Control of normal mobility and age related changes in mobility Flashcards
What is mobility?
Gait, transfers, bed mobility, stair walking
What are essential requirements for successful locomotion?
Progression: need to initiate and terminate locomotion and move body in desired direction.
Postural control: maintain body upright and stable in a dynamic environment
Adaptation: alter gait in response to dynamic environment and changing goals
What are phases of gait?
Stance: generate horizontal forces so we can keep moving, generate vertical forces to support body against gravity.
Swing: advance swing limb, position swing limb so that it’s ready to accept weight, avoid contact with ground and obstacles
What are descriptions of human gait cycle?
Symmetrical alternating gait patter: provides greatest dynamic stability with minimal control demands
Phase lag of 0.5: one limb initiates step cycle as other limb reaches midpoint of its own cycle
T/F: 60% of cycle is spent in stance and 40% in swing?
True.
of the 60%, 20 is spent in double limb stance
What are temporal and distance factors with gait?
Velocity: calculated from 10 m walk
Step length: allow you to identify asymmetry in gait
Step frequency: number of steps/min
Stride length: distance from one heel strike to ground contact with same foot
What is ambulation speed for normal young adults?
1.46 m/sec (3.26 mph)
Mean cadence of 1.9 steps/sec (112.5 steps/min)
Mean step length of 76.3 cm (30.05 in)
What are characteristics of gait velocity?
Step rates appear to be related to trying to minimize energy output.
Swing phase does not require much energy expenditure.
Self-select gait speed that minimizes energy expenditure
Slower speeds=increased variability
What are control mechanisms for gait?
Locomotion research on animals: CPG
Spinal generators produce stereotyped locomotor patterns with limited adaptive capabilities
Sensory info from periphery and descending control are essential
What is decorticate preparation?
dynamic stability
initiates reasonably normal goal directed behavior in neonatally decorticate animals.
No fine tuning done.
What is decerebrate preparation?
Improved coordination of activation patterns, compared to spinal preparation.
Weight support
Active propulsion
What is spinal preparation?
Near normal inter/intra limb rhythmic activation patterns.
Functionally modulates reflex action.
Executes other rhythmic movements concurrently
What is reactive equilibrium control?
Used in response to perturbation.
Involves somatosensory, vestibular, visual systems
How does somatosensory system play part in reactive equilibrium control?
Recovery from balance threats take place in distal to proximal sequence.
Strategy depends on timing of perturbation.
Trip early swing: increase flexion of swing limb and early heel rise of stance
Trip late in swing: lowering strategy with PF of swing foot to reach for ground.
T/F: if there is trip late in swing the body uses a raising strategy?
False: uses lowering strategy. PF of swing foot reaches for ground
T/F: if there is trip in early swing the body uses a raising strategy?
True: flexion of swing limb, early heel rise of stance limb
How does vision and vestibular system play role in reactive equilibrium control?
Vision: Helps determine speed, alignment of body to gravity
Vestibular: stabilizes head, stabilizes gaze during head movement, top down organization
What is proactive equilibrium control?
Vision used to identify and avoid/accommodate for obstacles.
We visually sample terrain 20% of time, with uneven surfaces this increases to 30%
Prediction, based on past experiences helps us proactively
How is gait initiated?
Muscles relax (gastroc and soleus)
Appearance of falling forward
Shift in COP: first movement is posterior to lateral toward swing limb
Steady velocity reached within 1-3 steps
What are turning strategies?
Spin turn: turn to right with foot forward, body spins around right foot
Step turn: turn to left with right foot forward. Weight is shifted to right foot so hip can externally rotate. Weight transfers to left foot.
Which turning strategy is more stable?
Step turn
T/F: four out of five falls occur during stair descent?
True
What are components of stair ascent and descent?
Ascent: differs from walking because forces needed are 2X greater than in level gait, knee extensors generate most of energy to move forward, greatest instability comes with contralateral toe off
Descent: key is eccentric contractions
What are adaptations to stair walking patterns?
Foot clearance and placement are critical.
Success largely depends on using visual cues.
With visual info about step height, we can program movements
What are essential characteristics of sitting to standing?
Generate sufficient torque needed to rise (progression)
Ensuring stability by moving COM from one BOS defined solely by feet (stability)
Ability to modify movements strategies depending on environmental constraints
What are phases of sit to stand?
1) weight shift or flexion momentum: flexion of trunk, body is stable, COM is moving within BOS of chair seat
2) Beginning of lift: horizontal and vertical motion of body must be coordinated, unstable phase
3) Lift or extension: extension of hips and knees, movement is vertical
4) Stabilization: body stability is achieved
What are sit to stand strategies?
Momentum transfer strategy: 4 phases listed above
Zero momentum strategy: flexing trunk to put COM over feet, more stability but need more force of LE
Armrests: assists in both stability and force generation, but not always an option
How do elderly use proactive adaptation?
Visual sampling: monitor terrain more
Implementation time: more difficulty monitoring step length
Obstacle avoidance: use slower approach speed, slower crossing speed, and shorter step length
How do elderly use reactive adaptation?
Trips (account for 1/3-1/2 of falls): need quick reactions of hip flexors of swing leg and PF of stance leg
Slips (account for 1/3 of falls): delayed and weaker muscle responses (rectus, abdominals, tib ant) result in trips during recovery from slips
What are gait changes in balance impaired older adults?
Walking patterns: decreased stride length and walking speed
Stride time: increased variability
Step width: increased (plus increased variability)
What are possible impairments causing age related gait changes?
Standing balance Cognition Increased fear of falling Sensory impairments Muscle weakness
What are effects of exercise programs on gait function in the elderly?
Exercise program can be effective in improving gait.
Programs have included intense PT, high intensity strengthening and aerobics
Greatest changes seen in those with slowest velocities prior to training
What are age related changes to mobility in elderly?
Gait initiation: try to keep COP and COG more closely aligned than young adults, minimizing unsteadiness
Stairs: walk with larger foot clearance in descending stairs
Sit to stand: increase flexion of trunk and have higher movement velocity, forces used are lower, overall time taken to rise is longer
