Announcements

1
Announcements

• File Intent to Graduate with Grad School
• By Friday, Sept 17
• HESS COMPS
• Friday, Oct. 2 930 start
• Sign up with Monica Luna by Friday, Sept. 18th
• Todays Plan
• Lecture some from 1 and 2 (measures methods)
• Finish up running video discussion

2
Structure and Function

• ESS 5306-001
• Lecture 2
• Reading Higgins (1977) Chapters 6, 7, 8
• James, Bates Dufek (2003)

3
Overview

• Perspectives on Movement
• Movement Constraints
• Structure and Function
• Inherent movement patterns
• Adaptation
• Developmental considerations
• Joint structure
• Movement Strategies

4
Movement Defined

• The definition of movement depends upon your
  perspective.
• Change in position (physics)
• Tool for problem solving (behavioral)
• For our purposes
• Some measurable change in position
• Extreme micro e.g. cell movement
• Extreme macro e.g. bird migratory patterns
• In-between e.g. sit to stand

5
Why study movement?

• Depends upon the goal and perspective

6
Benefits of Studying Movement

• To separate fact from fiction.
• After all WE are the movement experts, right?
• Example Goal Throw for maximum distance
• Question What is the optimum (best) angle of
  release?
• A) 45º
• B) gt 45º
• C) lt 45º

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Benefits of Studying Movement

• Observation
• Elite tennis players jump off the ground when
  serving.
• SoFact or Fiction?
• Coaches should teach young players to jump off
  the ground when serving.
• Fiction
• The Fact is that proper technique may result in
  player leaving the ground
• Reaching for the ball at highest point

8
Benefits of Studying Movement

• Observation
• Michael Johnson set world records in the 200 and
  400 m sprints by running with a very erect
  posture
• SoFact or Fiction?
• Young runners should imitate this technique
• Fiction
• The Fact is that Michaels technique results
  from his morphology and he is fast in spite of
  it, not because of it.

9
Movement Components
Physics / Mechanics
Biology / Structure

• Space (self, world)
• Force (internal, external)
• Time (duration, sequencing)
• and functions within real world constraints,
  thus
• 4. Gravity
• 5. Friction

• 6. Skeletal system
• 7. Muscular system
• 8. Nervous system
• ...and higher level cognitive influence
• 9. Perception
• 10. Abstraction

Somovement is complex, dynamic and multi-faceted
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Movement ExecutionFactors that determine the
movement

• Previous Experiences Perceptions
• Learning
• Fatigue
• Variability
• Constraints
• Interactions among these factors result in
  movement strategies.

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Movement Constraints

• Movement Constraint
• the confinement and restraining of input and
  output derived from various levels of system
  operation so as to produce order in the resulting
  movement.
• (Higgins, 1977 p. 44)

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Types of Movement Constraints

• Movement Constraints
• 1. Biomechanical
• 2. Environmental
• 3. Morphological

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Mechanical Constraints

• Limitations governed by physical laws.
• Examples
• Gravity (-9.81 m/s2)
• Inertia (Newtons 1st Law)
• F ma (Newtons 2nd Law)
• Friction ( µ Ff / FN )
• Air Resistance

14
Environmental Constraints

• Movement limitations caused by external spatial
  and temporal factors
• Hence, environmental

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Environmental Constraints

• Examples
• Temperature
• Wind
• Playing surface
• Rules of the game
• Equipment (including clothing, shoes, implements)
• Independent temporal control (music, pacing,
  competition)

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Morphological Constraints

• Limitations imposed by anatomical structure.
• Examples
• Muscle moment arm length (i.e., where it attaches
  relative to joint, biarticularity)
• Angle of insertion (e.g. points of attachment)
• Angle of pennation (e.g. fusiform, pennate,
  bipennate and effect on PSA and strength)
• Joint structure (e.g. vertebral column, knee)
• Muscle size/strength (e.g. PSA, rotator cuff,
  fiber size and type)
• Bone density (e.g. weight bearing)

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Biomechanics has to consider the Culmination of
all these Constraints on Performance
18
Structure vs. Function

• In the musculoskeletal system
• Structure (morphology) determines function
• Lots of examplesname some
• But is this a one-way relation?
• Does (can) function determine structure?
• Can you think of any examples?

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Structure Determines FunctionExamples of
Structure Dictating Function

• Knee Joint (condylar)
• Flexion and Extension
• Allows some anterior translation
• Also allows slight rotation
• Cervical Vertebrae
• Large range of motion (flexion, extension,
  rotation, lateral flexion)
• Small, and not weight bearing
• Lumbar Vertebrae
• Good range of motion in flexion and extension
  (less than cervical)
• Large, weight bearing
• Thoracic Vertebrae
• Very little range of motion (Why?)
• Fairly large but not as large as lumbar
• You should be able to think of other examples

20
Structure and Function
21
Form and Function

• Structure of the human musculoskeletal system
  somewhat dictates function
• Different joints allow rotations in only certain
  planes, while restricting motion in other planes
• Think of the joint structure and how the
  muscle-tendon complex crosses the joint
• Then think of the motion that is allowed at the
  joint
• Example Hip versus Knee

22
Types of Diarthrodial Joints
23
Types of Diarthrodial Joints
Plane or Gliding Joint Two flat surfaces slide
over one another (Ex Carpals)
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Other Types of Joints

• Synarthrodial or Fibrous
• Bones held together by fibrous articulations
• Little or no movement
• Example
• Sutures in skull
• Amphiarthrodial or Cartilaginous
• Hyaline cartilage or fibrocartilage holds joints
  together
• Little movement (but more than synarthrodial)
• Example
• Intervertebral discs

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Degrees of Freedom

• Degrees of Freedom (DOF)
• Number of planes in which a joint can move
• 1 DOF
• Uniaxial (hinge joint)
• Example Inter-phalangeal (flex-extend)
• 2 DOF
• Biaxial
• Example Wrist (flex-extend, ulnar-radial
  deviation)
• 3 DOF
• Triaxial
• Example Shoulder (flex-extend, abd-add, IR-ER)

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Summary of Joints

• 7 Types of Di-arthroidal Joints
• Hinge (elbow, inter-phalangeal)
• Pivot (radio-ulnar)
• Plane, Gliding (Vertebrae)
• Ellipsoid (metacarpal-phalangeal)
• Ball and Socket (hip, shoulder)
• Condylar (knee)
• Saddle (thumb)
• Degrees of Freedom

27
Inherent Movement Patterns

• Swing
• Flexion, extension, abduction, and adduction
• Spin
• Rotation
• Diagonal Movement Patterns
• Circumduction, combinations of swing and spin
• Symmetric (e.g. butterfly stroke, snatch)
• Asymmetric (e.g. aerials to induce or control
  twist, freestyle stroke)

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Diagonal MovementAdvantages of Diagonal Movement

• Greater muscle mass involved
• Increased force
• Interaction with gravity
• Body tilt effects muscle length and orientation
• Effects force and velocity, thus power
• Greater length of lever (moment) arm
• Increased moment of force (rotation)
• More segments involved in movement
• Greater velocity

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Diagonal PatternsMoment Arm Lengths
From Adrian Cooper, 1995
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Function Determines StructureTissue Adaptation

• Growth
• Hypertrophy, atrophy, remodeling
• Wolffs Law (1800s)
• Bone reacts to stress through remodeling
• Loss of bone density in a weightless environment
• Curvature of the spine in response to chronic
  muscular or external forces (e.g. kyphosis)
• Increase in bone density in response to increased
  load

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Structure, Function, AgeDevelopmental
Considerations
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Body Height Relationships
33
Body Mass Relationships
Adapted from Jensen, R. K. (1989). Changes in
segment inertia properties between 4 and 20
years. Journal of Biomechanics, 22, 529-536.
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Consequences of Development

• Linear Changes
• e.g. height, segment length, weight
• Non-linear Changes
• e.g. Moment of Inertia (I mr2)
• Influence on
• Torque (M I a)
• Angular Momentum (H I ?)
• What effects might these factors have on
  coordination during growth spurts?

35
Consequences of Constraints

• Effects on Movement Strategy
• A selected neuro-musculoskeletal solution for
  performance of a motor task (B.T. Bates)
• And this is a whole different ball of wax
• Numerous solutions to a single outcome are
  possibleespecially if it is a sub-max effort.
• Hence, the degrees of freedom problem
• (and a whole new can of worms)

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Take Home Message

• Assessment of performance is extremely dependent
  on movement constraints
• Which dictate strategies
• And thus affect performance
• Be wary when you bring your subjects into the
  lab, marker them up, slap leeds and electrodes on
  them, put cameras in front of their face and then
  tell them to just walk normal.

Pay no attention to the man behind the curtain!
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Readings/References

• Higgins (1977) Chapters 6, 7, and 8
• James, Bates Dufek (2003)
• These are posted online for your reading pleasure
  as well as reference

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For Next Time

• Rigid Body Analysis
• makn stick figures