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Responding to the Commentary on the Article: “Improving the Prediction of Maturity From Anthropometric Variables Using a Maturity Ratio”

Job Fransen, Adam Baxter-Jones, and Stephen Woodcock

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Effect of Skill Level on Allocation of Visual Attention in Volleyball Blocking

Jason C. Laffer, Aaron J. Coutts, and Job Fransen

Dynamic motor skills such as volleyball blocking rely on efficient perception–action coupling and are influenced by individual, environmental, and task constraints. However, limited research studies have assessed the effect of an individual constraint such as blocking skill on visual attention during an in-situ volleyball blocking task. Therefore, this study used a cross-sectional, observational design to investigate the gaze behavior of 18 male volleyball players (25.6 ± 4.9 years), of two different levels of blocking skill determined a priori according to success during an on-court blocking task. When compared to relatively unsuccessful players (RUS), the gaze of relatively successful players (RS) was observed to fixate more often (RUS: 0.7 ± 0.7 n, RS: 1.3 ± 0.3 n) and dwell for longer (Total; RUS: 12.2 ± 18.4%, RS: 48.0 ± 37.2%, Phase 4; RUS: 6.6 ± 8.8%, RS: 16.9 ± 12.4%) on the opposition spiker, demonstrating that important perceptual information about an opposing team’s attack lies within the behavior of the opposition spiker. More successful blockers were also observed to be taller (RUS: 181.8 ± 6.6 cm, RS: 192.6 ± 3.9 cm), longer in arm-span (RUS: 185.7 ± 5.6 cm, RS: 195.2 ± 5.6 cm), and heavier (RUS: 78.6 ± 11.4 kg, RS: 90.5 ± 8.5 kg). These results can consequently be used to develop a profile of the visual attention and physical attributes of successful blockers for use in developing talented players.

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Responses to a 5-Day Sport-Specific Heat Acclimatization Camp in Elite Female Rugby Sevens Athletes

Mitchell J. Henderson, Bryna C.R. Chrismas, Job Fransen, Aaron J. Coutts, and Lee Taylor

Purpose: To describe the physiological (resting core temperature, exercising heart rate, and sweat rate) and psychophysical (rating of perceived exertion, thermal sensation, and thermal comfort) responses to a short-term heat acclimatization (HA) training camp in elite female rugby sevens athletes. Methods: Nineteen professional female rugby sevens athletes participated in a 5-day HA camp in Darwin, Australia (training average: 32.2°C and 58% relative humidity). Training involved normal team practice prescribed by appropriate staff. Markers of physiological and psychophysical adaptations to HA were collected at various stages during the camp. Partial eta-squared effect sizes (from linear mixed-effects models), rank-biserial correlations (from Freidman tests), and P values were used to assess changes across the protocol. Results: Resting core temperature did not significantly change. Exercising heart rate showed a large and significant reduction from day 1 to day 5 (175 [13] vs 171 [12] beats·min−1), as did sweat rate (1.1 [0.3] vs 1.0 [0.2] L·h–1). Thermal sensation showed a large and significant reduction between day 1 and day 5 (median [interquartile range] = 5 [5–5.5] vs 4.5 [4–5]). Changes in rating of perceived exertion and thermal comfort were unclear. Conclusions: Beneficial cardiovascular adaptations were observed simultaneously across a full squad of elite female rugby sevens players (without expensive facilities/equipment or modifying training content). However, beneficial changes in resting core temperature, sweat rate, and thermal/effort perceptions likely require a greater thermal impulse. These data contribute to the development of evidence-informed practice for minimal effective HA doses in female team-sport athletes, who are underrepresented in the current research.

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Limiting Rise in Heat Load With an Ice Vest During Elite Female Rugby Sevens Warm-Ups

Mitchell J. Henderson, Bryna C.R. Chrismas, Christopher J. Stevens, Job Fransen, Aaron J. Coutts, and Lee Taylor

Purpose: To determine the effect of wearing a phase-change cooling vest in elite female rugby sevens athletes during (1) a simulated match-day warm-up in hot conditions prior to a training session and (2) a prematch warm-up during a tournament in cool conditions. Methods: This study consisted of 2 randomized independent group designs (separated by 16 d) where athletes completed the same 23- to 25-minute match-day warm-up (1) in hot conditions (range = 28.0°C to 35.1°C wet bulb globe temperature [WBGT]) prior to training and (2) in cool conditions (range = 18.8°C to 20.1°C WBGT) prior to a World Rugby Women’s Sevens Series match. In both conditions, athletes were randomly assigned to wearing either (1) the standardized training/playing ensemble (synthetic rugby shorts and training tee/jersey) or (2) the standardized training/playing ensemble plus a commercial phase-change athletic cooling vest. Group-wise differences in core temperature rise from baseline, global positioning system–measured external locomotive output, and perceptual thermal load were compared. Results: Core temperature rise during a match warm-up was lower in the hot condition only (−0.65°C [95% confidence interval = −1.22°C to −0.08°C], η p 2 = .23 [95% confidence interval = .00 to .51], P = .028). No differences in various external-load variables were observed. Conclusions: Phase-change cooling vests can be worn by athletes prior to, and during, a prematch warm-up in hot conditions to limit excess core temperature rise without adverse effects on thermal perceptions or external locomotion output.

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Additional Clothing Increases Heat Load in Elite Female Rugby Sevens Players

Mitchell J. Henderson, Bryna C.R. Chrismas, Christopher J. Stevens, Andrew Novak, Job Fransen, Aaron J. Coutts, and Lee Taylor

Purpose: To determine whether elite female rugby sevens players are exposed to core temperatures (Tc) during training in the heat that replicate the temperate match demands previously reported and to investigate whether additional clothing worn during a hot training session meaningfully increases the heat load experienced. Methods: A randomized parallel-group study design was employed, with all players completing the same approximately 70-minute training session (27.5°C–34.8°C wet bulb globe temperature) and wearing a standardized training ensemble (synthetic rugby shorts and training tee [control (CON); n = 8]) or additional clothing (standardized training ensemble plus compression garments and full tracksuit [additional clothing (AC); n = 6]). Groupwise differences in Tc, sweat rate, GPS-measured external locomotive output, rating of perceived exertion, and perceptual thermal load were compared. Results: Mean (P = .006, η p 2 = .88 ) and peak (P < .001, η p 2 = .97 ) Tc were higher in AC compared with CON during the training session. There were no differences in external load (F 4,9 = 0.155, P = .956, Wilks Λ = 0.935, η p 2 = .06 ) or sweat rate (P = .054, Cohen d = 1.09). A higher rating of perceived exertion (P = .016, Cohen d = 1.49) was observed in AC compared with CON. No exertional-heat-illness symptomology was reported in either group. Conclusions: Player Tc is similar between training performed in hot environments and match play in temperate conditions when involved for >6 minutes. Additional clothing is a viable and effective method to increase heat strain in female rugby sevens players without compromising training specificity or external locomotive capacity.

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Improving the Prediction of Maturity From Anthropometric Variables Using a Maturity Ratio

Job Fransen, Stephen Bush, Stephen Woodcock, Andrew Novak, Dieter Deprez, Adam D.G. Baxter-Jones, Roel Vaeyens, and Matthieu Lenoir

Purpose: This study aimed to improve the prediction accuracy of age at peak height velocity (APHV) from anthropometric assessment using nonlinear models and a maturity ratio rather than a maturity offset. Methods: The dataset used to develop the original prediction equations was used to test a new prediction model, utilizing the maturity ratio and a polynomial prediction equation. This model was then applied to a sample of male youth academy soccer players (n = 1330) to validate the new model in youth athletes. Results: A new equation was developed to estimate APHV more accurately than the original model (new model: Akaike information criterion: −6062.1, R 2 = 90.82%; original model: Akaike information criterion = 3048.7, R 2 = 88.88%) within a general population of boys, particularly with relatively high/low APHVs. This study has also highlighted the successful application of the new model to estimate APHV using anthropometric variables in youth athletes, thereby supporting the use of this model in sports talent identification and development. Conclusion: This study argues that this newly developed equation should become standard practice for the estimation of maturity from anthropometric variables in boys from both a general and an athletic population.

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Changes in Physical Fitness and Sports Participation Among Children With Different Levels of Motor Competence: A 2-Year Longitudinal Study

Job Fransen, Dieter Deprez, Johan Pion, Isabel B Tallir, Eva D’Hondt, Roel Vaeyens, Matthieu Lenoir, and Renaat M. Philippaerts

The goal of this study was to investigate differences in physical fitness and sports participation over 2 years in children with relatively high, average, and low motor competence. Physical fitness and gross motor coordination of 501 children between 6–10 years were measured at baseline and baseline+2 years. The sample compromised 2 age cohorts: 6.00–7.99 and 8.00–9.99 years. An age and sex-specific motor quotient at baseline testing was used to subdivide these children into low (MQ < P33), average (P33 ≤ MQ < P66) and high (MQ ≥ P66) motor competence groups. Measures of sports participation were obtained through a physical activity questionnaire in 278 of the same children. Repeated Measures MANCOVA and two separate ANOVAs were used to analyze differences in changes in physical fitness and measures of sports participation respectively. Children with high motor competence scored better on physical fitness tests and participated in sports more often. Since physical fitness levels between groups changed similarly over time, low motor competent children might be at risk for being less physically fit throughout their life. Furthermore, since low motor competent children participate less in sports, they have fewer opportunities of developing motor abilities and physical fitness and this may further prevent them from catching up with their peers with an average or high motor competence.

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A Longitudinal Analysis of the Executive Functions in High-Level Soccer Players

Adam Beavan, Vincent Chin, Louise M. Ryan, Jan Spielmann, Jan Mayer, Sabrina Skorski, Tim Meyer, and Job Fransen

Introduction: Assessments of executive functions (EFs) with varying levels of perceptual information or action fidelity are common talent-diagnostic tools in soccer, yet their validity still has to be established. Therefore, a longitudinal development of EFs in high-level players to understand their relationship with increased exposure to training is required. Methods: A total of 304 high-performing male youth soccer players (10–21 years old) in Germany were assessed across three seasons on various sport-specific and non-sport-specific cognitive functioning assessments. Results: The posterior means (90% highest posterior density) of random slopes indicated that both abilities predominantly developed between 10 and 15 years of age. A plateau was apparent for domain-specific abilities during adolescence, whereas domain-generic abilities improved into young adulthood. Conclusion: The developmental trajectories of soccer players’ EFs follow the general populations’ despite long-term exposure to soccer-specific training and game play. This brings into question the relationship between high-level experience and EFs and renders including EFs in talent identification questionable.

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The Influence of Restricted Visual Feedback on Dribbling Performance in Youth Soccer Players

Job Fransen, Thomas W.J. Lovell, Kyle J.M. Bennett, Dieter Deprez, Frederik J.A. Deconinck, Matthieu Lenoir, and Aaron J. Coutts

The aim of the current study was to examine the influence of restricted visual feedback using stroboscopic eyewear on the dribbling performance of youth soccer players. Three dribble test conditions were used in a within-subjects design to measure the effect of restricted visual feedback on soccer dribbling performance in 189 youth soccer players (age: 10–18 y) classified as fast, average or slow dribblers. The results showed that limiting visual feedback increased dribble test times across all abilities. Furthermore, the largest performance decrement between stroboscopic and full vision conditions was in fast dribblers, showing that fast dribblers were most affected by reduced visual information. This may be due to a greater dependency on visual feedback at increased speeds, which may limit the ability to maintain continuous control of the ball. These findings may have important implications for the development of soccer dribbling ability.

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The Applicability of a Short Form of the Körperkoordinationstest für Kinder for Measuring Motor Competence in Children Aged 6 to 11 Years

Andrew R. Novak, Kyle J.M. Bennett, Adam Beavan, Johan Pion, Tania Spiteri, Job Fransen, and Matthieu Lenoir

This study aimed to determine if the Körperkoordinationstest für Kinder (KTK) remained a valid assessment of motor competence following the removal of the hopping for height subtest (KTK3). Children (n = 2479) aged 6–11 years completed all KTK subtests (KTK4) and motor quotient sum scores (MQS) were determined for the KTK3 and KTK4. Classifications were established as MQS below percentile 5 (P5), MQS between percentile 5–15 (P15), MQS between percentile 15–50 (P15–50), MQS between percentile 50–85 (P50–85), MQS between percentile 85–95 (P85), and MQS higher than percentile 95 (P95). Pearson’s correlation (r = .97) and cross-tabs (Chi2 = 6822.53, p < .001; Kappa = 0.72) identified substantial agreement overall between the KTK3 and KTK4. However, when classified into separate age and gender categories, poor agreement (< 60%) was found in girls: P15 at 8–11 years and P85 at 6–7 years; and in boys: P5 and P15 at 6 years, P85 at 8 years, and P15 at 10 years. Researchers should consider these findings when selecting which KTK protocol to use.