Identifying Differences in Swimming Speed Fluctuation in Age-Group Swimmers by Statistical Parametric Mapping: A Biomechanical Assessment for Performance Development.

The aim of this study was to compare the assessment of swimming speed processed as a discrete variable and as a continuous variable in young swimmers. One-hundred and twenty young swimmers (60 boys: age = 12.91 ± 0.86 years; 60 girls: age = 12.46 ± 0.94 years) were analysed. The dataset for each sex was divided into three tiers: (i) tier #1 - best-performing swimmers; (ii) tier #2: intermediate-performing swimmers, and; (iii) tier #3 - poorest-performing swimmers. As a discrete variable, swimming speed showed significant sex and tier effects, and a significant sex*tier interaction (p < 0.001). Speed fluctuation showed a non-significant sex effect (p > 0.05), a significant tier effect (p < 0.001), and a non-significant sex*tier interaction (p > 0.05). As a continuous variable, the swimming speed time-curve presented significant sex and tier effects (p < 0.001) throughout the stroke cycle, and a significant sex*tier interaction (p < 0.05) in some moments of the stroke cycle. Swimming speed fluctuation analysed as a discrete variable and as a continuous variable can be used in a complementary way. Nonetheless, SPM can provide deeper insight into differences within the stroke cycle. Thus, coaches and practitioners should be aware that different knowledge about the swimmers' stroke cycle can be learned by assessing swimming speed using both methods.

Development of a video analysis protocol and assessment of fall characteristics in equestrian cross-country eventing.

Cross-country eventing is one of the highest-risk sporting activities for serious injury outcomes. This study investigated relationships between fall characteristics and high-risk falls at jumps in cross-country eventing. A video analysis protocol was systematically developed to analyze 87 video recordings of high-risk rider falls; defined as when the rider's head impacted the ground and/or where there was potential horse impact with the rider. Falls were classified according to competition type, jump type, horse-related, and rider-related factors. At least one high-risk fall characteristic was observed in 45 of 87 examined falls. Multivariable best subsets regression identified five independent variables explaining 38.4% of the variance in the number of high-risk falls. Increased likelihood of high-risk falls was associated with continuation of horse direction or speed upon rider ground impact, higher jump approach speed, changes in rider body posture upon landing, rider air jacket usage, and reduced rider fall time. The Eventing Fall Assessment Instrument (EFAI) video analysis protocol (attached as supplementary material) facilitated systematic examination of multiple characteristics associated with high-risk falls and identified likely influential characteristics. Based on EFAI and subsequent data analyses, findings suggest optimized approach speed for correct striding and take-off; jump design to enable run-out; and rider training could help reduce the occurrence of high-risk falls. Air jacket usage and their design characteristics warrant further investigation.

Maturity-related developmental inequalities in age-group swimming: The testing of 'Mat-CAPs' for their removal.

OBJECTIVES: To (1) examine the association between maturity timing and performance-based selection levels in (N=708) Australian male 100-m Freestyle swimmers (12-17 years); (2) identify the relationship between maturation status and 100-m Freestyle performance; and (3) determine whether Maturation-based Corrective Adjustment Procedures (Mat-CAPs) could remove maturation-related differences in swimming performance. METHODS: In Part 1, maturity timing category distributions ('Early', 'Early Normative', 'Late Normative' and 'Late') for 'All', 'Top 50%' and '25%' of raw swimming times were examined within and across age-groups. In Part 2, multiple regression analyses quantified the relationship between maturity offset (YPHV) and swimming performance. In Part 3, sample-based maturity timing category distributions were examined based on raw and correctively adjusted swim times for 12-17 year old age-groups. RESULTS: Based on raw swim times, a high prevalence of 'Early-maturing' swimmers, with large effect sizes was identified (e.g., 14 years 'All' - χ2 (3, 151=111.98, p<0.001; 'Early' v 'Late' OR=82.0 95%CI=4.77, 1409.9); while a complete absence of 'Late-maturers' was apparent in the sample (N=708). When maturity categories were re-defined based on sample mean±standard deviation, and when using the expected curvilinear trendline identified in Part 2, Mat-CAPs mitigated maturity timing biases across all age-groups and selection levels, and removed the Freestyle performance advantage afforded by advanced maturity timing and status. CONCLUSIONS: Removing the influence of maturation-related developmental differences could help improve youth swimmer participation experiences and improve the accuracy of identifying genuinely skilled age-group swimmers.

Sink or Swim? A survival analysis of sport dropout in Australian youth swimmers.

OBJECTIVES: To examine long-term participation and dropout rates in Australian youth swimming using survival analyses and to determine whether multiple individual, socio-demographic, and competition-related factors influenced dropout. DESIGN: Retrospective cohort study of registration and competitive performance data. METHODS: Part 1-Registration data from N = 17 161 female (n = 9400) and male (n = 7761) New South Wales (NSW) swimmers aged 10-15 years (inclusive). Part 2-Competition level involvement in a subsample of female (n = 1011) and male (n = 811) swimmers, aged 12-15 years, was also examined. To determine dropout rates and influential factors, Kaplan-Meier survival analyses supplemented by Cox regression were used. RESULTS: (1) Kaplan-Meier analyses identified median sustained participation rates of four years (95% CI = 3.93-4.06), with 15.9% maintaining participation over 10 years. Cox regressions identified age-group was associated with dropout (P < .001), with a 184.9% higher Hazard Rate (HR) for 10- vs 15-year-olds. Residential proximity to major cities was associated with dropout (P < .001), with urban swimmers reporting a 24.8% higher HR rate than rural swimmers. Sex and relative age were not associated with dropout. (2) The subsample median sustained participation was five years (95% CI = 4.79-5.20), with 25.3% maintaining participation for ten years. Level of competition was associated (P < .001), with an 86% higher HR when considering lower competition levels (ie, club/district v national). CONCLUSION: In a large representative sample of swimmers, survival analyses identified age-group, competition level, and city proximity were associated with increased swimming dropout rates.

Annual age-grouping and athlete development: a meta-analytical review of relative age effects in sport.

Annual age-grouping is a common organizational strategy in sport. However, such a strategy appears to promote relative age effects (RAEs). RAEs refer both to the immediate participation and long-term attainment constraints in sport, occurring as a result of chronological age and associated physical (e.g. height) differences as well as selection practices in annual age-grouped cohorts. This article represents the first meta-analytical review of RAEs, aimed to collectively determine (i) the overall prevalence and strength of RAEs across and within sports, and (ii) identify moderator variables. A total of 38 studies, spanning 1984-2007, containing 253 independent samples across 14 sports and 16 countries were re-examined and included in a single analysis using odds ratios and random effects procedures for combining study estimates. Overall results identified consistent prevalence of RAEs, but with small effect sizes. Effect size increased linearly with relative age differences. Follow-up analyses identified age category, skill level and sport context as moderators of RAE magnitude. Sports context involving adolescent (aged 15-18 years) males, at the representative (i.e. regional and national) level in highly popular sports appear most at risk to RAE inequalities. Researchers need to understand the mechanisms by which RAEs magnify and subside, as well as confirm whether RAEs exist in female and more culturally diverse contexts. To reduce and eliminate this social inequality from influencing athletes' experiences, especially within developmental periods, direct policy, organizational and practitioner intervention is required.