Validity and Reliability of 15 Hz Global Positioning System Units for Assessing the Activity Profiles of University Football Players.

Barr, M, Beaver, T, Turczyn, D, and Cornish, S. Validity and reliability of 15 Hz global positioning system units for assessing the activity profiles of university football players. J Strength Cond Res 33(5): 1371-1379, 2019-Global positioning system (GPS) units have recently become popular for monitoring and assessing the workloads of football players. Currently, there is a lack of studies examining the validity and reliability of these systems for that purpose, so the aim of the current study was to determine whether 15 Hz units (SPI HPU; GPSports, Canberra, Australia) could accurately be used to describe the physical demands of football. A series of cohort studies were conducted with Canadian university football players (n = 28). To assess the accuracy of the units' ability to measure high-velocity sprinting, 12 players performed multiple electronically timed 36.6 m sprints while wearing the units. To assess the interunit reliability, 5 players wore 2 units each during a training session. An analysis of the units' validity for measuring collisions was performed by comparing the correct number of tackles and blocks notated on video by an expert rater in 2 games with the number of collisions recorded by the units. The units were accurate for measuring high-sprinting velocities (coefficient of variation [CV] = 0.9%) and had good interunit reliability for recording distances at velocities between walking and sprinting CV (1.4-7.8%). The collision algorithm filter the accompanying software uses was found to have its best balance between precision and recall using a cut-off of 2.65g for linemen and 2.9g for nonlinemen. The devices used are effective at providing acceptably valid and reliable information to describe the physical demands of football. Position-specific locomotor zones are recommended when using GPS units with football players.