Biomechanics concepts

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Biomechanics concepts

  1. 1. BIOMECHANICS CONCEPTS BIOMECHANICS Study of Biological Systems by Means of Mechanical Principles father of Mechanics Sir Isaac Newton
  2. 2. Biology PhysicsSkeletal Muscular Nervous Mechanicssystem system system Kinetics Kinematics 22-Jun-12 P.Ratan (MPT, Ortho & Sports) 2
  3. 3. HUMAN MOVEMENT ANALYSIS BIOMECHANICS KINESIOLOGY KINETICS KINEMATICS FUNCTIONAL Linear Angular Linear Angular Position Position Velocity Velocity Force TorqueAcceleration Acceleration 22-Jun-12 P.Ratan (MPT, Ortho & Sports) 3
  4. 4. Basic types of Motion  Linear  Rectilinear  Curvilinear  Angular or rotational  Combined or general22-Jun-12 P.Ratan (MPT, Ortho & Sports) 4
  5. 5. Human Analysis Internal: mechanical factors creating and controlling movement inside the body External: factors affecting motion from outside the body22-Jun-12 P.Ratan (MPT, Ortho & Sports) 5
  6. 6. Kinematics Describes motion  Time  Position  Displacement  Velocity  Acceleration Vectors Angular and linear quantities 22-Jun-12 P.Ratan (MPT, Ortho & Sports) 6
  7. 7. Kinematics Formulas22-Jun-12 P.Ratan (MPT, Ortho & Sports) 7
  8. 8. Kinetics Explains causes of motion Axis  Mass  amount of matter (kg)  Inertia: resistance to being moved  Moment of Inertia (rotation) I = m·r2 22-Jun-12 P.Ratan (MPT, Ortho & Sports) 8
  9. 9. Kinetics Force: push or pull that tends to produce acceleration Important factor in injuries Vector22-Jun-12 P.Ratan (MPT, Ortho & Sports) 9
  10. 10. Kinetics  Idealized force vector  Force couple system F F’ F M=Fd d d d = = F F22-Jun-12 P.Ratan (MPT, Ortho & Sports) 10
  11. 11. Kinetics: Force  Force & Injury factors  Magnitude  Location  Direction  Duration  Frequency  Variability  Rate22-Jun-12 P.Ratan (MPT, Ortho & Sports) 11
  12. 12. Kinetics: Force System  Linear  Parallel  Concurrent  General  Force Couple22-Jun-12 P.Ratan (MPT, Ortho & Sports) 12
  13. 13. Center of Mass (COm) or Gravity (COG)  It is an imaginary point where there is intersection of all 3 cardinal plane.  Imaginary point where all the mass of the body or system is concentrated  Point where the body’s mass is equally distributed22-Jun-12 P.Ratan (MPT, Ortho & Sports) 13
  14. 14. Pressure  P = F/A  Units (Pa = N m2)  In the human body also called stress  Important predisposing factor for injuries22-Jun-12 P.Ratan (MPT, Ortho & Sports) 14
  15. 15. Moments of Force (Torque) Effect of a force that tends to cause rotation about an axis M = F ·d (Nm)  If F and d are Force through axis22-Jun-12 P.Ratan (MPT, Ortho & Sports) 15
  16. 16. Moments of Force (Torque)  Force components  Rotation  Stabilizing or destabilizing component22-Jun-12 P.Ratan (MPT, Ortho & Sports) 16
  17. 17. Moments of Force (Torque)  Net Joint Moment  Sum of the moments acting about an axis  Human: represent the muscular activity at a joint  Concentric action  Eccentric action  Isometric22-Jun-12 P.Ratan (MPT, Ortho & Sports) 17
  18. 18. Moments of Force (Torque)  Large moments tends to produce injuries on the musculo-skeletal system  Structural deviation leads to different MA’s22-Jun-12 P.Ratan (MPT, Ortho & Sports) 18
  19. 19. NEWTONIANLAWS of Motion22-Jun-12 P.Ratan (MPT, Ortho & Sports) 19
  20. 20. 1st Law of Motion A body a rest or in a uniform (linear or angular) motion will tend to remain at rest or in motion unless acted by an external force or torque Whiplash injuries 22-Jun-12 P.Ratan (MPT, Ortho & Sports) 20
  21. 21. 2nd Law of Motion  A force or torque acting on a body will produce an acceleration proportional to the force or torque  F = m ·a or T= I · F22-Jun-12 P.Ratan (MPT, Ortho & Sports) 21
  22. 22. 3rd Law of Motion For every action there is an equal and opposite reaction (torque and/or force) Contact forces: GRF, other players etc. GRF 22-Jun-12 P.Ratan (MPT, Ortho & Sports) 22
  23. 23. Equilibrium Sum of forces and the sum of moments must equal zero  F=0  M=0 Dynamic Equilibrium  Must follow equations of motions  F=mxa  T=Ix 22-Jun-12 P.Ratan (MPT, Ortho & Sports) 23
  24. 24. Work & Power  Mechanical Work  W= F ·d (Joules)  W= F ·d·cos ( )  Power: rate of work d  P = W/ t (Watts) W W  P = F ·v  P = F ·(d/t)22-Jun-12 P.Ratan (MPT, Ortho & Sports) 24
  25. 25. Mechanical Energy  Capacity or ability to do work  Accounts for most severe injuries  Classified into  Kinetic (motion)  Potential (position or deformation)22-Jun-12 P.Ratan (MPT, Ortho & Sports) 25
  26. 26. Kinetic Energy  Body’s motion  Linear or Angular  KE=.5·m·v2  KE =.5 ·I· 222-Jun-12 P.Ratan (MPT, Ortho & Sports) 26
  27. 27. Potential Energy  Gravitational: potential to perform work due to the height of the body  Ep= m·g·h  Strain: energy stored due to deformation  Es= .5·k·x222-Jun-12 P.Ratan (MPT, Ortho & Sports) 27
  28. 28. Total Mechanical Energy  Body segment’s: rigid (nodeformable), no strain energy in the system  TME = Sum of KE, KE , PE TME = (.5·m ·v2)+(.5 ·I · 2)+(m ·g ·h )22-Jun-12 P.Ratan (MPT, Ortho & Sports) 28
  29. 29. Momentum P  Quantity of motion  p=m ·v (linear)  Conservation of Momentum  Transfer of Momentum  Injury may result when momentum transferred exceeds the tolerance of the tissue  Impulse = Momentum22-Jun-12 P.Ratan (MPT, Ortho & Sports) 29
  30. 30. Angular Momentum  Quantity of angular motion  H=I · (angular)  Conservation of angular momentum  Transfer of angular momentum22-Jun-12 P.Ratan (MPT, Ortho & Sports) 30
  31. 31. Collisions Large impact forces due to short impact time Elastic deformation Plastic deformation (permanent change) Elasticity: ability to return to original shape Elastoplastic collisions  Some permanent deformation  Transfer and loss of energy & velocity Coefficient of restitution  e=Rvpost/Rvpre 22-Jun-12 P.Ratan (MPT, Ortho & Sports) 31
  32. 32. Friction Resistance between two bodies trying to slide Imperfection of the surfaces Microscopic irregularities - asperities Static friction  f< s·N f Kinetic  f=µk·N N22-Jun-12 P.Ratan (MPT, Ortho & Sports) 32
  33. 33. Friction Rolling: Lower that static and kinetic friction (100-1000 times) Joint Friction - minimized Blood vessels - atherosclerosis 22-Jun-12 P.Ratan (MPT, Ortho & Sports) 33
  34. 34. FLUID MECHANICS Branch of Mechanics Dealing with theProperties & Behaviors of Gases & Fluids
  35. 35. Fluid Flow  Laminar  Turbulent  Effects of friction on arterial blood flow22-Jun-12 P.Ratan (MPT, Ortho & Sports) 35
  36. 36. Fluid Forces  Buoyancy  Drag  Surface  Pressure  Wave  Lift  Magnus forces  Viscosity  Biological tissue must have a fluid component22-Jun-12 P.Ratan (MPT, Ortho & Sports) 36
  37. 37. Fluid Forces22-Jun-12 P.Ratan (MPT, Ortho & Sports) 37

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