neural control of gait Flashcards
Requirements of functional walking in the ‘Real World’
- walking requires the integration of motor and cognitive functions; such as attention, memory and planning (Lord & Rochester, 2007)
- Adaptable to meet the needs of the individual, environment and task
- Have minimum energy expenditure and movement time
Non-hierarchical tripartite control system (Zehr and Duysens, 2004)
- Supraspinal input from cortical and sub-cortical structures
- Spinal central pattern generators (CPG)
- Sensory feedback, primarily somatosensory (including receptors in muscles, tendons, joints and skin) but also vestibular and visual input
how the Non-hierarchical tripartite control system (Zehr and Duysens, 2004) works
- cortical & subcortical input initates terminates that movement
- CPGs then drive limbs movement
- sensory feedback augments motor control in order to adapt requirements of gait at that time
Central pattern generators (CPGs)
- CPGs are neuronal networks that produce rhythmic activation of muscles that control the limbs in the absence of sensory input
(Klarner & Zehr, 2018; Mackay-Lyons, 2002) - Locomotion is initiated and terminated by descending commands initiated by the cortex delegating motor commands to the CPGs controlling the upper and lower limbs
- Peripheral feedback informs the nervous system of local conditions to shape CPG output (i.e. stepping up a kerb). This facilitates the ability to modify limb movements whilst maintaining balance and posture
common pathological gait problems
- Antalgic Gait- limp
- Lateral Trunk Flexion on stance (Trendelenburg)
- Functional Leg-Length Discrepancy (hip hiking/hitching/circumduction on swing)
- Increased Base of Support / Wide Base Walk
- Inadequate Dorsiflexion/Footdrop/Lack of Heel Strike
- Excessive Knee
- Extension/Hyperextension in Stance
- Increased lateral weight shift
antalgic
- Reduced weight bearing / time spent on affected leg
- Stance phase shortened on affected side
- Corresponding increase in stance on unaffected side
Lateral Trunk Flexion (Trendelenburg gait)
- Trunk leans toward stance leg
- Shifts CoG nearer to fulcrum of stance hip
- Usually unilateral
- Bilateral = waddling gait
- Due to: Hip abductor weakness painful hip or leg-length discrepancy
- n.b. not the same as ‘hip hitching’
Functional Leg Discrepancy
- Swing leg appears / is functionally longer than stance leg
- Result of reduced AROM or PROM at the hip, knee or ankle
Common compensations:
* Circumduction, hip hiking/hitching
* Vaulting to assist toe clearance during the swing phase. Observed by plantar flexion of the contralateral ankle during single-limb support
Increased Base of Support / Wide Base Walk
- Normal walking base: 5-10 cm
- Common neurological causes = Instability
- Cerebellar ataxia
- Proprioception deficits
- Vestibular deficits
- Reduced balance
Inadequate Dorsiflexion/Footdrop/Lack of Heel Strike
Stance phase: Foot slap
Swing phase: Toe drag or tripping
Potential causes / hypotheses:
* Weak Tibialis Ant.
* Increased tone plantar flexors (neural)
* Contracture / decreased length plantar flexors
Excessive Knee Extension/Hyperextension in stance
Common causes:
* Increased tone quadriceps
* Weakness IR quadriceps
* Weak EOR hamstrings
Increased lateral weight shift
- Unable to stabilise medially (e.g. glut med) and therefore unable to control weight transfer during weight acceptance on stance leg
- Can occur to both affected and less affected side
Measuring Gait Capacity
- speed- 10meter walk test
- endurance- 2,6,12 minute walk test (sub-maximal test of aerobic capacity/ endurance)
- independence- functional ambulation catergories
