The development of physical performance in adolescent youth soccer players: the impact of maturation and training
Creators: name: McGoldrick, Cillian
Publisher: name: Zenodo
Year: 2024

description: Physical performance in soccer is dependent upon a multitude of fitness components for successful performance. Specifically, strength, speed, and power performance has been linked to game defining moments, and can aid youth players in transitioning through an academy structure. Despite the importance of the development of these qualities, little research has quantified the development of strength, speed, and power capabilities using reliable performance tests over durations similar to standard soccer season lengths. Research such as this could assist the applied practitioner in developing programming aimed at enhancing these qualities, and/or, provide normative data from which to use to compare individual/team magnitude of changes.The first study included in this thesis (Chapter 4) aimed to validate a strength test for use with youth soccer players. Specifically, we evaluated the reliability of two different isometric squat test (ISqT) protocols and compared the outputs and levels of reliability between the two, specifically in youth soccer players. A more time-efficient protocol was developed where participants self-selected their body position for use during the assessment as opposed to utilising a set knee joint angle. In addition, the minimum number of familiarisations required for data to stabilise was also evaluated for both protocols. The results of this study demonstrate that the isometric squat test is reliable for use in youth soccer populations. In addition, this study demonstrates that the self-determined protocol resulted in larger peak force values with data also stabilising at a faster rate.Subsequently, the following study aimed to determine the relationships between ISqT metrics which displayed acceptable reliability, and common global measures of speed and power. In addition, this study aimed to examine how change in ISqT performance metrics relates to changes in that of speed and jump performance. It was demonstrated that peak and relative peak force displayed the strongest relationships (44.1−53.8%) with different measures of speed and jump performance. Therefore, the results of Chapters 4 and 5 demonstrate the ISqT metrics which are both reliable and display statistically significant relationships with, and explain large proportions of the variability of measures of physical performance related to youth soccer.Chapter 6 then sought to utilise these metrics to longitudinally evaluate change to strength, speed, and power characteristics over a 7−8-month period. In addition, this study aimed to determine the change in physical performance of youth soccer players associated with a top tier soccer academy compared to that of an amateur soccer academy as an indication of the efficacy of the strength and conditioning specific training programme. Lastly, the influence of growth and maturation on these measures was also evaluated. The results of Chapter 6 show that measures of strength and jump performance improved in youth soccer players from the professional academy compared to the amateur academy over the study duration when proxy measures of maturation were controlled for. In addition, strength and 10m sprint performance was greater for the professional academy players compared to that of the amateur academy players. Lastly, maturation (percentage of estimated adult height) was shown to have demonstrated an effect on all measures of physical performance. It could be suggested from the results of this study that a primary reason for the difference in change between academy players was the inclusion of a strength and power specific programme.The final study of this thesis then aimed to determine the underpinning physiological adaptations which contribute to strength, speed, and power performance. Therefore, changes to vastus lateralis muscle architecture were examined following an 8-month period. We show that muscle thickness, pennation angle, fascicle length, and relative muscle thickness displayed no changes over the study duration. Furthermore, there was no observed interaction with measures of maturation. However, relative fascicle length was shown as statistically significantly longer post-intervention compared to pre-, but did not display any interaction with maturation, and was therefore likely related to the training programme undertaken.In conclusion, this thesis provides novel research in the areas of applied performance monitoring and development in youth soccer. Specifically, a novel testing methodology has been demonstrated to be reliable and capable of being utilised in the longitudinal monitoring of youth soccer players. Indeed, the self-determined isometric squat test protocol is likely more time efficient, autonomy supportive, and subjectively comfortable for the participant when compare to traditional testing methods. Changes to strength, speed, and power performance over a duration akin to that of a standard season length has demonstrated larger accelerative running, strength, and jump improvements for youth soccer players participating in structured and targeted strength and power training compared to amateur controls participating in pitchonly training. Nonetheless, it was also show here that maturation exerts the largest effect on all measures of strength, speed, and power performance. There is evidence of muscle morphological adaptations that may contribute to enhanced strength, speed, and power performance in elite youth soccer players likely a result of specific strength and power training.