INTRODUCTIONF FOR BIOMECHANICS * * * * * * * * * * * * * *

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INTRODUCTIONF FOR BIOMECHANICS
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When we study any part of knowledge we ask
ourselves these questions

• What
• Is the application of mechanical principles on
  the living organisms.
• Why
• Via this science we able to solve many medical
  problems that face the patients
• How
• Using it on designing exercise programs,
  orthotics and prosthesis, application of a
  technique etc even when we give an advice to a
  patient.

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Course Contents

• Forces
• Centre of Gravity (COG).
• Stability and Equilibrium.
• Force Systems.
• Simple Body Mechanics.
• Motion and Newtons laws.

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• Biomechanics of bone.
• Behaviour of bone under stress.
• Stress strain curve.
• Possible fracture patterns.
• Various loading modes.

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• Biomechanics of fracture fixation.
• Soft tissue biomechanics(muscle and cartilage)
• Regional biomechanics hip, knee, shoulder,
  spine.
• normal Gait.
• Pathomechanics of Gait.
• Mechanics of Posture.

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Kinesiology Biomechanics

• Kinesiology is the scientific study of human
  motion. (kinesis and ology)
• Biomechanics Is the application of mechanical
  principles on the living organisms.

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Forces

• Definition
• Physical quantity that tends to change state or
  shape of an object ( state means the speed or
  equilibrium). So force can generate, stop, or
  modify motion.
• Its unit is Newton (N).

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Force is a vector quantity

• That because it has a magnitude and direction.
• Represented graphically by an arrow(vector) has
  four characteristics
• 1-Magnitude ? length
• 2-Direction ? head
• 3-point of application ?tail
• 4-line of application ?angle with the
  horizontal (angle of pull).

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A Vector representing a force
(2)
(1)
(4)
(3)
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Gravitational force

• The force that attract any object to the Earth.
• The force by the gravity on an object is equal to
  its weight .
• W M x (g)
• (in Newton) (in kg)
• Where g9.8m/s or 10 N/kg

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• Magnitude the weight of the body.
• Direction downward.
• Point of application the center of gravity.
• Line of application 90 angle (perpendicular to
  the ground)
• (COG is an imaginary point that the body weight
  can be assumed to be concentrated and equally
  distributed.)

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Ground Reaction Force

• Magnitude gravity.
• Direction opposite to gravity.
• Line of application gravity.
• Point of application point of contact to the
  ground.

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Frictional force

• Its the resistance force generated when two
  surfaces pressed and slide on each others.

• Magnitude the pressure and coefficient of
  friction (µ) roughness.
• Directionlateral.
• Point of application the surface of contact.
• Line of application parallel to the surface

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pressure

• Definition It is the total force applied per
  unit area.
• PF/A
• Measured in (N/m2 ) or pascal

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Resistance

• force that tends to reduce or stop a moving
  object
• As air or water resistance, it depends mostly on
  the surface area

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Center Of Gravity(COG)

• Definition(center of mass)
• COG is an imaginary point that the body
  weight can be assumed to be concentrated and
  equally distributed, around which body can rotate
  freely in all direction.
• At which summation of all moments equal zero

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Location of COG

• Depends on the bodys shape and position.
• In objects possess a symmetrical shape and its
  mass are equally distributed it is located
  exactly in the center.
• For asymmetrical irregular bodies the COG will be
  nearer the larger and heavier end.
• In normal standing adult person its located
  anterior to the second sacral vertebra.

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Factors affect the location of COG in the human
body

• Age
• In newborn above the umbilicus.
• At two years at level of umbilicus.
• At five years below the level of the umbilicus.
• In adults anterior to the 2nd sacral vertebra.

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2-Sex

• The COG in males is higher than in females
• Because of
• The different mass distribution

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3- position of any part in relation to the others

• COG is always shifts to the heavy mass
• e.g. flexion and extension
• running.

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4-Addition and subtraction of weight

• By carrying a weight
• Pregnancy
• amputation