Abstract
Training prescription and monitoring of team-sport athletes rely on accurate quantification of player movement. Our aim was to determine the sensitivity, reliability and construct validity of measures derived from a wearable device incorporating Global Positioning System (GPS) and accelerometer technology to quantify the peak periods of rugby competition. Match movement data were collected from 30 elite and 30 sub-elite rugby union players across respective competitive seasons. Accelerometer and GPS measures were analysed using a rolling average to identify peak movement for epochs ranging from 5 to 600 seconds. General linear mixed modelling was used to quantify the effects of playing position and match-half on the peak movement and variabilities within and between players represented reliability of each measure. Mean positional differences and match-half changes were assessed via standardisation and magnitude-based decisions. Sensitivity of measures was quantified via evaluation of ("signal") and typical error of measurement ("noise"). GPS and accelerometer measures had poor sensitivity for quantifying peak movement across all epochs and both levels of rugby union competition (noise 4× to 5× the signal). All measures displayed correspondingly low reliability across most epochs and both levels of competition (ICC<0.50). Construct validity was evident in mean differences between playing positions and match halves that were consistent with expected activity profiles in rugby union. However, it was clear from the pattern of differences across epoch durations and levels of competition that GPS and accelerometer measures provided different information about player movement. The poor sensitivity and low reliability of GPS and accelerometer measures of peak movement imply that rugby union players need to be monitored across many matches to obtain adequate precision for assessing individuals. Although all measures displayed construct validity, accelerometers provided meaningful information additional to that of GPS. We recommend using accelerometers alongside GPS to monitor and prescribe match respresentative training.
Highlights
Using wearable global positioning systems (GPS) and inertial sensors to quantify athletic movement is an application of the technology long preceded by navigation and military applications [1]
Duration-specific grand means and standard deviations (SD) of each measure of maximum mean movement are shown in Tables 2, 3 & 4 to provide context for the positional differences and match-half changes
Maximum mean movement measured via GPS- and accelerometer-derived measures displayed very low to low within-match, between-half reliability (ICC range; 0.0 to 0.5) during both sub-elite and elite rugby union match-play
Summary
Using wearable global positioning systems (GPS) and inertial sensors to quantify athletic movement is an application of the technology long preceded by navigation and military applications [1]. Whilst GPS athlete tracking data can be of great value to practitioners, it has reduced validity and reliability for quantifying rapid changes of direction [11] and velocity [12, 13], estimating metabolic power [14] and for assessing short duration, high-velocity tasks that frequently occur in team sports [13, 15]. Positional and match-half differences in athlete maximal movement were underestimated by GPS technology when compared to accelerometers during professional rugby union match-play [17]. In light of these findings, authors recommended that researchers and practitioners use accelerometers alongside GPS technology to adequately quantify important positional differences and match-half changes in athlete movement during collision-based team sports [17]
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