Basic Biomechanical Factors and Concepts

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Basic Biomechanical Factors and Concepts

• Anatomy and Kinesiology
• 420024

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Outline

• Introduction
• Levers
• Anatomical Levers
• Laws of Motion

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Biomechanics

• Biomechanics - study of the mechanics as it
  relates to the functional and anatomical analysis
  of biological systems and especially humans

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Biomechanics

• Mechanics
• Mechanics is divided into
• Statics
• Dynamics

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Biomechanics

• Statics - study of systems that are in a constant
  state of motion, whether at rest with no motion
  or moving at a constant velocity without
  acceleration
• Dynamics - study of systems in motion with
  acceleration

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Biomechanics

• Kinematics kinetics
• Kinematics - description of motion and includes
  consideration of time, displacement, velocity,
  acceleration, and space factors of a systems
  motion
• Kinetics - study of forces associated with the
  motion of a body
• Mechanical advantage
• Load/effort or load divided by effort
• Ideally using a relatively small force, or effort
  to move a much greater resistance

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Outline

• Introduction
• Levers
• Anatomical Levers
• Laws of Motion

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Introduction to Levers

• Lever Simple machine that operates according to
  principle of torques
• Torque The turning effect of a force
• T Fd

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d
How can you change torque?
F
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d
F
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Function of Levers

• Two functions
• 1. Force
• 2. Speed/ROM

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Function of Levers

• Force
• Examples?
• Common traits?
• Rigid bar
• Fixed point
• Lever movement vs. resistance movement

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R
F
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Function of Levers

• Speed/ROM
• Examples?
• Common traits?
• Rigid bar
• Fixed point
• Lever movement vs. resistance movement

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R
F
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Components of a Lever System

• Lever Rigid bar
• Fulcrum Axis of rotation/fixed point
• Force
• Applied force (F)
• Resistance force (R)
• Moment arm d
• Applied force
• Resistance

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More Concepts

• Mechanical advantage
• Levers designed for force
• Mechanical disadvantage
• Levers designed for speed/ROM

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F
R
Mechanical advantage or disadvantage?
How does mechanical advantage affect movement of
the lever?
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Human Application?

• Lever?
• Bones (Not always a bar)
• Fulcrum?
• Joints
• Applied force?
• Muscles
• Resistance force?
• Weight of limb, external resistance

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Classification of Levers

• Lever classification based on the relative
  location of
• 1. Axis of rotation/fulcrum (A)
• 2. Resistance force (R)
• 3. Applied force (F)
• A R F

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First Class Lever

• Center (A) Axis of rotation/fulcrum
• Mechanical advantage
• Mechanical disadvantage
• Examples
• Crow bar
• Seesaw

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Advantage or disadvantage?
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Second Class Lever

• Center (R) Resistance force
• Mechanical advantage
• Always
• Mechanical disadvantage
• Never
• Examples
• Wheelbarrow
• Nutcracker

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Third Class Lever

• Center (F) Applied force
• Mechanical advantage
• Never
• Mechanical disadvantage
• Always
• Examples
• Rowing
• Shoveling
• Bat, tennis racket

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Baseball, tennis?
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Human Application

• First class lever
• Elbow extension against a resistance

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Mechanical advantage or disadvantage
(R) Resistance force
(F) Applied force
(A) Axis of rotation/fulcrum
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Human Application

• Second class lever
• Ankle plantar flexion

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Mechanical advantage or disadvantage?
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Human Application

• Third class lever
• Elbow flexion

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Mechanical advantage or disadvantage?
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In general, is the human body built for force
application or speed/ROM?