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24 Cards in this Set
- Front
- Back
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GRF forces applied to the foot by the ground...
Vertical? AP? ML? |
vertical: 120-140% BW
AP: 20% BW ML: 5% BW |
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when are the GRF forces anterior? posterior?
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- anteriorly directed at push off
- posteriorly directed at heel strike |
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when are GRF forces Lateral? Medial?
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- laterally directed at heel strike and initial contact
- medially directed as BW shifts back to CL limb |
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what are the 2 peaks of vertical GRFs
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1) Loading response: decellerates the angle of the foot (PF torque)
2) terminal stance: acceleration and push off |
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what two things will cause the peaks of vertical GRFs to be higher
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1) weigh more
2) clompy/heavy footed gait |
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when are GRFs for vertical lowest
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at end of midstance (deceleration)
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GRFs in the AP dirction are the _____ and _____ forces of gait
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braking and pushing forces (shear)
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GRFs in the vertical direction are the _____ and the _____ Forces of gait
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acceleration and deceleration of BW
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what direction are the AP GRFs during heel contact and what is it proportional to
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Posteriorly braking forces proportional to
1) step length 2) walking speed 3) desire to stop |
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what direction are the AP GRFs during terminal stance/pre swing
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pushing force of acceleration in anterior direction proportional to
1) step length 2) walking speed 3) desire to accelerate |
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Constant gait velocity requires
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balancing of the forces applied simultaneously to move forward (accelerate) or decelerate (brake)
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Butterfly effect represents...
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combined vertical and AP forces
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what effect does wider steps have on GRFs
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wider steps create greater ML forces ----> GRF is primarily directed MEDIALLY!
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GRFs....
1) create _____ 2) depend on _____ 3) Countered by: |
1) create external torques
2) depend on moment arms 3) countered by: muscle forces and passive structures |
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how can you increase your moment arm in your foot
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pushing off a more distal toe.... creates a longer more efficient lever arm
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where is teh CoP at heel contact (causing...)
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roughtly just lateral to the midpoint of the heel causing plantar flexion and eversion
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what happens to the path of center of pressure at midstance
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more lateral the force, the higher the arch of the foot
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what happens to the center of pressure at terminal stance
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should be located under the first/second metatarsals for proper push off
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External torques are produced by ______ whereas internal torques are produced by ______
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external torques produced by GRFs whereas internal torques are produced by muscle activation and passive tension
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Net joint torques has what to faults
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1) doesnt take into account co-activation of agonist-antagonist action
2) does not indicate the direction of movement |
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what happens if internal torques are too low (compared to external torques)
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gait deviations can result
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power =
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net torque X velocity
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positive power =
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concentric action or power generation
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negative power=
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eccentric action or power absorption
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