Test 3

Question 1

Gait analysis can be used to

Answer 1

-Provide a quatitative assessment of function or mobility (Frailty and fall risk in old adults)
-Support treatment options (Surgical options OA and CP, orthoses for CP)
-Examine disease state or progression (ie PD, MS, OA)

Question 2

Gait cyle: stace subphases

Answer 2

1-Loading response
2-mid-stance
3-terminal stance
4-pre-swing

Question 3

Gait cyle: stance subphases- loading response

Answer 3

inital contact to opposite toe off (double support)

Question 4

Gait cyle: stance subphases- mid-stance

Answer 4

opposite toe off to heel rise (single support)
foot is flat (data on foot is flat)

Question 4

Gait cyle: stance subphases- terminal stance

Answer 4

heel rise to opposite initial contact (single support)

Question 5

Gait cyle: stance subphases- pre-swing

Answer 5

opposide inital contact to tow odd (double support)

Question 6

Gait cyle: swing

Answer 6

1-inital swing
2-mid-swing
3-terminal swing

Question 7

Gait cyle: swing subphases- initial swing

Answer 7

tow off to feet adjacent (aligned)

Question 8

Gait cyle: swing- mid-swing

Answer 8

feet adjacent to tibia vertical

Question 9

Gait cyle: swing- terminal swing

Answer 9

tibia vertical to initial contact

Question 10

common spatiotemporal parameters

Answer 10

-temporal parameters (seconds)
-Spatial parameters (meters)
-Gait speed (meters/sec)

Question 11

temporal parameters

Answer 11

-step and stride time
-stance time and swing time
-single support time
-double support time

Question 12

spatial parameters

Answer 12

-step/stide length
-base width
-foot angle

Question 13

Ground reaction forces- kinetics: force exerted by the ground on the body

Answer 13

-offer insights into actions at each subphase of gait
-gait is just falling with style (propell and catch each gait cycle)

Question 14

joint angles- kinetics: The movment patterns without considering forces

Answer 14

-sensitive to changes with age, clinical considerations, and injuries
-stuied for years with “marker-based”optical methods
-newer technologies make this easier

Question 15

joint angles- kinematics: can be quite complicated

Answer 15

-occurs in three dimensions
-ankle, kmee, and hip all influence each other
-often focus is often on fewer joints/planes

Question 16

what should we measure: it depends on…

Answer 16

-the question you are trying to answer
-the information important/useful to your end user (what do we care about)
-the patient population or conditon
The literature is the best place to start when trying to understand what you should be measuring

Question 17

General findings from the literature with respect to aging and gait

Answer 17

-decreased gair speed, spatial parameters
-increased temporal parameters, variability
However, healthy older adults may have little to no change
Larger changes can occur with advanced age, additonof clinical conditons, reduced from executive function,ect

Question 18

Where should we measure it (in vs out of lab)

Answer 18

trade off between more controlled vs more realistic
normal vs perturbed (eg dual task)
-optimal gait vs stressed system
Assesed during functional tests?
-timed up and go, 6 minute walk test, self-paced walk test

Question 19

How do we measure it (with sensors)

Answer 19

-Temporal parameters (seconds): timing of heel strike and toe off
-Spatial parameters (m or m/s): requires integration of acceleration and displacment (more complex)
-joint angles (degrees): sensor on each segment or “rigid body”, requires integration of angular velocity to angular displacment

Question 20

How do we get displacment

Answer 20

accleration–> veolcity–> displacment
use numerical integration to get between

Question 21

getting displacment is complicated by…

Answer 21

-any offset in data will be greatly amplified (low frequency- eg gravity/calibration issue)
-Error in signal will accumulate (high frequency noise)
-Unknown inital conditons; just measure accleration (only able to determine changes from inital stae)

Question 22

getting from accleration to velocity (on way to displacement)

Answer 22

1-Remove high-frequency noise (low pass filter)
2-remove offset/gravity (detrend/high plass filter)
3-numerical intergration (trapezoidal integration)

Question 23

getting from velcity to displacment

Answer 23

1- remove offset (detrend/high pass filter)
2- numerical integration (trapezoidal integration)

Question 24

Joint angles- sagittal plane

Answer 24

-Relative angles between segements- can measure 3D at each joints, but focus is often sagittal

Question 25

sagittal knee joint angle; gait cycle

Answer 25

1. At heel strike, the knee is typically flexed (slightly), and continues to flex (absorbs load) as knee extensors work eccentrically 2. Knee then extends (knee extensors working concentrically) as body moves forward over stance limb) 3. Knee flexors as toe off approaches and plantarflexion occurs/heel begins to lift 4.Flexion continues to mid swing peak 5.Knee begins to extend in preperation for heel strike again

Question 26

Saggital knee joint angle: changes in knee flexion during gair can be related to: \

Answer 26

-pain, mucle function, flexibility, ect -Aging, injuries (eg ACL), OA, ect

Question 27

two common abnormaliteis in knee joint angle

Answer 27

-stiff knee gait -flexure contracture

Question 28

Stiff knee gait

Answer 28

-Reduced knee flexion at heel stike, midstance, and ir swing -common in OA: reduced ROM, bening= painful, Quad avoidance strategy -Knee arthroplasty to improve pain and function (less stiff knee gait)

Question 29

Flexion contracture

Answer 29

-inability to fully straighten knee -can occur w/ OA or other conditons: congenital deformities, rheumatoid arthritis, CP Can influence or be influenced by joints above or below

Question 30

Clinical case study- CP

Answer 30

CP results from damage to one or more areas of the developing brain -can occur pre or post natally -Numerous causes (eg premature birth, hypoxia) -various difficulties with gait

Question 31

Clinal case study: CP- 3 main differences

Answer 31

-anterior pelvic tilit -equinus- restricted dorsifelxion (toe walking) -reduved knee flexion (also see decreased extension at contact)

Question 32

Clinal case study: CP- cause and effect?

Answer 32

PLantarfleor (gastric/soleus) spasticity -results in equinus -results in reduced knee flexion at heel strike (and stance-locked) -Reduced in excessive ant pevlic tilt to progress forward- try to get over footl leaning to move forward

Question 33

clinical case study- Cp treatment

Answer 33

AFOS- equinus is prevented/lmited secondary anterior pelvic tilit and extended knee are resolved

Question 34

How do we measure joint angles with IMUs?

Answer 34

1. Need to get orientation estimates from IMUs -Angular velcity to angular displacement 2.compare orientations from segments on either side of the joint -angle of shank vs angle of thigh

Question 35

getting to angluar displacment (gyro) similar accumulation of erros...

Answer 35

-Bias instabilties- low freqeuncy offset changes -angluar random walk- stochastic noise (random noise in the data that accumulates when integrated) -unknown initial conditions- only able to determine changes from inital state

Question 36

getting to angluar displacement from angular velocity

Answer 36

-remove high frequency noise (low pass filter) -remove offset (remove bias) -numerical integration (trapezoidal integration) *** need to consider drift!!

Question 37

Zero velocity update (ZUPT) used on foot mounted sensors

Answer 37

-Foot is fixed to the ground (ie has zero veolicty) during the stance phase -can use this to "anchor" to output of the signal -Bring it back to zero and minimize any dift Can minimize error within a single sensor but teaming up with other sensors is most effective

Question 38

sensor fusion

Answer 38

-Combining data from different types of sensors to obtain estimates of displacment and orientation that have less uncertaininty

Question 39

sensor fusion- the elephant parable

Answer 39

-the accelerometer, gyroscope, and magnetometer are all measuring the same motion, but seeing it in different ways -Each sees different partial truths (all asses one part of whole, alone they are all wrong, together get better picture) -sensor fusion aims to exploit their strengths (while understnading their limitations) so that we can obtain a measure of the true motion

Question 40

important considerations: sensor fusion- kalman filters

Answer 40

-previous state (i-1) + current inputs (i) to estimate current state (i) -more complex weighting of sensors inputs -significanwork needed to create robust algorithms for different movments

Question 41

important considerations: machine learning- input raw IMU data and outputs joint angles

Answer 41

-Black box model -requires lots of trianing data -Can work well in ideal conditons, but may transfer poorly to others

Question 42

Other gait related considerations- physical activry assesment: estimates metabolic equivalents (METs) from accelerometr counts

Answer 42

-working metabolic rate in comparison to your resting metabolic rate (1 met= energy used while resting) -count is a measure of the number of peaks over a sufficeint threashold in a signal (soft of...)

Question 43

Other gait related considerations- physical activry assesment: detrmine activity level based on counts per minute

Answer 43

calculate based on shaking of sensor sed: 0-99cpm light: 100-1951cpm mod: 1952-5724 cpm vigorous: 5725-9498 cpm very vig: >9499cpm

Question 44

Other gait related considerations- activity classification

Answer 44

-suing inertial signals to classify time spent in various activites -can range in complexity and form: stationary vs dynamic- simply threashold of inertial data seperating all different types of activites- utilizes artificial intelligence (eg machine learning)