1. Perspectives on Walking in an Environment Işık Barış Fidaner BM 526 Project

2. Human Walking Environment ? Locomotion Gait

3. A walking human being Body Soul ____ Central Nervous System

4. Walking - Bird’s eye view Central Nervous System (CNS) Body situated in the Environment output channels input channels

5. 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

6. 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

7. 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)

8. Visual awareness Every pp phase must end before corresponding motor phase begins Perceptions are buffered in short-term memory (Meschner 2008)

9. 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)

10. 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)

11. 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)

12. 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)

13. 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)

14. The Millennium Bridge Opening ceremony in London, June 2000 (Racic et al. May 2009)

15. 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)

16. 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)

17. 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)

18. 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)

19. Effect of anxiety, fear of falling No significant change due to age difference Standing near height or edges causes anxiety Anxiety causes increased control on body posture Contrary to previous work, fear may be beneficial to protect one’s body from falling (Brown et al. 2006)

20. 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 science Musicology Civil engineering Psychology ….? Biomechanics

21. Conclusion: Different perspectives, separate disciplines Common object of study Multidisciplinary studies of walking Human Behavioral science Musicology Civil engineering Psychology ….? Biomechanics

22. Perspectives on Walking in an Environment Işık Barış Fidaner BM 526 Project