perspectives on walking in an environment
DESCRIPTION
BM 526 Project. Perspectives on Walking in an Environment. Işık Barış Fidaner. BM 526 Project. ?. Human. Walking. Environment. Gait. Locomotion. A walking human being. ____ Central Nervous System. Body. Soul. Walking - Bird’s eye view. Central Nervous System (CNS). output - PowerPoint PPT PresentationTRANSCRIPT
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Perspectives on Walkingin an Environment
Işık Barış Fidaner
BM 526 Project
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BM 526 Project
HumanWalkingEnvironment
?
LocomotionGait
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A walkinghuman being
Body Soul____Central Nervous System
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Walking - Bird’s eye view
Central Nervous System (CNS)
Body situated in the Environment
output channels
input channels
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Outputs of CNS
• Motor signals – Contract muscles to move forward while
controlling the body posture• Auxilliary signals– Movements to enhance the input – Lifting head to see your path
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Inputs to the CNS
• Visual– Spatiotemporal awareness to predict near future
• Audio– Musical sounds to regulate the sense of time
• External forces– Ground reactions to optimize energy consumption
• Balance– Anxiety, fear of falling to increase posture control
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Visual awareness
• Three phases of locomotion:1.Perception and processing
of the visual information (pp phase)
2.Execute the movement(motor phase)
3.Examine the consequences and adapt your behavior
(Meschner 2008)
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Visual awareness• Every pp phase must end
before corresponding motor phase begins
• Perceptions are buffered in short-term memory
(Meschner 2008)
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Visual awareness
• Locomotion is a complex variable behavioral contingency
• Shares same structure with other activities that require “thinking ahead” such as– Reading out loud– Dancing– Foraging
(Meschner 2008)
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Effect of music and rhythm
• Effect of music vs. raw metronome ranging through 50 to 190 BPM on walking vs. tapping finger, in terms of
• Synchronization– Adapting walking tempo to the music
• Spatialization– Effect on walking style, speed, step length etc.
(Styns et al. 2007)
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Effect of music and rhythm• Synchronization– Better sync in tapping– An optimum musical tempo exists
that maximizes sync in walking(near 120 BPM)
• Spatialization– Music makes us walk faster,
compared to raw metronome at same tempo
– An optimum walking tempo exists that maximizes step size(also near 120 BPM) (Styns et al. 2007)
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Resonance behavior• Step size resonates with
walking tempo • According to– fundamental frequency– damping factor
• 2 Hz (=120 BPM) resonance frequency in the long-term energy spectrum(Dougall et al. 2005)
• Spontaneous or self-selected tempo of human locomotion (Styns et al. 2007)
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External forces• Ground reaction force acts on
our body through feet• Body force acts on the ground
• GRF on a solid ground:– GRF does not vary with time– Muscles react to preserve body
posture• GRF on a flexible ground:
– Oscillating in vertical, anterior-posterior or lateral components
– Walking style and tempo adapts to the time dynamics of GRF
(Racic et al. May 2009)
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The Millennium Bridge• Opening ceremony in London, June 2000
(Racic et al. May 2009)
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The Millennium Bridge• Lateral oscillation up to 7 cm!• Spontaneous walking tempo– Vertical / Anterior: 2 Hz– Lateral component: 1 Hz
• Same with the bridge’s natural frequency of lateral oscillation!
• People synchronized their tempo to each other and the bridge, forming a positive feedback loop
(Racic et al. May 2009)
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External forces• Force plates– Records single steps
• Instrumented treadmill– Records a sequence of steps– Vertical and lateral GRF
increase with speed– Anterior GRF reaches a
maximum at 5.6 kmph (spontaneous speed)
• Time / frequency domain• Deterministic / stochastic
models(Racic et al. May 2009)
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Effect of anxiety, fear of falling
• Old and young subjects• Each stands on the platform– Higher or lower platform– At the edge or at the middle
• Recorded for each trial:– Galvanic skin conductance (GSC) to infer anxiety– Body center of mass (COM) and center of
pressure (COP) to estimate motor behavior
(Brown et al. 2006)
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Effect of anxiety, fear of falling
• Standing on the edge, or higher platforms caused:a) Increased GSC (anxiety)b) Decreased mean COM and
COP in anterior direction(leaning backwards)
c) Decreased stdev of COP and COM (more control)d) Increase in mean power frequency of COP
• (c) and (d) Increased stiffness in ankle joint
(Brown et al. 2006)
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Effect of anxiety, fear of falling
• No significant change dueto age difference
• Standing near height or edges causes anxiety
• Anxiety causes increasedcontrol on body posture
• Contrary to previous work, fear may be beneficial to protect one’s body from falling
(Brown et al. 2006)
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Conclusion:
• Buffering, spatiotemporal awareness• Resonance in step size,
optimum tempo of walking• Synchronize to structure,
positive feedback loop• Anxiety, fear of falling,
increased control
Behavioral scienceMusicology
Civil engineeringPsychology
….?
Biomechanics
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Conclusion:
• Different perspectives, separate disciplines
• Common object of study• Multidisciplinary studies
of walking
Human
Behavioral scienceMusicology
Civil engineeringPsychology
….?
Biomechanics
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Perspectives on Walkingin an Environment
Işık Barış Fidaner
BM 526 Project