Abstract
The aim of this study was to test the validity and the reliability of the G-Cog which
is a new BMX powermeter allowing for the measurements of the acceleration on X-Y-Z
axis (250 Hz) at the BMX rear wheel. These measurements allow computing lateral, angular,
linear acceleration, angular, linear velocity and the distance. Mechanical measurements
at submaximal intensities in standardized laboratory conditions and during maximal
exercises in the field conditions were performed to analyse the reliability of the
G-Cog accelerometers. The performances were evaluated in comparison with an industrial
accelerometer and with 2 powermeters, the SRM and PowerTap. Our results in laboratory
conditions show that the G-Cog measurements have low value of variation coefficient
(CV=2.35%). These results suggest that the G-cog accelerometers measurements are reproducible.
The ratio limits of agreement of the rear hub angular velocity differences between
the SRM and the G-Cog were 1.010 × ÷ 1.024 (95%CI=0.986–1.034) and between PowerTap
and G-Cog were 0.993 × ÷ 1.019 (95%CI=0.974–1.012). In conclusion, our results suggest
that the G-Cog angular velocity measurements are valid and reliable compared with
SRM and PowerTap and could be used to analyse the kinematics during BMX actual conditions.
Key words
cycling - performance - accelerometer - motion - BMX - reliability
