Kin8

• Motion

  A change of position or place of object or subject in relation to a fixed point or reference point
• Types of motion


  • Linear motion or translatory motion
  • Angular motion or rotatory motion
  • General motion
  • Reciprocating motion
  • Oscillatory motion

  
• Linear or translatory motion


  • All points of the object or body move at the same time, in the same direction, and the same distance with respect

  
• Types of linear motion


  • Rectilinear Motion – The path of the motion is a straight line
  • Curvilinear Motion – The path of the motion is curved

  
• Angular or rotatory motion


  • All points in the body simultaneously rotate in the same angular direction and across the same number of degrees
  • The fixed or pivot point for angular motion of the body point or segment is called axis of rotation
  • The axis is the point where motion of the rotating segment is zero

  
• Examples of rotatory motion


  • The motion of the earth about its own axis around the sun
  • The motion of wheels and the steering wheel about its own axis while driving a car
  • Flexion or extension of the elbow or the knee

  
• General motion


  • Combination of translation and rotation movement like walking

  
• Reciprocating motion


  • Repetitive up-and-down or back-and-forth linear motion
• Oscillatory motion


  • Object repeats the same motion continuously back and forth
• Linear kinematics


  Displacement, velocity, and acceleration
• Distance


  Scalar quantity that reflects the amount of space moved
• Displacement


  Vector quantity that reflects any change in position
• Speed


  Scalar quantity = Distance/time
• Velocity


  Vector quantity = Displacement/time
• Acceleration


  Vector quantity, the rate of change of velocity
• Many treatment approaches used in physical Therapy depend on accurate analyses and descriptions of human movement
• From the evaluation of these analyses and descriptions, impairments and functional limitations can be identified, diagnoses and prognosis of movement dysfunctions can be formulated, interventions can be planned, and progress can be evaluated
• Newton's laws of motion help to explain the relationship between forces and their effect on individual joints, as well as on the entire body

  
• Newton's First Law


  An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an force
• Key Terms Associated with Newton's First Law


  • Static equilibrium
  • Dynamic equilibrium
  • Inertia
  • Mass
  • Center of mass (gravity)
  • Mass moment of inertia
• Equilibrium

  Any condition in which all acting forces are cancelled by others resulting in a stable balanced system
• Static equilibrium


  Body's linear and rotational velocities are zero—the body is not moving
• Dynamic equilibrium


  Body's linear and/or its rotational velocity is not zero, but is constant
• Inertia


  Related to the amount of energy required to alter the velocity of a body
• Types of inertia


  • Resting inertia - inertia of the body during rest
  • Moving inertia - inertia of the body during motion
• Center of mass


  Point about which the mass of a body is evenly distributed in all directions
• Center of gravity


  Point about which the effects of gravity are completely balanced
• Mass moment of inertia


  Quantity that indicates a body's resistance to a change in angular velocity
• Example of mass moment of inertia


  • Diver altering their position to change angular velocity
• Fracture dislocation of the atlantoaxial joint during driving a car and a safety belt is used
• Transverse ligament of the atlas (TLA)


  Thick, strong band that maintains the odontoid process in contact with the anterior arch
• Newton's Second Law (Acceleration Law)

  The linear acceleration of a body is directly proportional to the force causing it, takes place in the same direction in which the force acts, and is inversely proportional to the mass of the body
• If the sum of the forces acting on a body is zero, acceleration is also zero and the body is in linear equilibrium
• Rotary or angular counterpart to Newton's second law

  A torque will cause an angular acceleration of a body around an axis of rotation, and the angular acceleration is directly proportional to the torque, takes place in the same rotary direction as the torque, and is inversely proportional to the mass moment of inertia

  
• Angular power


  Often used as a clinical measure of muscle performance
• The action of the forces produced between the ground and foot are illustrated during the contact phase of the "swing through" method of crutch-assisted walking
• Newton's Third Law (Law of Action-Reaction)


  For every action there is an equal and opposite reaction
• Newton's third law also has an angular equivalent, for example during an isometric exercise, the internal and external torques are equal and in opposite rotary directions