Biomechanics

• Newton's 1st Law


  Law of Inertia
• What is the law of inertia?

  a body will maintain a state of rest or constant velocity unless acted on by an external force that changes the state
• Newton's 2nd Law


  Law of acceleration
• What is the law of acceleration?

  A force applied to a body causes an acceleration of that body of a magnitude proportional to the force, in the direction of the force.
• Newton's 3rd Law


  Law of reaction
• What is law of reaction?


  For every action force there is an equal and opposite reaction force
• Inertia


  the resistance of a body to change its state of motion (either stationary or while moving)
• Benefits of Biomechanics to performers

  Make you more aerodynamic

  Reduce air drag

  Better understanding of movements
• Benefits of biomechanics to coaches

  Understand where the performer is losing time

  Coach in a way that increases their speed etc

  Help them develop movements
• Momentum


  the quantity of motion possesed by a moving body (mass x velocity)
• Force


  A push or a pull. Can cause a body at rest to move or cause a moving body to stop, slow down or change direction
• Internal force


  Generated by the contraction of skeletal muscle
• External force


  Weight, Reaction, Friction and air resistance
• 5 effects of force

  1) Create motion

  2) Accelerate a body

  3) Decelerate a body

  4) Change direction of a body

  5) Change shape of a body
• Net force


  The sum of all the forces acting on a body
• Vertical forces


  Weight and reaction force
• Weight


  Gravitational pull that the earth exerts on a body measured in newtons
• Reaction force


  The equal and opposite force of the body in response to gravity
• Horizontal forces


  friction and air resistance
• Friction


  A force that opposes motion between two surfaces that are in contact
• Factors that affect friction

  Roughness of ground surface

  Roughness of the contact surface

  Temperature

  Size of a normal reaction
• Air resistance


  force that opposes the motion of objects that move through the air

  Form of fluid friction
• Factors that affect air resistance


  Velocity- increase v means increase AR

  Shape

  Frontal cross sectional area

  Smoothness of surface
• What is streamlining and how can we do it?

  Creation of smooth air flow to minimise air resistance

  Teardrop or aerofoil shape
• What must we consider when we combine all vertical & horizontal forces?

  The state of motion
• What must the size & direction of arrows reflect?

  The magnitude & direction of the force acting on the body
• External forces that are in contact with the ground

  Friction → horizontally forwards from foot in contact with ground

  Reaction force→ upwards from foot in contact with the ground
• External forces that are drawn from the centre of Mass

  Weight → vertically downwards from com

  Air resistance→ horizontally backwards from com
• Where does reaction force occur?

  Occurs at both points of contact
• Centre of Mass


  The point at which the body is balanced in all directions. Its location is around the naval when standing up but can change. & more outside of the body
• Stability


  The ability of a body to resist motion
• Mass of body on stability

  greater the mass of a body means greater its inertia and stability - eg sumo wrestlers have a high mass
• Height of centre of mass on stability

  The lower the centre of mass the greater the stability - rugby players lower com when going in for a tackle
• Base of support on stability

  The wider base of support the more stability- wrestler widens base of support
• Line of gravity on stability


  The move central the line of gravity to the base of support, the more stability- eg deadlifting
• How do you maximise stability in sport?

  Base of support made larger

  Lower centre of mass

  Increased mass

  More centralised line of gravity
• Why may you wish to minimise stability in sport?

  May increase agility

  Increased speed and acceleration

  Range of motion
• Limb kinematic


  The study of movement using motion analysis technology- infra-red cameras linked up to a computer that provide vital feedback on limb positioning

  Measurements:

  Bone goniometry

  Displacement

  Velocity

  Acceleration
• Force plates


  measuring instruments that measure the ground reaction forces generated by a body standing on or moving across them- on a floor or wall. Provide instant and reliable results

  Most commonly used for:

  Gait analysis

  Balance

  Rehab and Physical therapy
• Wind tunnels


  Used to analyse the amount of air resistance an object is creating whilst in motion. Can be used for both small and large objects and allow adjustments to be made to designs for streamlining