Knes 300 - Principles of Human Movement

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Knes 300 - Principles of Human Movement

• Course Objectives
• 1) Learn about the relationship between
  mechanical principles and moving bodies.
• 2) Apply your knowledge of these mechanical
  principles to well-known skills.
• Why analyze movement?
• - Minimize injury, maximize performance, optimize
  technique.

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Knes 300 - Principles of Human Movement

• Qualitative vs. Quantitative Approaches
• Qualitative
• Description of quality without the use of
  numbers.
• Quantitative
• Involving the use of numbers.
• Ex. Long jump - That was a long jump vs. the
  jump was 18 feet in length

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Qualitative vs. Quantitative Descriptors

• Qualitative
• good
• poor
• long
• heavy
• flexed
• rotated
• dope
• tight

• Quantitative
• six meters
• three seconds
• fifty turns
• two players
• ten dollars
• 45 degrees
• 55 mph

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Qualitative vs. Quantitative Descriptors

• Qualitative does not mean general.
• A man walking down the street may also be stated
  a man is walking very slowly, appears to be
  leaning to the left, and is bearing weight on his
  right leg for as short a time as possible.
• Both Q and Q are important in the biomechanical
  analysis of human movement and while researchers
  rely heavily on quantitative techniques,
  clinicians, coaches, and teachers or physical
  activities regularly employ qualitative
  observations of their patients, athletes, or
  students to formulate opinions or give advise.

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Biomechanics

• The science involving the study of biological
  systems from a mechanical perspective.
• Statics and Dynamics are two major sub-branches
  of mechanics. Statics is the study of systems in
  a state of constant motion (at rest or constant
  velocity). Dynamics is the study of systems in
  which acceleration is present.
• Kinematics - describes the appearance of motion.
• Kinetics - the study of forces associated with
  motion (since Fma then acceleration is important
  variable in kinetic analyses).

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Chapter 1 - Sport Mechanics

• Mechanical Principles
• Technique
• Traditional training methods
• How to use this information

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Chapter 1 - Sport Mechanics

• Mechanical Principles
• Basic rules that govern an athletes actions.
• Ex.
• - Diver and gravity - optimal flight path
• - Wrestlers helped by gravity when getting
  opponent off balance
• - Ski jumpers using air resistance

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Chapter 1 - Sport Mechanics

• Technique
• - Patterns and sequence of movements that the
  athletes use to perform a sport skill.
• - Certain sports include a single skill such as
  discus throwing while tennis includes forehands,
  backhands, serves etc.
• - Each skill has a specific objective that with
  good technique may be achieved with the highest
  degree of efficiency and success.

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Chapter 1 - Sport Mechanics

• Traditional training methods
• - Many coaches and athletes still follow old,
  traditional methods in their workouts.
• - Trial and error methods demonstrate a lack of
  understanding of mechanical principles.
• - Copying world champions disregard differences
  in physique, training and maturity.
• - Analyze performances and teach movement
  patterns that produce efficient technique leading
  to better performances.

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Chapter 1 - Sport Mechanics

• How to use this information
• - Learn to observe, analyze, and correct errors
  in performance.
• - Assess the effectiveness of innovations in
  sport equipment.
• - Assess training methods for potential safety
  problems.
• - Assess the value of innovations in the ways
  sport skills are performed.
• - Know what to expect from different body types
  and different levels of maturity.

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Chapter 2 - Starting with Basics

• Body weight
• Mass
• Inertia
• Speed, Velocity and Acceleration
• Gravity
• Force
• Vectors
• Projectiles

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Chapter 2 - Starting with Basics

• Body weight
• - Newtons third law states that For every
  action there exists an equal AND opposite
  reaction
• - Bodys mass pulls on the earth and the earths
  mass pulls on the body. Scale reading reflects
  this mutual pulling taking into account the
  earths gravitational pull. The earths
  gravitational pull varies according to location
  (the further AWAY from the center of the earth,
  the smaller the gravitational pull - the less you
  weigh).

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Acceleration at Sea Level by Latitude
Latitude Acceleration Location
0 9.780 Nairobi, Kenya
10 9.782 Caracas Venezuela
20 9.786 Honolulu, Hawaii
30 9.793 Houston, Texas
40 9.802 Denver, Colorado
50 9.811 Bonn, Germany
60 9.819 Anchorage, Alaska
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Chapter 2 - Starting with Basics

• Mass
• - All objects that have substance or matter have
  mass.
• - The human body is composed of bones, muscles,
  fat, tissues and fluids all of which are
  substance or matter and have mass.
• - A heavyweight wrestler has more mass than a
  gymnast resulting in greater attraction between
  the earth and the wrestler than between the earth
  and the gymnast.

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Chapter 2 - Starting with Basics

• Inertia
• - Resistance to action or to change.
• - The desired of an object to continue doing
  whatever its doing - even when its moving.
• - All objects want to remain motionless, but if
  a force moves them, then they want to continue
  moving in the same direction at a constant speed.

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Chapter 2 - Starting with Basics

• Distance
• Total ground covered or traveled. A scalar.
• Displacement
• As the crow flies - A straight line between the
  beginning and the end. Measured in cm, m, km. A
  vector
• Speed
• Distance divided by time. 100 miles traveled in
  two hours average 50 mph.
• Velocity
• Displacement divided by time. 100 meters south
  divided by 10 seconds equal 10 meters per second
  in the south direction.

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Chapter 2 - Starting with Basics

• Speed, Velocity and Acceleration
• - A sprinter running the 100 m in 10 sec has an
  average speed of 10 m/s or 22 mph. This
  average speed indicates that the sprinter must
  have been going faster and slower at times to
  average the 22.
• - Velocity is a more precise description of
  speed - Giving it direction. Thus it includes
  both speed and direction - 20 mph due south.
• - The rate at which velocity changes is termed
  acceleration. It may be positive or negative.

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Chapter 2 - Starting with Basics

• Gravity
• - It is constant and it accelerates falling
  bodies at a rate of 32 feet per second per second
  or 9.8 meters per second per second.
• - It affects performance because the effects of
  gravity change the further you are from the
  center or core of the earth.
• - Ex. Mexico vs Moscow distances (elevations and
  equator).

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Chapter 2 - Starting with Basics

• Center of Gravity
• - The earths gravitational pull on the athlete
  is concentrated at the athletes center of
  gravity.
• - It represents the center of how the mass is
  distributed from head to toes. Muscle and bone
  are more dense and thus have more mass squashed
  into the space they occupy and thus the earth
  pulls more on those parts.
• - Ex. Males higher cog then females (hips)
• - Cog changes as limbs move and can be outside
  the body.

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Chapter 2 - Starting with Basics

• Force
• - A push or a pull that changes or tends to
  change the state of motion of an athlete or
  object.
• Force vector - refers to when the direction and
  amount of force is known.

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Force Vectors - Addition
Tip to Tail

Parallelogram
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Force Vectors - Subtraction
_




Tip to Tail
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Force Vectors - Multiplication
x
2



Tip to Tail
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c
a
b
What is abc and 2c-a3b and c-ba and a-b-c
and a-b-c? How many vectors can you add?
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Motion

• Linear
• Rectilinear (skydiver, putt on level ground)
• Curvilinear (parabolic trajectory, cannonball)
• Angular (Rotary)
• Rotates about an axis (wheels, spin dives,
  joints, curveballs)
• General
• Combination of linear and angular (sprinting)

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Projectile Motion

• To increase the horizontal distance (range) of a
  projectile you need to consider
• The velocity at release
• The angle at release
• The height at release

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Factors Influencing Projectile Trajectory
This scaled diagram shows the size and shape of
trajectories for an object projected at 10 m/s at
different angles.
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Chapter 2 - Starting with Basics

• Newtons Laws
• - Law of Inertia - a body will remain at rest or
  continue to move at a constant velocity unless
  acted upon by an external force.
• - Law of Acceleration - the acceleration of an
  object is directly proportional to the force
  causing it, it is in the same direction as the
  force and it is inversely proportional to its
  mass.
• - Law of Reaction - for every action there
  exists an equal and opposite reaction.

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Chapter 3 - Getting a Move On

• Action - Reaction
• Momentum
• Impulse
• Work
• Energy
• Rebound
• Friction

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Chapter 3 - Getting a Move On

• Action - Reaction
• This again is referring to Newtons third law
  (Law of Reaction).
• Ex. Sprinter pushing against the blocks and the
  earth pushing back on the attached block to
  propel the sprinter forward.
• The force produced by the sprinters muscles
  overcome inertia and she accelerates. This
  acceleration is proportional to how much force
  she applies the the time frame over which it is
  applied, and it is inversely proportional to her
  mass.

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Chapter 3 - Getting a Move On

• Momentum
• A moving athlete/object is an example of mass on
  the move. Because a certain amount of mass is
  moving we refer to this as the a/o momentum. It
  describes the quantity of motion that occurs. To
  increase momentum the a/o needs to increase
  either its mass or its velocity or both.
• Important in sports that have collisions and
  impact - football, bowling, billiards. Increase
  mass by putting on muscle to increase power and
  speed.
• Car accidents experts reconstruct crash scenes
  by determining which car had greater momentum.

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Momentum

• Testing the new Armed Forces barriers...
• From time to time someone asks what the concrete
  barriers are in front of controlled and secure
  buildings.  When told that the barriers will stop
  traffic, even trucks, from approaching the secure
  building I usually get a look of disbelief. 
  Looking for some footage like this to prove the
  point, in this test, the following parameters
  were used.  Read them and then watch the film.
• Truck 65,000 lbs.
• Speed 50 mph
• Kinetic Energy 5.5 MILLION ft. lbs.
• Stopped in 24 INCHES!

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Truck Video
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Chapter 3 - Getting a Move On

• Impulse
• To accelerate or to produce movement, an athlete
  needs to produce muscular force and create
  momentum. This force always takes time to
  produce and we refer to the application of force
  over a certain amount of time as impulse.
• Ex. Karate blow - Large force - short period of
  time. Bones 40 times stronger than concrete.
• Javelin throw - large force - long period of
  time. Strength and flexibility are important.
• High jump - large force - medium period of time.
  Not a full squat, but a quarter squat and rocking
  over the heel and backwards lean increase the
  amount of time over which to produce force.

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Chapter 3 - Getting a Move On

• Conservation of Linear Momentum
• Total amount of linear momentum of colliding
  bodies will be the same before and after the
  collision.
• If one body gains momentum then the other must
  lose momentum.
• Collisions cannot create or dissipate linear
  momentum but rather transfer it from one object
  to another.
• m1v1 m2v2 (m1 m2) (v)

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Conservation of Momentum

• In the absence of external forces, the total
  momentum of a given system remains constant.
• A 90 kg hockey player traveling with a velocity
  of 6 m/s collides head-on with an 80 kg player
  traveling a 7 m/s. If the two players entangle
  and continue traveling together as a unit
  following the collision, what is their combined
  velocity?
• Known m1 90 kg m280 kg v1 6 m/s v2 -7
  m/s
• m1v1 m2v2 (m1 m2) (v)
• (90 kg) (6 m/s) (80 kg) (-7 m/s) (90 kg 80
  kg) (v)
• 540 kg m/s 560 kg m/s (170 kg) (v)
• - 20 kg m/s (170 kg) (v)
• v 0.12 m/s in the direction of the 80 kg
  players original direction of travel

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Chapter 3 - Getting a Move On

• Work
• Mechanical work defined as force times distance.
  Ex. Filling shelves, throwing the javelin, ball
  slowed by turf, lifting weights.
• Different from physiological work in that for MW
  the object needs to move. A static or isometric
  contraction would involve PW but not MW. Unit is
  the Joule.

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Chapter 3 - Getting a Move On

• Power
• The rate at which work is done.
• It may be expressed as P W/t or P F x V
• In the metric system unit for Power is the watt
• Which is equivalent to 1 joule/second

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Chapter 3 - Getting a Move On

• Energy
• Defined as the capacity of an a/o to do work.
  Mechanical energy has three forms.
• Kinetic, Potential and Strain energy.
• Kinetic - moving energy KE ½ m v2
• Potential - location/position energy PE m g
  h
• Strain - stored energy

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Chapter 3 - Getting a Move On

• Conservation of Energy
• As a diver begins to fall towards water her
  potential energy is transformed into kinetic
  energy.
• A ball thrown into the air has both kinetic and
  potential energy throughout its flight or
  parabolic trajectory
• Ex. Rib cage testing device for crash dummies.

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Chapter 3 - Getting a Move On

• Rebound
• When objects/bodies separate (move apart) after
  a collision or impact occurs.
• Angle of incidence and angle of
  reflection/rebound measured with respect to the
  vertical.
• Coefficient of elasticity/restitution refers to
  the degree (amount) of recoil/bounce that objects
  have. The greater the bounce the greater the
  coefficient (value between 0 and 1) with 0
  signifying a completely inelastic object and 1
  signifying a completely elastic object.

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Angle of Reflection/Rebound
Incidence
Rebound
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Chapter 3 - Getting a Move On

• Rebound
• Affected by temperature and rebounding surface.
  Heat causes balls to bounce more while artificial
  turf also will cause a greater bounce.

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Chapter 3 - Getting a Move On

• Friction
• Force that occurs when an object moves or tends
  to move while in contact with another object.
• Reduce - wax skis, curling, bowling lanes
• Increase - rough gloves, cleats

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Mechanical Behavior of Bodies in Contact
What is friction?

• force acting over the area of contact between
  two surfaces
• direction is opposite of motion or motion
  tendency
• magnitude is the product of the coefficient of
  friction (?) and the normal reaction force (R)
  F ?R

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Chapter 3 - Getting a Move On

• Friction
• Three types - static, sliding and rolling.
• Static - seen in resting bodies, resists
  initiation of movement.
• Sliding - force that develops when two objects
  are sliding past each other.
• Rolling - when round object rolls past another.
• Factors affecting friction forces pressing two
  surfaces together, nature (texture) of surfaces,
  actual contact area.

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Chapter 3 - Getting a Move On

• Friction
• Pressure Force / Area
• One box exerts greater pressure against the
  floor than the other, thus squashing the
  microscopic irregularities found even on the
  smoothest of surfaces and by so doing it creates
  the same contact area as the other box.

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Mechanical Behavior of Bodies in Contact
For static bodies, friction is equal to the
applied force. For bodies in motion, friction is
constant and less than maximum static friction.
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Mechanical Behavior of Bodies in Contact
Is it easier to push or pull a desk across a room?
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Friction

• Coefficient of Friction
• The ratio of the force needed to overcome the
  Friction, to the force holding the surface
  together is called the coefficient of friction
• The coefficient is an experimentally derived
  value that depends on the nature of the contact
  surfaces. The larger the coefficient the more the
  surfaces cling to each other. A coefficient of 0
  would indicate completely frictionless surfaces.

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Vectors and Scalars

• Vectors - Two quantities - Magnitude and
  Direction
• Weight
• Velocity
• Displacement
• Acceleration
• All forces - friction, drag, lift, buoyancy etc.

• Scalars - Single quantity - Magnitude
• mass
• area
• distance
• temperature
• speed

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Formulas

• Weight m g
• PE m g h
• KE ½ m v2
• TE PE KE SE

• A ?v/t
• V ?displacement/t
• Speed ?distance/t
• Impulse F t
• Momentum m v
• Work F displacement
• Power Work / t

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Chapter 4 - Rocking and Rolling

• Angular motion
• Lever Systems
• Torque
• Types of levers
• Angular velocity
• Inertia, Centripetal and Centrifugal Force
• Rotary Inertia
• Angular Momentum

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Chapter 4 - Rocking and Rolling

• Angular motion
• Measured in degrees or revolutions, 360 degrees
  is equal to one full revolution, 180 is half, 90
  is one-quarter of a rev. and so on.
• Also referred to as spin, rotation, twist,
  swing, etc.

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Chapter 4 - Rocking and Rolling

• Lever Systems
• A lever is a simple machine that transmits and
  changes mechanical energy from one place to
  another.
• Always, Read, First
• Axis, Resistance, Force - What is in the middle
  will dictate the type of lever system (First,
  Second or Third Class).

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Chapter 4 - Rocking and Rolling

• Angular Motion
• Eccentric Force force applied a certain
  distance away from cog of object therefore
  causing rotation
• Centric Force force applied through the center
  of gravity of object creating linear motion
• Force couple two equal and opposite forces
  that cause rotation

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Chapter 4 - Rocking and Rolling

• Torque - A rotary, turning, or twisting effect
  produced by a force acting at a distance from the
  axis of rotation. The initiation of rotation
  requires the application of torque.
• Ex torque wrench, dumbbell curl.
• Torque is equal to force multiplied by the length
  of the force arm (the perpendicular distance
  between axis and point of force).

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Chapter 4 - Rocking and Rolling

• Torque
• A sum of torques may result in no motion
  (isometric contraction), angular motion (dumbbell
  curl) or linear motion (rowing boat).
• The perpendicular distance from where the force
  is applied to the axis of rotation is termed the
  torque arm, moment arm and force arm - all
  meaning the same thing.

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Torque video
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Chapter 4 - Rocking and Rolling

• Types of levers
• First Class - triceps extension, leg press
• Second Class - calf raises, rowing
• Favors the output of force at the expense of
  speed and range of motion.
• Third Class - biceps curl
• Always move the resistance through a larger range
  of movement than that moved by the force.

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Chapter 4 - Rocking and Rolling

• Mechanical Advantage
• It is a measure of the efficiency of a machine or
  a lever system. In other words what is the
  machines ability to magnify force or another way
  of expressing it is what is the output of the
  machine relative to its input
• MA FA divided by RA (FA/RA)

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Chapter 4 - Rocking and Rolling

• Mechanical Advantage
• Note that in third class levers the FA is always
  less than the RA so MA is less than 1.0, which is
  low mechanical advantage. Second class levers on
  the other hand are more efficient with MA greater
  than 1.0.
• We make adjustments to increase our mechanical
  advantage by using a crowbar in prying we
  increase the FA thus increasing the mechanical
  advantage or carrying a heavy load close to our
  bodies to reduce the RA and thus increase the
  mechanical advantage.

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Chapter 4 - Rocking and Rolling

• Angular velocity
• The rate of spin of an athlete or object. The
  rate of swing of a club or bat.
• However as the distance from the axis of rotation
  to the end of the bat increase so does the LINEAR
  velocity of the end of the bat. Therefore Linear
  velocity of a rotating segment is the product of
  the angular velocity and the radius (or distance
  from axis).

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Relationship of Linear and Angular velocities

• Lin. Vel Ang. Vel radius
• How fast a ball comes off the bat (lin vel) is
  equal to how fast you swing (ang vel) the bat
  times the length of the bat (radius)

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Chapter 4 - Rocking and Rolling

• Centripetal and Centrifugal Force
• Centripetal force is that force used to maintain
  an object moving around a circular path while
  centrifugal is the equal and opposite reaction to
  this centripetal force. While this force is
  affected by both the angular velocity and the
  mass of the object, it is the angular velocity
  which has a greater impact.

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Chapter 4 - Rocking and Rolling

• Rotary Inertia
• The resistance to rotate or follow a circular
  path.
• I S m r2
• Again the a/o wants to remain at rest or continue
  moving at a constant angular speed.
• To increase the rotary inertia of an object you
  increase BOTH the mass of the a/o and how far
  this mass is from the axis of rotation.

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Chapter 4 - Rocking and Rolling

• Angular Momentum
• Much like linear momentum, angular momentum
  refers to the product of the angular velocity
  times the rotational inertia of the a/o.

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Formulas

• Angular velocity
• ? ang. displ / t
• Angular acceleration ? ang. Vel. / t
• Torque F d
• Angular momentum Rotary Inertia ang vel

• Fc (m v2)/ r
• v is tangential velocity and r is radius of
  rotation
• Fc m r ?2
• ? angular velocity
• T I a
• a angular acceleration

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Chapter 5 - Dont be a Pushover

• Equilibrium, balance and stability
• Linear stability
• Rotary stability

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Chapter 5 - Dont be a Pushover

• Equilibrium or balance implies coordination and
  control
• Stability relates to how much resistance a/o put
  up against having their equilibrium disturbed.
  The more stable the a/o the more resistance the
  athlete generates against disruptive forces

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Chapter 5 - Dont be a Pushover

• Equilibrium, balance and stability
• Stable Unstable Neutral

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Chapter 5 - Dont be a Pushover

• Linear stability
• Defined as the resistance against being moved in
  a particular direction and resistance against
  being stopped or having its direction changed
  once it is moving.
• While at rest an a/os linear stability are
  govern by its mass and the frictional forces
  occurring between the a/o and the supporting
  surfaces.
• When in motion the a/os linear stability is
  directly related to momentum.

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Chapter 5 - Dont be a Pushover

• Rotary stability
• Defined as resistance to being tipped over or
  upended. Six factors that would increase
  stability
• 1) increase the base of support
• 2) the a/os line of gravity falls within the bos
• 3) lowering the center of gravity
• 4) increase body mass
• 5) base of support extends toward the oncoming
  force
• 6) line of gravity shifts toward an oncoming force

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Chapter 6 - Going with the Flow

• Hydrostatic Pressure
• Buoyancy
• Drag
• Lift

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Chapter 6 - Going with the Flow

• Hydrostatic Pressure
• Force exerted by a fluid like air or water.
• Ex. Blankets layered on you, sea level more
  blankets of atmosphere
• - Water is more dense than air thus weighs more,
  therefore pressure exerted by water increases
  with depth much faster than in air.

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Chapter 6 - Going with the Flow

• Buoyancy
• - Acts upward fighting gravity
• - Pressure increases with depth
• - Water presses on the athlete from all
  directions
• - Push from below (greater pressure) is greater
  than sides or above
• - This force from below is called buoyancy
• - Helium or hot air are also lifted by a buoyant
  force as a result of being lighter gases than
  normal air.

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Chapter 6 - Going with the Flow

• Center of Buoyancy
• - The place where the buoyant force concentrates
  its upward push on the athletes body.
• - Lungs and torso take up more space and weigh
  less compared to the legs.
• - Therefore the c of b is generally just below
  the rib cage, thus causing a torque which results
  in a tilted floating position.

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Chapter 6 - Going with the Flow

• To float or not to float that is the question
• - An a/o in the water has essential two forces
  acting upon it. Its weight will be pulling it
  down while the buoyant force will be pulling it
  up. Depending on which vector is greater - the
  a/o will float or sink.
• - Specific gravity is equal to the ratio between
  the density of the a/o and the density of water.
  If the spec. grav. is greater than one the a/o
  will sink, if it is less than one than it will
  float.

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Chapter 6 - Going with the Flow

• To float or not to float that is the question
• - Other factors that may affect your ability to
  float
• gender
• age
• lung capacity
• water temperature and density

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Chapter 6 - Going with the Flow

• Drag
• Varies according to
• Type of fluid (water or air)
• Density and viscosity of fluid (sticky and
  clingy)
• Shape and size of athlete
• But, most importantly it varies or it is most
  influenced by the relative velocity of object and
  fluid.

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Chapter 6 - Going with the Flow

• Drag
• Three types of drag are surface, form and wave
  drag.
• Surface drag is also called viscous drag or skin
  friction and the amount of surface drag is
  determined by the relative motion of object and
  fluid, the area of surface exposed to the flow,
  the roughness of the objects surface, and the
  fluid viscosity.

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Chapter 6 - Going with the Flow

• Drag
• Form drag is also called shape drag or pressure
  drag and the amount of form drag is determined by
  the relative motion of object and fluid, the
  pressure differential between the leading and
  trailing edges of the object, and the amount of
  surface acting at right angles to the flow.
• Streamlining refers to tapering both front and
  trailing edges so as to minimize the surface area
  hitting the flow on the front and the turbulent
  area on the back.

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Chapter 6 - Going with the Flow

• Drag
• Wave drag occurs at the interface between water
  and air. The amount of wave drag is determined
  by the relative velocity with which the object
  and wave meet, the surface area of the object
  acting at right angles to the wave, and the fluid
  viscosity.

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Chapter 6 - Going with the Flow

• Lift
• A force that acts perpendicular to the direction
  of motion.
• Three ways of developing lift are through an
  airfoil shaped object, modifying the angle of
  attack and through spin (lift caused by spinning
  balls is referred to as the Magnus Effect).

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Chapter 6 - Going with the Flow

• Lift and Magnus Effect
• A spinning object traveling through the air
  builds up high pressure on the side spinning into
  the airflow. Low pressure occurs on the side
  spinning with the airflow. The ball is deflected
  from high pressure to low pressure.

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Chapter 7 - Analyzing Sport Skills

• Objectives
• Special Characteristics
• Elite performances
• Divide into phases
• Divide into key elements
• Mechanical reasons

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Chapter 7 - Analyzing Sport Skills

• Determine the Objectives of the Skill
• - Rules of the sport
• Ex. Throwing the discus for distance and also
  for accuracy (land on selected sector) - speed of
  release, spin created, trajectory, stability to
  avoid foul. Volleyball - jump, spike, ball
  trajectory, touch net.
• Wt. Lifting - strength, balance, stability.
• - Be aware of ALL objectives required for the
  skill.

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Chapter 7 - Analyzing Sport Skills

• Special Characteristics
• Sport skills can be divided into different types
  based on a) manner and b) condition.
• A) Manner - skill performed once (nonrepetitive
  or discrete) or repeat sequentially (repetitive
  or cyclic).
• B) Condition - Predictable environment (closed
  skills) no need to make quick decisions because
  of sudden change
• Clean and jerk, synchronized swimming - easier
  practice
• Unpredictable environment (open skills) -
  presence of opposition or env. Cond. (wind,
  waves, rain, sun or field) Teach it by making it
  predictable and repetitive first, then add the
  opposition.

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Chapter 7 - Analyzing Sport Skills

• Study Top-Flight Performances of the Skill
• - Getting a picture of speed, rhythm, power,
  body positions, etc.
• - Tape it from various angles and watch it in
  slow motion.
• - Although body types differ, many common
  features exist. Ex. Golfers shifting their weight
  and rotating their hips

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Chapter 7 - Analyzing Sport Skills

• Divide the skill into phases
• - Makes your job of looking for errors easier.
  Not confused by watching too much at the same
  time.
• - Four common phases are Preparatory, Wind-up,
  Force and Follow-through.
• Prep - early mistakes will manifest themselves
  in the resultant outcome.
• Wind-up - muscle stretch, force over a long
  distance and time
• Force - apply it in the right sequence and for
  the rt amt of time
• Follow-through - maintain balance and continuity
  of motion.

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Chapter 7 - Analyzing Sport Skills

• Divide into key elements
• Once youve divided the skill into important
  phases, you can direct your attention towards
  dividing each phase into key elements.
• A key element are distinct actions that are
  essential to the success of each phase in the
  skill. Key elements are essential in good
  technique and contribute mechanically toward the
  success of the skill.

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Chapter 7 - Analyzing Sport Skills

• Mechanical reasons
• By far the most important step in analyzing a
  skill. This is what differentiates you from a
  coach that has learned his trade simply from
  being involved in the sport.
• Mechanics after all are the foundation of all
  sport techniques. These techniques are founded
  on mechanical principles/laws. Thus after
  choosing the key elements it is important to
  understand the mechanical purposes behind each
  element.

97
Chapter 7 - Analyzing Sport Skills

• Elite Idiosyncrasies
• Look for basic techniques that top athletes use.
• As you improve your analytical skill you will
  begin to disregard some actions elite athletes
  use that are personal idiosyncrasies and have no
  mechanical value (ie - Jordan sticking his tongue
  out!)
• Remember to take into account maturity, strength,
  flexibility, and endurance of a young immature
  athlete or novice.

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Chapter 8 - Identifying and Correcting Errors

• Observe complete skill
• Analyze each phase and its key element
• Use sport mechanics in your analysis
• Select errors to be corrected
• Decide on appropriate methods

99
Chapter 8 - Identifying and Correcting Errors

• Observe complete skill
• Observe and video record your athlete performing
  the skill from different positions. Front, back,
  90 degrees, left and right. Elements that are
  hidden from one point of view may be clear and
  unobstructed from another. Be careful if/when
  filming from the front - SAFETY comes first!!
• Choose a site with no or little distractions to
  you or your athlete, this way your athlete can
  concentrate on the skill.
• Make certain the athlete appears as large as
  possible within the field of view of the camera
  without cutting off any of the action.

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Chapter 8 - Identifying and Correcting Errors

• Observe complete skill
• Make certain your athlete has a proper warm-up
  prior to executing the skill forcefully or
  maximally. This will allow you to observe the
  athletes performance and get an overall
  impression.
• Keep the athlete enthuse by giving some positive
  feedback but refrain from offering instruction
  after or during each trial. Your athlete should
  not strive to impress you but rather give you a
  true measure of his/her performance.
• Use visual and auditory signals to gage the
  quality of the performance (loud foot slap on
  trip jump, or bad v-ball set.

101
Chapter 8 - Identifying and Correcting Errors

• Analyze each phase and its key elements
• Start with the result - lack of spiral or
  distance on a punt.
• Observe each phase of the skill in sequence
• Critically observe the first phase
  (preparation), then shift your attention to the
  second phase (acceleration) and finish with the
  follow-through.

102
Chapter 8 - Identifying and Correcting Errors

• Use sport mechanics in your analysis
• Ask yourself these questions
• Does your athlete have optimal stability when
  applying or receiving force?
• Is your athlete using all the muscles that make a
  contribution to the skill?
• Is your athlete applying force with the muscles
  in the correct sequence?
• Is your athlete applying the right amount of
  muscular force over the appropriate time frame?

103
Chapter 8 - Identifying and Correcting Errors

• Use sport mechanics in your analysis
• Ask yourself these questions
• Is your athlete applying force in the correct
  direction?
• Is your athlete correctly applying torque and
  momentum transfer?
• Is your athlete decreasing rotary resistance to
  spin faster and increasing rotary resistance to
  spin slower?

104
Chapter 8 - Identifying and Correcting Errors

• Select errors to be corrected
• After analyzing each phase and the key elements
  associated with each phase, find errors to
  correct.
• Rank each error in accordance to its importance.