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Front. Physiol. | doi: 10.3389/fphys.2018.00115

Validity of the Catapult ClearSky T6 local positioning system for team sports specific drills, in indoor conditions

  • 1Department of Physical Performance, Norwegian School of Sport Sciences, Norway

The aim of the present study was to determine the validity of position, distance travelled and instantaneous speed of team sport players as measured by a commercially available local positioning system (LPS) during indoor use. In addition, the study investigated how the placement of the field of play relative to the anchor nodes and walls of the building affected the validity of the system.
Method
The LPS (Catapult ClearSky T6, Catapult Sports, Australia) and the reference system (Qualisys Oqus, Qualisys AB, Sweden, (infra-red camera system)) were installed around the field of play to capture the athletes’ motion. Athletes completed five tasks, all designed to imitate team-sports movements. The same protocol was completed in two sessions, one with an assumed optimal geometrical setup of the LPS (optimal condition), and once with a sub-optimal geometrical setup of the LPS (sub-optimal condition). Raw two-dimensional position data were extracted from both the LPS and the reference system for accuracy assessment. Position, distance and speed were compared.
Results
The mean difference between the LPS and reference system for all position estimations was 0.21 ± 0.13 m (n=30166) in the optimal setup, and 1.79 ± 7.61 m (n=22799) in the sub-optimal setup. The average difference in distance was below 2% for all tasks in the optimal condition, while it was below 30% in the sub-optimal condition. Instantaneous speed showed the largest differences between the LPS and reference system of all variables, both in the optimal (≥35%) and sub-optimal condition (≥74%). The differences between the LPS and reference system in instantaneous speed were speed dependent, showing increased differences with increasing speed.
Discussion
Measures of position, distance, and average speed from the LPS show low errors, and can be used confidently in time-motion analyses for indoor team sports. The calculation of instantaneous speed from LPS raw data is not valid. To enhance instantaneous speed calculation the application of appropriate filtering techniques to enhance the validity of such data should be investigated. For all measures, the placement of anchor nodes and the field of play relative to the walls of the building influence LPS output to a large degree.

Keywords: kinematics, Position, Instantaneous speed, accuracy, Performance analyses, Physical demands

Received: 15 Nov 2017; Accepted: 05 Feb 2018.

Edited by:

Billy Sperlich, University of Würzburg, Department of Sports Science, Germany

Reviewed by:

Alessandro M. Zagatto, Faculdade de Ciências, Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP), Brazil
Grant M. Duthie, Australian Catholic University, Australia  

Copyright: © 2018 Luteberget, Spencer and Gilgien. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Miss. Live S. Luteberget, Department of Physical Performance, Norwegian School of Sport Sciences, Oslo, Norway, livesl@nih.no