Chapter 7 - Biomechanics Flashcards

1
Q

what does biomechanics examine?

A

the internal and external forces acting on the human body and the effects produced by these forces

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2
Q

what does biomechanics aid in?

A

technique analysis and the development of innovative equipment designs

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3
Q

where does the knowledge for biomechanics come from?

A

from sports medicine, athletic therapy, physical therapy, kinesiology and biomechanical engineering

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4
Q

Exchange of energy forces

A

biomechanics

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5
Q

quantitative analyses

A
  • involves measurement of variables that are thought to optimize or maximize performance
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6
Q

give 3 examples of quantitative analyses

A

1) pattern of forces using a force platform
2) sequence of muscle activity using electromyography (EMG)
3) 3D movements of each body segment using high speed cinematography

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7
Q

qualitative analyses

A
  • involves obtaining information, visually or auditorily to assess performance
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8
Q

what 4 things does qualitative analyses require?

A

1) a framework within which skilled performance can be observed
2) a set of principles with which movement can be analyzed
3) a checklist to use when identifying errors
4) techniques to use for error detection and correction

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9
Q

kinematics study of motion

A

the study of time and pace factors of a body in motion

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10
Q

what are the 4 variables used to describe motion?

A

time, displacement, velocity and acceleration

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11
Q

linear

A

straight line

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12
Q

angular

A

around an axis

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13
Q

time

A

temporal characteristics of a performance, either of the total skill or its phases

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14
Q

displacement

A

length and direction of the path an athlete or object takes from start to finish

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15
Q

angular displacement

A

direction of, and smallest angular change between the rotating bodys initial and final position

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16
Q

velocity

A

displacement per unit of time

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17
Q

angular velocity

A

angular displacement per unit of time

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18
Q

acceleration

A

rate of change of velocity

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19
Q

angular acceleration

A

angular velocity per unit of time

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20
Q

kinetics study of forces

A

focuses on the various forces that are associated with a movement

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21
Q

internal forces

A

generated by muscles pulling via their tendons on bones, and to bone-on-bone forces exerted across joint surfaces

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22
Q

external forces

A

acting from without, such as the force of gravity or the force from any body contact with the ground, environment, sport equipment or opponent

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23
Q

scalar quantities

A

have only magnitude (time)

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24
Q

give 3 examples of scalar quantities

A

speed, work, power

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25
Q

vector quantities

A

have magnitude and direction (force) displacement, velocity, momentum, lift

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26
Q

Straight line segments with one end defined as the tail and the arrow tip defined as the head

A

vectors

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27
Q

Levers

A

simple machines that augment the amount of work done by an applied force

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28
Q

fulcrum

A

a rigid body (i.e., long bone) that rotates about a fixed point (i.e., joint) called a fulcrum (F)

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29
Q

true or false: acting on the lever is a resistive force (R, i.e., weight of a limb segment) and applied force (AF, i.e., muscle contraction)

A

true

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30
Q

what are the 3 classes of levers?

A

a) first class
b) second class
c) third class

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31
Q

give an example of a first class lever

A

teeter-totter

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32
Q

give an example of a second class lever

A

wheelbarrow

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33
Q

give an example of a third class lever

A

barbaque tongs

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34
Q

factors affecting the moment of force

A

a balanced teeter-totter

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35
Q

newtons 1st law of motion

A

the law of inertia

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36
Q

the law of inertia

A

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

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37
Q

newtons 2nd law of motion

A

the law of acceleration

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38
Q

the law of acceleration

A

a force applied to a body causes an acceleration of that body of a magnitude proportional to the force, in the direction of the force, and inversely proportional to the body’s mass

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39
Q

newtons 3rd law of motion

A

the law of reaction

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40
Q

the law of reaction

A
  • for every action there is an equal and opposite reaction

- the 2 acting forces are equal in magnitude, but opposite in direction

41
Q

give an example of the law of reaction (newtons 3rd law of motion)

A

the sprinter exerts a force on to the blocks and simultaneously the blocks exert an equal force back onto the sprinter

42
Q

what is the action and what is the reaction in this example of newtons 3rd law?: the tires on a car push on the road and the road pushes on the tires

A

action: the tires on a car push on the road
reaction: the road pushes on the tires

43
Q

what is the action and what is the reaction in this example of newtons 3rd law?: while swimming, you push the water backwards and the water pushes you forward

A

action: while swimming you push the water backwards
reaction: the water pushes you forward

44
Q

what is the action and what is the reaction in this example of newtons 3rd law?: a rocket pushes out exhaust and the exhaust pushes the rocket forward

A

action: a rocket pushes out exhaust

Reaction: the exhaust pushes the rocket forward

45
Q

why are the models of human motion developed?

A

because the total movement capacity of all the body structures is to complex to accurately analyze

46
Q

why is the total movement capacity of all the body structures too complex to accurately analyze? (3 reasons)

A

1) anatomical difference in people related to race, age, gender, health and lifestyle
2) the body is susceptible to deformation and multi-segmental so that one segment affects the others during movement
3) sport skills occur in 3D often encountering all 3 planes and axis

47
Q

what are the 3 human body models?

A

1) particle model
2) stick figure model
3) rigid segment model

48
Q

particle model

A

used when the object of interest (the human body or an object) is airborne after being thrown, struck or kicked the body itself (i.e., jumping, diving, tumbling)

49
Q

stick figure model

A

used when the object is in contact with its environment and generally gross motor skills in 2D (i.e., sprint starts, running, non rotational dive)

50
Q

rigid segment model

A

used for more sophisticated quantitative analyses (3D) especially in multi-plane motions

51
Q

what 2 things are required for rigid segment model?

A

camera and 3D analysis

52
Q

what is the first preliminary step for analyzing human motion?

A

identify the system to be studied, which is to separate the object of interest from its surroundings

53
Q

what is the second preliminary step for analyzing human motion?

A

identify the frame of reference in which the movement takes place

54
Q

what is the third preliminary step for analyzing human motion?

A

identify the type of motion that is occurring, the body planes in which movement takes place (sagittal, frontal or transverse and
identify the axes of rotation about which rotational motion occurs (sagittal, frontal, or vertical)

55
Q

what are the 3 types o motion?

A

linear, general and angular

56
Q

motion

A

when all parts of the body move the same distance in the same direction at the same time

57
Q

linear motion (AKA translation)

A

refers to movement of the body as a unit without individual segment parts of the body moving relative to one another

58
Q

rectilinear motion

A

occurs when movement follows a straight line

59
Q

curvilinear motion

A

occurs when the movement path is curved

60
Q

angular motion (rotation)

A

occurs when a body moves along a circular path, through the same angle in the same direction and at the same time

61
Q

what is the point about which movement occurs?

A

the axis of rotation

62
Q

all joints are what type of motions?

A

angular motions

63
Q

general motion

A

a combination of linear and angular motion

64
Q

what does general motion include?

A

most athletic and many everyday activities

65
Q

causes of motion

A

the only cause of motion of the human body is the application of an external force

66
Q

force

A

any action, a push or pull, which tends to cause an object to change its state of motion by experiencing an acceleration

67
Q

constant velocity

A

occurs when an object is not accelerating

68
Q

linear motion

A

is caused by forces which act through a body’s centre of mass

69
Q

angular motion

A

caused by forces that do not go through the centre of mass

70
Q

centre of mass

A

located at the balance point of a body; a point found in or about a body where the mass could be concentrated

71
Q

where is the centre of mass generally?

A

generally 15cm (approx. 6inches) above the symphysis pubis, or approx. 55% of standing height in females and 57% in males

72
Q

does the centre of mass have to be inside the body?

A

no

73
Q

mass

A

a measure of inertia a constant what object is made up of

74
Q

what is mass measured in?

A

kilograms

75
Q

weight

A

measure of the force of gravity

76
Q

what is weight measured in?

A

newtons

77
Q

what makes the weight vary?

A

varies directly with the magnitude of the acceleration due to gravity (9.8m/s2)

78
Q

Weight = _____ x ______

A

mass x gravity

79
Q

Projectile Motion

A

any airborne object is a projectile, including the human body

80
Q

parabolic path

A

the path that the centre of mass of a projectile follows

81
Q

what is the parabolic path followed determined as?

A

determined only as a function of the projectiles takeoff velocity

82
Q

what are the objectives of the projectile motion (what do you want the object to do)?

A

height - max vertical distance
range - max horizontal distance
accuracy

83
Q

what is the optimum trajectory for distance?

A

35 degrees

84
Q

what is the first principle?

A

stability

85
Q

stability increases when there is…?

A
  • a lower centre of gravity
  • an increase in the base of support
  • the line of gravity is close to the centre of the base of support
  • mass increases
86
Q

what is principle #2?

A

maximum force

87
Q

how is maximum force achieved

A

by the use of all the joints that can be applied simultaneously

88
Q

more joints = more ______ = more _______

A

more joints = more muscles = more force

89
Q

what is the third principle?

A

maximum velocity

90
Q

how is maximum velocity achieved?

A

when the joints are sequences from largest to smallest

larger slower joints start the movement, faster smaller joints contribute once the preceding joint reaches peak velocity and slow down

91
Q

what is principle #4?

A

Impulse

92
Q

the greater the applied impulse the greater the _______

A

the greater the applied impulse the greater the change in velocity

93
Q

when does force absorption occur?

A

when momentum must be dissipated over time or distance (requires application of an impulse)

94
Q

what is the fifth principle?

A

linear motion

95
Q

movement usually occurs in the direction opposite that of the _______ force

A

movement usually occurs in the direction opposite that of the applied force

96
Q

what is principle #6?

A

Angular Motion

97
Q

how is angular motion produced

A

angular motion is produced by the application of a force acting at some distance from an axis, that is, by a torque

98
Q

what is the seventh principle?

A

angular momentum

99
Q

angular momentum is _____ when an athlete or object is free in the air (i.e., constant after takeoff)

A

angular momentum is constant when an athlete or object is free in the air (i.e., constant after takeoff)