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ABSTRACTThis study identified and profiled the types of player actions of Australian football players executed during high acceleration and/or deceleration efforts and identified how the duration exceeding the acceleration or deceleration threshold influenced the identified executed player actions. The commencing speed of the acceleration and deceleration efforts were also assessed. Acceleration and deceleration efforts of 22 Australian football players monitored with a 10-Hz GNSS device across two matches were analysed. Synchronised video footage of the matches was used to identify the player actions executed during acceleration and deceleration efforts. Linear mixed models were conducted to examine the relationship between commencing speed, player action, and duration exceeding the effort threshold. ‘Linear movement’ and ‘jump’ were the most frequently executed player actions for high accelerations and ‘stop’ and ‘being tackled’ for high decelerations. Significant differences were observed in commencing speed between player actions for the high deceleration efforts. Furthermore, it was found that a higher commencing speed was associated with an increased duration exceeding the deceleration threshold. These findings will help practitioners and researchers with selecting minimum-duration criteria for acceleration and deceleration efforts and provide an understanding of the types of player actions executed during these efforts.

ABSTRACTThis study assessed the interchangeability between 10-Hz multi-GNSS GPS devices (Vector®) and two optical tracking systems (TRACAB® and Second Spectrum®). The agreement between data from the optical tracking systems when processed with manufacturer and GPS-filtered software was also assessed. Thirty players competing in the English Premier League were monitored using three different tracking systems across five matches. To determine the interchangeability between systems, player movement variables including, total distance, high-speed running distance (19.8–25.2 km·h−1), sprinting distance (>25.2 km·h−1), efforts >19.8 km·h−1and maximal speed were compared. Equations were formed using linear regression and linear mixed-effects models to allow interchangeability of player movement variables between systems. Over half of the variance of most interchangeability equations were explained and associated with very strong positive correlations (r > 0.72). Small to huge differences were found between systems for most player movement variables. Data of optical tracking systems had decreased values in speed variables >19.8 km·h−1when processed through GPS software. This study provides equations for practitioners to interchange player movement variables between TRACAB, Second Spectrum and Vector GPS systems with reduced error. This will enable practitioners to combine and share data captured with different tracking systems to analyse and improve their training.

ABSTRACTThis study examines differences in weekly load between the first (FT) and the under 19 team (U19) within a professional football setting. Data were collected in 11 FT and 9 U19 players (2016-2017 season). FT data was divided into weeks with (FT-M1) or without (FT-M0) a mid-week match. Indicators were total distance (TD) and TD at 12-15, 15-20, 20-25 and >25 km‧h-1and were analysed as external load (m), intensity (m‧min-1) and load monotony (a.u.). TD-based load was higher for U19 compared to FT-M0 (very likely moderate) and FT-M1 (likely large). Differences at higher velocities were substantially less (trivial to possibly small), with TD >25 km‧h-1being lower than FT-M0 (very likely moderate) and FT-M1 (likely small). All intensity indicators were lower for U19 (likely small to almost certainly large). Load monotony was higher compared to FT-M1 (possibly small to almost certainly very large). Compared to FT-M0, monotony was higher for TD (possibly very large) and TD >25 km‧h‑1(possibly moderate) but lower for TD 12-15 (possibly small) and 15-20 km‧h‑1(likely moderate). So, despite higher weekly external loads at low velocity for elite youth players, external intensity and load variation increases when these players may transition to professional football.

ABSTRACTPurpose: Using elite youth soccer players’ maximal sprinting speeds collected from a criterion and non-criterion measure, we demonstrate how expert practitioner opinion can be used to determine measurement validity.Methods: Expert soccer practitioners (n = 50) from around the world were surveyed on issues relating to the measurement of maximal sprinting speed and 12 elite youth soccer players performed two maximal 40 m sprints, measured by 10-Hz GPS units (non-criterion) and a 100-Hz Laser (criterion). Setting statistical equivalence bounds as practitioner opinion of the practically acceptable amount of measurement error for maximal sprinting speed, we assessed agreement between GPS and Laser.Results: Survey respondents reported a combination of methods for deriving maximal sprinting speed (tests, training, match) but most did not assess system validity. Median value of the practically acceptable amount of measurement error for maximal sprinting speed was 0.20 m/s. Maximal sprinting speed was 8.79 ± 0.33 m/s (Laser) and 8.75 ± 0.32 m/s (GPS), and the mean difference was 0.04 (90% confidence interval −0.03 to 0.11) m/s. Using the median acceptable amount of measurement error, we set our lower and upper equivalence bounds to −0.10 m/s and +0.10 m/s, respectively. Equivalence testing showed Laser and GPS as likely equivalent measures (probability 93.7%).Conclusion: Using expert-informed equivalence thresholds represents a novel way to assess validity in sports performance research.

ABSTRACTIt is common practice amongst researchers and practitioners to monitor the effects of external load via electronic tracking systems. Both semi-automatic multiple camera systems and global positioning system technologies are used worldwide to quantify match-running. As soccer is a global game, the playing environments can differ, with heat and altitude being factors that may impact players running performance. Further, tactical and situational match factors may also have an effect on match-running performance. Therefore, the purpose of this article is to systematically review current literature on the environmental and situational factors affecting match-running in soccer. An electronic database search (PubMed, EBSCOHost and Web of Science) was conducted. Further articles known to the authors were also included. A total of 1806 studies were identified, with only 28 meeting the specific search criteria. The main findings were that trivial changes in match-running were observed with regards to possession, team formation and match status (win, lose, draw). Match-running was affected by temperatures as low as 20°C, with both high- and very-high speed running decreasing (8.5% and 15% respectively), whilst altitude lowers the number of high-speed efforts completed by players (7.1–25%). Findings indicate that environmental factors have a strong influence on the variability and differences observed in match-running performances from match-to-match. Further understanding of the effect of match factors on match-running would allow better planning to minimise possible detrimental factors, particularly in relation to gender.

ABSTRACTThis study investigated the positional differences in physical performance of elite youth footballers in a tournament scenario and the influence of team success and opponent quality on team physical and technical performance. Match performance observations were collected using a semi-automated multi-camera tracking system across 2 elite under-17 international club tournaments from all players and teams (n = 1,457 individual cases). Teams were classified based on their final tournament ranking as top (1–4 ranking), middle (5–8 ranking) and bottom (9–12 ranking). Technical performance measures were expressed in absolute terms and relative to the time the team was in ball possession. Positional differences in physical performance and the influence of team success and opponent quality on team match performance were identified using a generalised linear mixed model. Positional differences were similar to that observed in elite senior players. Top ranking teams performed a greater number of absolute and relative shots and shots on target than bottom teams (effect size = 0.67–0.82). Top ranking teams performed a greater number of relative tackles than bottom and middle teams (ES; 0.44 –0.70). When playing against top ranking opponents the number of absolute shots and shots on target, shot conversion and passing accuracy were lowest compared with playing against middle and bottom opponents (ES; −0.86 to −0.31). In an elite youth tournament setting, opponent quality and team success can influence match performance. These contextual factors should be considered when analysing match performance and used to inform team tactics, selection and substitution strategies.