Walking: History
Taub & Berman (1968):
* constraint induced or forced use. “forced use” of a sensory deprived animal by constraining the other limb.
* Conclusion: rehabilitate by engaging the limb in activities
Fossberg (1977):
* muscles of cats with transected spinal cords have the same muscle activity in normal cats. Cats are recruiting motor units.
* conclusion: lower limb activity can be activated under cetain situations.
Late 1800s: Sherrington Neural Control of Walking
* severed SC: hind limbs continued alternating movements
* conclusion: do not need influence of higher brain centers to walk
* monkeys: eliminated sensory info and resulted in rhythmic walking pattern
* Conclusion: removing sensory input on both sides resulting in pattern remains
*Motor task that involves…
- strength sufficient for the support of body weight: GRF. Stability before mobility.
- Stable enough to compensate for balance shifts. Maturation of the balance system.
- Adaptations to uneven surfaces.
Prenatal to postnatal stepping
- infants kick or step in utero
- at birth, elicit stepping pattern
- disappears at 2 months
-reappers at the start of walking
-continue kicking in supine
-same pattern in standing
Progression from stability to mobility
- standing with assistance
- standing alone
- mobility with 2 hands
- independent mobility
Gait is there an average time frame for emergence?
On average, infants begin to walk w/o assistance from 9-15 mo
* large time frame
* motor delay in gait is at 18 mo
Myelination occurs from caudal (head) to distal (legs)-at 9 months reaches the lower legs
* critical factor in gait emergence
Development of gait factors 1st yr
Components are developed from birth to 12 mo
* locomotion pattern (CPG): innate
* postural control in standing (at tabletop)
* motivation and navigation toward a distant object
* standing on one leg: stance phase stability (cruising)
* high guard posture
Components necessary for gait emergence
Motor production
* Stabilization
* Force or power
Sensory Apparatus
* vision
* vestibular
* somatosensory: tacile/pressure & proprioception
Sensory Contributions
Need all 3 to walk independently w/o thinking
Vision
* balance, steering, and avoiding obstacles
* visial optic flow
* stabilizing head: vision vertical
Vestibular system
* stabilization of head
* postural control
Somatosensory/proprioception
* feedback of body awareness
* tacile feedback from ground
First steps
- high step pattern
- wide BOS
- no push off
- knees flexed at stance
- upper limbs: no arm swing and high guard
- short steps
- synchronized patterns in legs
- waddling pattern
Walking Development
Development from the immature pattern of primary stepping
Gradual emergency of normal gait
* the joints demonstate increasinf complexity
* “synchronization”=moving simultaneously
* to “dissociation”=moving joints individually
* Syncrhonization (4.5 mo before first steps) –>dissociation (4.5 mo later after first steps)
Controlled fall: infants are leaning forward when walking, forward COM
Progression of gait
Ability to control equilibrium responses (postural control)
* falls forward with hands extended
* falls backwards on bottom
Ability to control single limb stance (32% at one year)
* able to change directions 15-18 mo
* heel strike at 2 years of age
* mature at 3 years of age with small improvements until 7 years if age
* COM stabalizes 7 year years of age
Other skills associated with walking
- Avoiding obstacles: stepping over objects, walking around objects, vision (downward gaze)
- protective responses: parachute and protective extension
- distance: knowing how far one travels
- navigation: moving from place to place using memory and landmarks
- cognitive processing: dual task emerging
Sensory contributions part 2
- stretching of hip flexors
- step length, appropriate frequency
- contributions of loading the limbs
-pressure sensors
-practice standing for long periods
The aging human: muscular system
- loss of muscle mass after age 60
- especially type II fibers
- may lead to sarcopenia (loss of muscle mass) in the elderly (increased protein breakdown, decrease protein synthesis)
- muscle changes to fat when there is disuse
- USE IT OR LOSE IT
*Skeletal system in older adult
- loss of vertebral body height (especially T/S with forward flexed posture)
- increased risk of fracture
The loss of tactile or cutaneous receptors
Disease
* type II diabetes with sensory nerve fiber loss: loss of tactile sensation
* peripheral nerve damage
* stroke
Aging
* loss of fine touch sensation
* loss of heat and cold sensation
* loss of pain perception
Loss of visual system
Loss of visual acuity:
* reading: accommodation or the lens does not bend to accommodste light
* distance
Diseases
* type II diabetes: retinal damage
* macular degeneration
* glaucoma
Vestibular System disuse in the elderly
Vestibular system is a use it or lose it system
Purpose:
* Acceleration (forward/up/down)
* head rotation: speed and movement
Elderly show a loss of:
* quick acceleration in movement (constant speed: no variation)
* cervical rotation
Maintain:
* forward head posture
* forward trunk posture
*Dulled response to protect their head
Protective responses
* reducsed ankle and hip strategy
* reduced speed of protective arm extension–parachute response (infant
* 20-30% lead injuries to the head
*Gait speed & associated with dementia
- gait can slow down cognitive decline (O2 & glucose)
- dementia causes decreased gait speed
- ppl with cognitive decline have decreased gait speed
- with dementia you lose the feeling of wanting to go for a walk
