Applications of ForcePlate Technology

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Applications of Force-Plate Technology

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• Dr. Alex, J. Y. Lee

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Introduction

• Force plates are used primarily to quantify the
  ground-reaction force (GRF) acting on the foot
  during human movement.
• Basic data include three GRF components,
  anteriorposterior, mediolateral, and vertical,
  and the ground-reaction moments (GRMs) about
  those 3 axes.
• The point of application of the GRF, the center
  of pressure, can be determined from GRF GRMs
  data.

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Locomotion

• Contact time, magnitude of vertical-impact peak,
  maximum vertical-reaction force, and
  vertical-loading rate are often studied.
• Vertical-GRF curves on rear- and midfoot
  strikers ankle taping and bracing on push-off
  mechanics.

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Components of the GRF during push-off from a
three-point stance
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Jumping Landing

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• Effective jumping and landing are essential for
  optimal athletic performance but must also be
  executed properly to prevent injury.
• Force-plate data can be used to evaluate
  athletes ability to regain balance on landing
  and their symmetry on landing, as well as
  estimate their predisposition to injury.

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Balance on Landing

• Time to stabilization (TTS) is calculated for
  single-leg landing onto a force plate.
• Stability is reached when the sequential average
  remains within 0.25 SDs of the overall average.

Colby et al. (1999). JOSPT, 444-454
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Symmetry on Landing

• Comparing the kinetic data between the involved
  and uninvolved limbs.
• Performs a drop landing onto two force plates
  (one for each foot)
• Functioning symmetrically maximum force
  loading rate

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Vertical GRFs recorded during a drop-jump landing
Time to Stabilization
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Predisposition to Injury

• As athletes mature, the forces on their bodies
  change with their size and strength and the
  changing nature of the sport activity.
• Post-pubescents incurred 3.2 times more anterior
  shear force and more valgus force when landing
  from a stride jump.

Hass et al. (2002) MSSE, 34(5), S253
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Postural Sway

• COP movement is a measure of postural sway during
  quite standing and is used to assess stability.
• Data are collected for 5-60 s, but the optimal
  trial duration is 20 s.
• Variables including total path length,
  mediolateral and anteroposterior amplitude, mean
  velocity, and SD of mean position.

Guskiewicz (2001) CJSM, 11(3), 182-189. LeClair
Riach (1996) CB, 11(3), 176-178.
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COP Path during a Single-Leg-Stance balance test

200 Hz for 20 s
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AMTI Balance Trainer
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