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Mechanics of Sprinting. D. Gordon E. Robertson, Ph.D. Biomechanics, Laboratory, School of Human Kinetics, University of Ottawa, Ottawa, CANADA. Domains. Temporal Time and durations Kinematic Motion description, e.g., range of motion, speed, acceleration Kinetic

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Mechanics of sprinting l.jpg
Mechanics of Sprinting

D. Gordon E. Robertson, Ph.D.

Biomechanics, Laboratory,

School of Human Kinetics,

University of Ottawa, Ottawa, CANADA


Domains l.jpg
Domains

  • Temporal

    • Time and durations

  • Kinematic

    • Motion description, e.g., range of motion, speed, acceleration

  • Kinetic

    • Causes of motion, e.g., forces, work, power


Temporal analysis l.jpg
Temporal Analysis

  • Race time

    • Stop watch

    • Timer

    • Videography (1 frame = 1/30th second)

    • Chronometer



Kinematic analysis l.jpg
Kinematic Analysis reaction time (0.174) of finalists

  • Description of motion without consideration of its causes

  • Motion description

  • Based on Calculus developed by Newton and Leibnitz

Isaac Newton, 1642-1727


Kinematic analysis7 l.jpg
Kinematic Analysis reaction time (0.174) of finalists

manual goniometer

  • Linear position

    • Ruler, tape measure, optical

  • Angular position

    • Protractor, inclinometer, goniometer

digital goniometer

optical goniometer

protractor


Kinematic analysis8 l.jpg
Kinematic Analysis reaction time (0.174) of finalists

  • Linear velocity

    • Radar gun

    • Speedometer

    • Videography

  • Angular velocity

    • RPM

    • Videography

radar gun


Kinematic analysis9 l.jpg
Kinematic Analysis reaction time (0.174) of finalists

  • Linear acceleration

    • Accelerometer

    • Videography

  • Angular acceleration

    • Videography

accelerometers


Motion analysis l.jpg
Motion Analysis reaction time (0.174) of finalists

  • Cinefilm, video or infrared video

  • Athlete is filmed and locations of joint centres are digitized

  • body is modeled as a system of connected segments

high-speed

cine-camera


Motion analysis11 l.jpg
Motion Analysis reaction time (0.174) of finalists

Biomechanics Laboratory


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Computerized Digitizing reaction time (0.174) of finalists

Ariel Performance Analysis System


Stick figure animation l.jpg
Stick Figure Animation reaction time (0.174) of finalists


Start phase l.jpg
Start Phase reaction time (0.174) of finalists

  • No motion permitted when gun sounds

  • No force on blocks 0.10 seconds before gun sounds

  • Gun fires and there is a delay before sprinter hears gun (unless blocks have speakers)

  • Delay between when gun fires and force is applied to blocks (time for message to reach muscles at 6 m/s)

  • Taller sprinters take longer to start


Acceleration phase l.jpg
Acceleration Phase reaction time (0.174) of finalists

  • Each athlete has his/her own rate of acceleration

  • The whole race takes between 43 and 48 steps

  • At maximum speed, stride length (1 stride = 2 steps) is over 4.5 metres long!

  • Can last to 70 metres


Last 60 metres of race l.jpg
Last 60 Metres of Race reaction time (0.174) of finalists


Constant velocity phase l.jpg
Constant Velocity Phase reaction time (0.174) of finalists

  • athletes achieve maximum, constant velocity between 50 and 70 metres

  • speed:

    • 9 – 12 metres / second

    • 32 – 43 kilometres / hour

  • foot achieves twice this velocity (86 km/h!)


Fastest sprinter in 1996 johnson or bailey l.jpg
Fastest Sprinter (in 1996) reaction time (0.174) of finalistsJohnson or Bailey?

  • Johnson’s 200 m record = 19.32 s

  • Each half = 9.66 s?

  • Bailey’s 100 m record = 9.84 s

  • US reporters claim Johnson is faster?

  • Johnson had running start for last 100 m

  • At 12 m/s Bailey can run 100 m in 8.33 s, 200 m time could be 18.17 (new WR)!

  • race in Toronto confirms Bailey is Fastest Man in the World


Kinetic analysis l.jpg
Kinetic Analysis reaction time (0.174) of finalists

Causes of motion

  • forces and moments of force

  • work, energy and power

  • impulse and momentum

  • Inverse Dynamics derives forces and moments from kinematics and body segment parameters (mass and centre of gravity)


Stride analysis l.jpg
Stride Analysis reaction time (0.174) of finalists

  • swing phase of one leg

  • world-class male & female sprinter

  • 50 m into 100 m competitive race (t =10.06 s)

  • analysis of hip and knee only (ankle forces not significant during swing)


Slide21 l.jpg

20. reaction time (0.174) of finalists

Flexing

0.

-20.

Trial: SR11BJ

Extending

Ang. vel.

Net moment

Flexor

300.

Power

0.

-300.

Extensor

Power (W) Moment (N.m) Angular vel. (/s)

Concentric

2000.

0.

-2000.

Eccentric

ITO

CFS

CTO

IFS

-4000.

0.0

0.1

0.2

0.3

0.4

Time (s)

  • Hip angular velocity & power

  • initial burst of power to create swing

  • 3000-4000 W peak power by iliopsoas and rectus femoris

  • latter burst to drive leg down

  • 2800-3600 W peak power by gluteals


Slide22 l.jpg

20. reaction time (0.174) of finalists

Extending

0.

-20.

Trial: SR11BJ

Flexing

Ang. vel.

Net moment

Extensor

300.

Power

0.

-300.

Flexor

Power (W) Moment (N.m) Angular vel. (/s)

Concentric

2000.

0.

-2000.

Eccentric

ITO

CFS

CTO

IFS

-4000.

0.0

0.1

0.2

0.3

0.4

Time (s)

  • Knee angular velocity & power

  • initial burst of power to stop flexion by muscle block not by knee muscles

  • small burst for extension

  • final burst to stop extension by eccentric contraction of hamstrings


Questions l.jpg
Questions? reaction time (0.174) of finalists


Thank you l.jpg
Thank you reaction time (0.174) of finalists


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