Biomechanical Analysis to Improve Technique

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Chapter 13

• Biomechanical Analysis to Improve Technique

2
Forms of Motion

• General motion
• Linear (translation) motion
• Rectilinear motion - motion along a straight
  line.
• Curvilinear motion - motion along a curved line.
• Angular motion (fixed point)

3
Keys Areas of Study

• Kinematics study of the time and space aspects
  of movement
• Kinetics study of the force and energy aspects
  of a performance.

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Kinetics

• Kinetics - the study of forces.
• Basic concepts related to kinetics
• Mass - the quantity of matter a body possesses.
• Inertia - resistance to a change in state of
  motion. Directly proportional to mass.

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Qualitative Analysis of Human Movement

• Requires knowledge of the specific biomechanical
  purpose of the movement and the ability to detect
  the causes of errors.
• Visual observation.

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Analyzing Skills Qualitatively

• Analyze technique and outcome.
• If technique (process) is correct, outcome
  (product) will be too.

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Analyzing Skills Qualitatively

• Too frequently we coach or teach to the outcome
  rather than the technique or process that
  produces the outcome.

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Role of Movement Analyst Bob Norman (1976)
Shirl Hoffman (1977)

• Recognize symptoms of malperformance
• Is performance acceptable? Is the goal attained?
• Process vs Product
• Trouble-shoot the cause of the malperformance
• Critical ability lacking
• Skill performance deficiency
• Psychosocial problem
• Prescribe cues to correct malperformance
• Make the appropriate intervention

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Analyzing Skills Qualitatively

• Hoffmann flow chart

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Was goal attained?
Define and clarify new goal
Yes
Redefine goal
No
Yes
Critical ability lacking?
Yes
Remedy deficit
Ample observations? Adequate info base?
No
No
Skill performance deficiency?
Technique error?
Cause of error known?
Modify technique
Yes
Y
Yes
No
Refocus attention on relevant stimuli
Perceptual error?
Yes
No
No
Emphasize temporal factors
Decision error?
Yes
Psycho-social problems?
Performance management techniques
Yes
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Critical ability lacking
If there is a mismatch between the individual
and the environment - modify the environment
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Mismatched Environment
Adapt the environment to the individual to
enhance chances of success.
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Photo by Erica Trout in Parade Magazine, 9/19/04
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Was goal attained?
Define and clarify new goal
Yes
Redefine goal
No
Yes
Critical ability lacking?
Yes
Remedy deficit
Ample observations? Adequate info base?
No
No
Skill performance deficiency?
Technique error?
Cause of error known?
Modify technique
Yes
Y
Yes
No
Refocus attention on relevant stimuli
Perceptual error?
Yes
No
No
Emphasize temporal factors
Decision error?
Yes
Psycho-social problems?
Performance management techniques
Yes
15
Skill Performance Deficiency

• We will come back to this shortly

16
Was goal attained?
Define and clarify new goal
Yes
Redefine goal
No
Yes
Critical ability lacking?
Yes
Remedy deficit
Ample observations? Adequate info base?
No
No
Skill performance deficiency?
Technique error?
Cause of error known?
Modify technique
Yes
Y
Yes
No
Refocus attention on relevant stimuli
Perceptual error?
Yes
No
No
Emphasize temporal factors
Decision error?
Yes
Psycho-social problems?
Performance management techniques
Yes
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Psychosocial problems.
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Psychosocial problems.

• I joined a health club last year, spent about
  400 and havent lost a pound.
• Apparently, you have to show up.

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Psychosocial problems.
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Bob Norman

• One of the most difficult problems which
  confronts coaches and teachers when they are
  teaching fundamental skills is that of detecting
  errors accurately and specifically.

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Bob Norman

• If the error detection is inaccurate or
  non-specific, the quality of instruction and the
  consequent learning on the part of the athletes
  will be poor.

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Bob Norman

• Causes, symptoms and idiosyncrasies
• Cause the actual mechanical reason for a
  movement. Forces, acceleration, etc
• Symptom a side-effect of a movement. Follow
  through.
• Idiosyncrasy something that occurs during
  movement that has nothing mechanically to do with
  the movement. Tongue sticking out

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Bob Norman

• In teaching and coaching, we too often focus on
  the symptoms and idiosyncrasies of a performance
  rather than the actual mechanics that determine
  what happens.

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Skill Performance Deficiency

• Mechanical objective of a skill
• momentum in particular direction(s)

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Bob Norman (1976)

• Mechanical objective of a skill
• Idiosyncrasy
• individual nuance of performance that has no
  direct influence on mechanics of performance
• Michael Jordans tongue
• Various batting stances

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How Often Have You Heard This?

• You need to stand ____ with the bat ______ to hit
  the ball.

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Unwarranted focus on static position of
batting stance
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Some People Just Dont Get It?
Physics is not the only science important in the
game of baseball its also a game of psychology,
of pitchers trying to stare down batters, and
batters trying to intimidate pitchers. And no
matter what you tell me, I dont believe that
some guy standing in the batters box with his
bat dangling loosely from his hands has nearly as
much power as a guy snarling and gripping the bat
hard, waving it menacingly over his head. It
may not be good science, but Ill bet the second
guy gets more hits.
Suzanne Sparacino, Commack NY Letter to the
editor, Discover magazine.
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Bob Norman (1976)

• Mechanical objective of a skill
• Idiosyncracy
• Symptom of an error
• what we see go wrong (kinematics)
• not high enough
• not fast enough
• wrong direction
• body positions

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How Often Have You Heard This?

• Swing level

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Swing Level?
Paul Popovich March 29, 1993.
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Say what you mean!
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Another Example

• The Follow Through
• Basketball shooting - Goose neck

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Follow through?

• As the knees straighten, release the ball and
  follow through with a flick of the wrist
• Follow through by snapping your wrist down, like
  you are reaching into the cookie jar.
• As you release the ball, snap your wrist
  downward, as if you are waving "good-bye" (called
  a "follow through"). When done correctly, the
  wrist snap will give the ball the correct amount
  of spin it needs.

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Followthrough
Symptom or Cause?
Game-winning shot vs Utah Jazz 19???
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Another Example

• Pitchers are told to lead with the elbow

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Lead with the elbow
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Shoulder External Rotation Symptom? or Cause? of
Great Performance?
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Bob Norman (1976)

• Mechanical objective of a skill
• Idiosyncracy
• Symptom of an error
• Cause of an error
• the underlying reason for the poor performance
• mechanically error in impulse application

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Mechanical Phases of skill performance

• Ritual Phase
• Full of idiosyncrasies, useful for mental focus
• Preparation
• Wind up
• Storage of elastic energy, increase ROM
  (Benefits?)
• Execution
• Acceleration
• Apply impulse to the body in the desired
  direction
• Follow through
• Bring moving parts to rest
• Safety, symptom of good performance

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Typical Coaching Advice
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Typical Coaching Advice
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Typical Coaching Advice
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Typical Coaching Advice
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More Glaring Examples of Bad Coaching
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Volleyball Underhand ServePeer Rating Evaluation
Sheetfrom a middle school session at IAHPERD
conference

• Is the arm which is holding the ball across the
  front of the body?
• Is the ball held at or below the waist?
• Is the body bent at the waist before the person
  hits the ball?
• Is the striking arm brought back with a straight
  elbow?
• Is the ball hit from a short toss or out of the
  hand?
• Does the hitting arm swing from the shoulder?
• Does the hitting arm swing straight, not across
  the body?
• Is the person stepping or standing with
  opposition?
• Is there a weight shift from the rear foot to the
  front foot when the ball is hit?
• Does the striking hand follow through at least as
  high as the head after the ball is hit?

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Possible reasons why the elderly walk slower

• Not willing to walk faster
• Wise enough to know that walking faster changes
  nothing
• Careful stepping due to slowing of reflexes
• Cautious
• Afraid of road hazards
• Afraid of falls due to OP, other catastrophes
• Not able to walk faster
• Reduced ability to maintain dynamic balance
• Reduced ROMs
• Reduced contents of fast-twitch muscle fiber
• Joint or muscle pathologies
• Reduce CV fitness

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Help! Ive Fallen and I Cant Get Up

• Phenomenon
• Individual cannot rise from the ground
• After a fall
• Gardening
• Housecare
• Why not? List possible reasons, according to the
  Hoffman Checklist
• Importance Develop an intervention for
  prevention
• Strength training?
• Flexibility training?
• Technique Training
• What technique? Old vs Young? Healthy vs Infirm?

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Analyzing Skills Qualitatively

• Understand the specific purpose of the skill from
  a biomechanical perspective.
• Identify the cause of technique error.
• Familiarity with the skill aids in analysis.

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Planning a Qualitative Analysis

• Identify the major questions of interest (What is
  the problem?).
• Determine the optimal perspective from which to
  view the movement.
• Select the optimal viewing distance.

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Planning a Qualitative Analysis

• Determine the optimal number of trials necessary
  to perform the analysis.
• Determine the effect of environmental factors on
  performance.
• Will a video recording help in analysis?

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Conducting a Qualitative Analysis

• Every performance of a motor skill is affected by
  the physical characteristics of the performer.

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Conducting a Qualitative Analysis

• These include the performer's critical abilities
• age,
• gender,
• anthropometrics,
• the developmental and skill levels at which the
  performer is operating,
• and any special physical or personality traits
  that may impact performance.

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Conducting a Qualitative Analysis

• Providing a novice, preschool-aged performer with
  cues for a skilled, mature performance may be
  counterproductive, since children are not simply
  scaled-down adults.

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Conducting a Qualitative Analysis

• The analyst should not overlook the potential
  value of non-visual forms of information (sound).
  
• Another potential source of information is
  feedback from the performer.

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Conducting a Qualitative Analysis

• Adding more than one analyst may enhance the
  thoroughness of the analysis.

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Quantifying Kinetics

• Tools for measuring kinetic quantities
• EMG
• Dynamography
• Force platforms

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Conducting a Qualitative Analysis

• Tools for measuring kinematic quantities
• Cinematography and videography.
• Optoelectric movement monitoring systems (LEDs)

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Conducting a Qualitative Analysis

• Electrogoniometers.
• Timing devices.
• Accelerometers.