Validity and reliability of a spatiotemporal gait-analysis system
narrow width of the carpet and requiring them to walk
on and off the carpet (19). Several low-cost systems
exist that use a single-camera setup, footswitches, ac-
celerometers, gyroscopes, and inertial measurement
units; however, results on the accuracy of spatial para-
meters are inconsistent or absent and it is questionable
whether some of these systems are reliable in persons
with gait deviations (e.g. forefoot contact at initial
contact) (19–30).
A 2-dimensional spatiotemporal gait analysis sys-
tem (SGAS) at relatively low-cost (approximately
one-tenth of the price of a GAITRite® system) was
developed that measures spatiotemporal gait parame-
ters in the sagittal plane using a single camera placed
perpendicular to the walkway. The camera can either
be used in a stationary position, or moved manually
along a parallel rail system to capture multiple strides
during a single walk. The SGAS uses custom software
for camera calibration and position and time measure-
ment (31). Individuals walk unobtrusively while their
gait is recorded with the camera. To our knowledge no
camera system using this calibration method has been
validated for assessing spatiotemporal gait parameters.
The aim of this study was to establish the concurrent
validity of the SGAS for assessing the spatiotemporal
parameters of gait in healthy subjects under 4 different
walking conditions: barefoot walking, shod walking,
and to mimic gait deviations that may result from neu-
rological or musculoskeletal disorders, toe walking and
slow walking. Furthermore, the minimum number of
footsteps needed to achieve reliable estimates of spa-
tiotemporal gait parameters, inter-rater and intra-rater
reliability, and measurement error were determined.
METHODS
Subjects
A sample of 33 healthy adults (13 men, 20 women, mean age
43 years, standard deviation (SD) 12 years) were recruited
from employees, their relatives, and visitors to our rehabilita-
tion centre through flyers posted at the centre (see Table I for
subject characteristics). Individuals were eligible if they were
Fig. 1. Spatiotemporal gait analysis system (SGAS): camera positioned
on a movable tripod and the computer screen with the software.
over 18 years of age, could walk independently, and were free
of musculoskeletal or neurological pathology. Data collection
took place at the human movement laboratory of our centre. The
study protocol was approved by the medical ethics committee
of the Academic Medical Centre of the Amsterdam University
Medical Centres (protocol number NL50002.018.14). All sub-
jects provided written informed consent.
Instrumentation
The SGAS consists of a high-definition 2.2-megapixel camera
with 50× optical zoom (f/1.8–4.2, 16:9), sampling at 50 Hz
(Panasonic Corporation, Osaka, Japan). Custom software on a
Windows computer with a high-definition multimedia interface
(HDMI) frame grabber was used for camera calibration, video
recording, and position and time assessment (TMSi, Oldenzaal,
The Netherlands). The SGAS software is available open source
(https://github.com/MvanBloemendaal/SGAS). The camera was
levelled and positioned on a movable tripod (camera dolly). In
this study, the camera was positioned at a height of 92 cm and
the perpendicular distance from a 10-m long walkway equals
Table I. Subject characteristics (n=33)
Characteristics Mean (SD)
Age, years
Body height, cm
Body mass, kg
Leg length, cm
Foot length, cm
Comfortable gait speed, m/s 43.1 (12.0)
177.9 (10.5)
76.0 (14.2)
92.4 (7.1)
26.5 (1.7)
1.2 (0.2)
Cadence, steps per min a
Step width, cm a
457
108.8 (8.7)
68.2 (6.9)
Gait cycle time, s a
Stride length left leg, cm a
Stride length right leg, cm a
a
1.1 (0.1)
137.2 (13.6)
137.2 (14.0)
At comfortable gait speed measured by the GAITRite® system.
Fig. 2. Calibration of the camera for determining the projection matrix.
J Rehabil Med 51, 2019