Abstract
This study aimed to investigate the validity and reliability of global (GPS) and local (LPS) positioning systems for measuring distances covered and sprint mechanical properties in team sports. Here, we evaluated two recently released 18 Hz GPS and 20 Hz LPS technologies together with one established 10 Hz GPS technology. Six male athletes (age: 27±2 years; VO2max: 48.8±4.7 ml/min/kg) performed outdoors on 10 trials of a team sport-specific circuit that was equipped with double-light timing gates. The circuit included various walking, jogging, and sprinting sections that were performed either in straight-lines or with changes of direction. During the circuit, athletes wore two devices of each positioning system. From the reported and filtered velocity data, the distances covered and sprint mechanical properties (i.e., the theoretical maximal horizontal velocity, force, and power output) were computed. The sprint mechanical properties were modeled via an inverse dynamic approach applied to the center of mass. The validity was determined by comparing the measured and criterion data via the typical error of estimate (TEE), whereas the reliability was examined by comparing the two devices of each technology (i.e., the between-device reliability) via the coefficient of variation (CV). Outliers due to measurement errors were statistically identified and excluded from validity and reliability analyses. The 18 Hz GPS showed better validity and reliability for determining the distances covered (TEE: 1.6–8.0%; CV: 1.1–5.1%) and sprint mechanical properties (TEE: 4.5–14.3%; CV: 3.1–7.5%) than the 10 Hz GPS (TEE: 3.0–12.9%; CV: 2.5–13.0% and TEE: 4.1–23.1%; CV: 3.3–20.0%). However, the 20 Hz LPS demonstrated superior validity and reliability overall (TEE: 1.0–6.0%; CV: 0.7–5.0% and TEE: 2.1–9.2%; CV: 1.6–7.3%). For the 10 Hz GPS, 18 Hz GPS, and 20 Hz LPS, the relative loss of data sets due to measurement errors was 10.0%, 20.0%, and 15.8%, respectively. This study shows that 18 Hz GPS has enhanced validity and reliability for determining movement patterns in team sports compared to 10 Hz GPS, whereas 20 Hz LPS had superior validity and reliability overall. However, compared to 10 Hz GPS, 18 Hz GPS and 20 Hz LPS technologies had more outliers due to measurement errors, which limits their practical applications at this time.
Highlights
In recent years, the tracking of team sport players has switched away from camera-based technology, which requires manual player labeling [1] and has problems with overlapping players, dress colors, and changes in light and shadow conditions [2]
It is noteworthy that the 20 Hz LPS, and the 18 Hz GPS, had more outliers due to measurement errors compared to the 10 Hz GPS during our standardized conditions, which limits their practical applications at this time
This study shows that 18 Hz GPS devices had better validity and reliability for determining distances covered and sprint mechanical properties than 10 Hz GPS devices
Summary
The tracking of team sport players has switched away from camera-based technology, which requires manual player labeling [1] and has problems with overlapping players, dress colors, and changes in light and shadow conditions [2]. To allow a meaningful interpretation of GPS and LPS data for the aforementioned practical applications, knowledge of the validity and reliability of the technologies for measuring the data of interest is essential [7] In this context, previous studies have focused on distances covered and velocity measurements (e.g., instantaneous, mean, or peak) using known distances combined with timing gates [6, 8] and theodolites [9], motion capture system [4, 10], or laser/radar [2, 11] derived velocities as the criterion measure. Further research is necessary to determine whether a true sampling rate above 10 Hz provides further improvement in the validity and reliability of GPS for measuring team sport-specific movement patterns [16]
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