Exploring the Science of Biomechanics in Kinesiology
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Kinesiology Books Publisher
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Kinesiology Books Publisher
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Study of internal and external forces acting
on human body and their effects
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Relatively young
•
Extremely diverse and multifaceted
•
Contributes significantly to our knowledge of
human movement
T
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Kinesiology Books Publisher
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Q
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Kinesiology Books Publisher
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Depends on
•
Environment
•
Availability of high-tech equipment
Q
Q
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Using high-tech instrumentation
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Usually intended for researchers
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Measuring variables to optimize athletic performance
•
Foot forces on sprinter’s blog
•
Muscle contraction sequence during running
•
3-D body segment movements during a high jump
Q
U
A
N
T
I
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Kinesiology Books Publisher
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Using sight and hearing
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Usually done by coaches and teachers
•
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Requires framework and a set of principles
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Kinesiology Books Publisher
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Two ways to describe human
motion
1.
Without reference to forces
causing motion
2.
Describing motion in terms of
forces that cause it
K
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Kinesiology Books Publisher
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Describing human motion without its forces
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Focusing on motion’s spatial and timing characteristics
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Measurements:
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Kinesiology Books Publisher
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Describing forces leading to motion
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I
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•
Muscles pulling on bones
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Bone-on-bone, inside joints
•
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•
Without contact (e.g., gravity)
•
From contact with ground,
opponent or equipment
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M
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Kinesiology Books Publisher
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Understanding and observing human
movements is complex
•
All body tissues undergo shape deformation
•
Most movements occur in three dimensions
•
3 models, simplify the study of human
movements:
•
P
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13
13
Kinesiology Books Publisher
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14
Kinesiology Books Publisher
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•
M
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Kinesiology Books Publisher
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M
a
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•
Amount of matter in an object
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Objects are reluctant to go change state of motion
•
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Reluctance of rotating object to change state of
motion
•
Depends on mass and its distribution around axis of
rotation
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Force of attraction between two bodies
•
E.g., human body and planet earth
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Kinesiology Books Publisher
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Kinesiology Books Publisher
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Kinesiology Books Publisher
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T
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Kinesiology Books Publisher
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•
Human movement composed of a number
of fundamental types of motion:
•
L
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21
21
Kinesiology Books Publisher
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•
All body parts move
same distance and
direction, at the same
time
•
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Body moves on a circular
path and rotates about
axis of rotation
•
Body segments rotate
about their joints
•
E.g., twisting somersault
•
Body / segments
move linearly and
rotate at the same
time
•
True for most
athletic and every
day activities
•
E.g., gymnastics
floor routine, diver
falling downward
and at the same
time rotating in a
somersault
•
Application of internal or external forces
•
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Kinesiology Books Publisher
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23
Kinesiology Books Publisher
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L
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•
Mechanical device performing angular motion
•
Components:
•
Axis of rotation
•
Fulcrum (pivot)
•
Lever attached to fulcrum
•
Human muscles, bones and joint work together
as lever systems
L
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Kinesiology Books Publisher
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25
25
Kinesiology Books Publisher
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H
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W
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K
Kinesiology Books Publisher
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•
Force is applied and if greater than resistance
•
Rotation at the axis / fulcrum occurs
•
T
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27
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Kinesiology Books Publisher
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•
W
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n
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v
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a
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/
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:
•
Moment of force or torque is produced
•
How much torque occurs?
•
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p
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How do you rotate
teeter-totter in your
direction?
28
28
Kinesiology Books Publisher
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No rotation: F=R, FA=RA
R
o
t
a
t
i
o
n
:
F
=
R
,
F
A
>
R
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:
F
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,
F
A
=
R
A
Kinesiology Books Publisher
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29
29
T
Y
P
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S
O
F
L
E
V
E
R
S
Kinesiology Books Publisher
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•
Levers perform different functions
•
Three basic types of lever exist
•
F
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t
c
l
a
s
s
•
S
e
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d
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•
T
h
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c
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•
Differ based on mechanics and how
these components are positioned
•
Axis
•
Resistance
•
Force
F
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A
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L
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Kinesiology Books Publisher
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•
Applied force and resistance on opposite side of axis, at un/equal
distance from one another
•
Example: crowbar
•
Human body: head flexion
31
31
S
E
C
O
N
D
C
L
A
S
S
L
E
V
E
R
S
Kinesiology Books Publisher
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•
Applied force and resistance on same side of axis; resistance closer
to axis
•
Example: wheelbarrow
•
Human body - hard to find: toe raise
•
Applied force and resistance on same side of axis; force closer to the
axis
•
Example: fishing
•
Human body – many: forearm flexion
T
H
I
R
D
C
L
A
S
S
L
E
V
E
R
S
Kinesiology Books Publisher
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33
33
Kinesiology Books Publisher
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34
34
Kinesiology Books Publisher
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•
L
a
w
o
f
I
n
e
r
t
i
a
•
L
a
w
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A
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•
L
a
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A
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–
R
e
a
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t
i
o
n
N
N
E
E
W
W
T
T
O
O
N
N
’
’
S
S
L
L
A
A
W
W
S
S
O
O
F
F
M
M
O
O
T
T
I
I
O
O
N
N
Kinesiology Books Publisher
35
S
S
I
I
R
R
I
I
S
S
A
A
A
A
C
C
N
N
E
E
W
W
T
T
O
O
N
N
Kinesiology Books Publisher
36
•
300 years ago
•
Explained effect of
forces acting on an
object
•
T
h
r
o
u
g
h
3
l
a
w
s
N
e
w
t
o
n
’
s
F
i
r
s
t
L
a
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“Objects will not change their state of
motion unless acted on by an
unbalanced external force”
L
L
A
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W
W
O
O
F
F
I
I
N
N
E
E
R
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T
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A
A
Kinesiology Books Publisher
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N
e
w
t
o
n
’
s
S
e
c
o
n
d
L
a
w
“Objects will experience a change in velocity
or acceleration proportional to the
unbalanced external force”
L
L
A
A
W
W
O
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F
F
A
A
C
C
C
C
E
E
L
L
E
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R
R
A
A
T
T
I
I
O
O
N
N
Kinesiology Books Publisher
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39
39
S
a
m
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m
a
s
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S
a
m
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f
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c
e
S
a
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a
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l
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r
a
t
i
o
n
Kinesiology Books Publisher
39
N
e
w
t
o
n
’
s
T
h
i
r
d
L
a
w
“For every action there is an equal and
opposite reaction; forces act in pairs that are
equal in magnitude and opposite in direction”
L
L
A
A
W
W
O
O
F
F
A
A
C
C
T
T
I
I
O
O
N
N
-
-
R
R
E
E
A
A
C
C
T
T
I
I
O
O
N
N
Kinesiology Books Publisher
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41
41
Kinesiology Books Publisher
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•
F
l
u
i
d
D
r
a
g
F
o
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c
e
s
:
T
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D
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a
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A
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F
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I
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D
D
D
D
Y
Y
N
N
A
A
M
M
I
I
C
C
S
S
Kinesiology Books Publisher
42
F
F
L
L
U
U
I
I
D
D
D
D
Y
Y
N
N
A
A
M
M
I
I
C
C
S
S
Kinesiology Books Publisher
43
•
Knowledge of the forces generated by a fluid
environment such as
•
W
a
t
e
r
•
A
i
r
•
W
a
t
e
r
+
A
i
r
•
All athletic event take place in a fluid environment
•
U
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a
f
f
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c
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d
:
g
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m
n
a
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,
d
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•
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:
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Acts in opposite direction to body’s travel and slows
it down relative to body’s
•
Velocity
•
Size and shape
•
Roughness
•
Fast-speed sports especially affected
•
velocity =
drag
2
(10x faster, 100 x more drag)
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Kinesiology Books Publisher
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S
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•
Body size and surface roughness = surface drag
•
B
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Thin layer of fluid adjacent to skin and carried along with body’s motion,
towing along outer fluid layers
•
L
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Small, streamlined, smooth, slow-moving bodies
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Smooth, layered flow pattern with no disturbance
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T
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Most human activities
•
Disturbed flow pattern that changes flow conditions
Kinesiology Books Publisher
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47
47
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Kinesiology Books Publisher
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48
48
Kinesiology Books Publisher
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P
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Main form of drag in fast-moving sports
•
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Velocity of air flow past object is too fast for air to follow body’s contour
•
Backflow occurs at object’s surface causing large, turbulent low-
pressure zone behind the body
•
This zone is continually formed and increases object’s work
•
Profile drag-reducing strategies
•
frontal surface area (e.g., lugers are supine)
•
sources of turbulence (e.g., speed skaters with arms behind
back)
•
D
r
a
f
t
i
n
g
Kinesiology Books Publisher
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50
50
M
A
G
N
U
S
E
F
F
E
C
T
•
A rotating body carries a boundary layer that
interacts with surrounding air
•
Boundary layer flow opposite to relative airflow
•
Air is slowed by friction
•
Zone of increased pressure created
•
Boundary layer flow same as relative airflow
•
Air is not slowed down
•
Zone of increased pressure created
•
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Kinesiology Books Publisher
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51
51
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Kinesiology Books Publisher
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52
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Kinesiology Books Publisher
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Kinesiology Books Publisher
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Kinesiology Books Publisher
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•
B
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1.
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2.
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Has to pass through base of support for balance
B
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A
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C
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Kinesiology Books Publisher
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S
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Kinesiology Books Publisher
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•
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•
Net internal force required to overcome static or
dynamic equilibrium
•
During critical performance times there is a trade-
off between maximizing stability and acquiring
speed
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58
58
Kinesiology Books Publisher
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Kinesiology Books Publisher
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60
60
Kinesiology Books Publisher
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Kinesiology Books Publisher
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•
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Kinesiology Books Publisher
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•
Subjective yet systematic evaluation of human
motion without measuring and using numbers
•
Based on visual observation or video recording
•
Allows discovery of movement tendencies and
generates immediate and specific feedback
•
Depends on coach’s understanding of skill
•
Based on a model integrating 4 aspects of quality
instruction
Kinesiology Books Publisher
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•
Can be described and identified for all skills
•
E.g., blocking a lineman
•
Secondary objectives may exist, referring to
speed or accuracy required
•
Skills with similar overall objectives are governed
by similar biomechanical principles
•
Throwing, striking, kicking object for maximal
horizontal surface
S
S
K
K
I
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L
L
L
L
O
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B
B
J
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Kinesiology Books Publisher
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D
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•
Should make sense to the coach and how the skill
is being defined and taught
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•
Their execution determines successful
accomplishment of biomechanical purpose of the
phase and overall performance of the skill
A
A
N
N
A
A
L
L
Y
Y
Z
Z
I
I
N
N
G
G
S
S
K
K
I
I
L
L
L
L
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Kinesiology Books Publisher
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•
Difficult task because of skill speed
•
Observation plan beforehand identifies what, why,
where and how observation will occur
•
Coaches must use vision (dominant), hearing and
feeling as well as look for tracks and traces
•
Confirm observation accuracy with athlete and
video recording (if possible)
O
O
B
B
S
S
E
E
R
R
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A
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T
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N
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M
A
A
N
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C
E
E
Kinesiology Books Publisher
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•
Error sources
•
Mental: concentration lapse or fear
•
Physical: lack of strength, poor habits
•
Detection is visual via direct observation video
analysis, or traces/marks observation
•
Correction
•
Should keep in mind athlete's physical and mental
abilities, competition level, age and development
level
•
Verbal, demonstration, video
•
Ongoing; 1-2 errors at a time starting with earlier
E
E
R
R
R
R
O
O
R
R
D
D
E
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T
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R
R
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T
T
I
I
O
O
N
N
Kinesiology Books Publisher
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•
Biomechanics is the physics of human movement with the main
goal to optimize performance by focusing on movement kinematics
and kinetics
•
Motion results from internal and external forces in ways that can be
understood via Newton’s laws
•
Fluid affects athletic performance via surface and profile drag and
Magnus effect
•
By manipulating base and centre of gravity characteristics athletes
can increase stability and reach equilibrium
•
Coaches and athletes use qualitative analysis to evaluate skills and
detect and correct errors
P
P
U
U
T
T
T
T
I
I
N
N
G
G
I
I
T
T
A
A
L
L
L
L
T
T
O
O
G
G
E
E
T
T
H
H
E
E
R
R
Kinesiology Books Publisher
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Delve into the intricacies of biomechanics within the field of kinesiology, covering topics such as quantitative and qualitative analysis, kinematics versus kinetics, motion concepts including mass, gravity, and inertia, types of motion, and causes of motion.
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Presentation Transcript
CHAPTER 9 The Science of Biomechanics Kinesiology Books Publisher 1
TABLEOF CONTENTS Types of Study Quantitative vs Qualitative Analysis Kinematics Versus Kinetics Motion Concepts Mass, Gravity, and Inertia Types of Motion Causes of Motion Lever Systems and Motion Mechanics Newton s Laws of Motion Law of Inertia Law of Acceleration Law of Action Reaction Fluid Dynamics Fluid Drag Forces: The Dynamics of Air Body Balance and Stability Control Equilibrium Balance Stability Qualitative Analysis of Human Motion Skill Objective Analyzing a Skill Observation of Performance Error Detection and Correction Kinesiology Books Publisher 2
THE SCIENCEOF BIOMECHANICS Study of internal and external forces acting on human body and their effects Relatively young Extremely diverse and multifaceted Contributes significantly to our knowledge of human movement Kinesiology Books Publisher 3
TYPESOF STUDY Quantitative versus Qualitative Analysis Kinematics Versus Kinetics Kinesiology Books Publisher 4
QUANTITATIVEVS. QUALITATIVE ANALYSIS Depends on Environment Availability of high-tech equipment Kinesiology Books Publisher 5
QUANTITATIVE ANALYSIS Using high-tech instrumentation Usually intended for researchers Measuring variables to optimize athletic performance Foot forces on sprinter s blog Muscle contraction sequence during running 3-D body segment movements during a high jump 6 Kinesiology Books Publisher 6
7 Kinesiology Books Publisher 7
QUALITATIVE ANALYSIS Using sight and hearing Usually done by coaches and teachers To identify and correct errors: Observe, analyze and correct. Requires framework and a set of principles 8 Kinesiology Books Publisher 8
KINEMATICVS. KINETICS Two ways to describe human motion 1. Without reference to forces causing motion 2. Describing motion in terms of forces that cause it Kinesiology Books Publisher 9
KINEMATICS Describing human motion without its forces Focusing on motion s spatial and timing characteristics Measurements: Time Displacement Velocity Acceleration 10 Kinesiology Books Publisher 10
KINETICS Describing forces leading to motion Internal forces Muscles pulling on bones Bone-on-bone, inside joints External forces acting on the body Without contact (e.g., gravity) From contact with ground, opponent or equipment 11 Kinesiology Books Publisher 11
MODELSOF HUMAN MOTION Understanding and observing human movements is complex All body tissues undergo shape deformation Most movements occur in three dimensions 3 models, simplify the study of human movements: Particle model Stick figure model Rigid body segment model 12 Kinesiology Books Publisher 12
Stick Figure Model Rigid Body Segment Model Particle Model Dot represents centre of mass Body segments = sticks Body segments = irregular 3-D volume Used when body or object is airborne and in flight Used when body in contact with other objects Used for sophisticated 3-D analyses i.e., projectile motion Describe gross motor skills in 2-D Includes shape deformation of body segments 13 Kinesiology Books Publisher 13
14 Kinesiology Books Publisher 14
MOTION CONCEPTS Mass, Gravity, and Inertia Types of Motion Causes of Motion Lever Systems and Motion Mechanics Kinesiology Books Publisher 15
MASS, GRAVITY, INERTIA Mass Amount of matter in an object Objects are reluctant to go change state of motion A measure of inertia Moment of Inertia Reluctance of rotating object to change state of motion Depends on mass and its distribution around axis of rotation Gravity Force of attraction between two bodies E.g., human body and planet earth Kinesiology Books Publisher 16
17 Kinesiology Books Publisher 17
18 Kinesiology Books Publisher 18
19 Kinesiology Books Publisher 19
TYPESOF MOTION Human movement composed of a number of fundamental types of motion: Linear motion / translation Angular motion / rotation General motion Kinesiology Books Publisher 20
All body parts move same distance and direction, at the same time Body / segments move linearly and rotate at the same time Translation: linear motion of the whole body Linear motion True for most athletic and every day activities General motion E.g., gymnastics floor routine, diver falling downward and at the same time rotating in a somersault Body moves on a circular path and rotates about axis of rotation Angular motion Body segments rotate about their joints E.g., twisting somersault 21 Kinesiology Books Publisher 21
CAUSESOF MOTION Application of internal or external forces Force is any action, push or pull, that tends to cause an object to change is state of motion by experiencing acceleration or as state of constant velocity Linear motion = force acting on centre of mass/ pivot point Angular motion = force not acting on centre of mass/ pivot point and result in torque (moment of force) Kinesiology Books Publisher 22
23 Kinesiology Books Publisher 23
LEVERSYSTEMSAND MOTION MECHANICS Lever system Mechanical device performing angular motion Components: Axis of rotation Fulcrum (pivot) Lever attached to fulcrum Human muscles, bones and joint work together as lever systems Kinesiology Books Publisher 24
25 Kinesiology Books Publisher 25
HOW DO LEVERS WORK Force is applied and if greater than resistance Rotation at the axis / fulcrum occurs To determine force amount, consider the length of force arm and resistance arm Kinesiology Books Publisher 26
HOW DO LEVERS WORK When lever rotate around and axis / fulcrum: Moment of force or torque is produced How much torque occurs? Therefore, with a longer force arm: Less force is needed Greater torque is produced 27 Kinesiology Books Publisher 27
No rotation: F=R, FA=RA Rotation: F>R, FA=RA How do you rotate teeter-totter in your direction? Rotation: F=R, FA>RA 28 Kinesiology Books Publisher Kinesiology Books Publisher 28 28
TYPESOF LEVERS Levers perform different functions Three basic types of lever exist First class Second class Third class Differ based on mechanics and how these components are positioned Axis Resistance Force 29 Kinesiology Books Publisher 29
FIRST CLASS LEVERS Applied force and resistance on opposite side of axis, at un/equal distance from one another Example: crowbar Human body: head flexion R Resistance A F A Force Kinesiology Books Publisher 30
SECOND CLASS LEVERS Applied force and resistance on same side of axis; resistance closer to axis Example: wheelbarrow Human body - hard to find: toe raise Resistance R F Force A A 31 Kinesiology Books Publisher 31
THIRD CLASS LEVERS Applied force and resistance on same side of axis; force closer to the axis Example: fishing Human body many: forearm flexion Resistance F R Force A A Kinesiology Books Publisher 32
33 Kinesiology Books Publisher 33
34 Kinesiology Books Publisher 34
NEWTONS LAWSOF MOTION Law of Inertia Law of Acceleration Law of Action Reaction Kinesiology Books Publisher 35
SIR ISAAC NEWTON 300 years ago Explained effect of forces acting on an object Through 3 laws Kinesiology Books Publisher 36
LAWOF INERTIA Newton s First Law Objects will not change their state of motion unless acted on by an unbalanced external force Kinesiology Books Publisher 37
LAWOF ACCELERATION Newton s Second Law Objects will experience a change in velocity or acceleration proportional to the unbalanced external force Kinesiology Books Publisher 38
Same mass Same force Same acceleration 39 Kinesiology Books Publisher 39
LAWOF ACTION-REACTION Newton s Third Law For every action there is an equal and opposite reaction; forces act in pairs that are equal in magnitude and opposite in direction Kinesiology Books Publisher 40
41 Kinesiology Books Publisher 41
FLUID DYNAMICS Fluid Drag Forces: The Dynamics of Air Kinesiology Books Publisher 42
FLUID DYNAMICS Knowledge of the forces generated by a fluid environment such as Water Air Water + Air All athletic event take place in a fluid environment Unaffected: gymnastics, dancing Affected: running, cycling, skiing, speed skating, swimming, badminton, baseball, etc. Kinesiology Books Publisher 43
DRAG FORCES: AIR Drag is a type of fluid force Profile drag; caused by object s size and shape Surface drag; cause by object s roughness Acts in opposite direction to body s travel and slows it down relative to body s Velocity Size and shape Roughness Fast-speed sports especially affected velocity = drag2 (10x faster, 100 x more drag) Kinesiology Books Publisher 45
SURFACE DRAG Body size and surface roughness = surface drag Boundary layer Thin layer of fluid adjacent to skin and carried along with body s motion, towing along outer fluid layers Laminar flow Small, streamlined, smooth, slow-moving bodies Smooth, layered flow pattern with no disturbance Turbulent flow Most human activities Disturbed flow pattern that changes flow conditions Kinesiology Books Publisher 46
Laminar flow Turbulent flow 47 Kinesiology Books Publisher 47
48 Kinesiology Books Publisher 48
PROFILE DRAG Main form of drag in fast-moving sports Characterized by turbulent flow Velocity of air flow past object is too fast for air to follow body s contour Backflow occurs at object s surface causing large, turbulent low- pressure zone behind the body This zone is continually formed and increases object s work Profile drag-reducing strategies frontal surface area (e.g., lugers are supine) sources of turbulence (e.g., speed skaters with arms behind back) Drafting Kinesiology Books Publisher 49
MAGNUS EFFECT A rotating body carries a boundary layer that interacts with surrounding air Boundary layer flow opposite to relative airflow Air is slowed by friction Zone of increased pressure created Boundary layer flow same as relative airflow Air is not slowed down Zone of increased pressure created Net difference in pressure on opposite sides of rotating object = Magnus force Magnus effect is mostly found in ping pong, tennis, soccer, and baseball 50 Kinesiology Books Publisher 50
