To administrate correct training dose and keep players fit over a long season, teams use movement-related parameters, such as sprint count, top speed and distance, to evaluate external training load. This is often accomplished by using a global navigation satellite system (GNSS). For such an approach to work, a system must measure what it is supposed to measure (validity) and provide similar results from time to time (test-retest reliability or repeatability). A newly published study used Team Pro to estimate the accuracy of movement-related parameters. The results show that Team Pro’s distance error was less than 5% (often much less) and top speed error was typically between 5–10%. The results indicate that Team Pro is amongst the most accurate and reliable devices currently on the market.
Several factors influence GNSS accuracy. Firstly, environmental factors such as conditions in the sky (e.g. clouds) and nearby buildings may influence satellite positioning accuracy. Although environmental factors can rarely be changed, it’s good to be aware of their existence. Secondly, sensor placement may play a small but measurable role. According to our own investigation, the installation of the GNSS receiver to upper back, as in the Team Pro shirt, yields to 1% better accuracy in speed and distance parameters than the installation of the same device to a chest strap. Thirdly, according to available research, 10Hz sampling rate (found in Team Pro) appears to be the “sweet spot”. Devices that sample at 10Hz have been shown to be more accurate than devices that sample at 1Hz or 5Hz, but no additional benefits have been observed if sampling rate is increased to 15Hz (Scott et al., 2016).
The most recent Team Pro validation study was conducted by a group of researchers at University of Connecticut, USA (Huggins et. al., 2020). Distance and top speed taken from Team Pro were compared against criterion measures over 40 m and 100 m straight-line runs completed at four different speeds: walking, jogging, running and sprinting. Validity was measured with standard error of the estimate (SEE) and repeatability with coefficient of variation (COV).
When analyzing distance over 100 m, Team Pro demonstrated good validity (SEE = 0.5–2.6%) and reliability (COV = 0.5–2.7%) for all speeds. For 40 m distance, validity and reliability were good for walking, jogging and running (SEE = 2.6–3.04%; COV = 2.6–3.1%) and moderate for sprinting (SEE = 7.5%; COV = 8.0%). With regards to top speed during linear runs, Team Pro demonstrated good validity (SEE = 2.9%) and reliability (COV = 2.43%) at sprint speed and moderate to poor validity (SEE = 7.9–12.3%) and good to poor reliability (COV = 1.38–12.86%) at lower speeds. Top speed was only analyzed during 100 m runs.
To evaluate ecological validity, Team Pro was also tested at team sport simulation circuit (TSSC). In TSSC, total distance showed good validity (SEE = 1.0–1.8%) and reliability (COV = 1.0–1.8%) and top speed showed good validity (SEE = 4.7%) and moderate reliability (COV = 5.17%).
The following categorization was used to verbalize results: 1) Good < 5%; 2) Moderate = 5-10%; 3) Poor > 10%.
Read abstract or buy full text here: HTTPS://JOURNALS.LWW.COM/NSCA-JSCR/ABSTRACT/2020/11000/THE_VALIDITY_AND_RELIABILITY_OF_GLOBAL_POSITIONING.8.ASPX
Scott, Macfarlane T. u., Tannath J. Scott, and Vincent G. Kelly. 2016. “The Validity and Reliability of Global Positioning Systems in Team Sport: A Brief Review.” Journal of Strength and Conditioning Research / National Strength & Conditioning Association 30 (5): 1470–90.
Huggins, Robert A., Gabrielle E. W. Giersch, Luke N. Belval, Courteney L. Benjamin, Ryan M. Curtis, Yasuki Sekiguchi, Jussi Peltonen, and Douglas J. Casa. 2020. “The Validity and Reliability of Global Positioning System Units for Measuring Distance and Velocity During Linear and Team Sport Simulated Movements.” Journal of Strength and Conditioning Research / National Strength & Conditioning Association 34 (11): 3070–77.
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Please note that the information provided in the Polar Blog articles cannot replace individual advice from health professionals. Please consult your physician before starting a new fitness program.