title: Monitoring accelerations with GPS in football: time to slow down?
abstract: The aims of the current study were to examine the magnitude of between-GPS-models differences in commonly reported running-based measures in football, examine between-units variability, and assess the effect of software updates on these measures. Fifty identical-brand GPS units (15 SPI-proX and 35 SPIproX2, 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 wk from 4 professional football players (N = 53 files) were also analyzed before and after 2 manufacturer-supplied software updates. There were substantial differences between the different models (eg, standardized difference for the number of acceleration >4 m/s2 = 2.1; 90% confidence limits [1.4, 2.7], with 100% chance of a true difference). Between-units variations ranged from 1% (maximal speed) to 56% (number of deceleration >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, but 1 of the updates led to large and small decreases in the occurrence of accelerations (-1.24; -1.32, -1.15) and decelerations (-0.45; -0.48, -0.41), respectively. Practitioners are advised to apply care when comparing data collected with different models or units or when updating their software. The metrics of accelerations and decelerations show the most variability in GPS monitoring and must be interpreted cautiously.
authors.affiliation: Football Performance and Science Department, ASPIRE Academy for Sports Excellence, Doha, Qatar.
authors.forename: Martin
authors.initials: M
authors.lastname: Buchheit
authors.forename: Hani
authors.initials: H
authors.lastname: Al Haddad
authors.forename: Ben M
authors.initials: BM
authors.lastname: Simpson
authors.forename: Dino
authors.initials: D
authors.lastname: Palazzi
authors.forename: Pitre C
authors.initials: PC
authors.lastname: Bourdon
authors.forename: Valter
authors.initials: V
authors.lastname: Di Salvo
authors.forename: Alberto
authors.initials: A
authors.lastname: Mendez-Villanueva
mesh_terms: D000054:Acceleration; D056044:Actigraphy / Q000295:instrumentation* / Q000592:standards; D054874:Athletic Performance; D004867:Equipment Design; D040362:Geographic Information Systems / Q000592:standards; D006801:Humans; D007590:Jogging; D008297:Male; D015203:Reproducibility of Results; D012420:Running; D012916:Soccer; D012984:Software; D013647:Task Performance and Analysis; D013997:Time Factors