Biomedical Engineering Reference
In-Depth Information
We investigated the effects of walking surface and visual feedback on basic gait
parameters and on the movement of the head in an integrated manner. This experi-
ment was conducted using a circular treadmill (CTM) at the MPI (see Fig.
6.2
and
caption for additional details). The effect of surface stiffness on gait characteristics
was controlled for by having participants walk in place and walk through space on the
same treadmill surface. Specifically, overground walking consisted of simply leading
the participant around on the stationary disc using the motorized handlebar. Station-
ary (“treadmill”) walking consisted of walking in place on the moving disc without
moving through space. If the difference in surface is a major determinant in caus-
ing the previously reported differences between overground and treadmill walking,
then we would expect this difference to disappear in this experiment. Visual feed-
back was also manipulated by having people walk while wearing a blindfold or not.
Walking speeds were controlled by moving either the disc or the handlebar at one of
four velocities (see caption of Fig.
6.3
), for the stationary and walking through space
conditions, respectively. The results demonstrated that there were indeed very few
differences observed between the gait parameters measured during stationary walk-
ing versus overground walking. Step length (Fig.
6.3
a) and walk ratio (Fig.
6.3
c) were
comparable across walking speeds. The exception was that for the slowest walking
speed (0.7m/s), the overground walking condition produced larger step lengths and
walk ratios in comparison to stationary walking. This particular effect is consistent
with previous findings that reflected higher walk ratios at slower overground walk-
ing speeds (e.g., [
90
]). This higher walk ratio at the slowest walking speed is likely
due to an increase in step length given that step frequency was virtually identical
across all conditions (see Fig.
6.3
b). Results also demonstrated that during stationary
walking there was a significant decrease in head sway (Fig.
6.3
d) and head bounce
(Fig.
6.3
e) compared to overground walking. As for the effect of vision, the results
demonstrated that, irrespective of the walking condition, step length and frequency
were unaffected by the presence or absence of visual feedback. This is in contrast
with above-described studies that did find significant decreases in both step length
and frequency [
50
,
74
].
In summary, with respect to basic gait parameters, there were hardly any differ-
ences between overground walking and stationary walking. Most notable was the
complete absence of an effect on step frequency, which has typically been the most
consistently observed difference in earlier studies. Our results are, however, con-
sistent with several other earlier studies that also did not find a difference between
overground and treadmill walking [
75
,
84
] and lend support to the notion that pre-
viously reported differences may be (partially) due to the fact that walking surfaces
were not controlled for. Another interesting finding is that stationary walking sig-
nificantly reduced the lateral (sway) and vertical (bounce) head movements. It is
currently unclear what the cause for this change is. However, it is thought that head
stabilization behavior helps organize the inputs from the visual, vestibular, and even
somatosensory systems [
13
]. It is possible that during treadmill walking head move-
ments are reduced in order to establish a more stable reference frame because of
the registered discrepancy between the proprioceptive sense that signals movement,
and the vestibular and visual senses that signal a stationary position. As for visual
