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Effects of optic flow on spontaneous overground walk-to-run transition

Kristof De Smet (UGent) , Philippe Malcolm (UGent) , Veerle Segers (UGent) , Matthieu Lenoir (UGent) and Dirk De Clercq (UGent)
(2009) Experimental Brain Research. 193(4). p.501-508
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Abstract
Perturbations of optic flow can induce changes in walking speed since subjects modulate their speed with respect to the speed perceived from optic flow. The purpose of this study was to examine the effects of optic flow on steady-state as well as on non steady-state locomotion, i.e. on spontaneous overground walk-to-run transitions (WRT) during which subjects were able to accelerate in their preferred way. In this experiment, while subjects moved along a specially constructed hallway, a series of stripes projected on the side walls and ceiling were made to move backward (against the locomotion direction) at an absolute speed of -2 m s(-1) (condition B), or to move forward at an absolute speed of +2 m s(-1) (condition F), or to remain stationary (condition C). While condition B and condition F entailed a decrease and an increase in preferred walking speed, respectively, the spatiotemporal characteristics of the spontaneous walking acceleration prior to reaching WRT were not influenced by modified visual information. However, backward moving stripes induced a smaller speed increase when making the actual transition to running. As such, running speeds after making the WRT were lower in condition B. These results indicate that the walking acceleration prior to reaching the WRT is more robust against visual perturbations compared to walking at preferred walking speed. This could be due to a higher contribution from spinal control during the walking acceleration phase. However, the finding that subjects started to run at a lower running speed when experiencing an approaching optic flow faster than locomotion speed shows that the actual realization of the WRT is not totally independent of external cues.
Keywords
Optic flow, Human gait, Spatiotemporal characteristics, Walk-to-run transition, Overground

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Chicago
De Smet, Kristof, Philippe Malcolm, Veerle Segers, Matthieu Lenoir, and Dirk De Clercq. 2009. “Effects of Optic Flow on Spontaneous Overground Walk-to-run Transition.” Experimental Brain Research 193 (4): 501–508.
APA
De Smet, Kristof, Malcolm, P., Segers, V., Lenoir, M., & De Clercq, D. (2009). Effects of optic flow on spontaneous overground walk-to-run transition. Experimental Brain Research, 193(4), 501–508.
Vancouver
1.
De Smet K, Malcolm P, Segers V, Lenoir M, De Clercq D. Effects of optic flow on spontaneous overground walk-to-run transition. Experimental Brain Research. 2009;193(4):501–8.
MLA
De Smet, Kristof, Philippe Malcolm, Veerle Segers, et al. “Effects of Optic Flow on Spontaneous Overground Walk-to-run Transition.” Experimental Brain Research 193.4 (2009): 501–508. Print.
@article{664113,
  abstract     = {Perturbations of optic flow can induce changes in walking speed since subjects modulate their speed with respect to the speed perceived from optic flow. The purpose of this study was to examine the effects of optic flow on steady-state as well as on non steady-state locomotion, i.e. on spontaneous overground walk-to-run transitions (WRT) during which subjects were able to accelerate in their preferred way. In this experiment, while subjects moved along a specially constructed hallway, a series of stripes projected on the side walls and ceiling were made to move backward (against the locomotion direction) at an absolute speed of -2 m s(-1) (condition B), or to move forward at an absolute speed of +2 m s(-1) (condition F), or to remain stationary (condition C). While condition B and condition F entailed a decrease and an increase in preferred walking speed, respectively, the spatiotemporal characteristics of the spontaneous walking acceleration prior to reaching WRT were not influenced by modified visual information. However, backward moving stripes induced a smaller speed increase when making the actual transition to running. As such, running speeds after making the WRT were lower in condition B. These results indicate that the walking acceleration prior to reaching the WRT is more robust against visual perturbations compared to walking at preferred walking speed. This could be due to a higher contribution from spinal control during the walking acceleration phase. However, the finding that subjects started to run at a lower running speed when experiencing an approaching optic flow faster than locomotion speed shows that the actual realization of the WRT is not totally independent of external cues.},
  author       = {De Smet, Kristof and Malcolm, Philippe and Segers, Veerle and Lenoir, Matthieu and De Clercq, Dirk},
  issn         = {0014-4819},
  journal      = {Experimental Brain Research},
  language     = {eng},
  number       = {4},
  pages        = {501--508},
  title        = {Effects of optic flow on spontaneous overground walk-to-run transition},
  url          = {http://dx.doi.org/10.1007/s00221-008-1648-6},
  volume       = {193},
  year         = {2009},
}

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