Final Flashcards
Mechanical Properties
how the body as a whole responds to loading
- strength
- deformation
- stiffness
- compliance
Strength
largest load a body can withstand before failure
Deformation
A change in dimension-load causes deformation
ex. a rubberband has elastic deformation
Stiffness
Resistance to displacement or deformation
Rigidity of an object/tissue/material
=change in load/change in deformation
Compliance
The ‘pliability’ of an object/tissue/material
*a compliment to stiffness
=change in deformation/change in load
Joint Stiffness
Joint angular displacement as a function of torque
=Change in torque/change in joint angle
Joint Stiffness Graph (walking)
squiggly lines
Joint Stiffness Graph (Running)
Straight lines, seperated
Limb Stiffness
combined effect of all involved joint (Ankle, knee, hip)
+
Whole body center of mass displacement, in combination with vertical ground reaction force (GRF)
Lower Limb Stiffness Model (Walking)
Inverted Pendulum Model
Lower Limb Stiffness Model (Running)
Spring-mass model
How do you measure stiffness
Use the straight line of displacements instead of measuring the curve
Gait
pattern of movement of limbs during locomotion
Locomotion
important roles in human activities, mostly walking and running
Gait Cycle
single sequence from one heel strike to the next heel strike of the same limb
Stance phase
when the foot is in contact with the ground(60%GC)
Heel strike-foot flat-heel rise-toe off
Initial contact-mid stance- terminal stance- pre swing
Swing phase
When the foot is off the ground (40%GC)
Toe off-initial swing-mid swing-terminal swing-heel strike
Single limb support occurs…
from mid stance to pre-swing phase
3 tasks of Gait Cycle
- Weight acceptance on foot once it is on the ground
- Support body weight on a single leg
- Advance swing limb in front of body
Spatial Variables
- step length
- stride length
- step width
Temporal Variables
- single limb support time
- Double limb support time
- cadence
- speed
Step length
distance between heel of one foot to the heel of the other foot
Stride Length
Distance between successive point of heel contact of the same foot.
=Step length x 2
Step Width
distance between center lines of two feet, perpendicular to the plane of walking
Cadence
=Number of steps (left&right/time
Inversely proportional to step length
When step length increases, cadence…
decreases
Walking speed
walking distance/time
Vertical GRF Graph
curvy M graphs with dotted line at 100% body weight
Anterior-Posterior Graph
-20 to 20% body weight
Medial-Lateral GRF Graph
-5-5% body weight, wiggly graph right on 0% body weight
Vertical GRF (Fy) -equations-
Fy= m*(g +ay)
If ay=0 then Fy = body weight
If ay>0 then Fy Increases and Fy is > body weight
If ay<0 then Fy decreases and Fy is < body weight
Peak Vertical GRF
120% of body weight
Peak Anterior-Posterior GRF
20% of body weight
Peak Medial-Lateral GRF
5% of body weight
Joint Moment in Gait
Take a look at the GRF vector and depending on the way it’s pulling the joint will show the join moment…
ex. a GRF behind the knee will cause knee flexion
Running Gait-stance phase
35-39% of GC
Running Gait-swing phase
61-65% of GC
Faster running speed results in…
- shorter gait cycle and lower percentage of stance phase.
- No double-limb support
- Joint angle ROM increases since running has higher ankle, knee and hip joint ROM>
Foot strike pattern -walking
rearfoot strike
Foot strike pattern- running
rearfoot strike (most runners)
or forefoot or midfoot strike
-Rearfoot displays a distinct impact transient in early stance
-Forefoot has no impact transient in early stance
-Active peak vertical forces near mid stance are generally similar
Strike patterns (Running) and injury
RFS has high vertical loading rates that are correlated to injuries such as tibial stress fractures
FFS has lower injury risk
COM (walking)
Highest COM=Midstance due to inverted pendulum
PE is highest in midstance
KE is lowest in midtance
COM PE and KE are out of phase
COM (running)
Lowest COM= midstance
PE is lowest in midstance
KE is lowest in midstance
COM PE and KE are in phase
Foot and Ankle Complex
- provides a base of support to maintain balance
- Serves as an energy source and energy sink, is involved with energy exchanges
- Positive work in walking/running
Forefoot Structure
Forefoot-metatarsals/phalanges
Midfoot Structure
Navicular, Cuboid, Three Cuneiforms
Hindfoot Structure
Talus, Calcaneus
Metatarsal-Phalangeal Joints
MTP Joints
- support the body
- provide traction
- control the forward motion of the COM during propulsion
Stress Fractures
- result from a microtrauma to bone from
1. uncontrolled foot landing
2. Hard landing on the ground
3. Improper spring of the foot action
Foot Spring
Responsible for transferring forces from achilles tendon to forefoot
- Decrease in tension in spring will increase the strain on the metatarsals
- In terminal stance phase(push-off) the decrease in tension in the spring will shift the GRF and contact area from the toes to the metatarsals
Ankle Sprains
Mostly inversion… eversion rarely happen because of longer lateral malleolus and stronger deltoid ligaments
Knee Complex
Tibiofemoral Joint with 2 degrees of freedom
- Flexion/Extension
- Internal/External Rotation
Patellofemoral Joint
Knee Injuries
Ligamentous sprains
Meniscal tears
Osteoarthritis
Knee Ligament Injuries
ACL caused by: -suddenly slowing down and changing direction -stopping suddenly -receiving a direct blow to the knee -landing awkwardly from a jump
Patellofemoral Pain Syndrome
Stress is the key component cause
- patellofemoral joint reaction force
- contact area between patella and femur (too small)
- Changes based on knee angle (Contact area increases as knee flexion angle increases)
Hip Joint
Ball and Socket 3 Degrees of Freedom F/E I/E AB/AD
Sagittal Plane
Flexion/Extension
Frontal Plane
Abduction/adduction
Transverse Plane
Inversion/Eversion
Iliofemoral Ligament
Extension
External Rotation
Pubofemoral
Abduction
Extension
External Rotation
Ischiofemoral
Internal Rotation
Extension
Adduction
Gait Retraining for hip abnormalities
8 sessions mirror and verbal feedback on lower extremity alignment
1-4=15 min to 24, more feedback
5-10=30 min run time and decreased feedback
Shoulder Complex
Joints:
- acromioclavicular joint
- Glenohumeral joint
- Sternoclavicular Joint
Articulation= scapulothoracic articulation
Rotator Cuff
- supraspinatus
- infraspinatus
- teres minor
- subscapularis
- keep the ball and socket joint in tack
Shoulder Impingement
- single most common shoulder pathology
- rotator cuff is a common source of pain in shoulder
- happens when the tendons in the shoulder are irritated/inflamed or degenerated from repetitive overhead motions or structural abnormalities in shoulder.
Mobility of Shoulder
provides a wide range of motion, elbow as a hinge so the hands may reach in different directions
Dexterity
eg. writing, play piano
Object manipulation
eg. hold a bottle
Daily life activities
eating, communication
Lower Limb Function
- Load carriage
- Stability
- Locomotion
Amputation Stats
- Over 1.6 million experienced limb amputation in US
- 3.6 million in 2050
- 2/3 of the amputations are lower limb
Limb Amputation causes
- Dysvascular disease (54%)
- Trauma (45%)
- Cancer
Functional mobility
- Lack of muscles & sensory feedback (unilateral amputees)
- Gait asymmetries & increased use of intact limb
- Will result in some degenerative changes, secondary impairments (knee OA in intact limb)
Amputee Walking Gait
Whole body COM is moving downward- upward direction
-if trailing limb positive work decreases it will result in increased leading limb share of COM redirection, increase GRF loading in leading leg, secondary impairments
Passive Prothesis
- store & return small amounts of energy
- incapable of emulation normal ankle function
Power Prosthesis
- uses a series elastic actuator and a motor (both passive and motorized elements) to emulate ankle foot functions
- significantly decreases intact leg peak resultant force by 2-11% during walking .75-1.5 m/s
- decreases metabolic cost by 8% in walking at .75-1.5 m/s
Running Prothesis
-Carbon Fiber prosthetic foot
compresses and then returns to normal shape as push off
-compression and decompression of the blade enable the release of energy at push off, and reduce metabolic cost of running
-“C” shaped-jogging and distance running, storing and releasing energy over time
-“J” shaped-sprinting, quick energy recovery
Torque=
Force x Lever Arm
Also called a moment of force
First Class Lever
Effort and Load are equal distance from fulcrum
Second Class Lever
Load is before Effort (Can Take a Heavier Load)
Ex=Calf raises , push up
Third Class Lever
Effort is before Load (Has larger range of motion, lower weight)
Ex=bicep curls
velocity =
change in displacement/change in time
inelastic collision
travel together after collision
elastic collision
bounce off each or all of the KE is transferred to the other object
Projectile Motion equations
Vfy=Viy+gdeltat
Yf=Viydeltat + 1/2gdeltat^2
Xf=Vix*deltat
Vxi=Vxf
Axis of Rotation
A fixed point about which an object rotates
Clockwise
negative
Counterclockwise
positive
Radian
arc length/radius
Degrees to radians
pie/180
Radians to degrees
180/pie
Angular displacement (omega)
change in angular displacement/change in time
UNIT HAS TO BE RADIANS before multiplied by another quantity
Shank
another term for the displacement in angular kinematics
Tangential Velocity
r*omega
Coefficient of Restitution
h= e^2*H
h =bounce height
H=drop height
Angular Momentum =
Inertia x angular velocity
=mk^2*omega
