Biomechanics

• Force: a push or pull that alters the state of motion of a body.
• Inertia: the resistance of a body to change its state of motion, whether at rear or while moving.
• Law of inertia: a body continues in a state of rest or uniform velocity unless acted upon by an external or unbalanced force.
• Law of acceleration: a body’s rate of change in momentum is proportional to the size of the force and acts in the same direction.
• Law of reaction: for every action force applied to a body there is an equal and opposite reaction.
• N1 example: a football will remain at rest untill the external force (foot) acts upon it.
• N2 example: the acceleration of a netball pass is proportional to the force applied by the player and it is in the same direction as the force.
• N3 example: when serving, a tennis player pushes downwards on the ground and the ground pushes upwards on the player.
• Distance: the total length of path.
• Displacement: the shortest straight line from point A to B.
• Distance and displacement are both measured in metres.
• distance = speed x time
• displacement = velocity x time
• final velocity - initial velocity = acceleration x time
• force = mass x acceleration
• momentum = mass x velocity
• Force: a push or pull that tends to alter the states or motion of a body.
• Balanced force: when two or more forces acting on a body are equal in size but opposite in direction, all forces cancel out
• Unbalanced force: forces are unequal in size, a net force acts.
• Net force: the overall force acting on a body when all forces are considered, aka resultant force.
• weight: acts down from the centre of mass
• Balance: keeping the centre of mass over base of support
• Centre of mass: the point at which body is balanced in all directions and from where weight appears to act.
• Factors affecting stability:

  1. line of gravity
  2. base of support
  3. height of centre of mass
  4. mass of object
• Stability: a measure of how easily a body is moved from a position of equilibrium or balance.
• Line of gravity: an imaginary line extending vertically downward to the ground from the centre of mass
• Base of support: the area enclosed by the points of contact with the ground
• Analysing movement trough technology:

  1. limb kinetics
  2. force plates
  3. wind tunnels
• Kinematics: the study of motion in relation to time and space. A 3D image will be created allowing joint and limb efficiency to be evaluated.
• Measurements of limb kinematics:

  • bone goniometry
  • displacement
  • velocity
  • acceleration
• Advantages of limb kinematics:

  • knowledge of movement
  • data is immediately available
  • coaches can use the analysis to make changes to technique
• Disadvantages of limb kinematics:

  • expensive
  • results don’t take into account the person’s body structure
  • lab conditions make some movement difficult to perform
• Force plates measure ground reaction force (GRF)
• Force plates are mostly used for:

  • gait analysis
  • balance
  • rehab and physical therapy
• Advantages of force plates:

  • fast and accurate
  • analysis of gait, take off and landing
  • identifying technique
  • results are useful to plan conditioning
• Disadvantages of force plates:

  • equipment of expensive
  • lab conditions make some movements difficult
• Wind tunnels are used to analyse the amount of air resistance an object is creating while in motion
• Wind tunnels use pressure sensors to measure pressure.
• Advantages of wind tunnels:

  • equipment or techniques can then be adapted to increase the aerodynamics
• Disadvantages of wind tunnels:

  • equipment is expensive and usually in a certain location
  • competition environment may be difficult to recreate