Integrating video tracking and GPS to quantify accelerations and decelerations in elite soccer

The aim of this study was to analyze the degree of agreement comparing number and distance covered in different acceleration and deceleration sections registered by a video tracking system (MEDIACOACH) and a GPS device (WIMU PRO) during official competition. Data from a Spanish professional club were registered over the course of a season. First, the descriptive statistics presented more bursts of accelerations and decelerations in WIMU PRO than in MEDIACOACH, whereas the distances covered recorded by both systems were similar. Second, negative relationships were found (i.e., negative bias) comparing WIMU PRO to MEDIACOACH in the number of accelerations and decelerations between 0/1 m/s2 and ½ m/s2 (p < 0.05), and in the distances covered in accelerations and decelerations (p < 0.05) between 0/1 m/s2 and in accelerations and decelerations registered between 2/3 m/s2 and more than 3 m/s2. Moreover, the differences in means (i.e., standardized mean bias) across the two devices were trivial (> 0.19) and small (0.2–0.59) for most variables. The standardized typical errors in the estimate (TEE) were moderate (0.3–0.59) and small to moderate (0.1–0.29 to 0.3–0.59), respectively. Also, the Intra class Correlation Coefficients (ICCs) for agreement and consistency between systems showed good and excellent values (> 0.90). The magnitude of change in means (%) between systems, defined as the percentage change between the numbers or values, was below 14% and 7% for number and distances covered, respectively. All scores in the smallest worthwhile change were lower than 9% and in the coefficients of variation were lower than 95% and 15%, respectively. Thus, both systems demonstrated an acceptable degree of agreement and could be useful in analyzing players’ acceleration demands in professional soccer. However, caution is required when interpreting the results and a comparison with a gold standard is required in order to validate both systems.

Analysis of goalkeepers’ game performances at the 2016 European Football Championships

Background: Despite a substantial body of literature on the physical and technical demands of outfield players in football, there is little information regarding the performance of goalkeepers. Objective: The aim of this study was to analyse the game performance profiles of goalkeepers at the 2016 European Football Championships. Methods: A total of 30 goalkeepers from 15 games played during the 2016 European Football Championships were analysed using the InStat® video tracking system. Results: The results showed that goalkeepers covered a mean total distance of 4819 m, ranging from 4036 m to 6640 m. Overall, 68% of distance travelled was attributed to walking, whereas 0.8% was due to high-intensity activities. The goalkeepers of teams that lost matches covered significantly (p < 0.05) longer distances while sprinting than those of teams that drew or won the matches. Goalkeepers of teams that drew significantly (p < 0.05) had a greater number of passes than those goalkeepers of teams that won or lost. Conclusion: The current results have implications for soccer coaches to structure training sessions and tactical strategies for goalkeepers. The ability of goalkeepers to meet the physical and technical demands of a match could directly influence the successful execution of skills and the outcome of the competition.