KEY KNOWLEDGE BIOMECHANICAL PRINCIPLES FOR ANALYSIS OF MOVEMENT (PART 1)

Transcription

1 VCE PHYSICAL EDUCATION UNIT 3 AOS 1 KEY KNOWLEDGE BIOMECHANICAL PRINCIPLES FOR ANALYSIS OF MOVEMENT (PART 1) Presented by Chris Branigan Study design dot point: Biomechanical principles for analysis of human movement including: angular and linear kinetic concepts of human movement: Newton s three laws of motion, inertia, mass, force, momentum and impulse angular and linear kinematic concepts of human movement: distance, displacement, speed, velocity, acceleration and projectile motion (height, angle and speed of release) equilibrium and human movement: levers (force, axis, resistance and the mechanical advantage of anatomical levers), stability and balance (centre of gravity, base of support and line of gravity) Chris Branigan & Edrolo

2 What s in this lesson? Concept Difficulty Concept reference Questions Measurements tools in biomechanics KK Force KK Inertia KK Momentum (Linear & Angular) KK Impulse KK Chris Branigan & Edrolo

3 What is biomechanics? Biomechanics is the science that studies living things from a mechanical perspective. Using the principles of physics associated with movement and forces, biomechanics can help to develop and refine human movement. Pioneers: The Fosbury Flop Chris Branigan & Edrolo

4 KK Measurement tools in biomechanics Theory summary Technology can be used in biomechanics to measure aspects such as joint angles, velocity and force. Explanation Video analysis can be qualitative and quantitative: If you simply review a video over and over, watch it slow motion, or compare it to future performances, the analysis is qualitative More advanced technology (optoelectronic motion analysis) allows biomechanists to record the performer and transmit the recording to a computer where information such as distances, speeds, forces and momentum can be analysed Types of technology Some types of technology used by biomechanists are: Goniometry: used to measure joint angle Accelerometres: measure the acceleration of the body Light gates: which can measure velocity Force plates: which measure the force imparted by the object above Electromyography: which record the electrical activity within a muscle prior to a contraction Chris Branigan & Edrolo

5 KK Force (n.) A push or a pull. Force Theory summary Force is defined as a push or a pull. Forces can affect objects in two ways: Change the shape of the object Move the object All forces produce or alter movement. Calculating force Force can be calculated the following way: Force (N) = Mass x Acceleration Forces influencing sporting performance Friction Air and Water Resistance Drag Force Gravitational Force Weight (weight = mass x gravity) Source: Source: Chris Branigan & Edrolo

6 KK Inertia (n.) The tendency for a body to resist a change in its state of motion, whether that state is at rest or moving with a constant velocity. Inertia Theory summary The tendency for a body to resist a change in its state of motion, whether that state is at rest or moving with a constant velocity. Source: Chris Branigan & Edrolo

7 KK Inertia (n.) The tendency for a body to resist a change in its state of motion, whether that state is at rest or moving with a constant velocity. Momentum (Linear & Angular) Theory summary Momentum is equal to the mass of the object multiplied by its velocity. The units of momentum are therefore kg m/s/: momentum = mass x velocity Explanation An object that has zero velocity (stationary) will have zero momentum If two objects have the same mass, then the object which has the greater velocity will have the greater momentum, similarly if two objects have the same velocity the object with the greater mass will have the greater momentum. Objects with a greater momentum are more difficult to stop. Consider catching a tossed medicine ball versus catching a tossed volleyball. Source: Chris Branigan & Edrolo

8 KK Speed (n.) How quickly an object covers distance. Velocity (n.) How quickly an object is changing position, relative to its starting position. Momentum (Linear & Angular) Linear Motion Speed Velocity Speed = distance/time Velocity = displacement/time It is important to note that velocity is expressed as both the size and direction. For example the ball moved at 30m/s north. This means that velocity has changed if either the size, direction or both change. Acceleration How quickly an object changes its rate of motion is called acceleration and is measured using the following equation: Acceleration = change in velocity/time. Acceleration can be both positive (getting faster) and negative (getting slower) It is important to note that when acceleration is equal to zero, it doesn t necessarily mean that the object is stationary, it means that the object is not speeding up or slowing down, that its rate of movement is constant. Source: Chris Branigan & Edrolo

9 KK Linear Motion (n.) Movement of the body along a straight or curved path. Momentum (Linear & Angular) Angular Motion Angular distance Angular distance is measured in degrees and measures the amount of degrees an object passes through from start to finish. So an object that rotates twice has travelled 720degrees. Angular displacement Angular displacement is measured in degrees and measures the amount of degrees the object moves from the starting point. So an object that rotates twice has a displacement of 0degrees Angular speed Angular speed is the measure of how quickly angular distance is covered. So, if it took four seconds to complete two rotations then the angular speed is 180degrees per second. Angular velocity Angular velocity is the measure of how quickly the object has moved from its starting point and in what direction it has moved (clockwise or anticlockwise). In the above scenario the displacement would be 0 degrees per second. Angular acceleration Angular acceleration is the measure of the rate of change of angular position. It can be positive (speeding up) and negative (slowing down). Source: Chris Branigan & Edrolo

10 KK Impulse (n.) The change in momentum in an object. Impulse Theory summary To change the momentum of an object, a force must be applied over a period of time. Impulse is equal to the force applied multiplied by the length of time the force was applied: Impulse = Force x Time Explanation In sport, any change in momentum will be due to changes in velocity, as the mass will remain constant. A change in momentum can be caused by a large force being applied over a short period of time, or a smaller force being applied over a longer period of time. Manipulating impulse can reduce the risk of injury, particularly in landing sports, such as gymnastics. Source: Source: Chris Branigan & Edrolo

11 KK Measurement tools in biomechanics Multiple choice activity At the AFL Draft Combine, properly set up light gates are used in preference to a stop watch because: A. They are more accurate. B. They are more valid. C. They are more specific. D. I don t know. Chris Branigan & Edrolo 2017 (Written by the author) 11

12 KK Measurement tools in biomechanics Multiple choice Response At the AFL Draft Combine, properly set up light gates are used in preference to a stop watch because: A. They are more accurate. B. They are more valid. C. They are more specific. D. I don t know. Chris Branigan & Edrolo 2017 (Written by the author) 12

13 KK Force Multiple choice activity Friction, air resistance and gravitational force are all forces that can be beneficial and detrimental to performance. Identify the answer which has an example of how, each force listed earlier, has been limited by the cyclist (the correct answer is in the same order). A. Slim wheels, tight clothing, bike built of light materials. B. Tight clothing, slim wheels, bike built of light materials. C. Bike built of light materials, slim wheels, tight clothing. D. I don t know. Chris Branigan & Edrolo 2017 (Written by the author) 13

14 KK Force Multiple choice Response Friction, air resistance and gravitational force are all forces that can be beneficial and detrimental to performance. Identify the answer which has an example of how, each force listed earlier, has been limited by the cyclist (the correct answer is in the same order). A. Slim wheels, tight clothing, bike built of light materials. B. Tight clothing, slim wheels, bike built of light materials. C. Bike built of light materials, slim wheels, tight clothing. D. I don t know. Chris Branigan & Edrolo 2017 (Written by the author) 14

15 KK Inertia Multiple choice activity Which of the following weights would have the greatest amount of inertia? A. 5 kilos B. 3 kilos C. 2 kilos D. I don t know. Chris Branigan & Edrolo 2017 (Written by the author) 15

16 KK Inertia Multiple choice Response Which of the following weights would have the greatest amount of inertia? A. 5 kilos B. 3 kilos C. 2 kilos D. I don t know. Chris Branigan & Edrolo 2017 (Written by the author) 16

17 KK Momentum (Linear & Angular) Multiple choice activity Summation of momentum harnesses the use of multiple body parts to generate the greatest amount of momentum. Identify the answer which, for a golfer, has the body parts moving in the correct order during the downswing. A. Wrists, shoulders, torso, waist, hips B. Hips, waist, torso, shoulders, wrists C. Torso, shoulders, wrists D. I don t know. Source: Chris Branigan & Edrolo 2017 (Written by the author) 17

18 KK Momentum (Linear & Angular) Multiple choice Response Summation of momentum harnesses the use of multiple body parts to generate the greatest amount of momentum. Identify the answer which, for a golfer, has the body parts moving in the correct order during the downswing. A. Wrists, shoulders, torso, waist, hips B. Hips, waist, torso, shoulders, wrists C. Torso, shoulders, wrists D. I don t know. Source: Chris Branigan & Edrolo 2017 (Written by the author) 18

19 KK Impulse Multiple choice activity Identify the answer which best explains what the athlete does in the video, with their technique, to increase the amount of impulse. A. Throws the lightest kegs over first B. Faces away from the bar, bends their legs, swings the keg between their legs and then up and over their head. C. Stands on a wooden platform, rather than on the sand. D. I don t know Source: Chris Branigan & Edrolo 2017 (Written by the author) 19

20 KK Impulse Multiple choice Response Identify the answer which best explains what the athlete does in the video, with their technique, to increase the amount of impulse. A. Throws the lightest kegs over first B. Faces away from the bar, bends their legs, swings the keg between their legs and then up and over their head. C. Stands on a wooden platform, rather than on the sand. D. I don t know Source: Chris Branigan & Edrolo 2017 (Written by the author) 20

21 What s in this lesson? UNIT 3 The principles covered in this lesson are rarely working in isolation. During many sporting actions, several of the biomechanical principles are involved. Being able to identify which principle, or principles, are being used by an athlete and how applying these principles correctly can improve sporting performance will be the basis of assessment for this topic. Concept Theory summary Measurements tools in Biomechanics Force Inertia Momentum (Linear & Angular) Impulse Technology used in biomechanics to measure aspects such as joint angles, velocity and force. Video analysis can be qualitative and quantitative: Mass x Acceleration For every technique and every athlete there is a sweet spot that allows for the generation of force. An athlete cannot keep increasing acceleration infinitely and doesn t have ever increasing strength to deal with ever increasing mass. The tendency for a body to resist a change in its state of motion, whether that state is at rest or moving with a constant velocity. Mass x Velocity For the majority of sporting performances, as mass increases, velocity decreases. Therefore; like above, there is a sweet spot which once the mass increases beyond that point the reduction in velocity has a detrimental effect on momentum. Force x Time It is important to realise that an athlete does not have an infinite amount of time to apply their force, so often the sport itself, applies constraints which can limit impulse e.g. a shot putter throws out of a limited space, which limits their movements and as a consequence their impulse. Chris Branigan & Edrolo

22 The copyright in substantial portions of this material is owned by the Victorian Curriculum and Assessment Authority. Used with permission. The VCAA does not endorse this product and makes no warranties regarding the correctness or accuracy of its content. To the extent permitted by law, the VCAA excludes all liability for any loss or damage suffered or incurred as a result of accessing, using or relying on the content. Current and past VCAA exams and related content can be accessed directly at We do our best to make these slides comprehensive and up-to-date, however there may be errors. We'd appreciate it if you pointed these out to us! Chris Branigan & Edrolo