Download GAIT AND LOCOMOTION

HUMAN LOCOMOTION
Irfan
HUMAN LOCOMOTION
“RESTORING GAIT-GETTING PEOPLE
UP
AND RUNNING-IS ONE OF THE CORE
ELEMENTS OF PHYSIOTHERAPY.”
PROFESSOR R. TALLIS
FRONTLINE NOV 2001
2
LOCOMOTION
DEFINED BY THE OXFORD ENGLISH
DICTIONARY AS;
“The act, fact, ability, or power of moving.
3
LOCOMOTION IN HUMANS
• Locomotion is a complex task in humans which has
evolved through the maturation of many differing
but harmoniously interlinked systems of control
within the CNS.
• Although locomotion is a voluntary action once
initiated it does not require conscious direction
under normal circumstances for that individual.
4
LOCOMOTION
CAN BE SEPARATED INTO TWO
COMPONENTS
GAIT
manner of walking or running
study of supraspinal controls.
WALKING automatic pattern or action.
study of Central Pattern
Generators.
5
LOCOMOTION
• Walking is a basic requirement of daily life as
well as one of the most complex.
• The goal of walking is to move forward.
6
Gait
• movements that produces locomotion
• including, for humans:
–
–
–
–
walking,
running,
swimming,
cycling, etc
• characteristics:
– energy-economical, particularly walking
– flexibility to cope with different speeds, terrains etc.
– sophisticated control mechanisms (bipedal gait inherently
unstable)
7
ESSENTIAL REQUIREMENTS
• Progressive Requirement Basic locomotory patterns that move the body in the required
direction.
• Stability Requirement –
The ability to maintain the body up against gravity.
• Adaptive Requirement –
The ability to adapt locomotion to the demands of the
environment.
PROGRESSIVE REQUIREMENT
•
•
•
•
•
•
•
A) Pattern Generation
B) Timing
C) Coordination
D) Initiation
E) Motivation
F) Purpose
G) Altering Locomotion
Pattern generation
• Spinal Cord
The spinal cord is necessary but not sufficient for the expression of even
the most rudementary of stepping behaviour (Bronstein, Brandt and
Woollacott 1996)
• Central Pattern generators
Neuronal networks in the spinal cord capable of producing rhythmical
movements such as walking. (Mackay-Lyons 2002)
Produce stereotyped locomotor patterns
Each limb has its own pattern generator ( Leonard 1998)
• Descending tracts
Provide modulation to the spinal circuitry during locomotion
Descending Tracts which system?
• Tops up excitation to the extensor motor neurons during
stance phase?
• Tops up excitation to the flexor motor neurone pool
during swing phase?
• Is excitatory during stance and swing phase and
generally enhances postural tone?
• Is involved in more complex walking.
Timing
• Somatosensory System
– input comes from afferent receptors in muscles tendons skin.
– Gives us information on orientation of body parts, movement of body parts,
muscle tension, orientation of support surfaces and body with reference to support
surface.
• Visual System
visual clues help in alignment, step frequency and even step length. Gives us
movement relative to environment.
• Cerebellum
Timing cannot be considered without considering the cerebellum
Co-ordination
Cerebellum
• receives a huge amount of information during locomotion.
• If information is unexpected the olive is able to modify
walking via the reticulospinal, vestibulospinal and rubrospinal
tracts.
• The cerebellum does not initiate walking but is more involved
in the modulation of CPGs where necessary.
• In order to learn to cope with a variety of of complex environments there is
a need to be exposed to different situations to enable the cerebellum to
develop strategies.
• It is also thought that the cerebellum can alter step cycle according to
visual information received.
• The overall function of the cerebellum is improved inter and inter limb coordination
Initiation
Basal ganglia
• Thought to be involved in initiation and termination of activity
• processing of sensory stimuli
• attaching emotional and situational significance to sensory input
Reticulospinal system
• Involved in increasing the sensitivity of the CPGs via the release of
glutamate. Therefore has a role in initiation
Motivation
• Limbic System
Involved in core emotions / motivations (eg fight or flight reactions)
Purpose
Cortex
• Known functions include :
– cognitive aspects of motor control
– visuomotor co-ordination
– motor planning
• Cortical neurons
– often fire before the onset of movement
– typically fire phasically during locomotion
– increase intensity of activity during swing phase.
Altering locomotion
Cortex
• During normal level path unobstructed locomotion the cortical level
involvement is minimal: when the animal is required to go over barriers in
the travel path or is constrained to place its paws on a specific location
(such as rungs of a ladder) the intensity (but not the phase) of the activity
in the corticospinal tract increases dramatically (Bronstein et al 2003)
Altering locomotion
Central pattern generators
• It is thought highly likely that there are separate networks for each limb
and that these can be segmentalised and recombined for different types of
locomotion under differing modulatory and presynaptic controls (Beheshti
1997)
• Extensive “sculpting “ of CPG networks by using different combinations of
basic cellular and synaptic processes creates a variety of alternative
functional circuits, each with the capacity to generate a distinct motor
pattern within a family of function-related behaviours (MacKay-Lyons
2002)
STABILITY REQUIREMENT
• A) Modulation of Postural tone
• B) Alignment
A) Modulation of postural tone
Midpontine neuronal structures
– caudal tegmental field (ventral and dorsal)
– stimulation of VTF --> increase level of extensor muscle tone
– stimulation of DTF --> reduces extensor muscle tone
Cerebellum
– provides regulation of postural control appropriate to the phase of
walking
A) Modulation of postural tone
Reticulospinal system
– postural tone is created and sustained during locomotion by a balance
of the inhibitory effects on stretch reflexes (lateral reticulospinal ) and
the facilitatory effects on the extensor tone ( medial reticulospinal )
– Receives input from many sources and fires in all phases of locomotion.
B) Alignment
spinal cord
vestibular system
visual system
joint receptors
muscle spindles
golgi tendon organs
cutaneous
ADAPTIVE REQUIRMENT
• A) Reactive Balance Strategies
• B) Proactive Balance Strategies
Reactive balance Strategies
• Ongoing modification
• The three sensory systems contribute to
reactive balance strategies during walking.
• Cerebellum plays a crucial role in reactive
balance strategies
Proactive Balance Strategies
• Primarily mediated by the visual system which is used to identify potential
obstacles in the environment and then predict the destabilising effect of
performing simultaneous tasks
(Shumway-Cook, Woollacott 2002)
• Avoidance Strategy
– change foot placement, increase ground clearance, change direction or stop)
• Accommodation Strategy
– Locomotion is adapted over a longer time.(e.g. reduced step length when
walking on ice)
(Shumway-Cook, Woollacott 2002)
Note:
•Alternating periods of double and single support
•About 70:30 split between single and double support in normal
walking
27