EDU 2462
Download
1 / 38

EDU 2462 Biophysical Foundations of Human Movement 1 - PowerPoint PPT Presentation


  • 332 Views
  • Updated On :

EDU 2462 Biophysical Foundations of Human Movement 1. Lecture 2 BIOMECHANICS. 2 Broad Categories. Kinematics - describes movement - “How far?” - “How fast?” - “Where did it go?” - “At what rate?”. Kinetics investigates causes of movement and measures the underlying forces at work.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'EDU 2462 Biophysical Foundations of Human Movement 1' - Michelle


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Slide1 l.jpg

EDU 2462

Biophysical Foundations of Human Movement

1

Lecture 2 BIOMECHANICS


2 broad categories l.jpg
2 Broad Categories

  • Kinematics

    • - describes movement

    • - “How far?”

    • - “How fast?”

    • - “Where did it go?”

    • - “At what rate?”

  • Kinetics

    • investigates causes of movement and measures the underlying forces at work


Function of biomechanics l.jpg
Function of Biomechanics

  • Internal and external forces acting on the human body determine the performance of a motor skill

  • The nature of these forces, their impact and our adaptations to them is crucial to the effectiveness of the skill’s performance


Forces l.jpg
FORCES

  • Objects move when acted upon by a force greater than the resistance to movement provided by the object.

  • The force may:

    • produce motion (a golf club striking a ball)

    • stop motion (brakes on a bike)

    • positively accelerate (from jog to sprint)

    • negatively accelerate (from sprint to jog)

    • change the direction of the object (tennis serve).


Slide5 l.jpg

Forces can be measured by:

  • magnitude eg. size/number of muscle fibres

  • direction eg. running = horizontal movement

  • point of force application

    eg. feet placement prior to jump

  • line of action of force eg. topspin in tennis


Summation of forces l.jpg
Summation of Forces

  • If several forces act at any one time, the net force will cause the object to move or

    deform.

Summation of forces may be...


1 sequential l.jpg
1. Sequential

  • When the correct sequence of bodyparts is used to generate great force

  • To achieve the maximum power, each preceding segment must contribute maximally before the next segment follows on

    eg. Volleyball spike; T-ball hit;

    cricket bowl


Slide8 l.jpg

Larger body parts are the slower

movers

A Throw

  • F1

    hips

    F2

    shoulders

    F3

    arms

    F4

    wrists

The speed of the projectile depends on

the speed of the last part of the

body at the time of release/contact

Smaller body parts are the fastest

movers


Slide9 l.jpg

  • 2. Simultaneous

  • summation of the forces involves an explosive action of all body parts at the same time to generate the greatest force eg. the high jump; vault take-off


Inertia l.jpg
INERTIA

  • If a body is at rest, it will tend to stay at rest

  • Once an object is moving in a straight line, it will continue to move with constant velocity

    unless

    a force acts upon it to change its speed/direction

    Inertia =

    the object’s resistance to this change in its state of motion.


In linear motion l.jpg
In linear motion...

  • In linear motion (motion in a straight line),

    inertia = the mass of the object

  • The larger the mass, the greater the inertia

    (and vice versa)  the harder it is to move.

    eg. to increase inertia, a greater mass is added


Angular motion l.jpg
Angular Motion

  • Refers to circular motion around an imaginary line called anaxis of rotation.

  • There are 3 primary axes of rotation:

1.Longitudinal (top-bottom)

2. Transverse (left-right)

3. Sagittal (front-back)


Slide13 l.jpg

Longitudinal axis

eg. A figure skater when doing a spin has his arms and free leg extended away from the longitudinal axis of his body. His spin is slow. When he brings these limbs closer to his body, he is bringing his mass closer to the axis of rotation, reducing the moment of inertia and spinning faster.

Photo : http://www.northstarnet.org/eakhome/skating/kevin/spin.html - Technical Figure Skating Spin page


Slide14 l.jpg

Film: http://www.northstarnet.org/eakhome/skating/kevin/spin.html - Technical Figure Skating Spin page


Centre of gravity l.jpg

  • In the picture the red triangle is the fulcrum or the

  • Balancing point.

  • Generally the Centre of Gravity of the body is

  • about half an inch above the navel and straight back

  • near the backbone.

  • At this point there would be equal weight on the

  • left and right side of the fulcrum and thus the

  • body can be balanced as shown in the diagram.

Centre of Gravity

  • The center of the mass of an object.

  • The location around which the mass of an object is balanced.

  • Not necessarily within the mass of the object.


Slide16 l.jpg

  • The human body’s centre of gravity can be altered by merely lifting your arms over your head (heightens the C of G).

  • Males and females have different

    C of G locations:

    • Adult males - more mass in chest and shoulders  higher C of G (57% of standing height)

    • Adult females - 55% of standing height


Centre of gravity and stability l.jpg
Centre of Gravity merely lifting your arms over your head (heightens the C of G).and Stability

  • The force of

    gravity always acts

    downwards

  • Stability (or equilibrium)

    is attained when the

    Centre of Gravity is over the base of

    support.

  • Stability = the body’s resistance to movement

Photos: http://j-views.com/content/culture/Sumo/ - Grand Sumo Photos Jan 21, 1999


Slide18 l.jpg

Stability depends on: merely lifting your arms over your head (heightens the C of G).

a) The height of the C of G - the closer it is to the base of support, the more stable.

eg. more stable -standing or lying?

b) The size of the base of support - the larger the base of support, the more stable

Photos: http://j-views.com/content/culture/Sumo/ - Grand Sumo Photos Jan 21, 1999


Slide19 l.jpg

c) merely lifting your arms over your head (heightens the C of G).Line of gravity - a body becomes less stable as the line of the C of G moves closer to the edge of the base of support

Photos: http://j-views.com/content/culture/Sumo/ - Grand Sumo Photos Jan 21, 1999


Slide20 l.jpg

d) merely lifting your arms over your head (heightens the C of G).Mass - generally the larger the mass, the greater the stability IF the force is applied

e) Friction - applies when you move any two surfaces against each other. Friction works in a direction opposite to the direction of motion.Generally, the greater the degree of friction, the greater stability

eg. studs in football boots  friction

 more stability and more effective motion

* too much friction however can lead

to injuries (eg. long studs in dry ground)


Torque l.jpg
TORQUE merely lifting your arms over your head (heightens the C of G).

  • All bodies will rotate easiest about their Centre of Gravity.

  • If a force is applied on either side of the Centre of Gravity, the object will rotate.

  • This rotational force is called torque.

  • Torque = the product of the amount of force applied

    the distance from the centre of gravity at which the force applied.


Slide22 l.jpg

Practical Application: merely lifting your arms over your head (heightens the C of G).

The Tackling Process

Coaches often tell their players to tackle a runner low. In this way, the runner's feet will be rotated in the air in the direction of the tackle.

REMEMBER!

  • Centre of Gravity - the point in a body's

    distribution of mass at which all of the

    mass can be considered to be concentrated.

  • Torque -a force that tends to produce rotation or

    twisting


Slide23 l.jpg

eg. Compare the force required to merely lifting your arms over your head (heightens the C of G).

push a person off-balance when

they have their arms folded in

front of themselves and when their

arms are outstretched.

  • Because torque is a product, the same torque can be applied to an object at different distances from the center of mass by changing the amount of force applied

  • Less force is required farther out from the Centre of Gravity than closer in.


Slide24 l.jpg

So, by tackling a merely lifting your arms over your head (heightens the C of G).

runner low, far from

the centre of gravity,

it takes less force to

tackle him than if he

were tackled high

Diagram: http://www.howstuffworks.com/physics-of-football1.htm


Slide25 l.jpg

Furthermore, if a runner is hit merely lifting your arms over your head (heightens the C of G).

exactly at his centre of gravity,

he will not rotate, but instead

will be driven in the direction

of the tackle eg. the “big hit”

or impact tackle

Photos: Planet-Rugby Photo gallery


Levers l.jpg
LEVERS merely lifting your arms over your head (heightens the C of G).

Velocity =

the rate at which a

body moves from

one location

to another

  • a bar or rigid structure

  • hinged at one point around which the structure can turn when a force is applied to it

  • the bones act as levers which are pulled and moved by the forces generated by muscles.

  • can be used to enhance either

    the force, or the velocity

    of movement


Slide27 l.jpg

Load

Force

Resistance arm

Force arm

Fulcrum/Axis

  • There are three different types of levers, that vary in the position of the load, fulcrum and appliedforce.

  • The names are:

    • Class I

    • Class II

    • Class III


Slide28 l.jpg

What would happen if we merely lifting your arms over your head (heightens the C of G).

moved the axis closer to

a) the load? b) the force?

a) this lengthens the force

arm  increases power

b) this lengthens the

resistance arm increases speed


Types of levers l.jpg
Types of Levers merely lifting your arms over your head (heightens the C of G).

Load

Force

  • Class I lever

  • axis between force

    and resistance

    eg. see-saw

Fulcrum/Axis


Slide30 l.jpg

  • Class II lever merely lifting your arms over your head (heightens the C of G).

  • increases power  slow speed

    eg. wheelbarrow

Load

Force

Fulcrum/Axis

Allows person to lift

heel off ground


Slide31 l.jpg

  • Class III lever merely lifting your arms over your head (heightens the C of G).

  • increases speed and range of motion  little power

eg. catapult

Load

Force

Fulcrum/Axis

Elbow

Allows person to lift

a weight with their hand


Slide32 l.jpg

Because the end of a lever

moves faster than any other

point on that lever.


Slide33 l.jpg

A increase the speed and range of motion of the arm to which they are attached.

A1

d 1

Time (same)

B

B1

d 2

Time (same)


Bernoulli s principle l.jpg
Bernoulli’s Principle increase the speed and range of motion of the arm to which they are attached.

  • In a moving fluid, an area of high velocity ~ relative low pressure

  • An area of low velocity has a relative high pressure.

  • The further distance the particles have to move the faster they have to move.

An aircraft’s wing is designed to give lift as it moves through the air


Slide35 l.jpg

Applying this to Sport... increase the speed and range of motion of the arm to which they are attached.

  • Note the angle of the ski-jumper’s body vs that of the aircraft’s wing

  • Spin

  • applying spin to a ball creates a pressure differential

  • Top Spin

  • High velocity on top of the ball, low velocity on the bottom  ball will lift

  • Back Spin is the reverse.


Slide36 l.jpg

  • Curving and Swinging increase the speed and range of motion of the arm to which they are attached.

  • The ball can be made to swing by shining one side of the ball or presenting the seam to the wind.

  • This different type of surface on either side of the ball causes a pressure differential in flight.

The ball on top is smooth and has a laminar flow. It has more drag.

This ball has a rough surface (a turbulent flow) and has less drag  travels more easily through the air

Photos: Science of Baseball (www.exploratorium.org)


Slide37 l.jpg

  • Streamlining & Drag increase the speed and range of motion of the arm to which they are attached.

  • Because water does not flow smoothly around the body, low pressure turbulence forms behind the swimmer - effectively tugging them backwards (drag)

  • streamlining decreases the turbulent flow and  the pressure differential  less drag.

Photos; AIS Swimming homepage www.ais.org.au


Resources and further reading l.jpg
Resources and Further Reading increase the speed and range of motion of the arm to which they are attached.

  • ssep.bwfund.org/stu/activities/sports.html

    - heaps of sport science activities

  • http://www.exploratorium.org - huge science site with special sport section looking at science of baseball, ice hockey, cycling, skateboarding etc.

  • http://www.howstuffworks.com/physics-of-football1.htm

    - great site which talks about biomechanics and kicking, momentum and impulse when tackling etc.

  • http://www.hittingacademy.com/ohalibrary/library1

    - the physics and science behind baseball

  • Text:Abernethy et al p.105-180