The biomechanic of human movement

• Biomechanics


  A science concerned with forces and the effect of these forces on and within the human body
• Mechanics


  A branch of science that explores the effects of forces applied to solids, liquids and gases
• Importance of biomechanics


  • Helps choose the best technique to achieve best performance with consideration to body shape
  • Reduces risk of injury by improving the way we move
  • Helps design and use equipment that contributes to improved performance
• Much of the content will directly or indirectly relate to Newton's three laws of motion
• Motion


  Movement and path of a body
• Types of motion


  • Linear
  • Angular
  • General
• Linear motion


  A body and all parts connected to it travel the same distance in the same direction and at the same speed
• Examples of linear motion


  • Swimming
  • Sprint events
• Improving performance in linear motion activities focuses on modifying or eliminating technique faults that contribute to any non-linear movements</b>
• Velocity


  The rate of positional change of an object, calculated using displacement divided by time
• Speed


  How fast an object is moving, calculated by dividing distance by time
• Acceleration


  The ability to increase speed quickly
• Factors affecting acceleration


  • Requires substantial force production by calf, quadriceps, gluteal and upper body muscles
  • Improving overall strength and strength-related power
  • Increasing/strengthening pushing motion of foot while keeping centre of gravity low and forward, combined with driving arm action
• Momentum


  A product of mass and velocity, most significant in impact or collision situations
• Momentum (biomechanics)


  A term commonly used in sport, referring to the way in which momentum carried a player over the line in a game of football
• Momentum


  A product of mass and velocity, expressed as momentum = mass × velocity (M = mv)
• The application of the principle of momentum is most significant in impact or collision situations
• A truck travelling at 50 kilometres per hour that collides with an oncoming car going at the same speed would have a devastating effect on the car because the mass of the truck is much greater than that of the car
• Collisions between players in sporting events tend to exhibit different characteristics to that of objects due to a range of factors, including mass differences of the players, elasticity, and evasive skills of players
• Linear momentum


  When an object or person is moving in a straight line
• Angular momentum


  When bodies generate momentum but they do not travel in a straight line, such as a diver performing a somersault with a full twist, a tennis serve, football kick, discus throw and golf swing
• Angular momentum


  • Affected by angular velocity, the mass of the object, and the location of the mass in respect to the axis of rotation
• Centre of gravity


  The point at which all the weight is evenly distributed and about which the object is balanced
• In a rigid object such as a cricket ball or billiard ball, the centre of gravity is in the centre of the object
• If the object has a hollow centre, such as a tennis ball or basketball, the centre of gravity is located in the hollow centre of the ball
• Some objects commonly used in sport are not exactly spherical or have an evenly distributed mass, such as the tenpin bowling ball or the lawn bowl, and have a 'bias' where the mass is slightly redistributed to one side
• In the human body, the position of the centre of gravity depends upon how the body parts are arranged; it can even move outside the body during certain movements
• Skilled high jumpers and long jumpers both lower the centre of gravity in the step or steps immediately preceding take-off to propel their body over a slightly longer vertical path
• The Fosbury flop technique in high jump is more efficient because the centre of gravity does not need to clear the bar by the same margin as is required in conventional jumps, such as the scissors
• To balance on your hands as in a handstand, or on your head and hands as in a headstand, the centre of gravity must be controlled by the base of support
• Most learners find it difficult to assume headstand and handstand positions because they do not push their centre of gravity far enough forward prior to the kick-up
• Line of gravity


  An imaginary vertical line passing through the centre of gravity and extending to the ground, indicating the direction that gravity is acting on the body
• When we are standing erect the line of gravity dissects the centre of gravity so that we are perfectly balanced over our base of support
• Movement occurs when the line of gravity changes relative to the base of support, creating a momentary state of imbalance causing the body to move in the direction of the imbalance
• In specialised sporting movements, the precision with which the line of gravity moves in relation to the base of support directly affects the quantity and quality of movement
• Base of support


  Imaginary area that surrounds the outside edge of the body when it is in contact with a surface
• Base of support


  • Affects stability or ability to control equilibrium
  • A narrow base of support allows the centre of gravity to fall close to the edge, only a small force is needed to make the person lose their balance
  • A wide base of support is essential for stability because the centre of gravity is located well within the boundaries
• The further the centre of gravity from the base


  The more unstable is the body or object
• Athletes using the base of support to their advantage

  • Gymnast performing a pirouette
  • Wrestlers widening their base of support
  • Tennis players lowering the centre of gravity and widening the base of support
  • Swimmers on the blocks widening their feet and moving the centre of gravity forward
  • Golfers spreading their feet to at least the width of their shoulders
• Fluid mechanics is a branch of mechanics that is concerned with properties of gases and liquids