Comparison of GPS and IMU systems for total distance, velocity, acceleration and deceleration measurements during small-sided games in soccer

Abstract

Physical variables from soccer training are commonly quantified by using global positioning systems (GPS) and/or inertial measurement unit (IMU) systems. More studies are needed to compare both systems, taking into account that both are frequently used to measure physical load. The purpose of this study was to (i) compare IMUs (PlayerMaker™) to ten Hz GPS (Polar Team Pro) units during a square running protocol (SRP) to investigate the accuracy of distance measured and intra-unit reliability of the devices and (ii) compare IMUs and GPS units for measurements of total distance (TD), very high intensity running (VHIR), accelerations and decelerations during small-sided games (SSGs) in semi-professional soccer. Four subjects ran theSRP whilst wearing two IMU units and three GPS units to compare the accuracy of distance measured and examining the intra-unit reliability. Fifteen male soccer players participated in the SSGs where the players’ physical variables were simultaneously captured by a foot-mounted IMU in addition to GPS units. IMU and GPS were respectively 2% and 1% from actual distance, whereof both systems had a coefficient of variation at~1%. In the SSGs, the IMU measured~4% higher TD compared to the GPS. VHIR measured by the IMUs were around 18% lower while the IMUs measured~39% more accelerations and~35% more decelerations compared to the GPS. Both systems measure close to actual distance. In SSGs, IMU measures higher distances below VHIR while the GPS measures higher distance above VHIR. IMUs measure a higher number of accelerations and decelerations during SSGs.

Keywords

• Motion analysis
• player tracking
• global positioning system
• inertial measurement unit