Biomechanical Principles and Applications - … Principles and Applications ... Seven Principles of Biomechanical Analysis

© Thompson Educational Publishing, Inc., 2003. All material is copyright protected. It is illegal to copy any of this material. This material may be used only in a course of study in which Exercise Science: An Introduction to Health and Physical Education (Temertzoglou/Challen) is the required textbook.

SECTION

15Biomechanical Principles and Biomechanical Principles and

ApplicationsApplications


Biomechanical Principles and ApplicationsBiomechanical Principles and Applications

►► Definition of biomechanicsDefinition of biomechanics►► Scientific models reduce things to their Scientific models reduce things to their

essentials and establish a basis, not only for essentials and establish a basis, not only for understanding how things work, but also for understanding how things work, but also for predicting how they will behave and, predicting how they will behave and, ultimately, for influencing them to behave in ultimately, for influencing them to behave in ways we wantways we want

►► Example: anatomical positionExample: anatomical position►► Sir Isaac Newton’s Three Laws of Motion Sir Isaac Newton’s Three Laws of Motion


Equilibrium and the Conservation of Energy Equilibrium and the Conservation of Energy

►► Newton’s theory (and biomechanics) rests on two Newton’s theory (and biomechanics) rests on two assumptions: physical equilibrium and the assumptions: physical equilibrium and the conservation of energy. Equilibrium is posited in conservation of energy. Equilibrium is posited in his First Law and the conservation of energy in his First Law and the conservation of energy in his Third Law.his Third Law.

►► Equilibrium can be thought of as kind of a Equilibrium can be thought of as kind of a “perfect” situation“perfect” situation where more than one force where more than one force acts on the body but, because the sum of forces acts on the body but, because the sum of forces is zero, no change in velocity results.is zero, no change in velocity results.


Equilibrium and the Conservation of EnergyEquilibrium and the Conservation of Energy

►► The conservation of energy principle states that The conservation of energy principle states that energy can never be created or destroyed, but energy can never be created or destroyed, but can only be converted from one form to can only be converted from one form to another.another.


Isaac Newton’s “Model Universe” Isaac Newton’s “Model Universe”

►► 1. The Law of Inertia1. The Law of Inertia►►Every object in a state of uniform motion tends Every object in a state of uniform motion tends

to remain in that state of motion unless an to remain in that state of motion unless an external force is applied to it.external force is applied to it.

►► 2. The Law of Acceleration2. The Law of Acceleration►►A force applied to a body causes an acceleration A force applied to a body causes an acceleration

of that body of a magnitude proportional to the of that body of a magnitude proportional to the force, in the direction of the force, and inversely force, in the direction of the force, and inversely proportional to the body’s mass. proportional to the body’s mass.

►► 3. The Law of Reaction3. The Law of Reaction►►For every action there is an equal and opposite For every action there is an equal and opposite

reaction. reaction.


Types of Motion Types of Motion

►► It is important to distinguish between two types of It is important to distinguish between two types of motion:motion:

►► Linear (or Translational) MotionLinear (or Translational) MotionMovement in particular direction (and would include Movement in particular direction (and would include the resultant of more than one linear force acting the resultant of more than one linear force acting on an object). Example: a sprinter accelerating on an object). Example: a sprinter accelerating down the track. down the track.

►► Rotational MotionRotational MotionMovement about an axis. The force does not act Movement about an axis. The force does not act through the centre of mass, but rather is “offthrough the centre of mass, but rather is “off--centre,” and this results in rotation. Example: icecentre,” and this results in rotation. Example: ice--skater’s spin.skater’s spin.


Examples of Rotation Principles Examples of Rotation Principles

►► IceIce--SkatingSkating►► The iceThe ice--skater begins to skater begins to

spin with arms spread spin with arms spread apart then suddenly brings apart then suddenly brings them closer to the body. them closer to the body. The end result of The end result of tightening up is that the tightening up is that the skater’s spin (angular skater’s spin (angular velocity) increases, velocity) increases, seemingly miraculously. seemingly miraculously.


Examples of Rotation PrinciplesExamples of Rotation Principles

►► Gymnastics Gymnastics ►► Following a series of Following a series of

rapid somersaults in a rapid somersaults in a tight position, the tight position, the gymnast does a forward gymnast does a forward flip with the body flip with the body positioned more or less positioned more or less straight. By opening up, straight. By opening up, the gymnast increases the gymnast increases the moment of inertia, the moment of inertia, thereby resulting in a thereby resulting in a decrease in angular decrease in angular velocity.velocity.


Examples of Rotation PrinciplesExamples of Rotation Principles

►► DivingDiving►► After leaving the high After leaving the high

diving board, the diver diving board, the diver curls tightly and then curls tightly and then opens up just before opens up just before entering the water. By entering the water. By opening up before opening up before entry, the diver entry, the diver increases the moment increases the moment of inertia, thereby of inertia, thereby slowing down the slowing down the angular velocity.

��

��

��

��

��

��

��

��

��

angular velocity.


Seven Principles of Biomechanical AnalysisSeven Principles of Biomechanical Analysis

►► The Coaching Association of Canada’s National The Coaching Association of Canada’s National Coaching Certification Program (NCCP) Level 2 Coaching Certification Program (NCCP) Level 2 Theory course sets forward seven principles that Theory course sets forward seven principles that can be grouped into four broad categories: can be grouped into four broad categories:

(1) stability, (1) stability, (2) maximum effort, (2) maximum effort, (3) linear motion, and (3) linear motion, and (4) angular motion.(4) angular motion.



►► STABILITY STABILITY Principle 1:Principle 1: The lower the centre of mass, the The lower the centre of mass, the larger the base of support, the closer the centre of larger the base of support, the closer the centre of mass to the base of support, and the greater the mass to the base of support, and the greater the mass, the more stability increases.mass, the more stability increases.Four subcomponentsFour subcomponentsExample: Sumo wrestling Example: Sumo wrestling



►► MAXIMUM EFFORTMAXIMUM EFFORTPrinciple 2:Principle 2: The production of maximum force The production of maximum force requires the use of all possible joint movements requires the use of all possible joint movements that contribute to the task’s objective.that contribute to the task’s objective.Examples: golf, bench press Examples: golf, bench press



►► MAXIMUM VELOCITYMAXIMUM VELOCITYPrinciple 3Principle 3: The production of maximum : The production of maximum velocity requires the use of joints in order velocity requires the use of joints in order ––from largest to smallest.from largest to smallest.Examples: hockey Examples: hockey slapshotslapshot, hitting a golf ball , hitting a golf ball



►► LINEAR MOTIONLINEAR MOTIONPrinciple 4:Principle 4: The greater the applied The greater the applied impulse, the greater the increase in velocity.impulse, the greater the increase in velocity.Example: slamExample: slam--dunking a basketballdunking a basketball



►► LINEAR MOTIONLINEAR MOTIONPrinciple 5Principle 5: Movement usually occurs in the : Movement usually occurs in the direction opposite that of the applied force.direction opposite that of the applied force.Examples: high jumper, cyclists, runners Examples: high jumper, cyclists, runners



►► ANGULAR MOTIONANGULAR MOTIONPrinciple 6:Principle 6: Angular motion is produced by Angular motion is produced by the application of a force acting at some the application of a force acting at some distance from an axis, that is, by torque.distance from an axis, that is, by torque.Principle is also known as the principle of the Principle is also known as the principle of the production of angular motion production of angular motion Example: baseball pitchers Example: baseball pitchers



►► ANGULAR MOMENTUMANGULAR MOMENTUMPrinciple 7Principle 7: Angular momentum is constant when : Angular momentum is constant when an athlete or object is free in the air.an athlete or object is free in the air.This principle is also known as the principle of This principle is also known as the principle of conservation of angular momentum, and its key conservation of angular momentum, and its key component is the fact that, once an athlete is component is the fact that, once an athlete is airborne, he or she will travel with constant angular airborne, he or she will travel with constant angular momentum. momentum. Example: Diver Example: Diver

Documents

Biomechanical Principles and Applications - … Principles and Applications ... Seven Principles of Biomechanical Analysis