Exam 3 Flashcards
Compared to adults, a child’s stride length is
Shorter
Compared to an adult, a child’s cadence is
Higher
Compared to an adult, a child’s gait speed is
Lower
If we wanted to compare stride length in children and adults, how would we do it?
Normalize it by height and look at stride length as a % of height
What was the goal of the Chester, Tingley and Biden study?
Examine kinetic and kinematic differences in kids 3-13
How is cadence measured?
Steps per second
What is the relationship between cadence and cycle time?
Cadence is the INVERSE of cycle time
Cycle time =
1/cadence
How would you describe gait kinetics?
Moments
How would you describe gait kinematics?
Osteokinematics of gait
What were the results of the Chester, Tingley and Biden study?
There is very little difference between the kinematics of the 3-4 yr olds, 7-8 yr olds, and 9-13 yr olds.
BUT there is a difference in max hip flexion between the 3-4 yr old group and the 9-13 group (but not statistically significant)
At what age does a child’s gait kinematics look like an adults?
3-4 years old
Are joint moments between 3 year olds and older kids the same?
No
Sutherland says that gait “stabilizes” by what age and matures at what age?
Stabilizes by 3
Matures by 7
GRF behind the ankle’s center of rotation will cause what?
Plantarflexion
GRF behind the center of rotation at the knee will cause what?
Flexion
GRF in front of the hips center of rotation will cause what?
Flexion
GRF behind the hips center of rotation will make it want to do what?
Extension
GRF in front of the knees center of rotation will push the knee into
Extension
GRF in front of the ankle’s center of rotation will cause what?
Dorsiflexion
What are we talking about when we say joint moments?
The moments that the muscles are creating, NOT the moments that gravity or acceleration are creating
What do joint moments act against?
GRF
What is GRF made up of?
Forces against gravity and the forces accelerating the body through the gait cycle
How does gravity not make us fall down?
Muscles counteract gravity
Gravity and acceleration create a moment about the ____ and our muscles counteract that moment in the _____ direction
Hip
Opposite
What equipment do you need to record joint moments?
3D motion analysis system and force plate
The older children had greater
Peak plantarflexion moment
The younger children had the
Least plantarflexion moment
How do you measure kinetics?
(N*m)/kg
Are kinetics normalized? How?
yes- normalized to body weight. that’s why its / by kg
What did Chester, Bingley, and Biden use for their statistical analysis?
MANOVA
Which age group DOES have different kinematics?
Toddlers (1-3)
Children at age 1 have a (higher/lower) step frequency than adults
Higher- 180 steps/min
Do toddlers age 1 have reciprocal arm swing?
No- they hold their arms in “high guard”
What is the position of the hips, knees, and ankles during toddler (1 yr) gait?
Hip- externally rotated
Knees- remains flexed
Ankles- PF at heelstrike, DF during swing phase dominished
What three things at the hip are all increased during swing phase for a toddler? (1)
Hip flexion
APT
Hip abduction
Single-limb stance is (increased/decreased) for toddlers
Decreased
Toddlers have a (wide/narrow) BOS
Wide
Where is our center of mass?
Slightly in front of S2
What is the definition of COM, according to Neumann?
Each body has a point where the COM is evenly distributed
What happens to COM when subjected to gravity?
COM of a body closely coincides with its center of gravity
What is COG?
Point at which the effects of gravity are completely balanced
What is the point where all of the mass of the object is concentrated?
Center of mass
Will an object rotate when supported at its COM?
No- there is no net torque acting on the body and it will remain in static equilibrium
An object balances on its
COM
How will an object move when kicked in line with its COM?
Without rotating
How will an object move when kicked above or below its COM?
Will rotate around COM
The exact point of COM will be in the center of
Rotation
Are COM and COG synonymous?
Yes
Is there only one COM in our entire body?
No- each body segment has its own COM, but we sum them all up when considering COM
The COM of the entire body moves relative to what?
The body segments
When someone falls, they are doing what?
Rotating around the COM/COG
What is the importance of the Fosbury flop?
COM goes underneath the body during a high jump
What is the equation for potential energy?
Mass x gravity x height
What is potential energy?
Energy that could be converted into acceleration if the object fell to the groun
What is kinetic energy?
Energy created by the acceleration of a moving body
When is kinetic energy greatest during gait?
When the COM is at it’s lowest point
When during gait is the COM at it’s lowest point?
IC or opposite IC
When is potential energy at it’s greatest point?
When the COM is at the highest point
When is the COM at it’s highest point during the gait cycle?
Feet adjacent
Why isn’t the COM at exactly 50% of body height?
The top half of the body weighs more than the bottom half
Where does COM reside along the M-L axis?
Right in the middle because the body is symmetrical in the frontal plane
Where does COM reside along the vertical axis?
Height of S2
Where does COM reside along the AP axis?
Right in front of S2
If someone has a R side above knee amputation, what does that do to their COM?
COM will move higher and to the L side because w/o the leg, the mass is concentrated higher and on the left
What did the data from Orendurff suggest?
Relationship between vertical and ML displacement of COM excursions changes substantially with walking speed
What is a sinusoidal pattern?
Sine wave
As speed increases, vertical displacement of COM
Increases
As speed increases, ML displacement of COM
Decreases
What test could Orendurff use for within subject data?
Paired t test or repeated measures ANOVA
BUT they should use repeated measures ANOVA with Bonferroni
What is postural sway?
constant displacement and correction of the COG within the BOS
Are COM and COP the same thing?
NO
What is COP?
The location of the GRF where your feet are pushing on the ground to control your COM
Which leads which? (COP/COM)
COP leads COM
(COM/COP) oscillates about the (COM/COP) to keep the person balanced
COP oscillates about the COM
What happens to COP during quiet standing?
COP falls almost directly under COM because the accelerations are very small. GRF very close to vertical
Does COM need to stay within the BOS at all times?
No- only during quiet standing
Does the COM need to stay within the BOS during movement?
No- dynamic stability can be preserved despite short periods in which the body is unsupported
How do you measure COP?
Force plates
If we are standing still and only looking at the transverse plane, will the COM and COP be far apart?
No
What are the 3 functions of the gait cycle?
PT intervention
Surgical intervention
Document change
What 2 things make gait?
Controlled fall + recovery
What creates momentum to set the body up for a fall?
Swinging limb
During which phase does the outstretched limb catch the body?
Early stance
What is the interval between IC of each foot?
Step length
What are your double limb support phases?
IC, LR, Preswing
What are the 3 functional tasks of gait?
Weight acceptance (stance)
Single limb support (stance)
Swing limb advancement (swing)
What is the fxn of weight acceptance?
Stability
Shock absorption
Forward progression
What is the fxn of single limb support?
Stability
Forward progression
What is the fxn of swing limb advancement?
Foot clearance
Limb advancement
Which phases are weight acceptance?
IC, LR
Which phases are single limb support?
Midstance
Terminal stance
Which phases are swing limb advancement?
Preswing
Initial, mid, terminal swing
What are the 3 critical events that help normal gait?
ROM
Torque demand
Muscle activity
What is ROM of the hip during IC?
20 degrees flexion
What is ROM of the knee during IC?
5 degrees flexion
What is ROM of the ankle during IC?
Neutral
Which phases have your heel rocker?
IC, LR
What is ROM of the hip during LR?
20 degrees flexion
What is ROM of the knee during LR?
15 degrees flexion
What is ROM of the ankle during LR?
5 degrees PF
What is ROM of the hip during midstance?
Neutral
What is ROM of the knee during midstance?
5 degrees flexion
What is ROM of the ankle during midstance?
5 degrees DF
Which phase do you have the ankle rocker?
Midstance
What is ROM of the hip during terminal stance?
20 deg apparent hyperextension
What is ROM of the knee during terminal stance?
5 degrees flexion
What is ROM of the ankle during terminal stance?
10 degrees DF
During which phases do you have the forefoot rocker?
Terminal stance
What is ROM of the hip during preswing?
10 deg apparent hyperextension
What is ROM of the knee during preswing?
40 deg flexion
What is ROM of the ankle during preswing?
15 deg PF
What is ROM of the hip during initial swing?
15 deg flexion
What is ROM of the knee during initial swing?
60 deg flexion
What is ROM of the ankle during initial swing?
5 deg PF
What is ROM of the hip during midswing?
25 deg flexion
What is ROM of the knee during midswing?
25 deg flexion
What is ROM of the ankle during midswing?
Neutral
What is ROM of the hip during terminal swing?
20 deg flexion
What is ROM of the knee during terminal swing?
5 deg flexion
What is ROM of the ankle during terminal swing?
Neutral
What is the critical event during IC?
Heel first contact
What is the critical event during LR?
Hip stability
Controlled knee flexion
Ankle PF
What is the critical event during midstance?
Controlled tibial advancement
What is the critical event during terminal stance?
Controlled ankle DF with heel rise trailing limb
What is the critical event during preswing?
Passive knee flexion to 40
Ankle PF
What is the critical event during initial swing? (in terms of knee flexion and hip flexion)
Knee flexion to 60
Hip flexion to 15
What is the critical event during midswing?
Further hip flexion to 25
Ankle DF to 0
What is the critical event during terminal swing?
Knee extension to neutral
What muscle activity is occurring during IC at the ankle?
Pretibials (ant tib)
What muscle activity is occurring during LR at the ankle?
Pretibials
What muscle activity is occurring during midstance at the ankle?
Calf
What muscle activity is occurring during terminal stance at the ankle?
Calf
What muscle activity is occurring during preswing at the ankle?
None
What muscle activity is occurring during initial swing at the ankle?
DF
What muscle activity is occurring during midswing at the ankle?
DF
What muscle activity is occurring during terminal swing at the ankle?
DF
What muscle activity is occurring during IC at the knee?
None
What muscle activity is occurring during LR at the knee?
Quads
What muscle activity is occurring during midstance at the knee?
Quads then none
What muscle activity is occurring during terminal stance at the knee?
None
What muscle activity is occurring during preswing at the knee?
None
What muscle activity is occurring during initial swing at the knee?
2 jt flexors
Short biceps
What muscle activity is occurring during mid swing at the knee?
Short head biceps
What muscle activity is occurring during terminal swing at the knee?
Quads
What muscle activity is occurring during IC at the hip?
Hip extensors
What muscle activity is occurring during LR at the hip?
Hip extensors
Hip abductors
What muscle activity is occurring during midstance at the hip?
None
What muscle activity is occurring during terminal stance at the hip?
None
What muscle activity is occurring during pre-swing at the hip?
Minimal add. longus
What muscle activity is occurring during initial swing at the hip?
2 jt flexors
Hip flexors
What muscle activity is occurring during mid swing at the hip?
Flexors then extensors
What muscle activity is occurring during terminal swing at the hip?
Hamstrings then glutes
What three movements make up pronation?
DF
Eversion
Abduction
What three movements make up supination?
Inversion
Adduction
PF
What position is the calcaneus in during rearfoot valgus?
Eversion
What position is the calcaneus in during rearfoot varus?
Inversion
What are you looking for with rearfoot varus/valgus?
How the calcaneus lines up with talus, tibia, fibula
What are you looking for with forefoot varus/valgus?
How the forefoot lines up with the calcaneus
Rear foot inverted (rearfoot varus) means the medial side of the ____ will be elevated
Heel
Forefoot varus and rear foot normal means the medial side of the ____ is elevated
Forefoot
How do we compensate for rearfoot and forefoot varus?
STJ pronation, leaves the foot in an unstable position
Where in the gait cycle do we see the most pronation?
LR going into midstance
Where in the gait cycle do we see supination?
Preswing
What are the normal biomechanics of the foot during the LR of gait?
Eversion of calcaneus
Inward rotation of talus
Medial rotation of ankle joint axis
Internal rotation of tibia
What happens to the patellofemoral mechanics during excessive pronation?
Increasing IR of tibia
Where is the greatest pressure on the foot at heel strike?
Heel
Where is the greatest pressure on the foot at midstance?
Midfoot
Where is the greatest pressure on the foot at toe off?
First toe
Where do you have greater ground reaction forces on the foot when walking?
Heel (heel strike) and metatarsal heads (push off)
Why is there a small peak in force when the foot initially hits the ground?
Rearfoot striking
What are the three rockers of normal gait?
Heel (first)
Ankle (second)
Forefoot (third)
What is the heel rocker characterized by?
Heel strike at IC and ankle PF
What is the ankle rocker characterized by?
Tibial advancement over the foot and DF
What is the forefoot rocker characterized by?
Heel rise, forefoot DF, and ankle PF
What is directional stability?
Stability of a moving body about an axis that is perpendicular to its direction of motion
If a vehicle is directionally stable, what is produced in a direction opposite to the rotational disturbance?
Restoring moment
What does stability mean?
That after a perturbation the system will return to baseline
What is the opposite of stability?
Chaos
What does instability mean?
The system will deviate further from baseline (fail/blow up)
What are examples of unstable systems?
Things that grow exponentially (population growth)
Define postural stability
The ability to maintain the position of the body and COM within the stability limits
True or false- the term stability can be equated with balance or equilibrium
True
True or false- stability limits do not change according to the task
False- stability limits change according to the individual’s biomechanics/environment
What are 3 ways you can increase the stability of an object?
Increasing the base of support
Lowering the COM
Increasing the mass of the system
Is the area of COP excursion during standing sway considered to be a valid and reliable measure of balance?
Yes
What is a more valid measure of balance in older adults?
Sway with a closed base of support
What does closed BOS mean?
Feet together
What does an open BOS mean?
Feet shoulder width apart
Sway is a valuable measure of what?
Static balance
Area of sway (eyes closed) is _____ than the area of sway (eyes open)
Larger
What are some ways to measure sway path?
Sway path length
Sway path length (AP or ML)
AP or ML sway range
Why do we study balance with perturbations?
Because perturbations are repeatable in an experimental setting
What would a greater COP distance or COP velocity following perturbation indicate?
Poorer balance
What are the three strategies used to control standing balance?
Ankle strategy
Hip strategy
Step strategy
What is important to note about both the ankle and hip strategy?
They can both turn into the step strategy
Motion of the platform backwards during the Horak study would cause the subject to sway
Forward
If the ankle muscles turn on after the hip muscles, which strategy does this indicate?
Hip strategy
Motion of a platform forward would cause a subject to sway
Posteriorly
What sway occurred in the young adult group?
Posterior sway causing ankle PF
What sway occurred in aging group 1?
7/12 were normal, but proximal & distal muscles were significantly delayed sompared to young adults
What sway occurred in aging group 2?
5/12 shows REVERSALS of distal proximal respose. Quads fired before anterior tib.
What does the quads firing before the ant tip indicate in aging group 2?
A hip strategy instead of an ankle strategy
Older adults have (shorter/longer) muscle latency responses (especially distal responses)
Longer
True or false- younger adults use the hip strategy more
False- older adults use the hip strategy more
What does EMG activation look like in late independent walking for children?
Ankle strategy pattern
EMG activations take place quickly after perturbation
How does EMG activity look different in a child with CP?
Antagonist and agonist muscles activated during the isometric test.
Neurotypical showed only agonist muscles activating during isometric test
What is it called (in a child who has CP) when their agonist and antagonist muscles activate isometrically at the same time?
Co-contraction
What is a typical pattern of EMG activity in a baby in regards to trunk extensors?
Trunk extensors activate earlier to anterior deltoid
At what points in the walking gait cycle are the ground reaction forces the greatest?
LR, terminal stance
What was the THM of the Chester Tinglet and Biden study?
Kinematics between groups were not different but kinetics WERE significantly different
How much does the COM move up and down during neurotypical gait?
5 cm
How much does the COM move from side to side during neurotypical gait?
4 cm
