Exam 1 Flashcards
Basic Functions of Gait
Propulsion
Shock absorption
Stance stability
Energy conservation
The Gait Cycle =
One stride
Spatial Descriptors of Gait
Stride Length
Step Length
Step Width
Foot Angle
Stride Length
Measured heel to heel (ex: right heel to next right heel contact)
Normal = 144 cm or 1.44 m
Step Length
Measured heel contact to opposite heel contact
Normal = 72 cm
Step Width
Measured between heel centers
Normal = 8-10 cm
Foot Angle
The angle between the foot (thru 2nd ray) & the line of progression
Normal = 5-7 deg
(>7 is toe out, <5 is toe in)
Temporal descriptors of Gait
Cadence
Stride Time
Step Time
Cadence
Step Rate
Steps/min
Stride Time
Avg. is ~1 second
Time for full gait cycle
Step Time
Time for completion of one step
Avg = ~0.5 seconds
Spatiotemporal Descriptor: Walking Speed
Average = 1.37 meters/second
Gait Speed =
Cadence (steps/min) x Stride Length (cm)
How can you increase speed/walk faster?
Increase stride (or step) length
Increase cadence
Or both
Heel Contact
The instant heel comes into contact with the ground; the start of stance phase 0%
Foot Flat
Instant the entire plantar surface of foot contacts the ground (8% or 0.08 seconds in)
Mid stance
Center of mass passes directly over supporting lower extremities/pelvis
30%
Heel off
Instant the heel comes off the ground (40%)
Push-off
Period of ankle plantar flexion to propel forward (between heel off & toe off)
Toe off
Instant toe comes off the ground (60%)
Ends stance phase & Starts swing phase
Loading Response
~ initial contact until single limb support
Pre Swing
During end of stance phase, limb is preparing to swing
As Speed Increases…
-Gait Cycle Duration Decrease
-Cadence increases
-Stance Phase % decreases
-Swing Phase % increases
-Double Limb Support % decreases
-Step Width decreases
How could you increase your stride length if you are moving at a constant speed?
Decrease your cadence
(stance time would increase because you’d be taking less steps)
What is a motor unit made of?
Alpha Motor Neurons & Muscle fibers it innervates
What does EMG measure?
The electrical activity of the Action Potential moving alone the motor unit (basically how active the motor units are)
IT DOES NOT RECORD FORCE!
What are the two Strategies for Neuron Activation?
1). Recruitment- initial activation of specific motor neurons & their associated muscle fibers
2). Rate Coding- Discharge rate of sequential action potentials down motor unit
What does the Henneman Size Principle state about recruitment of motor neurons?
Smaller motor neurons are recruited before larger motor neurons.
Larger motor units are recruited as force requirement increases.
What muscle fiber type is recruited first?
Slow Oxidative
What type of contraction recruits less motor units when activating muscles?
Eccentric. Its more force per motor unit, therefore fewer motor units are needed to give force
Unfused Tetanus vs Fused Tetanus
Unfused = repeating A.P. that generated series of summated twitches, but freq. is not high enough to prevent a drop in force from occurring before the next A.P.
Fused = interval between twitches shortens & there is a stable level of muscle force
EMG analyses provide insight on:
Timing of Muscle Activation & Amplitude of Muscle Activation
Force Plates provide a measurement of
Amplitude
Duration
Phasic Characteristics
Frequency
Inverse Dynamics
GRF decreases as you go up the body segment.
Joint Moment
rotational effect produced by a force
Center of Mass
unique point where the weighted relative position of the distributed mass sums to zero
Center of Pressure
point of application where the vertical ground reaction force is said to act
Pressure Equation
Pressure = Force/Area
*therefore force = pressure x area
Why is Pressure Important?
Force doesn’t change but when its distributed over a larger area, the pressure at any given point is less.
Platform Pressure Systems (emed)
functional assessment of the plantar surface of the foot (single foot step or multiple)
Loadsol
new tech, very linear, very durable, as app for immediate feedback
What bones & ligaments make up Medial Longitudinal Arch?
idk
What bones & ligaments make up Transverse Arch?
idk
What bones & ligaments make up Lateral Longitudinal Arch?
idk
Pronation consists of
Eversion
ABduction
Dorsiflexion
Supination consists of
Inversion
ADDuction
Plantarflexion
What movement occurs most at Talocrural Joint?
Dorsiflexion/Plantarflexion
This is sagittal plane
What movement occurs most at Subtalar Joint?
Inversion/Eversion
*lots of ABD/ADD too
This is frontal plane
What is First Ray Axis? Why is it significant?
All bones in line in 1st column; it is independent from other 4 metatarsals and has a few oblique axes
What is Fifth Ray Axis? Why is it significant?
the 4th and 5th metarsals together; it has tri-planar axes
Sagittal Plane Kinematics: Ankle
10-15 deg DF
20 deg PF
How much ROM do you need in 1st MTP joint to have a good push-off?
~65 deg motion
*if not, compensate by excessive toe out
Extrinsic Foot Muscles: Anterior Compartment
Ant. Tib (dorsiflexion, inversion)
Eccentric action at heel contact to decelerate PF
controls pronation in Stance phase produces DF in Swing Phase for foot clearance
Extrinsic Foot Muscles: Lateral Compartment
Fibularis Longus & Brevis
Pronate!
primary- eversion, secondary- PF
Extrinsic Foot Muscles: Posterior Compartment
Plantarflexors (gastroc, soleus, Tibialis posterior, FDL, FHL, etc)
control motions of pronation/supination
Active in most of Stance Phase
Eccentrically control DF until heel off
Concentric burst from heel off to toe off
Tibialis Posterior activation in Gait analysis
active in all of stance phase to eccentrically control pronation in first 1/2 of stance phase
second 1/2 of stance phase it helps foot supinate
Sagittal Plane Kinematics: Hip
30 deg flexion
10 deg extension
Sagittal Plane Kinematics: Knee
60 deg flexion
-5 deg extension
Frontal Plane Kinematics: Hip
5 deg ABD
5 deg ADD
Frontal Plane Kinematics: Knee
5 deg valgus (ABD)
5 deg varus (ADD)
When is knee flexion highest?
Midswing
Transverse Plane Kinematics: Hip
10 deg IR
7 deg ER
Transverse Plane Kinematics: Knee
5 deg IR & ER
Hip Abductors muscle activity in gait
-active at end of swing phase to prepare for weight acceptance
-most active during first 40% of cycle
Knee Extensors Muscle activity in Gait Cycle:
Vasti- most active after heel strike, controls knee flexion (eccentrically helps with shock absorption)
Rectus Femoris- after toe off helps flex hip (2 joint muscle)
Knee Flexors Muscle activity in Gait Cycle:
most active just before and just after heel contact
before= decelerate knee ext.
after= assist with hip ext. & provide stability
Hip Joint Torque Sagittal
early stance- hip ext torque
2nd 1/2 of stance- hip flexion
early swing- concentric hip flexion
late swing- extensor torque
Hip Joint Torque Frontal
Stance = large ABD torque
Glute Med- eccentric to concentric contraction in stance
Swing= concentric
Knee Joint Torques Sagittal
Early Stance= brief initial flexion torque followed by Large ext torque
Knee Joint Torques Frontal
Stance = Internal ABD torque (GRF pushes knee into ADD so its the external torque)
Six Determinants of Gait
Hip Flexion
Pelvic Rotation
Pelvic Drip
Knee Flexion
Foot/Ankle Motion
Lateral Displacement of the Body
