Biomedical Engineering Reference
In-Depth Information
(b)
(a)
0.8
Time to start
Time to stop
Start acceleration
Stop deceleration
3
0.7
2.5
0.6
2
Mann et al., 1979
0.5
1.5
0.4
Breniere & Do, 1986
1
0.3
0.5
1
1.5
2
0.5
1
1.5
2
Walking speed (m/s)
Fig. 6.1
Starting and stopping. The time (
a
) and accelerations (
b
) during starts (
solid line
)and
stops (
dotted line
) as a function of steady walking speeds.
Shaded regions
indicate standard errors
of the means. Also plotted (
panel a
) are the individual results (
small dots
), mean results (
large
dots
) from two earlier studies. To illustrate the general trends, linear regressions are shown on all
individual results (
black lines
)
consistent with earlier reports [
90
], and the WR at these slower walking speeds was
also more variable. The relative invariance of WR in natural (and controlled) walking
underlines its usefulness as a clinical diagnostic tool for detecting abnormal gait but
also to the scientific study of human locomotion in general.
The time that it takes to reach a steady walking speed depends on the desired
speed (see Fig.
6.1
). It took an average of 2 and 3 s to reach walking speeds of
0.5 and 2m/s, respectively. The relationship between the time it took to stop and
walking speed was very much the same. The dependence on walking speed, however,
contradicts findings by Breniere and Do [
11
] who found that the time it takes to reach
the desired walking speed is independent of walking speed. Dependence on walking
speed has been found by others [
60
,
71
], although we observe that in natural walking
humans take more time to start and stop than in laboratory settings. To illustrate these
differences Fig.
6.1
also includes the data from Breniere and Do [
11
] and Mann et al.
[
71
] together with our own results. One possible cause for this difference is the
protocol used in laboratory experiments [
96
]. Specifically, whereas earlier studies
typically use an external “go” signal, our participants were free to start and stop as
they pleased.
