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Introduction: Relative age effects (RAEs) refer to the overrepresentation of players born earlier in the selection year compared to late-born players within the same age category. To date, the origins and mechanisms of RAEs are still unclear. To evaluate the development of RAEs in terms of age group and selection level, we analyzed data of all registered child and adolescent football players in Switzerland.Methods: Age category, selection level, and birthdate from all licensed 101,991 Swiss child and youth football players assigned to a specific team [9,149 girls (9.0%) and 92,842 boys (91.0%); age range: 4.6–19.6 years] were analyzed. Additionally, out of 1,128 clubs, 54 clubs provided their documented waiting lists (1,224 players). Birthdate distributions were split by age category, sex, and birth quarter (Q1 = January to March, Q4 = October to December). RAEs were calculated using odds ratios (Q1 vs. Q4) with 95% confidence intervals (95% CI).Results: We found small RAEs among U8 players (OR 1.44 [95% CI 1.31, 1.59]) and U10 (OR 1.24 [95% CI 1.16, 1.32]). The RAE was negligible in all other age categories, independent of gender. In children's football, 5,584 (71.3%) teams performed selections. In teams without selection, there were no obvious RAEs. However, teams with selections for the same age category showed small RAEs with an overrepresentation of Q1 athletes in the first team (OR = 1.29 [95% CI 1.24, 1.35]) and inverse RAEs with an underrepresentation of Q1 athletes in the last team (OR = 0.85 [95% CI 0.82, 0.89]). Only small RAEs were observed on the waiting lists for the U8 (OR = 1.48 [1.13, 1.95]).Discussion and Conclusion: RAEs have a small, but consistent effect on participation in Swiss children's football at the grassroots level. Contrary to expectations, no inverse RAEs were found on the waiting lists. Nonetheless, first time coach selections seem to be the origin of RAEs. To protect young athletes from discrimination, RAE biases should be analyzed and eliminated at all stages of sport participation, selection, and dropout situations. Modifications to the organizational structure of sport and athlete development systems are recommended to prevent RAE-related discrimination in youth sports.

As young football players develop important technical and tactical skills during competitive matches, this study investigated quantity and quality of technical and tactical actions in real game conditions in a 4v4 compared to the traditional 7v7 match format. In total, three matches of each format were played by 103 young football players (10.3±0.6 years) and video monitored for subsequent manual tagging of technical and tactical events. Based on the number of technical and tactical actions in the 7v7 matches, players were classified as dominant or non-dominant and changes in these subgroups were assessed during the 4v4 match format. The 4v4 match format significantly (P<0.001) increased total number of actions per player per minute compared to the 7v7 matches (5.59±1.44 and 2.78±0.73, respectively) and the number of successful (2.88±0.92 and 1.15±0.49, respectively) and unsuccessful (1.05±0.42 and 0.67±0.23, respectively) actions. Both dominant and non-dominant players increased their number of actions during the 4v4 compared to 7v7 match format. Despite a missing significant interaction effect, there was a larger percentage increase in number of actions for the non-dominant players (143%) compared to dominant players (72%) in 4v4. The 4v4 match format shows twice as many technical and tactical actions in real game conditions and, therefore, may improve players’ skill development.

Introduction To perform a successful action in football, players must constantly recognize the given affordances and their surroundings on the field before and during action (McGuckian et al., 2020). Therefore, having the ability to temporarily detach the view from the ball and move the head to scan the environment to identify and recognize information, could affect the quality of the subsequent action (Jordet et al., 2020). This ability might depend on players technical skills, which give a player more opportunities to exploit given affordances (Aksum et al., 2021). Explicit verbal coaching instructions are used to develop these skills in trainings and games. However, there is little evidence that support this coaching strategy. The aim of this study was to investigate how scanning activity without, and with instruction affect player’s performance in 4v4 elite U19 female football players. Hypotheses were: i) scan frequency is higher in more skilled players, ii) instruction leads to higher scan frequency, and iii) higher scan frequency increases the quality of the subsequent action. Methods Twenty-five (17.57 ±0.69 years) female players were recruited from two elite football clubs. All players participated twice in a 4v4 small-sided game (SSG). The first SSG was conducted with no special rules. At the beginning and during mini-breaks of the second SSG, players were instructed to constantly look away from the ball and scan the environment before the first ball touch (Jordet et al., 2020). SSG’s were video captured and will be analyzed by three experts. Frequency and time of scans before and during action as well as quality and speed of subsequent technical-tactical action will be assessed. Dependent variables will be analyzed using two factorial (instruction x group) analyses of variance (i, ii) and mixed models (iii). Results As the present study was conducted recently, the results will be presented at the conference. However, a previous pilot study showed significantly higher scan frequency after instruction in higher skilled U17 female football players (p < 0.001). It also appeared that higher skilled players are more likely to take advantage of instruction in terms of speed and quality of the subsequent actions. Discussion This study could provide important initial insights into the scanning activity of U19 female football players. Further, implications for coaching instruction on scanning activity and how this affects the quality of subsequent actions, may impact future coaching strategies. References Aksum, K. M., Pokolm, M., Thue Bjørndal, C., Rein, R., Memmert, D., & Jordet, G. (2021). Scanning activity in elite youth football players. Journal of Sports Sciences, 39(21), 2401-2410. https://doi.org/10.1080/02640414.2021.1935115 Jordet, G., Aksum, K. M., Pedersen, D. N., Walvekar, A., McCall, A., & Priestley, D. (2020). Scanning, contextual factors, and association with performance in English premier league footballers: An investigation across a season. Frontiers in Psychology, 11, Article 553813. https://doi.org/10.3389/fpsyg.2020.553813 McGuckian, T. B., Cole, M. H., Chalkley, D., Jordet, G., & Pepping, G.-J. (2020). Constraints on visual exploration of youth football players during 11v11 match-play: The influence of playing role, pitch position and phase of play. Journal of Sports Sciences, 38(6), 658-668. https://doi.org/10.1080/02640414.2020.1723375