Origins of Relative Age Effects in Youth Football - A Nationwide Analysis

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

Validity and reliability of a portable gait analysis system for measuring spatiotemporal gait characteristics: comparison to an instrumented treadmill

Gait analysis serves as an important tool for clinicians and other health professionals to assess gait patterns related to functional limitations due to neurological or orthopedic conditions. The purpose of this study was to assess the validity of a body-worn inertial sensor system (RehaGait®) for measuring spatiotemporal gait characteristics compared to a stationary treadmill (Zebris) and the reliability of both systems at different walking speeds and slopes.; Gait analysis was performed during treadmill walking at different speeds (habitual walking speed (normal speed); 15 % above normal walking speed; 15 % below normal walking speed) and slopes (0 % slope; 15 % slope) in 22 healthy participants twice 1 week apart. Walking speed, stride length, cadence and stride time were computed from the inertial sensor system and the stationary treadmill and compared using repeated measures analysis of variance. Effect sizes of differences between systems were assessed using Cohen's d, and limits of agreement and systematic bias were computed.; The RehaGait® system slightly overestimated stride length (+2.7 %) and stride time (+0.8 %) and underestimate cadence (-1.5 %) with small effect sizes for all speeds and slopes (Cohen's d ≤ 0.44) except slow speed at 15 % slope (Cohen's d > 0.80). Walking speed obtained with the RehaGait® system closely matched the speed set on the treadmill tachometer. Intraclass correlation coefficients (ICC) were excellent for speed, cadence and stride time and for stride length at normal and fast speed at 0 % slope (ICC: .91-1.00). Good ICC values were found for stride length at slow speed at 0 % slope and all speeds at 15 % slope (ICC: .73-.90). Both devices had excellent reliability for most gait characteristics (ICC: .91-1.00) except good reliability for the RehaGait® for stride length at normal and fast speed at 0 % slope and at slow speed at 15 % slope (ICC: .80-.87).; Larger limits of agreement for walking at 15 % slope suggests that uphill walking may influence the reliability of the RehaGait® system. The RehaGait® is a valid and reliable tool for measuring spatiotemporal gait characteristics during level and inclined treadmill walking

Effects of Mindfulness Practice on Performance-Relevant Parameters and Performance Outcomes in Sports: A Meta-Analytical Review

Mindfulness as a present-oriented form of mental training affects cognitive processes and is increasingly considered meaningful for sport psychological training approaches. However, few intervention studies have examined the effects of mindfulness practice on physiological and psychological performance surrogates or on performance outcomes in sports.; The aim of the present meta-analytical review was to examine the effects of mindfulness practice or mindfulness-based interventions on physiological and psychological performance surrogates and on performance outcomes in sports in athletes over 15 years of age.; A structured literature search was conducted in six electronic databases (CINAHL, EMBASE, ISI Web of Knowledge, PsycINFO, MEDLINE and SPORTDiscus). The following search terms were used with Boolean conjunction: (mindful* OR meditat* OR yoga) AND (sport* OR train* OR exercis* OR intervent* OR perform* OR capacity OR skill*) AND (health* OR adult* OR athlete*).; Randomized and non-randomized controlled studies that compared mindfulness practice techniques as an intervention with an inactive control or a control that followed another psychological training program in healthy sportive participants were screened for eligibility.; Eligibility and study quality [Physiotherapy Evidence Database (PEDro)] scales were independently assessed by two researchers. A third independent researcher was consulted to achieve final consensus in case of disagreement between both researchers. Standardized mean differences (SMDs) were calculated as weighted Hedges' g and served as the main outcomes in comparing mindfulness practice versus control. Statistical analyses were conducted using a random-effects inverse-variance model.; Nine trials of fair study quality (mean PEDro score 5.4, standard deviation 1.1) with 290 healthy sportive participants (athletics, cyclists, dart throwers, hammer throwers, hockey players, hurdlers, judo fighters, rugby players, middle-distance runners, long-distance runners, shooters, sprinters, volleyball players) were included. Intervention time varied from 4 weeks to over 2 years. The practice frequency lasted from twice daily to just once a week, and the mean session time covered 50-60 min. In favor of mindfulness practice compared with the control condition, large effects with narrow confidence limits and low heterogeneity were found for mindfulness scores [SMD 1.03, 90% confidence interval (CI) 0.67-1.40, p < 0.001, I 2 = 17%]. Physiological performance indices depicted wide confidence limits accompanied with very large heterogeneity. However, the effect sizes remained very large, with confidence limits that did not overlap zero (SMD 3.62, 90% CI 0.03-7.21, p = 0.10, I 2 = 98%). Moderate to large effects were observed for both psychological performance surrogates (SMD 0.72, 90% CI 0.46-0.98, p < 0.001, I 2 = 14%) and performance outcomes in shooting and dart throwing (SMD 1.35, 90% CI 0.61-2.09, p = 0.003, I 2 = 82%).; Mindfulness practice consistently and beneficially modulates mindfulness scores. Furthermore, physiological and psychological surrogates improved to a meaningful extent following mindfulness practice, as well as performance outcomes in shooting and dart throwing. It seems reasonable to consider mindfulness practice strategies as a regular complementary mental skills training approach for athletes, at least in precision sports; however, more high-quality, randomized, controlled trials on mindfulness practice and performance improvements in diverse sport settings are needed

Risk of SARS-CoV-2 transmission from on-field player contacts in amateur, youth and professional football (soccer)

Objective To investigate the risk of transmission among potentially infectious SARS-CoV-2-positive football players while participating in training or matches at amateur, youth and professional levels. Methods Between August 2020 and March 2021, football players who tested positive for SARS-CoV-2 and participated in matches or training during the period of potential contagiousness were identified through media search (professional level) and a nationwide registry in Germany (amateur and youth level) to determine symptoms, source of infection and hygiene measures adopted. The definition of potentially infectious players was based on the time of a positive PCR testing and symptom onset. Transmission-relevant contacts on the pitch were evaluated through doubly reviewed video analysis. Results Out of 1247 identified football matches and training sessions (1071 amateur and youth level, 176 professional level), 104 cases (38 training sessions, 66 matches) with 165 potentially infectious players were detected. Follow-up PCR testing at the professional level (44 cases) revealed no transmission. At the amateur and youth level, the combination of partial PCR testing (31 of 60 cases) and symptom monitoring within 14 days post-exposure (46 of 60 cases) identified 2 of 60 matches in which follow-up infections occurred that were attributed to non-football activities. This is consistent with the video analysis of 21 matches demonstrating frontal contacts were <1 per player-hour (88%, 30 of 34 players), each lasting no longer than 3 s. Conclusion On-field transmission risk of SARS-CoV-2 in football is very low. Sources of infections in football players are most likely not related to activities on the pitch

Beneficial effects of an intergenerational exercise intervention on health-related physical and psychosocial outcomes in Swiss preschool children and residential seniors: a clinical trial

Background. Intergenerational exercise possesses the potential to becoming an innovative strategy for promoting physical activity in seniors and children. Although this approach has gained attraction within the last decade, controlled trials on physical and psychosocial effects have not been performed yet. Methods. Sixty-eight healthy preschool children (age: 4.9 y (SD 0.7)) and 47 residential seniors (age: 81.7 y (7.1)) participated in this five-armed intervention study. All participants were assigned to either an intergenerational (IG), peer (PG) or a control group (CON). Children were tested on gross motor skills (TGMD-2), jump performance and handgrip strength. Social-emotional skills questionnaires (KOMPIK) were assessed by kindergarten teachers. Seniors performed the Short Physical Performance Battery (SPPB), including gait speed. Arterial stiffness parameters were also examined. Questionnaires assessing psychosocial wellbeing were filled in with staff. IG and PG received one comparable exercise session a week lasting 45 minutes for 25-weeks. CON received no intervention. Measurements were performed before and after the intervention. Results. In children: IG improved all measured physical parameters. When adjusted for baseline values, large effects were observed in favor of IG compared to CON in TGMD-2 (Cohen's d=0:78 [0.33;1.24]) and in handgrip strength (d=1.07 [0.63;1.51]). No relevant differences were found in KOMPIK between groups (-0.38<d≤0.14). In seniors: IG showed moderate to very large improvements in all main physical performance (0.61<d≤2.53) and psychosocial parameters (0.89<d≤1.20) compared to CON. Conclusion. IG children showed large benefits in motor skills compared to CON while IG seniors benefit especially in psychosocial wellbeing and functional mobility necessary for everyday life. Intergenerational exercise is comparable and in certain dimensions superior to peer group exercise and a promising strategy to integratively improve mental health as well as physical fitness in preschool children and residential seniors

Performance, stride characteristics, and muscle activity while running with a traditional compared to a newly developed running shoe

A new running shoe cushioning technology has been developed intending to dampen the landing impulse during running while allowing a powerful and direct push-off. We aimed to compare this newly developed technology to traditional running shoes in regard to endurance performance, spatiotemporal stride characteristics, ground reaction forces, and muscle activity. In a randomized crossover design, 13 recreational runners (age 24.9±1.2 years, height 1.68±0.07 m, body mass 62.8±6.0 kg, weekly running distance >30 km) were tested twice, once with their own traditional shoes and (with a 2-week run-in and a 6-week wash-out period) with shoes featuring the new technology. The two-day testing procedure consisted of a graded exercise running test to assess lactate threshold (LT) on day one. On the following day, muscle activity, ground reaction forces and spatiotemporal stride characteristics at two velocities (80% and 95% LT velocity) were recorded on an instrumented treadmill. Finally, 4 km time trial performance was assessed. Magnitude-based inferences were calculated to compare the two shoe conditions. Ground reaction force was likely higher at 95% LT (+5.7%) and possibly higher at 80% LT (+2.2%) with the newly designed shoes, while muscle activity was likely reduced in the tibialis anterior and biceps femoris muscles during push-off. Spatiotemporal stride parameters, physiological markers during the graded exercise test as well as time trial performance showed trivial or unclear differences between the conditions. The observed differences between the shoe conditions in ground reaction forces and muscle activity were insufficient to elicit improvements in selected performance parameters

Does a single session of high-intensity interval training provoke a transient elevated risk of falling in seniors and adults?

Balance and strength training can reduce seniors' fall risk up to 50%. Available evidence suggests that acute bouts of neuromuscular and endurance exercise deteriorate postural control. High-intensity endurance training has been successfully applied in different populations. Thus, it seemed valuable to examine the acute effects of high-intensity interval training (HIIT) on neuromuscular performance in seniors and young adults.; The acute impact of a HIIT session on balance performance and muscle activity after exercise cessation and during post-exercise recovery was examined in young and old adults. We intended to investigate whether a transient exercise-induced fall-risk may occur in both groups.; 20 healthy seniors (age 70 (SD 4) years) and young adults (age 27 (SD 3) years) were examined on 3 days. After exhaustive ramp-like treadmill testing in order to determine maximal heart rate (HRmax) on the first day, either a 4 × 4 min HIIT at 90% of HRmax or a control condition (CON) was randomly performed on the second and third day, respectively. Balance performance (postural sway) was assessed during single limb stance with open eyes (SLEO) and double limb stance with closed eyes (DLEC). EMG was recorded for the soleus (SOL), anterior tibialis (TIB), gastrocnemius (GM) and peroneus longus (PL) muscles at the dominant leg. All measures were collected before, immediately as well as 10, 30 and 45 min after HIIT and CON, respectively.; Compared to CON, HIIT induced significant increases of postural sway immediately after exercise cessation during SLEO in both groups (adults: p &lt; 0.001, Δ = +25% sway; seniors: p = 0.007, Δ = +15% sway). Increased sway during DLEC was only found for seniors immediately and 10 min after HIIT (post: p = 0.003, Δ = +14% sway, 10 min post: p = 0.004, Δ = +18% sway). Muscle activity was increased during SLEO for TIB until 10 min post in seniors (0.008 &lt; p &lt; 0.03) and immediately after HIIT in adults (p &lt; 0.001).; HIIT training may cause an acute 'open-fall-window' with a transient impairment of balance performance for at least 10 min after exercise cessation in both groups. Occluded vision in seniors seems to prolong this period up to 30 min. Thus, the advantage of HIIT with regard to time efficiency seems debatable when considering transient HIIT-induced impairments of neuromuscular function

More than just a side effect: Dynamic knee valgus and deadbug bridging performance in youth soccer players and alpine skiers have similar absolute values and asymmetry magnitudes but differ in terms of the direction of laterality

From a preventative perspective, leg axis and core stabilization capacities are important for soccer players and alpine skiers; however, due to different sport-specific demands, the role of laterality clearly differs and may result in functional long-term adaptations. The aims of this study are 1) to determine whether there are differences in leg axis and core stability between youth soccer players and alpine skiers and 2) between dominant and non-dominant sides, and 3) to explore the outcomes of applying common sport-specific asymmetry thresholds to these two distinct cohorts. Twenty-one highly trained/national-level soccer players (16.1 years, 95% CI: 15.6, 16.5) and 61 alpine skiers (15.7 years, 95% CI: 15.6, 15.8) participated in this study. Using a marker-based 3D motion capture system, dynamic knee valgus was quantified as the medial knee displacement (MKD) during drop jump landings, and core stability was quantified as the vertical displacement during deadbug bridging exercise (DBB $_{displacement}$ ). For the analysis of sports and side differences, a repeated-measures multivariate analysis of variance was used. For the interpretation of laterality, coefficients of variation (CV) and common asymmetry thresholds were applied. There were no differences in MKD or DBB $_{displacement}$ between soccer players and skiers or between the dominant and non-dominant sides, but there was an interaction effect side*sports for both variables (MKD: p = 0.040, η$^{2}$ p = 0.052; DBB $_{displacement}$ : p = 0.025, η$^{2}$ p = 0.061). On average, MKD was larger on the non-dominant side and DBB $_{displacement}$ laterality on the dominant side in soccer players, whereas this pattern was reversed in alpine skiers. Despite similar absolute values and asymmetry magnitudes of dynamic knee valgus and deadbug bridging performance in youth soccer players and alpine skiers, the effect on the direction of laterality was opposite even though much less pronounced. This may imply that sport-specific demands and potential laterality advantages should be considered when dealing with asymmetries in athletes

Comparison of the ‘11+ Kids’ injury prevention programme and a regular warmup in children’s football (soccer) : a cost effectiveness analysis

Objective: To evaluate a potential reduction in injury related healthcare costs when using the '11+ Kids' injury prevention programme compared with a usual warmup in children's football. Methods: This cost effectiveness analysis was based on data collected in a cluster randomised controlled trial over one season from football teams (under-9 to under-13 age groups) in Switzerland. The intervention group (INT) replaced their usual warmup with '11+ Kids', while the control group (CON) warmed up as usual. Injuries, healthcare resource use and football exposure (in hours) were collected prospectively. We calculated the mean injury related costs in Swiss Francs (CHF) per 1000 hours of football. We calculated the cost effectiveness (the direct net healthcare costs divided by the net health effects of the '11+ Kids' intervention) based on the actual data in our study (trial based) and for a countrywide implementation scenario (model based). Results: Costs per 1000 hours of exposure were CHF228.34 (95% CI 137.45, 335.77) in the INT group and CHF469.00 (95% CI 273.30, 691.11) in the CON group. The cost difference per 1000 hours of exposure was CHF-240.66 (95% CI -406.89, -74.32). A countrywide implementation would reduce healthcare costs in Switzerland by CHF1.48 million per year. 1002 players with a mean age of 10.9 (SD 1.2) years participated. During 76 373 hours of football, 99 injuries occurred. Conclusion: The '11+ Kids' programme reduced the healthcare costs by 51% and was dominant (ie, the INT group had lower costs and a lower injury risk) compared with a usual warmup. This provides a compelling case for widespread implementation

Balance and gait performance after maximal and submaximal endurance exercise in seniors: is there a higher fall-risk?

Impaired balance and gait performance increase fall-risk in seniors. Acute effects of different exercise bouts on gait and balance were not yet addressed. Therefore, 19 healthy seniors (10 women, 9 men, age: 64.6±3.2years) were examined on 3days. After exhaustive treadmill testing, participants randomly completed a 2-km treadmill walking test (76±8% VO2max) and a resting control condition. Standing balance performance (SBALP) was assessed by single limb-eyes opened (SLEO) and double limb-eyes closed (DLEC) stance. Gait parameters were collected at comfortable walking velocity. A condition×time interaction of center of pressure path length (COPpath) was observed for both balance tasks (p<0.001). Small (Cohen's d=0.42, p=0.05) and large (d=1.04, p<0.001) COPpath increases were found after 2-km and maximal exercise during DLEC. Regarding SLEO, slightly increased COPpath occurred after 2-km walking (d=0.29, p=0.65) and large increases after exhaustive exercise (d=1.24, p<0.001). No significant differences were found for gait parameters. Alterations of SBALP after exhaustive exercise might lead to higher fall-risk in seniors. Balance changes upon 2-km testing might be of minor relevance. Gait is not affected during single task walking at given velocitie