.3º
244
Q

What is angular velocity?

A
  • The rate of change in angular position
  • Measured in units of degrees/sec or radians/sec
  • Angular velocity = Angular displacement/time
245
Q

Angular acceleration

A
  • The rate of change in angular velocity
  • Measured in units of deg/s2 or rad/s2
246
Q

Angular motion vectors

A
  • Oriented perpendicular to the lintear displacement of a point on a rotating body
247
Q

What is the relationship between linear and angular displacement?

A

The larger the radius of rotation (r), the greater the linear distance (s) traveled by a point on a rotating body

248
Q

What is the relationship between linear and angular acceleration?

A

The acceleration of a body in angular motion can be resolved into two perpendicular linear acceleration components:

  • Tangential Acceleration
  • Centripetal Acceleration
249
Q

What is tangential acceleration?

A
  • Component of acceleration of angular motion directed along a tangent to the path of motion
  • Represents change in linear speed
250
Q

What is tangential acceleration a measure of?

A

Tangential acceleration is a measure of how the tangential velocity of a point at a certain radius changes with time

Just like linear acceleration but its particular to the tangential direction

251
Q

What is centripetal acceleration?

A
  • Linear acceleration directed toward the axis of rotation
  • Represents change in direction
252
Q

Angular momentum and factors that affect it

A
  • Rotational analog of linear momentum
  • Moment of inertia about it’s axis
  • Distribution of mass with respect to the axis or rotation
  • Angular velocity of the body
253
Q

Units for angular momentum

A

Kg · m2/s

254
Q

What is a multi-segmented object?

A

Sum of angular momenta of individual segments

255
Q

Local term of multi-segmented object

A

Segments angular momentum about its own segmental CG

256
Q

Remote term for multi-segmented object

A

Segments angular momentum about its total body CG

257
Q

Angular interpretation of Newton’s First Law

A
  • The angular momentum of an object remains constant unless a net external torque is exerted on it
  • Newton’s first law does not require that the angular velocity be constant
258
Q

Angular Interpretation of Newton’s Second Law of Motion

A
  • The change in angular momentum of an obejct is proportional to the net external toruque exerted on it, and this change is in the direction of the net external torque
  • The net external torque exerted on an object is proportional to the rate of change in angular momentum
259
Q

Transfer of Angular Momentum

A
  • Transfering angular velocity
  • Changing total body axis of rotation
    • Asymmetrical arm movements
    • Rotation of the hips
260
Q

Change in Angular Momentum

A
  • Dependent only on the magnitude and direction, but also on the length of time
    • Linear impulse = Ft
    • Angular impulse
261
Q

Angular Interpretation of Newton’s Third Law of Motion

A

For every torque exerted by one object on another, the other object exerts an equal torque back on the first object but in the opposite direction

262
Q

What is a fluid?

A
  • A substance that flows or continuously deforms when subjected to a shear stress
  • Both liquids and gases are fluids
  • Air and water are fluids that commonly exert forces on the human body
263
Q

Relative velocity

A

Velocity of a body with respect to the velocity of something else, such as the surrounding fluid

  • Wind, water
264
Q

What is laminar flow?

A

Characterized by smooth, parallel layers of fluid

  • Like cyclist apparel that reduces drag
265
Q

Turbulent flow

A

Flow characterized by mixing of adjacent fluid layers

  • High pressured fluid mixing with low pressure fluid
266
Q

Relevant fluid properties

A
  • Density - Ratio of mass to volume
  • Specific weight or specific gravity
    • Ratio of the weight of an object to the weight of an equal volume of water
      • Salt-water vs. fresh-water
  • Viscosity - internal resistance of a fluid to flow
267
Q

What is buyancy

A
  • A fluid force with
    • Magnitude
    • Direction
    • Point of application being a body’s center of volume
268
Q

Archimedes’ Principle

A
  • The buoyant force acting on a body is equal to the weight of the fluid displaced by the body:
    • Buoyant foce = displaced fluid volume x fluid specific weight
    • Fb = VdY
269
Q

What determines whether a body floats or sinks?

A
  • Floating occurs when the buoyant force is greater than or equal to body weight
  • Sinking occurs when body weight is greater than the buoyant force
  • The equation of static equilibrium for vertical force can be used to answer the question
270
Q

When holding a large quantity of inspired air in her lungs, a 22 kg girl has a body volume of 0.025 m3. Can she float in fresh water if g equals 9810 N/m3? Given her body volume, how much could she weigh and still be able to float?

A

m = 22 kg

V = 0.025 m3

fluid specific weight = 9810 N/m3

Fb (buoyant force) = fluid displaces volume –> (0.025 m3)(9810 N/m3) = 245.25 N = critical point

then determine weight

wt = (22 kg)(9.81 m/s2) = 215. 82 N - she will float

271
Q

What is drag?

A
  • A force caused by the dynamic action of a fluid that acts in the direction of the free stream fluid flow
  • Generally a resistance force that tends to slow the motion of a body moving through a fluid
272
Q

What factors affect total drag force?

A
  • Drag force
  • The coefficient of drag
  • Fluid density
  • Body surface area that is perpendicular to the fluid flow
  • Relative velocity of the body with respect to the fluid
273
Q

What is skin friction?

A
  • Drag derived from friction in adjacent layers of fluid near a body moving through the fluid
  • AKA surface drag and viscious drag
    • Swimmers shave body, wear certain types of swimsuits
274
Q

What factors affect the magnitude of skin friction? (What increases skin friction?)

A
  • Relative velocity of fluid flow (velocity of fluid over the skin)
  • Surface area of the body over with the flow occurs (bigger or smaller swimmer)
  • Roughness of the body surface
  • Viscosity of the fluid
275
Q

What is form drag?

A

Derived from a pressure differential between the lead and rear sides of a body moving through a fluid. (kind of like turbulent flow)

  • boat going through water, high pressure at the front, low pressure at the back

AKA profile drag or pressure drag

276
Q

Form drag increases with

A
  • The relative velocity of fluid flow
  • The magnitude of the pressure gradient between the front and rear ends of the body
  • The surface area of the body perpendicular to the fluid flow
277
Q

Why do they add dimples to golf balls?

A

Golf balls with dimples travel further because air wraps around smooth golf balls and not dimpled balls

278
Q

What is wave drag?

A

Drag derived from the generation of waves at the interface between two different fluids, such as air and water

*increased wave drag due to the air and water mixing

279
Q

What increases wave drag?

A
  • Vertical oscillation of the body with respect to the fluid (swimmers looking up in the water and is more vertical than horizontal)
  • Relative velocity of the body in the fluid
280
Q

What is lift?

A
  • A force acting on a body in a fluid in a direction perpendicular to the fluid flow
  • Generally a resistance force that tends to slow the motion of a body moving through a fluid
281
Q

What factors affect lift force?

A
  • Force of lift
  • Coefficient of force
  • Fluid density
  • Body surface area perpendicular to the fluid flow
  • Relative velocity of the body
282
Q

What is a foil?

A

A shape capable of generating lift in a fluid

(Surfboard)

283
Q

How is lift generated by a foil?

A

Lift generated by a foil is directed from the region of relative high pressure on the flat side of the foil toward the region of relative low pressure on the curved side of the foil

284
Q

Bernouli Principle

A
  • An expression of the inverse relationship between relative velocity and relative pressure in a fluid flow
  • Regions of low relative velocity are associated with relative high pressure
  • Regions of high relative velocity are associated with relative low pressure
285
Q

Factors of the Bernouli Principle

A
  • Pressure
  • Specific weight of the fluid
  • Elevation
  • Relative velocity
  • Acceleration of gravity
  • A constant
286
Q

What is the magnus effect?

A
  • Deviation in the trajectory of a spinning object toward the direction of the spin
  • Results from the magnus force
    • Throwing a curve or kicking a curve, “bending”
    • Due to the pressure differential causing the bending in the object during trajectory
287
Q

What is magnus force?

A

Results from a pressure differential created by a spinning body

  • Topspin - relative low velocity flow, relative high pressure on top and relative high velocity flow and relative low pressure on the bottom of the ball, magnus force directed downward
  • Backspin - relative high velocity flow and relative low pressure on the top, relative low velocity flow and relative high pressure from the bottom, magnus force directed upward
288
Q

Radius of Gyration

A
  • Represents an objects mass distribution with respect to a given axis of rotation
  • Units of moment of inertia consist of mass multiplied by units of length squared (kg x m2)

Biomechanics (1 decks)

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