biomechanics

• biomechanics is used to: analyse performance, maximise efficiency of movement and reduce injuries
• force is the push or pull factor that alters the state of motion of a body
• inertia is the resistance of a body to a change in its state or motion
• velocity is the rate of change in displacement
• momentum is the quantity of motion possessed by a body
• acceleration is the rate of change in velocity
• newton has 3 laws

  1. law of inertia
  2. law of acceleration
  3. law of reaction
• law of inertia says a body continues in a state of rest or uniform motion unless acted upon by an external force
• the law of inertia can be seen in sport with a golf shot off the tee as the ball is in rest until the club is struck
• law of acceleration says a body's rate of change of momentum is proportional to the size of the force acted upon it
• law of acceleration can be seen in sport with a golf shot, the more force applied by the club the further the ball will travel
• law of reaction says for every action force applied to a body there is an equal and opposite reaction force applied
• momentum = mass x velocity
• velocity = displacement / time taken (m/s)
• acceleration = change in velocity / time taken (m/s^2)
• force = mass x acceleration (N)
• internal force is the contraction of skeletal muscles
• external force is a force that acts on an object from outside the body.
• force has 5 effects on the body

  1. create motion
  2. accelerate a body
  3. decelerate a body
  4. change direction of a body
  5. change shape of a body
• resultant force is the sum of all forces
• if net force = 0, force is balanced and there's no change in motion
• if net force = >0 force is unbalanced and there is a change in motion
• vertical forces are reaction and weight
• horizontal forces are friction and air resistance
• weight always acts downwards form the bodies centre of mass
• friction is the force that opposes motion between two surfaces that are in contact with each other
• friction is affected by 4 factors

  1. roughness of ground surface
  2. roughness of contact surface
  3. temperature
  4. size of reaction
• we need to manipulate friction to accelerate, decelerate and for a change in direction
• air resistance is the force that opposes motion of a body travelling through the air
• air resistance is affected by 4 factors

  1. velocity
  2. shape (aerodynamics)
  3. frontal cross sectional area
  4. smoothness of surface
• limb kinematics is the study of movement in relation to time and space
• limb kinematics gives a 3D or optical motion analysis records the position of the limb in space during a sporting action
• limb kinematics can measure: acceleration, displacement and velocity
• coaches use limb kinematics to adjust technique, improve performance and reduce risk of injury by correcting technique
• positives of limb kinematics is that immediate analysis is received and it gives accurate objective data
• negatives of limb kinematics is that it is limited to lab conditions, works for a limited amount of sports, is expensive and does not account for individual differences
• force plates are used to measure ground reaction force in lab conditions
• force plates are used to investigate: size and direction of forces, acceleration rates and power outputs
• how do force plates work?

  when stepped on or in contact with a body an electrical output proportional to the force applied is generated on a computer
• force plates are used to measure: balance, explosive strength, running technique and used during rehab