Article

Humans use visual optic flow to regulate average walking speed. Among many
possible strategies available, healthy humans walking on motorized treadmills
allow fluctuations in stride length (Ln) and stride time (Tn) to persist across
multiple consecutive strides, but rapidly correct deviations in stride speed
(Sn=Ln/Tn) at each successive stride, n. Several experiments verified this
stepping strategy when participants walked with no optic flow. This study
determined how removing or systematically altering optic flow influenced peoples'
stride-to-stride stepping control strategies. Participants walked on a treadmill
with a virtual reality (VR) scene projected onto a 3m tall, 180 degrees
semi-cylindrical screen in front of the treadmill. Five conditions were tested:
blank screen ("BLANK"), static scene ("STATIC"), or moving scene with optic flow
speed slower than ("SLOW"), matched to ("MATCH"), or faster than ("FAST") walking
speed. Participants took shorter and faster strides and demonstrated increased
stepping variability during the BLANK condition compared to the other conditions.
Thus, when visual information was removed, individuals appeared to walk more
cautiously. Optic flow influenced both how quickly humans corrected stride speed
deviations and how successful they were at enacting this strategy to try to
maintain approximately constant speed at each stride.
These results were
consistent with Weber's law: healthy adults more-rapidly corrected stride speed
deviations in a no optic flow condition (the lower intensity stimuli) compared to
contexts with non-zero optic flow. These results demonstrate how the temporal
characteristics of optic flow influence ability to correct speed fluctuations
during walking.
CI - Copyright (c) 2017 Elsevier B.V. All rights reserved.

Langue : ANGLAIS