Basic Biomechanical Factors and Concepts

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Basic Biomechanical Factors and Concepts

Anatomy and Kinesiology

420:024

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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 system‘s 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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F

d How can you change torque?

10F

d

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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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F R

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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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F R

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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

RowingShovelingBat, tennis racket

27Baseball, tennis?

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Human Application

First class lever Elbow extension against a resistance

29(A) – Axis of rotation/fulcrum

(F) – Applied force

(R) – Resistance force

Mechanical advantage or disadvantage

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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?