Validity and reliability of GPS for measuring instantaneous velocity during acceleration, deceleration, and constant motion

TLDR

The study evaluated the validity and reliability of 5‑Hz and 10‑Hz GPS units for measuring instantaneous velocity during straight‑line running, including acceleration, deceleration, and constant speed. Three participants completed 80 straight‑line running trials wearing paired 5‑Hz and 10‑Hz GPS units, with instantaneous velocity measured by a tripod‑mounted laser as the criterion, and validity was assessed by standard error of estimate while reliability was evaluated by typical error (coefficient of variation) and Pearson correlation. The 10‑Hz GPS units were two to three times more accurate (CV 3.1–11.3%) and up to six times more reliable (CV 1.9–6.0%) than 5‑Hz units, making them suitable for detecting performance changes in straight‑line running, though researchers should consider inherent match‑to‑match variation.

Abstract

In this study, we assessed the validity and reliability of 5 and 10 Hz global positioning systems (GPS) for measuring instantaneous velocity during acceleration, deceleration, and constant velocity while straight-line running. Three participants performed 80 running trials while wearing two GPS units each (5 Hz, V2.0 and 10 Hz, V4.0; MinimaxX, Catapult Innovations, Scoresby, VIC, Australia). The criterion measure used to assess GPS validity was instantaneous velocity recorded using a tripod-mounted laser. Validity was established using the standard error of the estimate (± 90% confidence limits). Reliability was determined using typical error (± 90% confidence limits, expressed as coefficient of variation) and Pearson's correlation. The 10 Hz GPS devices were two to three times more accurate than the 5 Hz devices when compared with a criterion value for instantaneous velocity during tasks completed at a range of velocities (coefficient of variation 3.1-11.3%). Similarly, the 10 Hz GPS units were up to six-fold more reliable for measuring instantaneous velocity than the 5 Hz units (coefficient of variation 1.9-6.0%). Newer GPS may provide an acceptable tool for the measurement of constant velocity, acceleration, and deceleration during straight-line running and have sufficient sensitivity for detecting changes in performance in team sport. However, researchers must account for the inherent match-to-match variation reported when using these devices.