KPE 315 Advanced biomechanics

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KPE 315 Advanced biomechanics Powered By Docstoc
					KPE 315 Advanced biomechanics

   "When you can measure what you
    are speaking about, and express it in
    numbers, you know something about
    it." (William Thomson, Lord Kelvin.
    Popular Lectures and Addresses,
    1891-1894).
Introduction
 True science investigates and brings
  to human perception such truths and
  such knowledge as the people of a
  given time and society consider most
  important. Art transmits these truths
  from the region of perception.
    Leo Nikolaevich Tolstoy
Perception
   You teach me baseball and I'll teach you
    relativity...No we must not You will learn about
    relativity faster than I learn baseball.
    --Albert Einstein
   I was told over and over again that I would never
    be successful, that I was not going to be
    competitive and the technique was simply not
    going to work. All I could do was shrug and say
    'We'll just have to see'.
    --Dick Fosbury won an Olympic gold medal at the
    1968 Mexico City Games after he invented a
    revolutionary high-jump technique.
Or do you feel like this …
   Nobody in football should be called a
    genius. A genius is a guy like Norman
    Einstein.
    --Joe Theismann
Introduction
   Biomechanics –
    the application of
    mechanical laws
    to living
    structures,
    specifically to the
    locomotor system
    of the human
    body (Dorllandès
    illustrated Medical
    Dictionary)
    Outline
   What is biomechanics?
   Who uses
    biomechanics?
   How do
    biomechnanicsts
    approach sports
    movements?
   Introductory analysis of
    human movement – “a
    brain stormer!”
   Cognitive thinking
How useful is a knowledge of
Biomechanics?
   Very useful
   Not very useful
   Definitely a pain in
    the butt!
   Your answer will
    determine the
    application of
    mechanics in your
    professional life.
   The question is -
    will this course
    change your
    opinion?!
Physical education teacher
   Physical education means that the
    learners individual dimensional
    needs – physical, intellectual, social,
    emotional and spiritual – are
    satisfied explicitly through all forms
    of physical activity.
To the coach
   From the beginner
    to elite athlete
    technique is
    always part of the
    coaching program.
To the athlete
   The experimental
    literature does not
    cover the value of
    mechanical analysis
    for the advanced
    athlete, but empirical
    evidence seems to
    indicate somewhat
    greater value at the
    higher skill levels.
The Biomechanist
   Biomechanics aims to explain the
    mechanics of life and living. From
    molecules to organisms, everything
    must obey the laws of mechanics.
  Biomechanists analyse
  movement in reference to:

Table 1. A schematic of movement characteristic components


Time     Space       Force            Abstraction

Duration Self     Internal-external    Quality

Sequencing world Biological-physical
    Time aspects of human movement
 The duration of human-movement and the separate actions or
  phases of a movement pattern are usually measured in
  milliseconds, seconds and minutes.
 The initial analysis of a movement, is to determine the duration
  of each body segments displacements.
 When compared to the total time of the movement, the
  relationships of displacements with respect to different body
  parts can be determined. This is known as the sequencing of
  actions.
 When time is related to space (3-D) we can determine the
  positions, displacement, velocities and accelerations of body
  parts.
    Spatial aspects of human movement
 The spatial analysis uses several different
  spatial frames of reference.
 For the body it is the anatomical
  framework.
 For the World we move in the Cartesian
  (rectangular with three perpendicular axes
  x,y, and z) coordinate framework is used.
 This framework quantifies up-down;
  forward-back and side-to-side movement.
Translatory, rotary motion and general
                motion
     Translatory motion is motion from one plane to
      another, with each part of the body moving an
      equal distance in a linear or curved path.

     Rotary motion is the body or body segment
      rotating around an axis.

     Human movements are complex and involve a
      combination of rotation and translation - known
      as general motion.
Axes and planes
 Three imaginary planes (Cardinal)
  divide the body in half by mass are
  known as the:
 Sagittal
 Frontal
 Transverse planes.
The Sagittal plane
   The Sagittal plane
    divides the body
    vertically into left
    and right halves in
    which forward and
    backward
    movements of the
    body occur
The frontal plane
   The frontal plane
    splits the body
    vertically in front
    and back halves in
    which lateral
    movements of the
    body occur.
The transverse plane
   The transverse plane
    separates the body
    into top and bottom
    halves in which
    horizontal and body
    and body segment
    movements occur
    when the body is in
    the erect standing
    position.
Anatomical reference axes
 When a segment of a human body
  moves, it rotates around an
  imaginary axis of rotation that
  passes through a joint to which it is
  attached. There are three axes:
 The Frontal (mediolateral) axis
 The Longitudinal axis
 The Anterior-posterior axis
The Frontal axis
   The Frontal axis
    (mediolateral) is an
    imaginary line
    around which
    saggital plane
    rotations occur.
The Longitudinal axis
   The Longitudinal
    axis is an
    imaginary line
    around which
    transverse plane
    rotations occur.
The Anterior-posterior axis
   The Anterior-
    posterior axis is an
    imaginary line
    around which
    frontal plane
    rotations occur.
Forces
   Internal forces – muscle contraction
    that applies a force to a bone.

   External force – a force exerted on a
    body from outside the system, from
    some other body.
Quality
 How is this defined if the same force
  and identical movements are
  produced?
 What is that innate quality that
  defines exceptional movement?
Different methods for movement analysis

    Different models for studying
     movement. Choose one or design
     your own!
    POSSUM
    Factor-results
    Holistic principle model
     POSSUM

   This system uses a number of continuums to
    describe human movement.

 Purpose:     Projection: height range speed
 Observation: initial path: vertical 45
               horizontal or below
 System of studying: ROM Speed of motion
 Understanding:     Mechanics of motion
 Movement:          Segment or whole body
Factors-results method
   This is a hierarchical structure to
    depict factors that determine the
    movement result. This method will be
    needed for the presentation (see OH).
Holistic – principle method
   This method aims to accomplish a
    comprehensive description of movement
   1) Describing the movement.
   2) Setting the performance goal.
   3) Identifying the anatomical, mechanical
       and environmental considerations.
   4) Determining the biomechanical
       principles for successful performance
       of movement.
   5) Assessing the performance based on
       these principles.
Sports skill analysis

   Apply the definitions of style, skill,
    and technique to the following sports
    movement from the video clip.
Definitions
 Skill - a general movement pattern
  adapted to a particular activity or
  sport.
 Technique - a particular type of
  movement of the same skill
 Style - an individual adaptation of a
  technique.
Practical sports movement analysis
    In your groups determine:
       •   1)   Which movements are personal style?
       •   2)   Define the skill of the movement.
       •   3)   What is the technique used here?
       •   4)   What is the performance objective?
       •   5)   List the constraints associated with the
                movement.
Questions-continued
   6)    Is the movement occurring in an open or
          closed environment?
   7)    Is it a discrete or continuous skill.
   8)     Describe the arms and legs at take off in
          reference to their planes and axes
   9)     List the biomechanical factors, and then the
          mechanical principles and then note the
          critical features. (For example for a free throw
          the biomechanical factor would be optimal
          force application for accuracy and height , and
          then the mechanical principles are angle of
          release, speed of release and height of release
          and then note the critical features are
          segmental energy transfer, and arm release
          angle at 90 degrees.)
   10)   How would you describe the quality of
          movement?
Cognitive Thinking
    A cognitive approach requires the following
     steps that resemble the force-analysis
     system.
    Write down the “known”
    Write down the “unknowns”
    Draw out the scenario (visual skills used
     here)
    Draw a free body diagram.
    Find the relevant equations and define steps
     for solving the problem.
        Solve using cognitive thinking
       Determine the acceleration of the two masses 4 and 3 kg when a
        horizontal force of 9 N is applied.
       Known m1 4.00 kg and m1 3.00 kg F = 9 N
       Unknown acceleration of system.
       Draw a free body diagram

                                                    y
    F               m2
              m1                                           x
Find   the relevant equations and define steps for solving the problem.
F = ma
Fx = (system) = Fx = (m1 + m2) a
a = F / m1 + m2
a = 9 / 4 + 3 a = 9/7 a = 1.29 ms-2
      Sample Question 2
   An applied force of 50 N is
    used to accelerate an
    object to the right across a
    frictional surface. The
    object encounters 10 N of
    friction. Use the diagram to
    determine the normal force,
    the net force, the mass, and
    the acceleration of the
    object. (Neglect air
    resistance.)
    Solution
   Known: F gravity = 80 N, friction force = 10 N and force
    applied = 50 N
   Unknown: force normal; mass; acceleration and force
    net.
   Apply relevant equations and define steps for solving
    the problem
   Since there is no vertical force acceleration, there is no
    vertical net force. Therefore F normal = Force gravity = 80 N
Solution
   Mass can be calculated by using F = m acceleration (due to
    gravity) = m = F/ a = m = 80 / 9.81 (you can use 10 for ease)
    = 8 kg or 8.15 kg.
   Fnet is the sum of all the force acting on the system
   In the vertical direction F normal = Force gravity = 80 N
   In the horizontal direction force applied = 50 N and in the
    opposite direction Force friction opposes the motion by 10 N.
    By vector addition 50 N + -10 = 40 N
   To determine acceleration use F= ma or a = F/m a = 40 / 8 =
    5 ms-2.

				
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