Biomechanical movement

• Linear Motion

  Motion is a straight or curved line, with all body parts moving the same distance at the same speed in the same direction.
• Newton's First Law - Inertia 


  Every body continues in its state of rest or motion in a straight line, unless compelled to change that state by external forces exerted upon it.
• Newton's Second Law - Acceleration


  The rate of momentum of a body (or the acceleration for a body of constant mass) is proportional to the force causing it and the change that takes place in the direction in which the force acts.
• Newton's Third Law - Reaction


  To every action force, there is an equal and opposite reaction force.
• Inertia

  The resistance an object has to a change in its state of motion.
• Law of Inertia - Application


  In a penalty, the ball will remain on the spot (in a state of rest) unless it is kicked by the player (an external force is acted on it).
• Law of Acceleration - Application

  When the player kicks the ball during the game, the acceleration of the ball (rate of change of momentum) is proportional to the size of the force. The harder the ball is kicked, the further and faster it will travel.
• Law of Reaction - Application 


  When a footballer jumps up (action) to a win a header, a force is exerted on the ground in order to gain height. At the same time, the ground exerts an upward force (equal and opposite) upon the player.
• Scalar Quantity 


  When measurements are described in terms of just their size or magnitude.
• Speed

  The rate of change of distance
• Speed = Distance covered/Time taken
• Distance 


  The length of the path a body follows when moving from one position to another.
• Distance = Speed X Time taken
• Centre of Mass

  The point of concentration of mass - the point of balance of the body
• Factors affecting stability

  • The height of the centre of mass - lowering the centre of mass will increase stability
  • Position of the line of gravity - should be central over the base of support to increase stability
  • Area of support base - the more contact points, the larger the base of support becomes and the more stable the performer becomes
  • Mass of the performer - the greater the mass, the more stability there is because of increased inertia
• Levers

  Consist of three main components:

  • Fulcrum
  • Resistance
  • Effort
• 1st Class Lever - Extension at the elbow

  
• 2nd Class Lever - Plantarflexion at the ankle

  
• 3rd Class Lever - Flexion and Extension at the knee

  
• Mechanical Advantage

  When the effort arm is longer than the resistance arm. The lever system can move a large load over a short distance and required little force. However it has a small range of motion and is difficult to generate speed and distance.
• Mechanical Disadvantage

  When the resistance arm is greater than the force arm. The lever system cannot move as heavy a load, but can move it quickly. It has a large range of movement.
• 2nd Class Lever

  • Mechanical Advantage - Can generate much larger forces and has to lift the whole body weight
  • Mechanical Disadvantage - Slow, with a limited range of movement
• 1st and 3rd Class Lever

  • Mechanical Advantage - Large range of movement and any resistance can be moved quickly
  • Mechanical Disadvantage - Cannot apply much force to move an object