Monitoring Accelerations With GPS in Football: Time to Slow Down?

Buchheit M., Al Haddad H., Simpson B.M., Palazzi D., Bourdon P.C., Di Salvo V., Mendez-Villanueva A.

The aims of the current study were:To examine the magnitude of between-GPS-models differences in commonly reported running-based measures in football.
To examine between-units variability.
To assess the effect of software updates on these measures.

Fifty identical-brand GPS units (15 SPI-proX and 35 SPI-proX2, 15 Hz, GPSports, Canberra, Australia) were attached to a custom-made plastic sled towed by a player performing simulated match running activities.
GPS data collected during training sessions over 4 weeks from 4 professional football players (N = 53 files) were also analyzed before and after 2 manufacturer-supplied software updates.

Substantial differences were observed between different GPS models, with standardized differences ranging from 1.4 to 2.7 for various measures.
Between-units variations ranged from 1% (maximal speed) to 56% (number of decelerations >4 m/s²). Some GPS units measured 2–6 times more acceleration/deceleration occurrences than others.
Software updates did not substantially affect the distance covered at different speeds or peak speed reached. However, one of the updates led to decreases in the occurrence of accelerations and decelerations.
Practitioners are advised to exercise caution when comparing data collected with different models or units or when updating their software. Metrics related to accelerations and decelerations show the most variability in GPS monitoring and must be interpreted cautiously.

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