Levers, Rockers, and GRFs Flashcards Preview

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Flashcards in Levers, Rockers, and GRFs Deck (17)
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1

What is determined by the perpendicular distance between the action of the vector and the center of joint rotation?

Lever arm

2

What is the mean load bearing line, taking into consideration forced acting in all 3 planes?

Ground reaction force

3

What is the product of the force times the lever arm (the rotational potential of the forces that act on a joint)?

Torque moment

4

What is the GRF during initial contact?

PF moment due to force vector being behind heel

5

What happens to the GRF during midstance?

shifts in front of ankle causing DF

6

What are the 3 rocker phases?

1. heel strike
2. stance phase
3. toe off

7

What happens at first rocker (heel strike)?

eccentric quads and ant tib, pronation with flattening of medial arch

8

What happens at second rocker (stance phase)?

progressive DF of ankle, eccentric gastroc and soleus

9

What happens at third rocker (toe off)?

foot rotates of met heads, supinates, heel into varus
tib post locks midfoot to act as rigid lever
pushoff via triceps surae contraction

10

What does a softer heel cause?

quick to foot flat = more stability at knee

11

What does a firmer heel cause?

better 1st rocker, but more isntability

12

What does a soft toe cause?

short toe level, small DF moment, high knee flexion moment

13

What does a rigid toe cause?

long toe lever, high DF moment, high knee extension moment

14

What does a stiff ankle cause?

more resistance met when moving forward at midstance (rapid increase in DF and knee extension moment)

15

What does a free ankle cause?

DF moment increases slowly, knee flexion moment

16

What does a longer heel lever cause?

encourages knee flexion at loading response (shorter heel lever is safer)

17

What is standard socket alignment for transtibial amputations?

5 degrees flexion, 5 degrees adduction