Biomedical Engineering Reference
In-Depth Information
navigation were conducted on long-range navigational capabilities with and without
the use of visual information.
6.2 Gait and Biomechanics
One of the major goals of the CyberWalk project was to enable natural and uncon-
strained walking on a treadmill based system. This original challenge introduced
many questions and we highlight two of those here. First, in order to enable natural
and unconstrained gait, a description of typical gait characteristics was needed. For
instance, at what speed do people normally walk, how do they start and stop walking,
how often and how much do they turn? Second, there is still a debate in the literature
as to whether gait characteristics during treadmill walking are the same as during
overground walking. Thus, we conducted a series of studies to address these ques-
tions. The results were intended to assign tangible constraints on a system intended
to support natural walking (e.g., on the accelerations required and the size of the
walking surface).
6.2.1 Natural Unconstrained Walking
There is, in fact, very little literature on natural unconstrained walking. One reason
for this is a previous lack of measurement technologies suitable to capture gait with
sufficient accuracy. In recent years, however, Global Positioning Systems (GPS) are
providing a promising solution to this problem [
70
,
101
]. For instance, Terrier and
colleagues used a highly accurate GPS to show that inter- and intra-subject variability
of gait characteristics can be measured outdoors [
107
,
108
]. Moreover, GPS data
can be combined with Inertial Measurement Unit (IMU) technologies to develop
highly accurate measurement systems with high data rates [
104
]. Nevertheless, the
few available studies that report GPS data are still highly constrained in a fashion
reminiscent of laboratory research. For instance, participants are often asked to follow
a modulated pace/frequency [
86
,
106
,
108
],which is known to significantly increase
energy cost [
115
] or to walk/run along a predefined path [
32
,
104
,
106
,
107
]. In
studies where walking behavior was not constrained, data were collected over several
days at very low sampling rates to form a picture of overall “behaviors” rather than
basic gait parameters such as step length and frequency [
26
,
70
,
76
,
85
,
110
].
We conducted a study of unconstrained outdoor human walking that differed from
previous studies in that we observed people walking for an extended period of time
(1h) and completely at their own volition [
97
]. We measured the position of the trunk
and rotational rates of the trunk and head. The high accuracy required to capture
trunk position outdoors was achieved by using a Carrier-Phase Differential GPS
setup (C-DGPS). The C-DGPS utilizes a secondary static GPS unit (master station)
to correct for errors in a mobile rover GPS (Novatel Propak, V3-L1). The rover
