GRF

Question 1

Vertical GRF

Answer 1

perpendicular to supporting surface
most commonly analyzed in biomechanics

Question 2

A/P GRF

Answer 2

parallel to supporting surface in the direction of movement

Question 3

M/L GRF

Answer 3

parallel to supporting surface and perpendicular to direction of movement

Question 4

First peak of vertical GRF

Answer 4

occurs during loading response
deceleration of downward movement of body
called impact peak

Question 5

Second peak of GRF

Answer 5

occurs during terminal stance
propulsion/push-off from plantar flexors

Question 6

Dips of GRF

Answer 6

-occurs during midstance
-dip happens because we accelerate upwards, unloading from ground
-coincides with peak of vertical displacement

Question 7

A/P GRFs description

Answer 7

-braking force through first half of stance phasev(dips)
-propulsive force during second half of stance phase (peaks)
-average about 20% of bodyweight

Question 8

M/L GRFs description

Answer 8

-avg about 5% of bodyweight
-medially directed through most of stance phase

Question 9

How can we tell how much force or torque is acting on each joint?

Answer 9

embedded force sensor
inverse dynamics

Question 10

Inverse Dynamics

Answer 10

Kinematics
GRF
Anthropometrics

estimation of force and torque acting on a joint based on several measurements

Question 11

Inverse Dynamics Output

Answer 11

at each lower extremity jt there is a net internal joint force & net internal joint moment

Question 12

Internal forces and moments (of inverse dynamics)

Answer 12

muscle contraction
passive soft tissue stretch/tension
bony contact forces

Question 13

External Moments

Answer 13

-represents the torque applied to the joint by external forces
-internal torque is counteracts it
-knee OA is an example

Question 14

What joint does GRF directly act on?

Answer 14

foot/ankle

Question 15

Backward Trunk Lean

Answer 15

-causes the GRF vector to shift posteriorly in comparison to hip joint
-shifts external hip moment from flexion to extension, aiding in hip extension
-decreases internal moment hip extensors have to produce

Question 16

Forward Trunk Lean

Answer 16

-likely shifts the GRF force vector anteriorly
-shifts external knee moment from flexion to extension, aids in knee extension
-reduces internal moment the knee extensors have to produce

Question 17

This component of the ground reaction force provides information about “braking” and “propulsive” forces during walking

Answer 17

Anterior/Posterior

Question 18

This component of the ground reaction force generally has two peaks - an impact peak and a propulsive peak

Answer 18

Vertical

Question 19

This is the method researchers use to estimate joint forces and moments at the ankle, knee, and hip during locomotion

Answer 19

Inverse Dynamics

Question 20

What is not a contributor to internal forces and moments?

Answer 20

Ground reaction force

Question 21

Why is it important to consider joint moments as a physical therapist?

Answer 21

Joint moments can be an indicator or predictor of joint pathology

Question 22

What muscle is not generally active during the loading response of “normal” walking gait?

Answer 22

Iliopsoas

Question 23

This muscle is active during the loading response and helps initiate hip extension during the walking gait cycle.

Answer 23

Gluteus maximus

Question 24

This muscle helps eccentrically control knee flexion during initial contact and the loading response of the gait cycle.

Answer 24

Vastus lateralis

Question 25

This subcomponent of gait refers to one’s ability to dynamically control their trunk and COM in the frontal plane during gait.

Answer 25

Postural stability

Question 26

This movement construct can be observed by comparing movement of the right and left limbs during gait.

Answer 26

Symmetry