USE OF GPS AND ACCELEROMETERS IN SPORTS

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USE OF GPS AND ACCELEROMETERS IN SPORTS AND
PHYSICAL ACTIVITY Léger Luc, Bekraoui Nabyl
(Universite de Montreal, Canada) INTRODUCTION.
The quantitative and qualitative mea-sure of
physical activity, motion and gesture in task and
time-motion analyses of day-to-day activities and
sports and fitness testing as well, are important
for fitness train-ers, health practitioners and
epidemiologists. Visual and video observations,
logbooks and recall questionnaires have been used
for a long time while GPS and accelerom-eters are
more recent in that field. QUANTITATIVE METHODS.
However quantitative meth-ods such as GPS and
accelerometers are not oriented toward
qualitative measures. Forward and backward
dis-placements could not be differentiated
specific gestures such as kicking, throwing could
not be identified nor inter-action with partners
or opponents. Thus they could not re-place visual
methods but complement those particularly for
rapid computation of quantitative measures of
acceleration, speed, displacement, orientation
and even position. VALIDATION STUDIES. The
general principles behind GPS and accelerometers
will be described along with main advantages and
disadvantages. Of course, the technical
characteristics of available models (particularly
the sam-pling frequency, memory...) affect those.
Focus is made on commercially available and
affordable models (Garmin E-Trek MAP-76A GPS
(1Hz) RT3 accelerometer (1Hz).). Some validity
results are based on the utilization of two
common running multistage field tests as the
criterion methods. Both tests use an audio signal
to set the speed between equidistant 50-m markers
along a 400-m track or at each end of a 20-m
shuttle course. Frequency of sound signal is
increased at each stage to yield regular mean
speed increments. In the forward running track
test, speed is maintained constant during the
stage while there are accelerations and
decelerations with 180 degree direc-tion changes
in the shuttle test. With common 1 Hz sam-pling
rate of commercial devices, the GPS is better
than the accelerometer to indicate accurate
changes in speed, displacement, direction and
position. However, none of the 1-Hz sampling rate
device is good enough to detect impor-tant and
short (lt 1 s) change of speed). New high sampling
frequency devices such as the Garmin GPS 18 (5
Hz) or the Antaris U-Blox (4Hz) improve greatly
the accuracy of the measures when rapid changes
are occurring... SPORT APPLICATION. The rest of
the presentation will fo-cus in reviewing
applications of these tools in sport studies such
as football, cycling or running. Keywords Sport
Performance, Sport science, Testing 12thAnnual
Congress of the ECSS, 1114 July 2007, Jyväskylä,
Finland I