The validity of raw custom-processed global navigation satellite systems data during straight-line sprinting across multiple days.

Crang, Z.L.; Duthie, G.; Cole, M.H.; Weakley, J.; Hewitt, A.; Johnston, R.D.

Objectives:

Determine the validity of instantaneous speed and acceleration.
Investigate the variation in validity over time (multiple sessions) for global navigation satellite systems (GNSS) devices.
Design:
Repeated measures.

Methods:
10-Hz GNSS devices from Statsports (n=2, Apex Pro) and Catapult (n=2, Vector S7) were examined, while a speed laser manufactured by MuscleLab (n = 1, LaserSpeed) was the criterion measure, sampling at 2.56 kHz, with data exported at 1000 Hz. Ten participants completed 40 m sprinting and changes of pace on three separate days. Root mean square error (RMSE) was used to assess the magnitude and direction of the difference between GNSS and criterion measures (instantaneous speed, instantaneous acceleration). Linear mixed models were built to assess the difference in validity across days.

Results:
RMSE ranged from 0.14 to 0.21 m·s⁻¹ and 0.22 to 0.47 m·s⁻² for speed and acceleration, respectively, showing strong agreement. There were small variations in the agreement to criterion between days for both devices for speed (Catapult RMSE=0.12 to 21 m·s⁻¹; Statsports RMSE=0.14 to 0.17 m·s⁻¹) and for acceleration (Catapult RMSE=0.26 to 0.47 m·s⁻²; Statsports RMSE=0.22 to 0.43 m·s⁻²) across all movements. There was a negative linear relationship between speed and acceleration error as speed increased.

Conclusions:
Wearable microtechnology devices from Catapult (Vector S7) and Statsports (Apex Pro) have suitable validity when measuring instantaneous speed and acceleration across multiple days. There may be small variations during different sessions and over the speed spectrum.

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