biomechanics basics

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Biomechanics Basics. Bio. Mechanics. Physical Therapy. Biomechanics. Ideal Fluids. Viscous Fluids. Fluids. Biological Systems Osseous Joints & Ligaments Muscles & Fasciae Cardiovascular CNS PNS Organs of senses Integumentary Respiratory Digestive Urogenital Lymphatic - PowerPoint PPT Presentation

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  • Biomechanics Basics

  • BiomechanicsBiological SystemsOsseousJoints & LigamentsMuscles & FasciaeCardiovascularCNSPNS Organs of sensesIntegumentaryRespiratoryDigestiveUrogenital LymphaticDuctless glandsHealth professionApplication of Scientific PrinciplesMovement DysfunctionClinical practice, research, educationPathologyPrevention, evaluation, treatmentFluidsIdeal FluidsViscous FluidsCompressible Fluids

    SolidsDeformableBodiesMaterial strengthElasticityPlasticityRigid BodiesStaticsDynamicsKinematicsKineticsFrom Smidt GL. Biomechanics and Physical Therapy.Physical Therapy. 64(12): 1807-08, 1984.

  • BiomechanicsStudy of mechanics in the human body

    Mechanicsstatics bodies @ rest or moving w/ constant velocitydynamics bodies in motion undergoing acceleration

  • BiomechanicsBiological SystemsOsseousJoints & LigamentsMuscles & FasciaeCardiovascularCNSPNS Organs of sensesIntegumentaryRespiratoryDigestiveUrogenital LymphaticDuctless glandsHealth professionApplication of Scientific PrinciplesMovement DysfunctionClinical practice, research, educationPathologyPrevention, evaluation, treatmentFluidsIdeal FluidsViscous FluidsCompressible Fluids

    SolidsDeformableBodiesMaterial strengthElasticityPlasticityRigid BodiesStaticsDynamicsKinematicsKineticsFrom Smidt GL. Biomechanics and Physical Therapy.Physical Therapy. 64(12): 1807-08, 1984.

  • DefinitionKinematics

    Kinetics

  • Kinematic VariablesTemporal characteristicsPosition or locationDisplacementVelocityAcceleration

  • Linear versus Angular KinematicsPosition or locationDisplacement (d vs. )Velocity (v vs. )Acceleration (a vs. )

  • KineticsForces

    Mechanical action or effect applied to a body that tends to produce acceleration

    Push or pull

  • Kinetics - ForcesMutual interaction between 2 bodies - produces deformation of bodies and/or - affects motion of bodies

  • Force (vector)Point of application

    Direction

    Magnitude

  • MassQuantity of matter (kg)

    Center of Mass

  • Force SystemsLinear

    Parallel

    F1F2F1F2F3

  • Force SystemsConcurrent

    General

    F1F2F1F3F3F2F4

  • Force SystemsForce Couple

    F1F2

  • Center of Mass/GravityPoint at which bodys mass is equally distributed

    Balance point

  • PressureForce / Area

  • Moment or Force / Torque (T) Degree to which a force tends to rotate an object

    Torque twist

    Moment bend

  • Moment or Force / Torque (T) T = f * ma

    ma = moment arm, lever arm, torque arm

    Shortest distance () from AOR to line of force

  • Moment T = F * maT = 20 lbs. * 12 in.T = 240 in-lbs.

  • MomentsCoxa Varum

  • Newtons Laws of Motion

  • Law of Inertia (1)Body at rest or in uniform motion will tend to remain at rest or in uniform motion unless acted upon by an external force

  • Law of Acceleration (2)a f causing it

    Acceleration acts in same direction as f

    f = m * a

  • Law of Reaction (3)Every action = & opposite reactionBiomechanics Book- w = mg+ w = mg

  • Law of ReactionGround Reaction Forces

  • EquilibriumAt rest (static) or Constant linear/angular velocities (dynamic)Sum of forces = 0 (3d)Sum of moments = 0 (3d)

  • Work and PowerWork = Force * distance

    Power = Work / time

  • Momentumquantity of motion

    p = m * v (linear)

    Bigger & faster they are, the harder they hit

  • First Class Lever

  • First Class Lever

  • First Class Leverfew in body

    Triceps on olecranon

    Splenius Capitis on OA joint

  • First Class Lever

  • Mechanical AdvantageM. Adv. = FR / FE

    M. Adv. = EA / RA (forces levers)

    M. Adv. > 1 advantageM. Adv. < 1 disadvantage

  • Second Class Lever

  • Second Class Lever

  • Second Class AdvantageM. Adv. always > 1

  • Second Class LeverVery few in body

    Heel raise (fixed distal segment)

    Eccentric: G is FEmuscle is FR

  • Second Class Lever

  • Third Class Lever

  • Third Class Lever

  • Third Class DisadvantageM. Adv. always < 1

  • Third Class LeverMost common

    Concentric contractions

    Exchange between 2nd and 3rd class levers

  • Third Class Lever

  • Inefficient Human Body?3rd class:FE > movement of distal segment (goal)

    2nd class:FE (gravity) < movement of distal segment > control

  • Forces Acting on HumanInternal- muscles, ligaments, tendons, bones

    External- Gravity, wind, water, another person

  • StressInternal resistance of a material to an imposed load

    = force / area

    Pascal = 1 N/m2

  • Axial StressAxial (Normal) stress ()- compressive- tensile

    Shear stress ()- forces acting parallel or tangential

  • StrainChange in shape or deformation as a result of an imposed external load/stress

    shape / original shape L / L0Compressive,tensile, shear(angulation)

  • Strain

  • Linear Stress-Strain CurvesAB

  • Stress and StrainSlope = /

    as slope stiffness

  • Stress and Strain

  • Stress and StrainElastic Region stiffness

    Youngs Modulus (E) = slope in elastic region

    E = /

  • Mechanical Stress and StrainWet BoneDry BoneGlassAluminumSteel

  • Poissons Effect/RatioApplied compressive load tensile stress & strain

  • Poissons Effect/RatioApplied tensile load compressive stress & strain

  • Poissons Ratio = - (transverse strain / axial strain)

    = - (t / a)

  • ViscoelasticityViscosityresistance to flowability to lessen shear forceElasticityability to return to original shape after deforming load is removed

  • ViscoelasticityPurely elastic returns to original shape w/ no energy loss

  • ViscoelasticDelayed return response and loss of heat energy (hysteresis)

  • ViscoelasticElastic effects - rate of elastic return dependent on material propertiesViscous effects (time-dependent properties)- Creep- Stress-Relaxation

  • Creep TestMaterial/tissue is subjected to a sudden, constant load ()

    Constant is maintained

    Deformation () is recorded over time

    Measure of viscoelastic nature of material

  • CreepTissue deforms rapidly 20 sudden load (elastic)

    Continues to deform or creep beyond initial deformation (viscous)

    Definition material deforms as a function of time under the action of a constant load

  • Creep FSU

  • Creep FSU

  • Stress RelaxationConstant strain () level

    Develops an initial resistance or stress at that held deformation

    At that held deformation the stress () or relaxes

  • Stress Relaxation

  • Stress Relaxation

  • Stress RelaxationViscoelastic SolidViscoelastic Fluid

  • CreepEffect of temp.

    temp rate of creep