The purpose of this study was to examine the physical match profiles of professional soccer players using 3 and 5 min fixed and rolling averages as well as fixed 1 min averages, with considerations to training prescription. Twenty-nine, professional U23 soccer outfield players competed across 17 competitive matches during the 2017/18 season, equating to a total of 130 separate physical match profiles. Match activities were recorded using global positioning system (GPS) devices with integrated micro-electrical mechanical systems (MEMS), recording total distance (TD), high-speed running (HSR) and metabolic power (MP). For each individual match profile and variable, 1, 3 and 5 min peak, post-peak, and average values were calculated using fixed-time epochs (FIXED) and rolling averages (ROLL). Linear mixed models were employed to examine the differences in the dependent variables as a function of the method of measurement. Results revealed significantly higher peak values, for relative TD, relative HSR and relative MP when employing the ROLL sampling method, in comparison to the FIXED method, for both 3 min and 5 min epoch lengths. Analysis of epoch length revealed significantly higher peak values, across all positions, for relative TD, relative HSR and MP for 1 min epochs, in comparison to 3 min and 5 min epochs. The data offers a novel insight into the appropriate identification of physical demands during youth soccer match-play.Researchers and practitioners should consider the sampling method and epoch length when assessing the physical demands of competitive match-play, as well as when designing and prescribing sport-specific conditioning drills.

FC Barcelona is a multi-sport organization that adopts a talent identification approach that emphasizes the technical, psychological, and perceptual-cognitive attributes. It is unclear within this type of sporting selection model whether the relative age effect (RAE) exists. Consequently, the aim of the study was to evaluate the RAE across multiple sports and age groups at FC Barcelona. The birthdates of all players (n = 6,542) affiliated to each sport [male basketball (n = 1,013), male (n = 3,012) and female (n = 449) soccer, male futsal (n = 761), male handball (n = 999), and male indoor roller hockey (n = 308)] across all age groups from U10 to Senior were recorded. These were then categorized into quartiles from the start of the selection year (Q1 = Jan-Mar; Q2 = Apr-Jun; Q3 = Jul-Sep; Q4 = Oct-Dec) and analyzed for (a) each sport; (b) each age group, irrespective of the sport; and (c) each age group within each sport, using Chi-squared statistics and odds ratios (ORs) with 95% confidence intervals (CIs). Birthdates across the entire club revealed a RAE (Q1 = 46.1%, Q2 = 27.1%, Q3 = 17.1%, and Q4 = 9.7%, χ 2 = 29.8, P < 0.01), with OR in Q1, Q2, and Q3 representing a 4.76 (95% CIs: 1.96-11.57), 2.80 (1.12-7.03), and 1.77 (0.67-4.63) increased likelihood for selection when compared to Q4, respectively. Despite FC Barcelona's approach to talent identification and development, the RAE was still present within youth age groups (<18 years old). The current findings provide support that the RAE is more prevalent within regionally popular sports and reduces with increasing age; however, given the talent identification processes within FC Barcelona's sporting model, additional factors beyond the physical attributes, such as enhanced psychological and perceptual-cognitive attributes, in those born earlier in the selection year might further influence the RAE. Consequently, current results provide indirect evidence to suggest that sociological and psychological determinants might be a greater influence on the presence of RAE in sporting environments that prefer to consider technical and perceptual-cognitive attributes in their talent development programs.

Abstract:Purpose: To examine the relationship between oxygen uptake kinetics (VO2 kinetics) and physical measures associated with soccer match-play, within a group of highly trained youth soccer players. Methods: Seventeen highly trained youth soccer players (age: 13.3 ± 0.4 yr, selfassessed Tanner Stage: 3 ± 1) volunteered for the study. Players initially completed an incremental treadmill protocol to exhaustion, to establish gaseous exchange threshold (GET) and VO2max (59.1 ± 5.4 mL.kg-1.min-1). On subsequent visits players completed a step transition protocol from, rest-moderate intensity exercise, followed by an immediate transition from moderate-severe intensity exercise (moderate: 95%GET, severe: 60%∆), during which VO2 kinetics were determined. Physical soccer-based performance was assessed using a maximal Yo-Yo Intermittent Recovery test level 1 (Yo-Yo IR1) and via GPS derived measures of physical soccer performance during soccer match-play, 3 2 x 20min, 11 v 11 matches, to gain measures of physical performance during soccer match-play. Results: Partial correlations revealed significant inverse relationships between the unloaded to moderate transition time constant (tau) and: Yo-Yo IR1 performance (r = -0.58, P = 0.02) and GPS variables (Total distance (TD): r = -0.64, P = 0.007, High speed running (HSR): r = -0.64, P = 0.008, High speed running efforts (HSReff): r = -0.66, P = 0.005). Conclusion: Measures of VO2 kinetics are related to physical measures associated with soccer match-play and could potentially be used to distinguish between those of superior physical performance, within a group of highly-trained youth soccer players.

To assess the between-game variation in measures of physical performance during 11 v 11 soccer match-play, over a short period of time, in highly trained youth soccer players. A single cohort observational study design was employed. Physical match performance data were collected from 17 male, highly trained youth soccer players (age: 13.3 ± 0.4 y) over three, 2 x 20min, 11 v 11 matches. Using 10 Hz GPS, the variables selected for analyses were total distance (TD), high-speed running (HSR), very high-speed running (VHSR), number of high-speed running efforts (HSReff) and number of very high-speed running efforts (VHSReff). Match data was also separated into cumulative 5 min epochs, to identify the peak 5 min epoch and the mean of the cumulative 5 min epochs for each match. Variability was quantified using the coefficient of variation (CV), Standard error of measurement (SEM) and intra-class correlation coefficient (ICC). Between- and within-player smallest worthwhile changes (SWC) were also calculated for each variable to aid in the interpretation of the data. Analysis of the variance between games reported a low CV for TD (3.8%) but larger CVs for HSR (33.3%), HSReff (35.4%) and VHSR and VHSReff (59.6 and 57.4 %, respectively). Analysis of 5 min epochs (peak and average) found an increase in the CVs beyond that of the values reported for the whole match. Between-player SWC in high intensity physical performance data ranged from 24.7 - 42.4 %, whereas within-player SWC ranged from 1.2 - 79.9%. The between-game variability of high and very high intensity activities in youth soccer players, across three soccer matches over a short period of time (2 weeks), is relatively 'large' and specific to the individual, thus highlighting the need for caution when interpreting physical performance data between games and players.