Control of normal mobility and age related changes in mobility

Question 1

What is mobility?

Answer 1

Gait, transfers, bed mobility, stair walking

Question 2

What are essential requirements for successful locomotion?

Answer 2

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

Question 3

What are phases of gait?

Answer 3

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

Question 4

What are descriptions of human gait cycle?

Answer 4

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

Question 5

T/F: 60% of cycle is spent in stance and 40% in swing?

Answer 5

True.

of the 60%, 20 is spent in double limb stance

Question 6

What are temporal and distance factors with gait?

Answer 6

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

Question 7

What is ambulation speed for normal young adults?

Answer 7

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)

Question 8

What are characteristics of gait velocity?

Answer 8

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

Question 9

What are control mechanisms for gait?

Answer 9

Locomotion research on animals: CPG
Spinal generators produce stereotyped locomotor patterns with limited adaptive capabilities
Sensory info from periphery and descending control are essential

Question 10

What is decorticate preparation?

Answer 10

dynamic stability
initiates reasonably normal goal directed behavior in neonatally decorticate animals.
No fine tuning done.

Question 11

What is decerebrate preparation?

Answer 11

Improved coordination of activation patterns, compared to spinal preparation.
Weight support
Active propulsion

Question 12

What is spinal preparation?

Answer 12

Near normal inter/intra limb rhythmic activation patterns.
Functionally modulates reflex action.
Executes other rhythmic movements concurrently

Question 13

What is reactive equilibrium control?

Answer 13

Used in response to perturbation.

Involves somatosensory, vestibular, visual systems

Question 14

How does somatosensory system play part in reactive equilibrium control?

Answer 14

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.

Question 15

T/F: if there is trip late in swing the body uses a raising strategy?

Answer 15

False: uses lowering strategy. PF of swing foot reaches for ground

Question 16

T/F: if there is trip in early swing the body uses a raising strategy?

Answer 16

True: flexion of swing limb, early heel rise of stance limb

Question 17

How does vision and vestibular system play role in reactive equilibrium control?

Answer 17

Vision: Helps determine speed, alignment of body to gravity

Vestibular: stabilizes head, stabilizes gaze during head movement, top down organization

Question 18

What is proactive equilibrium control?

Answer 18

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

Question 19

How is gait initiated?

Answer 19

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

Question 20

What are turning strategies?

Answer 20

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.

Question 21

Which turning strategy is more stable?

Answer 21

Step turn

Question 22

T/F: four out of five falls occur during stair descent?

Answer 22

True

Question 23

What are components of stair ascent and descent?

Answer 23

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

Question 24

What are adaptations to stair walking patterns?

Answer 24

Foot clearance and placement are critical.
Success largely depends on using visual cues.
With visual info about step height, we can program movements

Question 25

What are essential characteristics of sitting to standing?

Answer 25

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

Question 26

What are phases of sit to stand?

Answer 26

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

Question 27

What are sit to stand strategies?

Answer 27

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

Question 28

How do elderly use proactive adaptation?

Answer 28

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

Question 29

How do elderly use reactive adaptation?

Answer 29

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

Question 30

What are gait changes in balance impaired older adults?

Answer 30

Walking patterns: decreased stride length and walking speed
Stride time: increased variability
Step width: increased (plus increased variability)

Question 31

What are possible impairments causing age related gait changes?

Answer 31

Standing balance
Cognition
Increased fear of falling
Sensory impairments
Muscle weakness

Question 32

What are effects of exercise programs on gait function in the elderly?

Answer 32

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

Question 33

What are age related changes to mobility in elderly?

Answer 33

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