Q4E Case Study 5 – Screening of an Elite Triple Jumper
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Proposed Subject usage:
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Coaches, Podiatry, Physiotherapy, Strength and Conditioning |
Objective
- To show how Quintic video analysis and RSscan pressure plate can be used within an in season fitness screening assessment.
- To calculate the peak forces, loading rates and weight profile during a back squat.
- To identify any possible injuries due to leg dominance, asymmetry or potential high loading rates.
Introduction
Force
A body’s state of being in rest (stationary) or in motion can be changed by the action of another body. The action exerted by this body that causes the change is termed a force.
Therefore a body in motion can accelerate, decelerate or have the path of motion altered by the force another body exerts on it. Alternatively a body at rest can be made to move when an external force is placed upon it.
Force is measured in Newton’s (N). A force of 1N is the force that will produce an acceleration of 1ms-2 in a body of 1Kg mass.
Force (N) = Mass (Kg) x Acceleration (ms-2)
Rate of Force Development
Strength work has been shown to improve performance particularly for sprinters, and jumpers but it is not beneficial in developing rate of force – the speed with which force is achieved. For example it takes around 400 ms to develop maximum force during a squat exercise, but the foot-ground contact time in during the sprint phase of a triple jump is around 90 ms. Therefore if an athlete cannot generate force quickly, they cannot continue to accelerate down the runway.
Rate of Force Development (Nms-1)= Force exerted (N) / Time (S)
Method
Video footage was taken at 50hz, along with RSscan data at 100Hz. The video has been calibrated and digitised, Raw data collected from the 1 metre RsScan plate has been exported into excel, pressure distribution peak force and loading rates have been calculated. (See spreadsheets below). Still images have been exported from the video to illustrate the athlete’s body position at key points.
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Quintic software functions used:
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Results
Bodyweight 71.6Kg (702.4N)
Peak Force (PF): 4309N, (6.13 Body Weights (BW))
PF occurs at frame: Quintic: 117, RsScan: 37
Peak Rate of Force Development (PRFD) occurs at frame: Quintic: 101, RsScan: 21
PRFD:4800Ns-1
Rate of Force Development (RFD) @ PF: 2300Ns-1
Elapsed time between PRFD and RFD @ PF: 0.32s
Left/Right Force Distribution at PF: 41% / 59%
Toes/Heels Force Distribution at PF: 57% / 43%
Knee angle at PF: 251/109º
Angular velocity of the knee at PF: 153.8º/s
80Kg Bar
 Peak Force: 4309N |
 Peak Rate of force development: 4800Ns-1 |