Understanding the force-deflection behavior of the sternum is an important element in designing devices for implants for chest wall deformity repair. Human growth and variability makes a single measure of the stiffness difficult to determine. This work takes empirical data from the literature to develop aggregate sternal force-deflection models. Statistical methods were used to determine possible groupings based on patient age and the effect of gender. It was found that three age groups could be used, representing childhood (4-10 years), adolescence (11-19 years), and adulthood (26-53 years). Gender was found to have a statistical p-value of 0.068, 0.0611, and 0.012, respectively, in the proposed age groups. Jittering of the data was used to account for human variability and assumptions made in data comparisons. The jittered results followed that of the initial data set. Childhood force-deflection behavior follows a relatively constant stiffness, adolescence experiences a growth period of increasing stiffness, and adulthood stiffnesses again begin to stabilize around a relatively constant value.

Organised sport is one potential antidote to the global youth inactivity crisis. Therefore, understanding why young people drop out constitutes a key research endeavour. In part I of this series, we developed and validated a new Youth Sport Dropout Questionnaire (YSDQ). In part II, we used the YSDQ-LV (49-item long version) to examine dropout in 960 university students from seven European countries. A four-stage analysis investigated the relative and combined importance of dropout reasons. Three items—the rocks—were statistically more important: “I prioritised schoolwork and had no time left to take part in sport”; and “I found other things that I enjoyed doing more than sport”; and “I found it stressful when I did not perform/play as well as I expected”. On average, however, these rocks were rated as “moderately important”, along with 19 reasons (the pebbles) rated as “slightly important to moderately important”, and the remaining 27 reasons (the sand) rated as “slightly important to not at all important”. These findings suggest that sport dropout is not caused by a single reason but is underpinned by a dynamic tricky mix of reasons—a series of rocks, pebbles, and sand unique to each young person.

Despite the widespread health benefits of physical activity, globally, four out of five adolescents are insufficiently active. Sport participation, a key vehicle for physical activity, diminishes by as much as 80% as children get older. To date, no theoretically grounded, validated research measure of dropout exists. In this two-paper series, we attempt to resolve this issue via the development, initial validation, and application of the Youth Sport Dropout Questionnaire. In the current paper—Part I—we used the COM-B framework to design and initially validate the Youth Sport Dropout Questionnaire. Three sequential studies were conducted. Study 1 includes a review of the existing literature, an expert consultation, and participant focus groups. Study 1 generated 49 reasons for youth sport dropout. Study 2 explored the functionality of the 49 items in a sample of 479 students. Exploratory factor analysis revealed a 28-item four-factor solution. Study 3 tested the dimensionality and reliability of scale in a sample of 648 students from seven European countries. Confirmatory factor analysis supported a final 16-item, four-factor solution, suggesting that reasons for dropout behavior were captured by capability (C), opportunity (O), motivation (M) with the important new addition of injury (I). This initial validation supports the YSDQ as a rigorous research tool to capture the reasons underpinning youth sport dropout behavior.

Research shows that the coaching workforce in most countries is composed of a blend of volunteers and part-, and full-time paid individuals. However, the exact makeup of this workforce across the youth sport1 participation spectrum is not well understood. While previous studies have sought to understand the coaching landscape, very few studies have focused specifically on the youth sport landscape. Given the societal importance of youth sport and the positive contribution that coaches make, this is an area that needs further attention. Using a mass survey methodology, this study aimed to create a detailed picture of the current landscape of youth sport coaching in the United Kingdom. Findings show some similarities to previous workforce audits. For example, youth sport coaching is primarily a voluntary activity (62%)—yet, opportunities to access paid positions have grown. Moreover, findings also show that the youth sport workforce is not a homogenous entity. This signals the need for further research to gain an accurate understanding of the needs and wants of coaches individually, and in their specific working environments, before implementing any recruitment or development programmes.