This study examined the acute effects of the 'Slingshot' on bench-press performance, prime-mover surface electromyographic (sEMG) amplitude, and barbell velocity during maximal and submaximal bench-pressing in competitive male powerlifters. Fifteen male powerlifters (mean ± SD age: 27.05 ± 5.94 years; mass: 94.15kg; 1RM bench-press: 139.7 ± 16.79kg) participated in the study. Bench-press strength, average barbell velocity, and sEMG amplitude of the prime mover muscles (triceps brachii, pectoralis major and anterior deltoid) were measured during two conditions; 'Raw' (without use of any assistance) and 'Slingshot' [using the 'Slingshot' to perform both the weight achieved during 'Raw' 1RM testing (Raw max/SS), and absolute 1RM using the 'Slingshot' (SS)]. The results showed that the 'Slingshot' significantly increased bench press 1RM performance by a mean ± SD of 20.67kg ± 3.4kg. Barbell velocity and stick point analysis indicate that this improvement is likely driven by an increase in peak and pre-stick barbell velocity as triceps RMS was lower throughout all rep max phases with the 'Slingshot'. The 'Slingshot' also caused reductions in RMS, specifically of the triceps at all rep ranges but barbell velocity was better maintained in the last reps of all sets. These data indicate that the 'Slingshot' specifically de-loaded the triceps muscle throughout all rep ranges and provide assistance to maintaining barbell velocity under fatigue during later repetitions of multiple-repetition sets. The 'Slingshot' training aid could therefore be used in de-load phases of bench press training or as an over-reaching and velocity training aid.

IV-LIST OF FIGURES V-LIST OF TABLES VI-LIST OF ABBREVIATIONS CHAPTER 1-INTRODUCTION 1.1 Background 1.2 General aims of this thesis 1.3 Overview of thesis CHAPTER 2-REVIEW OF LITERATURE 2.1 Talent identification 2.1.1 Talent identification in soccer 2.1.2 Talent development 2.1.3 Limitations of talent identification 2.1.3.1 The relative age effect 2.1.3.2 Maturation-selection phenomenon 2.1.3.3 Growth and maturation 2.1.3.4 Challenges of talent identification 2.1.4 Limitations of talent development 2.1.5 Talent identification-summary 2.2 Physical characteristics of soccer 2.2.1 Physical characteristics of professional soccer 2.2.1.1 Running characteristics of professional soccer 2.2.1.2 Strength and power characteristics of professional soccer 2.2.1.3 Anthropometric and morphologic characteristics of professional soccer 2.2.1.4 Physical characteristics of professional soccer-summary 2.2.2 Physical characteristics of youth soccer 2.2.2.1 Running characteristics of youth soccer 2.2.2.2 Strength and power characteristics of youth soccer 2.2.2.3 Anthropometric and morphologic characteristics of youth soccer 2.2.2.4 Physical characteristics of youth soccer-summary 2.2.3 Physical characteristics of soccer-summary 2.3 Physical performance testing in soccer 2.3.1 Evaluating running characteristics of soccer 2.3.1.1 Evaluating running characteristics of soccerendurance 2.3.1.2 Evaluating running characteristics of soccerlinear sprint speed 2.3.1.3 Evaluating running characteristics of soccer-COD/agility 2.3.2 Evaluating strength and power characteristics of soccer 2.3.2.1 Evaluating strength characteristics of soccer 2.3.2.2 Evaluating power characteristics of soccer 2.3.3 Evaluating anthropometric and morphologic characteristics of soccer 2.3.4 Physical performance testing in soccer-summary 2.4 Physical performance testing for talent identification and development 2.4.1 Physical performance testing for talent identification 2.4.2 Physical performance testing for talent development 2.5 Literature review-summary 2.6 Aims VII-SYNTHESIS (LITERATURE REVIEW-CHAPTER 3) CHAPTER 3-RELIABILITY AND VALIDITY OF COMMONLY USED FIELD-BASED FITNESS TESTS IN YOUTH SOCCER PLAYERS 3.1 Introduction 3.2 Methods 3.3 Results 3.4 Discussion 3.5 Conclusion VIII-SYNTHESIS (CHAPTER 3-CHAPTER 4) CHAPTER 4-CHANGE OF DIRECTION AND AGILITY PERFORMANCE ASSESSMENT IN PROFESSIONAL YOUTH SOCCER PLAYERS 4.1 Introduction 4.2 Methods 4.3 Results 4.4 Discussion 4.5 Conclusion IX-SYNTHESIS (CHAPTER 4-CHAPTER 5) CHAPTER 5-A COMPARISON OF OBJECTIVE AND SUBJECTIVE EVALUATION METHODS OF PHYSICAL QUALITIES IN PROFESSIONAL YOUTH SOCCER PLAYERS 5.1 Introduction 5.2 Methods 5.3 Results 5.4 Discussion 5.5 Conclusion X-SYNTHESIS (CHAPTER 5-CHAPTER 6

Wilson et al. Tensiomyography Reflects Skeletal Muscle Architecture improved contractile properties, alongside improvements in muscle function within an untrained population. Furthermore, the observed associations between Dm and muscle architecture suggest that TMG contractile property assessments could be used to obtain information on muscle geometry.

To optimize use of available resources, professional academies develop strategies to assess, monitor, and evaluate players as they progress through adolescence toward adulthood. However, few published reports exist using longitudinal study designs to examine performance throughout adolescence and the transition from youth to professional soccer. We examined differences in the age of player recruitment alongside longitudinal performance differences on field‐based fitness tests of successful vs. unsuccessful graduates across the entire age spectrum recruited by a professional soccer academy. Altogether, 537 youth soccer players volunteered to participate. We recorded the age of recruitment, biannual fitness test performance, and subsequent success in attaining a senior professional contract at the club across a period of 12 years. Only 53 (10%) of players were successful in obtaining a professional contract, with 68% of players who became professional being recruited at 12 years of age or older. Individuals recruited at an earlier age did not display a higher probability of success in attaining a professional contract. Bayesian regression models reported a consistent interaction between age and group for data on all performance measures. Moreover, “successful” academy graduates only physically outperformed their “unsuccessful” counterparts from age ~13‐14 years onward, with either no differences in performance, or performance on physical fitness tests favoring “unsuccessful” players prior to this age. Findings suggest that high achievers during childhood and early adolescence may not develop into successful senior professionals, raising concerns about the predictive utility of talent identification models.

Subjective and objective assessments may be used congruently when making decisions regarding player recruitment in soccer, yet there have been few attempts to examine the level of agreement between these methods. Therefore, we compare levels of agreement between subjective and objective assessments of physical qualities associated with youth soccer performance. In total, 80 male youth soccer players (13.2 ± 1.9 years), and 12 professional coaches volunteered to participate. Players were objectively assessed using five fitness measures: Yo-Yo Intermittent Recovery Test Level 1; Countermovement vertical jump; Functional Movement Screen™; 5/20m sprint; alongside anthropometric measures.Additionally, coaches subjectively rated each player on the same five physical qualities using 5-point Likert scales. Inter-rater agreement between ratings from lead and assistant coaches were established for each age group. Moreover, Bayesian regression models were fitted to determine how well coach ratings were able to predict fitness test performance. Although inter-rater agreement between lead and assistant coaches was moderate-to-substantial (ω=0.48-0.68), relationships between coaches subjective rating's and corresponding fitness test performance were only highly related for the highest and lowest performing players. We suggest that while ratings derived from objective and subjective assessment methods may be related when attempting to differentiate between distinct populations, concerns exist when evaluating homogeneous samples using these methods. Our data highlight the benefits of using both types of measures in the talent identification process.