FINAL Flashcards
What are the 3 Essential Requirements of Locomotion?
Progression
Postural Control
Adaptability
What is progression?
coordinating patterns of muscle activity to move the body in a desired direction
What is postural control?
maintaining postural orientation and stability for locomotion
What is adaptability?
– meeting desired locomotor goals across a variety of task and environmental contexts
What is the “gait cycle”?
the events that occur between initial contact (i.e., heel strike) of one foot and the subsequent initial contact (i.e., heel strike) of the same foot
During each gait cycle (100%), the lower limb undergoes a stance phase (60%) and a swing phase (40%)
What is the stance phase?
Heel strike to toe-off (i.e., foot is in contact with the ground)
What are the sub-phases of the stance phase?
initial contact (heel strike) -> loading phase -> mid-stance -> terminal stance
Double support (10%) -> Single-support (40%) -> Double Supp (10%) -> Single-supp (40%)
What is the goal of the stance phase?
– generate vertical forces (postural control) and horizontal forces (progression) against the support surface in a manner that is sufficiently flexible to accommodate a variety of tasks and environmental characteristics (adaptability)
What is the swing phase?
Time between toe-off and heel strike (i.e., when the foot is not in contact with the ground)
What are the sub-phases of the swing phase?
initial swing -> mid-swing -> terminal swing
What is the goal of the swing phase?
advancement (progression) and repositioning (postural control) of the lower limb in a manner that is sufficiently flexible to allow for foot clearance in a variety of task and environmental contexts (adaptability)
The part of the gait cycle in which both feet are on the ground is termed _________.
Double stance
What are the gait patterns?
Kinematic patterns (spatiotemporal)
Kinematic patterns (Joint rotations/COM)
Muscle Activation Patterns
What is the step portion of Kinematic patterns (spatiotemporal)?
process of moving one limb forward
Step length: distance from the heel strike of one foot to the subsequent heel strike of the other foot
Step time: time required to take one step
What is the stride portion of Kinematic patterns (spatiotemporal)?
process of making one step with each foot (i.e., completing one gait cycle)
Stride length: distance from the heel strike of one foot to the subsequent heel strike of the same foot
Stride time: time required to take one stride
What is the cadence portion of Kinematic patterns (spatiotemporal)?
number of steps per unit time (e.g., 120 steps/min)
What is the speed portion of Kinematic patterns (spatiotemporal)?
verage distance traveled per unit time (e.g., 1.4 m/s, 4.6 ft/s)
An individual’s preferred walking speed is the speed that requires what?
minimal energy expenditure
As we increase walking speed what variables of Kinematic patterns (spatiotemporal)?
both stance and swing time decrease, but stance phase becomes progressively shorter relative to swing phase
60/40 Stance/Swing ratio for walking switches to 40/60 for running (double support disappears)
As we decrease walking speed what variables of Kinematic patterns (spatiotemporal)?
stance time gets longer, while swing time stays relatively constant
What is the Kinematic Patterns (Joint Rotations/COM)?
There are characteristic kinematic patterns that occur during the gait cycle
The combined effect of the individual pelvic and lower limb joint rotations is a smooth forward progression of the body’s centre of mass (COM)
What 2 characteristics are involved in Kinematic Patterns (Joint Rotations/COM)?
Vertical
Mediolateral
What is the vertical characteristic in Kinematic Patterns (Joint Rotations/COM)?
Maximum: midpoint of single-support
Minimum: midpoint of double-support
What is the mediolateral characteristic in Kinematic Patterns (Joint Rotations/COM)?
Maximum right: midpoint of right limb stance
Maximum left: midpoint of left limb stance
Several key determinants function to minimize vertical displacement of the COM (what are they)?
Pelvic rotation, lateral pelvic displacement, knee flexion, knee/ankle coordination
What are the limitations of Kinematic Patterns and Energy Expenditure During Gait?
Studies have shown that some of the projected key determinants do not impact vertical displacement of the COM
Lower limb joints must undergo large motions and torques to maintain a level COM path, which increases the required energy expenditure
More recently, it has been suggested that reducing energy expenditure associated with?
with gait requires smooth mechanical transfer of kinetic and gravitational energies (involves up-down movement of COM)
What is the inverted pendulum model?
The stance leg essentially acts as an inverted pendulum that the COM vaults over
What is Potential energy (gravitational)?
energy possessed by an object due to the height of its COM
What is kinetic energy?
energy possessed by an object due to its motion
What is Law of Conservation of Mechanical Energy?
“energy cannot disappear” (in a closed system)
What is
Midpoint of single-support?
MAX potential energy, MIN kinetic energy
What is Midpoint of double-support?
MIN potential energy, MAX kinetic energy
T or F: Smooth vertical sinusoidal fluctuations in COM position results in an efficient and ongoing transfer between potential energy and kinetic energy?
True
Muscle Activation Pattern: What is the goal of the stance phase?
generate vertical forces (postural control) and horizontal forces (progression) against the support surface
What are the phases involved in postural control?
Initial contact
loading phase
mid-stance and terminal stance
What is initial contact?
ground reaction force creates an ankle plantarflexion and knee flexion moment
What is loading phase?
eccentric contractions of the ankle dorsiflexors and knee extensors resist the GRF-induced moments
What is Mid-stance & terminal stance?
contraction of the hip abductors maintains pelvic stability; contractions of the hip extensors and knee extensors maintain lower limb stability
What is the progression of muscle activation patterns?
Mid-stance & terminal stance: contraction of the ankle plantarflexors (and hip extensors) propels the body over the foot
The ankle plantarflexors are responsible for?
a majority of the propulsive force generated during the stance phase
Muscle Activation Pattern: What is the goal of the swing phase?
advancement (progression) and repositioning (postural control) of the lower limb
Muscle Activation Pattern: What is the progression of the swing phase? - initial swing
Initial swing: contraction of the hip flexors propels the lower limb forward, contraction of the hip flexors and ankle dorsiflexors shortens the lower limb (clearance)
Muscle Activation Pattern: What is the postural control of the swing phase? - terminal swing
Terminal swing: eccentric contraction of the hip extensors slows the lower limb, contraction of the ankle dorsiflexors prepares the foot for heel strike
What are the adaptations of gait and why?
Involves adapting the strategies used to accomplish progression and postural control in the face of changing task and environmental conditions
Reactive postural control for unexpected perturbations
Anticipatory postural control for expected disturbances
What is the reactive portion of adaptation of gait?
Reactive postural adjustments are integrated into step cycle during recovery from unexpected perturbations
Distal perturbed leg muscles and hip and trunk muscles play a role
Arm movements commonly used during balance recovery in gait and for protection
Most falls in the elderly occur as a result of a?
trip or fall
Most falls in the elderly occur as a result of a?
trip or fall
Strategy used for balance recovery depends on?
where in the step cycle the trip occurred
What is the early swing phase?
elevate swinging limb
Flexor torque through the swinging limb to lift higher
Extensor torque in stance limb to increase height of body
What is the late swing phase?
lower swinging limb
Plantarflexion of ankle in swinging limb
Knee extension in swing limb to reach down
Shortened step length
What is the anticipatory factors of adaptation of gait?
Prediction is used to minimize destabilizing forces
e.g., APAs to movement of own limbs (develop with experience)
Visually activated strategies modify gait in response to perceived threats
What is Obstacle Crossing factor?
Higher obstacle, greater range of COM movement in anteroposterior and vertical directions, but not mediolateral
Keeps COM within safe limits
What is Surface conditions (slippery) factor?
Reduce stance duration and loading speed
Shorter stride length
Increase muscle stiffness (compliant)
What is the incline factor?
Increased muscle activity
Longer step lengths and reduced cadence (uphill)
Shorter step lengths and higher cadence (downhill)
What is the incline factor?
Increased muscle activity
Longer step lengths and reduced cadence (uphill)
Shorter step lengths and higher cadence (downhill)
What is the turning factor?
Depends on front foot
Right turn with right foot in front = “spin turn”
Left turn with right foot in front = shift weight to right leg, externally rotate left hip and step onto left leg and turn until right leg steps in new direction (“step turn”)
Step turn more stable
Deceleration prior to turn uses ankle strategy
What are rhythmic movements?
Repetitive performance of the same motor act
Flying, breathing, swallowing, vomiting, locomotion
What are Central Pattern Generators (CPGs)?
The basic pattern for rhythmic movements thought to be controlled by oscillating circuits within the spinal cord (CPGs)
Non-rhythmic movements thought to be under greater cortical control
Where are Central Pattern Generators (CPGs)?
Transect the CNS at various points and observe locomotion to identify contributions of different parts of motor system
What is Decorticate (“no cortex”) preparation?
basal ganglia, cerebellum, brainstem, spinal cord intact
What is Decerebrate (“no cerebrum”) preperation?
cerebellum, brainstem, spinal cord intact
What is Decerebrate (“no cerebrum”) preperation?
cerebellum, brainstem, spinal cord intact
What is Spinal preparation?
spinal cord only intact
How do Central Pattern Generators (CPGs) work? - Half-Centre Model
Reciprocal inhibitory circuits underlie the rhythmicity
Flexor-extensor “half-centres”
Both receive descending and ascending input but once initiated, no further inputs are needed
Half-centres are connected to each other through inhibitory interneurons
What are the 3 steps of the half-centre model?
1) The CPG will be initiated through the activation of neuron A or B (whichever is closest to threshold)
2) If A is active, it drives neuron C and inhibits neuron B
3) Discharge of A slowly declines (hyperpolarization, neurotransmitter depletion)
4) Reduced inhibition to B eventually turns B on (post-inhibitory rebound)
5) When B is active, it drives neuron D
The end result is a process that “cycles” back and forth and generates rhythmic alternating flexion and extension movements
The rhythmic pattern generated by the CPG is analogous to?
activity generated by the crossed extensor reflex (is elicited when a flexor withdrawal reflex is activated)
Although CPGs can produce this rhythmic stepping pattern, supraspinal and sensory inputs are required for?
weight support, dynamic postural stability, and adaptation
Although CPGs can produce this rhythmic stepping pattern, supraspinal and sensory inputs are required for?
weight support, dynamic postural stability, and adaptation
Parts of the brain for CPGs?
Cerebellum
-Weight support and -improved coordination
Basal Ganglia
-Dynamic postural stability
-Initiation of gait
Cerebral Cortex
-Adapt the pattern to task/environmental demands
-Feedforward (predictive) control
-Exerts influence through corticospinal pathway
How is a CPG “turned on” in the intact CNS?
Descending drive from the brain
How is a CPG “turned on” experimentally?
Stimulating area of brainstem or midbrain
Stimulating cutaneous afferents
Apply exogenous excitatory neurotransmitter
What is Neonate walking?
Step-like movements in newborn infants when corticospinal tract development is incomplete
What is Rhythmic leg movements?
in spinal cord injured patients
Evoked by cutaneous and spinal cord stimulation
What is Sleep related periodic leg movements?
in locomotor rhythm
What are Vibration-induced air stepping?
Vibrate one or both limbs in neurologically intact subjects and evoke rhythmic activation of hip and knee in simulated weightlessness
What are Vibration-induced air stepping?
Vibrate one or both limbs in neurologically intact subjects and evoke rhythmic activation of hip and knee in simulated weightlessness
T or F: Rhythmic pattern can be produced without any continuing sensory feedback? Why?
True
CPG can be strongly influenced by signals from peripheral sensory receptors
How do Sensory signals contribute to maintenance of rhythmic activity?
Without sensory feedback (i.e., de-afferented cat), the frequency of rhythmic activity generated by the CPG slowly declines until it stops
If sensory system intact, rhythmic activity continues
Evidence: Rhythmic activity does not last in de-cerebrate AND de-afferented cats
How do Sensory signals initiate phase transitions?
Cutaneous and proprioceptive signals inform when switch from stance to swing occurs
Evidence: Prevent hip extension to prolong stance phase and the rhythmicity stops
CPG circuit is waiting for sensory feedback to inform whether it is time for the phase transition
CPG requires feedback to indicate hip is in position and limb is unloading before going from stance to swing
How do Sensory signals initiate phase transitions?
Cutaneous and proprioceptive signals inform when switch from stance to swing occurs
Evidence: Prevent hip extension to prolong stance phase and the rhythmicity stops
CPG circuit is waiting for sensory feedback to inform whether it is time for the phase transition
CPG requires feedback to indicate hip is in position and limb is unloading before going from stance to swing
How do Sensory signals regulate magnitude of motor activity?
Somatosensory signals inform amplitude of muscle activity required
Evidence: Blockade of muscle spindle activity in ankle extensors results in a 50% reduction in EMG activity generated by CPG during stance
Indicates that the stretch reflex contributes to force production during stance
How do Sensory signals allow adaptation of the normal motor pattern to environment?
Stumbling corrective response” – elevate swinging limb
Combination of muscle (spindles, GTOs) and cutaneous afferents
Evidence: Stimulating a cutaneous nerve on the top of the foot (superficial peroneal nerve) generates the same muscle activity observed during a stumble
Activity generated depends on leg position (mimicking early or late swing)
How are reflexes modulated?
Reflexes are modulated from descending (brain), spinal (CPG), and afferent sources
What is Task-dependent modulation?
Reflexes in the legs are affected by movement of the arms
Indicates an inter-limb connection for reflex modulation
What is phase-dependant modulation?
H-reflexes are progressively inhibited from sitting to standing to walking to running
What is reflex reversal?
Reflexes can be excitatory in one circumstance and inhibitory in another
GTOs activate inverse stretch reflex (inhibit active muscle) in non-dynamic condition but activate excitatory reflex during stance in locomotion
Cutaneous reflexes switch from excitatory to inhibitory across the gait cycle
How? Complex interneuron connectivity
What is reflex reversal?
Reflexes can be excitatory in one circumstance and inhibitory in another
GTOs activate inverse stretch reflex (inhibit active muscle) in non-dynamic condition but activate excitatory reflex during stance in locomotion
Cutaneous reflexes switch from excitatory to inhibitory across the gait cycle
How? Complex interneuron connectivity
Reflex modulation is a great way to move towards?
Gives ideas about how gait can be adapted to different task/environmental demands
Challenges to Gait Obstacle Clearance?
Reactive - “stumble-corrective response”
Anticipatory – APAs and visually activated strategies to adjust for perceived threats
Learning and memory
Inter-limb transfer
Sensory systems
With instruction to keep foot clearance as low as possible without touching the object + auditory feedback, people can learn to?
step over an object more effectively
EXS:
Treadmill
Foam sticks that passively fold back on touch
Auditory signal that indicates height of object clearance
The learning associated with reduced object clearance heights transfers to what body part?
the trailing leg
Information gained during object crossing with the leading leg is transferred to trailing limb
What is visual information in obstacle clearance?
Visual information about the obstacle configuration is used to select a context-specific locomotor program
Next a memory of the somatosensory signals associated with the crossing with the lead limb is created and transferred to regions supporting movement of the trailing leg
What is visual information in obstacle clearance?
Visual information about the obstacle configuration is used to select a context-specific locomotor program
Next a memory of the somatosensory signals associated with the crossing with the lead limb is created and transferred to regions supporting movement of the trailing leg
Obstacle Clearance and Dual-tasking?
Gait requires attention and the attentional resources required increases with added gait demands
People are more likely to contact an obstacle when simultaneously performing a cognitive task
Effect is greater when the secondary task introduced during “pre-crossing” vs “crossing”
Whether or not the gait task or the cognitive task is “prioritized” in terms of allocation of attentional resources is context-specific
Gait or a secondary task can be prioritized based on instructions
Gait will be prioritized with increasing challenge (i.e., higher obstacle height)
Cell-phone use seems to almost always receive priority over gait…
What is the step portion of Kinematic Patterns (Spatiotemporal)?
process of moving one limb forward
Step length: distance from the heel strike of one foot to the subsequent heel strike of the other foot
Step time: time required to take one step
What is the stride portion of Kinematic Patterns (Spatiotemporal)?
process of making one step with each foot (i.e., completing one gait cycle)
Stride length: distance from the heel strike of one foot to the subsequent heel strike of the same foot
Stride time: time required to take one stride
What is the cadence portion of Kinematic Patterns (Spatiotemporal)?
number of steps per unit time (e.g., 120 steps/min)
What is the speed portion of Kinematic Patterns (Spatiotemporal)?
average distance traveled per unit time (e.g., 1.4 m/s, 4.6 ft/s)
Compared to younger adults, healthy older adults generally demonstrate? (kinematic patterns (spatiotemporal)
Decreased walking speed
Decreased step length
Increased step width
These 3 have Even further declines in elderly with history of falls ^
Increased stance phase time
Decreased swing phase time
Decreased single support time
Compared to younger adults, healthy older adults generally demonstrate? (kinematic patterns (Joint rotations/COM))
Decreased rotations about the ankle, knee, and hip
Decreased vertical displacement of the COM (increased energy expenditure)
Compared to younger adults, healthy older adults generally demonstrate? (muscle activation and joint kinetic patterns)
Increased co-activation (ankle dorsiflexors and plantarflexors in loading phase)
Decreased power absorption at heel strike (knee extensors)
Decreased power generation at toe off (ankle plantarflexors)
Decreased ability to co-vary lower limb segment moments to generate a net extensor support moment (for dynamic stability)
Compared to younger adults, healthy older adults generally demonstrate? (Gait variability)
There is initial evidence that in groups of older adults similar for gait speed and muscle strength, differences in gait variability can predict falling risk
Too much or too little variability can indicate fall risk
Generally, gait patterns used by healthy older adults are similar to those used by?
younger adults in challenging conditions (e.g., walking on a slippery surface)
Therefore, it has been suggested that gait changes in older adults may relate more to changes in postural control than locomotor control
The rate of torque development is more important than what for balance recovery?
The rate of torque development is more important than muscle strength for balance recovery following a slip/trip
Compared to younger adults, healthy older adults generally demonstrate the following in response to a slip/trip?
Slower onset latencies and decreased activity levels in the postural control muscles (i.e., slower rate of torque production)
Increased trunk motion and arm motion
Anticipatory control of gait depends on the ability to modify gait patterns in response to?
visual cues related to obstacles and potentially destabilizing environmental conditions (e.g., slippery surface)
Compared to younger adults, healthy older adults in Age-related changes in anticipatory control of gait generally?
Require more time to implement an appropriate response strategy
Use more conservative strategies for crossing over obstacles (e.g., slower approach speed, slower crossing speed, shorter crossing step length)
Older adults with history of falls show greater what during obstacle crossing?
mediolateral COP displacement and velocity during obstacle crossing
Age-related changes in dual task gait performance?
Reaction time to an auditory stimulus is increased (i.e., slower) during gait in older adults but shows no change in younger adults
The attentional demands of obstacle avoidance are increased compared to younger adults
Increased rate of obstacle contact when performing secondary task
Increased rate of error on cognitive task when simultaneously walking
Both pre-crossing and crossing phases are affected by dual-tasks in older adults
*Balance confidence and fear of falling also relate to?
Control of gait
Gait disorders often impact the?
the performance of activities of daily living and are one of the most debilitating consequences of neurologic pathology
Type of gait disorder depends on?
Type and extent of neurologic pathology
Type and extent of impairments
Use of compensatory strategies
How to classify gait disorders?
Patients commonly classified into patient sub-groups to assist in clinical decision-making (e.g., for determining treatment/intervention)
No single approach has universal acceptance
2 common approaches to classifying gait disorders?
Diagnostic
Pathophysiological
2 common approaches to classifying gait disorders?
Diagnostic
Pathophysiological
What is the diagnostic approach?
(traditional)
Grouped on neurologic pathology
Limitation – same pathology, many gait patterns
What is the pathophysiological approach?
(recent)
Describes specific impairments that impair gait (e.g., paresis, spasticity)
Advantage – tailor treatment to specific patients
What is paresis (motor weakness)?
Motor cortex pathology (i.e., upper motor neuron lesion)
Stroke, cerebral palsy
UMN lesion -> decreased descending drive to lower motor neurons -> decreased motor unit recruitment -> weakness
What happens to lower limb muscles during specific portions of the gait cycle?
Lower limb muscles contract both concentrically (i.e., generate movement) and eccentrically (i.e., control movement) during specific portions of the gait cycle
Lower limb paresis can result in?
Inability to generate sufficient propulsive force (e.g., ankle plantarflexor paresis)
Inability to restrain unwanted motion (e.g., ankle dorsiflexor paresis causes the foot to drop after heel strike)
What are the consequences and compensation of Plantar flexor paresis?
Reduced ankle plantarflexion at toe off = flat foot gait
Consequences: reduced limb velocity during swing, reduced step length, reduced walking speed
Compensation: increased hip flexor activity at toe off
What are the consequences and compensation of Dorsiflexor paresis?
Consequences: Reduced ability to control ankle plantarflexion following heel strike = slap foot gait; Reduced ability to shorten the limb during the swing phase = drop foot gait
Compensation: excessive hip and/or knee flexion during swing = steppage gait
What are the consequences and compensation of Knee extensor paresis?
Consequence: Reduced ability to control knee flexion during heel strike
Compensation: Forward trunk lean generates knee extension torque
Increases stability of knee during stance, but high stress on knee structure
What are the consequences and compensation of Hip flexor paresis?
Reduced hip flexor
torque during swing phase
Consequence: reduced knee flexion and limb velocity during swing phase, reduced step length and walking speed
Compensation: circumduction, contralateral vaulting, contralateral trunk lean to help improve foot clearance during swing
What are the consequences and compensation of Hip abductor paresis?
Reduced ability to control frontal plane rotation of pelvis during stance phase
Consequence: contralateral pelvic drop – “Trendelenburg gait”
Compensation: ipsilateral trunk lean to improve foot clearance during swing
What is Trendelenburg gait?
Weak hip abductors cause hip to pop out to side
Paresis of ankle plantarflexors and hip flexors have a major effect on?
walking speed
After a stroke what happens with walking speed?
Correlation between walking speed and ankle plantarflexor moment, hip flexor moment generated at toe off in paretic limb
Ankle plantarflexor moment at toe off is most important variable for determining walking speed
What happens to mobility when someone has Spasticity (hypertonia)? (Lots of info)
Motor cortex pathology (i.e., upper motor neuron lesion)
Stroke, cerebral palsy
UMN lesion -> decreased descending drive to lower motor neurons -> increased LMN stretch reflex excitability -> increased passive resistance to stretch
A spastic lower limb muscle demonstrates increased muscle activity during the portion(s) of the gait cycle in which the muscle is being lengthened (i.e., when the antagonist is contracting)
What is the plantarflexor spastcity stance?
Dorsiflexion during terminal swing -> spastic ankle plantarflexors contract -> flat foot (or forefoot) initial contact rather than a heel strike
Continued contraction of ankle plantarflexors during stance causes the knee to be relatively extended and the foot to be relatively plantarflexed (“equinovarus”)
What is the plantarflexor spastcity swing?
Extended knee in terminal stance impairs toe off (decreased propulsive force)
Continued contraction of ankle plantarflexors during the swing phase
What is the consequence of Extended knee in terminal stance impairs toe off (decreased propulsive force)?
increased demand on hip flexors to propel the limb forward
What is the consequence of Continued contraction of ankle plantarflexors during the swing phase?
Consequence: increased demand on hip and knee flexors to shorten the limb to prevent the foot from contacting the ground (e.g., toe drag)
Some individuals demonstrate phase-dependent effects of locomotor spasticity. What is the swing and stance when this occurs?
Stance – increased lengthening velocity -> increased muscle activity
Swing – increased lengthening velocity -> no increased muscle activity
What happens during hamstring spasticity? What is the consequence of it?
Hip flexion during the swing phase causes spastic hip extensors (knee flexors) to contract, which results in a flexed knee position at initial contact and in stance
Consequence: increased demand on knee extensors to prevent limb from collapsing during stance
What is Rigidity (hypertonia) in mobility?
e.g., hypokinetic basal ganglia (Parkinson’s)
Stiff, slow, shuffling gait
What are the coordination abnormalities of mobility? (Abnormal synergies)
Abnormal synergies (e.g., stroke): stereotyped abnormal patterns of coordinated muscle activity that occur during functional movements of the limbs, resulting in an inability to recruit muscles and control individual joints
Abnormal synergies that occur during gait include?
Extension synergy: contraction of all extensor muscles during the stance phase
Flexion synergy: contraction of all flexor muscles during the swing phase
What is coactviation oof coordination abnormalities?
Coactivation (e.g., stroke, cerebral palsy): Activation of agonist and antagonist muscles around a joint (this is normally minimized during gait)
What is the Coordination abnormalities of Ataxia (e.g., cerebellar degeneration)?
impaired intersegmental coordination
Characteristics of an “ataxic gait” include?
Wide-based and staggering
Irregular stepping pattern
Delays in the timing of specific events during the gait cycle (e.g., peak knee flexion during the swing phase)
Characteristics of an “ataxic gait” include?
Wide-based and staggering
Irregular stepping pattern
Delays in the timing of specific events during the gait cycle (e.g., peak knee flexion during the swing phase)
What are the musculoskeletal impairments of abnormal mobility?
Musculoskeletal impairments often develop secondary to neurological impairments
Ankle plantarflexor contracture: gait similar to plantarflexor spasticity
Knee flexor contracture: gait similar to hamstring spasticity
Hip flexor contracture: forward trunk lean during mid-stance and terminal stance
What are Relevant techniques/modalities for abnormal gait?
LiteGait – Gait trainer
coordination/patternig, CPG activation, strengthening
Power Plate – Vibration trainer -tone, strengthening
Therasuit -patterning, strengthening
What are the Sensory/perceptual impairments?
Somatosensory Deficits
Vestibular Deficits
Visual Deficits
What are Somatosensory Deficits?
Impaired stance-swing transition
Wide-based and staggering gait
What are Vestibular Deficits?
Impaired head stabilization (“blurred vision” during gait)
Slower walking speed and longer double-support time
What are Visual Deficits?
Impaired anticipatory strategies (e.g., obstacle avoidance)
What happens to mobility when someone has a cognitive impairment?
Individuals with a variety of neurological pathologies demonstrate impaired dual-task performance (e.g., stroke, Parkinson’s disease, traumatic brain injury)
Reduced walking speed
Impaired cognitive task performance
Individuals with cognitive impairments (e.g., dementia) demonstrate a slower walking speed and a higher rate of obstacle contact
Reaching and grasping skills are vital to the performance of?
many activities of daily living
Similar to other motor skills, control of reach and grasp involves?
Interaction between nervous system and musculoskeletal system
Contextual interaction between the individual, task, and environment
Key components of reach and grasp skills include?
1) Locate the object
2) Reach for the object
3) Grasp the object
Each of the components of reach and grasp skills involves?
Motor system – coordination eye and head movements (locate), coordinate arm and hand movements (reach and grasp)
Sensory/Perceptual systems – sensory input to locate and identify object; guide arm and hand movements
Each of the components of reach and grasp skills involves?
Motor system – coordination eye and head movements (locate), coordinate arm and hand movements (reach and grasp)
Sensory/Perceptual systems – sensory input to locate and identify object; guide arm and hand movements
What happens during the locating component of reach and grasp? (Possible issues along with it?)
Object location impacts movements required
Reduced ability to coordinate eye and/or head movements to locate objects could impact reach and grasp skills – train it!
Lesions affecting transmission of visual input can lead to a complete loss of portions of the visual field
Lesions affecting processing of visual input can lead to?
Inability to attend to objects in half of the visual field
Visual neglect: lack of awareness of contralateral half of visual field
Visual extinction: unable to simultaneously detect stimuli in each half of the visual field
Impaired ability to plan and control eye movements toward an object can cause what? (Give an example)
(e.g., problems breaking gaze fixation)
What is the reaching for the object component?
Reaching movements are associated with joint coordination to achieve straight-line hand trajectories and bell-shaped velocity profiles (i.e., acceleration then deceleration)
Start slow – pick up speed – then slow back down
The goal of the reach influences the?
velocity profile
What components of reaching for the object affect the ratio of acceleration?
Reach to grasp something – decrease ratio of acceleration time to deceleration time
Pointing – increase ratio of acceleration time to deceleration time
Grasp and manipulate – decrease ratio of acceleration time to deceleration time
Neurologic pathologies that affect movement planning and coordination can impair?
the hand trajectory during a reaching movement (e.g., timing, direction, magnitude)
Multiple neurologic pathologies result in slowed reaction and?
movement times during reaching tasks (e.g., stroke, cerebral palsy, cerebellar degeneration, Parkinson’s Disease)
What is Impaired inter-segmental coordination?
Various neurologic pathologies (especially cerebellar pathologies)
Various neurologic pathologies (especially cerebellar pathologies) result in impaired intersegmental coordination during reaching tasks? (2)
Dysmetria -> undershooting slow movements, overshooting fast movements
Decomposition -> initial vertical (shoulder) and later horizontal (elbow) movement
Individuals who have had a stroke demonstrate abnormal synergies (e.g., upper limb flexor synergy) that result in an impaired ability to?
Perform isolated joint movements
Selectively control individual joints
An impaired ability to perform isolated joint movements explains most of the what?
variance in hand trajectory and end-point error during reaching movements in individuals who have had a stroke.
What is involved in the grasping the object component?
Grip aperture refers to how “open” the hand is
During the reach, we spend MOST of the time opening the hand
Maximum grip aperture occurs ~5/6 into the reach, then closing begins
“Trigger” to signal hand closing seems to be mostly spatial
If uncertainty about object size, grip aperture is increased
What is involved in the grasping the object component?
Grip aperture refers to how “open” the hand is
During the reach, we spend MOST of the time opening the hand
Maximum grip aperture occurs ~5/6 into the reach, then closing begins
“Trigger” to signal hand closing seems to be mostly spatial
If uncertainty about object size, grip aperture is increased
When someone has Parkinson’s Disease what happens when grasping the object?
Associated with slower hand opening (i.e., bradykinesia) and smaller grip aperture during grasping tasks
Medication (levodopa) is associated with improved grasping movement performance (e.g., faster hand opening, wider grip aperture)
When someone has Stroke what happens when grasping the object?
There is evidence that each cerebral hemisphere makes specific contributions to the control of reach and grasp tasks
A study with stroke patients that measured impairments in the limb ipsilateral to the lesion found that (right and left hemispheric lesions)
Right hemispheric lesions: slower movement times and an impaired ability to coordinate reach and grasp movements
Left hemispheric lesions: delayed hand shaping movements and an impaired ability to appropriately scale grip aperture and grip forc
What are the 2 parts included in functional lateralization?
Right and left hemispheres
Two functional “streams” of parallel processing of visual information. What are they?
Dorsal and ventral streams
Dorsal stream (where) contributions to visual system?
Posterior parietal lobe
Sub-conscious processing of spatial information related to object (e.g., position, size, orientation)
Ventral stream (what) contributions to visual system?
Inferior temporal lobe
Conscious perception of specific aspects of an object (e.g., form, shape, colour)
Ventral stream (what) contributions to visual system?
Inferior temporal lobe
Conscious perception of specific aspects of an object (e.g., form, shape, colour)
Evidence for the existence of these two visual streams comes from studies using the?
Ebbinghaus illusion
What is the Ebbinghaus illusion?
Individuals presented with two discs that are the same size, but appear to be different sizes
When asked to estimate the size of each disc (ventral/perception stream) using their thumb and finger, individuals estimate the discs to be different sizes (INCORRECT)
When asked to reach out and grasp each disc (dorsal/action stream), individuals appropriately scale their grip aperture to the size of the discs (CORRECT)
Evidence that posterior parietal lobe is also involved with?
Planning and control of eye movements toward an object
Planning and control of arm and hand movements toward an object
Lesions involving the posterior parietal lobe may impact an individual’s ability to?
Locate and/or track an object
Use spatial information about an object (i.e., size, shape, orientation) to appropriately control the arm movement and hand positioning during reach and grasp tasks
Primate (deafferentated) and human (severe peripheral neuropathy) studies suggest that somatosensory input is not required to?
produce reasonably accurate simple (i.e., single joint) reaching movements
Somatosensory input plays an important role in
The production of complex (i.e., multiple joints) reaching movements
The adaptive (feedback) control of grip force during grasping movements – i.e., mismatch between the expected and actual properties of an object (e.g., heavier than expected, more slippery than expected)
Real life example – adapting when something starts to slip out of your hand
Somatosensory input plays an important role in
The production of complex (i.e., multiple joints) reaching movements
The adaptive (feedback) control of grip force during grasping movements – i.e., mismatch between the expected and actual properties of an object (e.g., heavier than expected, more slippery than expected)
Real life example – adapting when something starts to slip out of your hand
Control mechanisms depend on the nature of the task, what are the 2 components involved in this?
Pointing task
Reach and grasp task
What body parts are involved in the pointing task?
the arm, forearm, and hand are controlled as a single unit
What body parts are involved in the reach and grasp task?
: the arm and forearm are controlled as a single unit (i.e. “reach”), while the hand is controlled separately (i.e., “grasp”)
Although reach and grasp components occur together (i.e., hand is shaped to grasp object while you reach), they are controlled by different brain areas which are?
Reach – brainstem nuclei, indirect descending pathways
Grasp – motor cortex, direct descending pathways
Although reach and grasp components occur together (i.e., hand is shaped to grasp object while you reach), they are controlled by different brain areas which are?
Reach – brainstem nuclei, indirect descending pathways
Grasp – motor cortex, direct descending pathways
Cerebellum has roles in controlling other aspects of reach and grasp task performance, what are they?
Anticipatory (feedforward) postural control strategies that accompany upper limb movement
Control of hand positioning during grasping tasks (especially precision grip)
Anticipatory (feedforward) and reactive (feedback) control of grip force during grasping tasks
It has been suggested that the CNS plans and controls upper limb movements by?
Using end-point coordinates to plan a movement trajectory
Controlling position of hand relative to movement trajectory
Evidence: People tend to move in straight lines with similar velocity profiles
What do Distance programming theories suggest?
the CNS programs movements based on muscle activation required to move the required distance
Movement speed affects the resulting control strategy used are?
Fast movements – correction based on visual feedback not possible (<190 ms); control is solely via initial movement (agonist muscles)
Slow movements – correction based on visual feedback is possible (>260 ms); control is via corrective movements (agonist and antagonist muscles)
What do Location programming theories suggest?
the CNS programs to achieve a predetermined relative level of tension/stiffness between agonist and antagonist (i.e., every location corresponds to a unique balance of tension/stiffness between opposing muscles
Joints like a door on a spring – relative tension portions of the spring determines door position (muscles = springs; door = limb)
Evidence for location programming includes?
deafferented primates and humans with somatosensory loss pointed to targets without visual feedback
Accuracy for trials with and without hand perturbations applied were similar
If distance-programming was used, accuracy during the perturbation trials would have been worse since movement programming would have been based on the perceived distance to move the hand
Practical considerations – Control theories of reach and grasp (lots of info)?
It is likely that both distance and location programming are used to guide upper limb movements, with the strategy used dependent on the task and environmental context
Incorporate different types of movements into reach and grasp training such as?
Fast movements of varying amplitude to improve accuracy of initial, feedforward movements
Slow movements with visual feedback to improve accuracy of corrective, feedback movements
When reaching to point, people generally have a _______ period of deceleration compared to when reaching to grasp an object?
Shorter
Visual _______ refers to the inability to detect stimuli in both the right and left visual field at the same time?
Extinction
