The validity of real-time data generated by a wearable microtechnology device.

The purpose of this study was to investigate the validity of global positioning system (GPS) and micro-electrical-mechanical-system (MEMS) data generated in real-time via a dedicated receiver. Post-session data acted as criterion as it is used to plan the volume and intensity of future training and is downloaded directly from the device. 25 professional rugby league players completed two training sessions wearing a MEMS device (Catapult S5, firmware version: 2.27). During sessions, real-time data was collected via the manufacturer receiver and dedicated software (Openfield v1.14) which was positioned outdoors at the same location for every session. GPS variables included total-, low- (0 to 3 m∙s-1), moderate- (3.1 to 5 m∙s-1), high- (5.1 to 7 m∙s-1) and very-high-speed (> 7.1 m∙s-1) distances. MEMS data included total session PlayerLoad™. When compared to post-session data, mean bias for total-, low-, moderate-, high- and very-high-speed distances were all trivial, with the typical error of the estimate (TEE) small, small, trivial, trivial and small respectively. Pearson correlation coefficients for total-, low-, moderate-, high- and very-high-speed distances were nearly perfect, nearly perfect, perfect, perfect and nearly perfect respectively. For PlayerLoad™, mean bias was trivial whilst TEE was moderate and correlation nearly perfect. Practitioners should be confident that when interpreting real-time speed-derived metrics, the data generated in real-time is comparable to that downloaded directly from the device post-session. However, practitioners should refrain from interpreting accelerometer derived data (i.e. PlayerLoad™) or acknowledge the moderate error associated with this real-time measure.