To test the concurrent validity of data from 2 different global positioning system (GPS) units for obtaining mechanical properties during sprint acceleration using a field method recently validated by Samozino et al.
Thirty-two athletes performed maximal straight-line sprints, and their running speed was simultaneously measured by GPS units (sampling rate: 20 or 5 Hz) and either a radar or laser device (devices taken as references). Lower-limb mechanical properties of sprint acceleration (theoretical maximal force, theoretical maximal speed, maximal power) were derived from a modeling of the speed–time curves using an exponential function in both measurements. Comparisons of mechanical properties from 20- and 5-Hz GPS units with those from reference devices were performed for 80 and 62 trials, respectively.
The percentage bias showed a wide range of overestimation or underestimation for both systems (-7.9% to 9.7% and -5.1% to 2.9% for 20- and 5-Hz GPS), while the ranges of its 90% confidence limits for 20-Hz GPS were markedly smaller than those for 5-Hz GPS. These results were supported by the correlation analyses.
Overall, the concurrent validity for all variables derived from 20-Hz GPS measurements was better than that obtained from the 5-Hz GPS units. However, in the current state of GPS devices’ accuracy for speed–time measurements over a maximal sprint acceleration, it is recommended that radar, laser devices, and timing gates remain the reference methods for implementing the computations of Samozino et al.
Nagahara is with the Sports Performance Laboratory, National Inst of Fitness and Sports in Kanoya, Kanoya, Japan. Botter and Rejc are with the Dept of Medical and Biological Sciences, University of Udine, Udine, Italy. Koido is with the Faculty of Health and Sport Sciences, and Shimizu, the Sports Research and Development Core, University of Tsukuba, Tsukuba, Japan. Samozino is with the Laboratory of Exercise Physiology (EA4338), University of Savoy Mont Blanc, Savoy, France. Morin is with the Laboratory of Human Motricity, Education Sport and Health, University of Nice Sophia Antipolis, Nice, France.