The Physiological and Genetic Factors Underpinning Powerful Actions in Elite Youth Soccer

There is no information available in the scientific literature that documents a specific assessment protocol for analysing a soccer player’s maximal power capabilities. As soccer-associated muscular power has not previously been investigated, it is not known how important power is in elite soccer and, if it is, the physiological and genetic determinants of soccer-associated power remain unknown. Such information could be used to optimise soccer-specific talent identification and development strategies. With this in mind, the overriding aim of our thesis was to investigate the physiological and genetic factors underpinning powerful actions in elite youth soccer. When devising an assessment of soccer-associated muscular power, there needs be a detailed analysis of the specific actions performed during elite competitive match-play that can be described as powerful. The aims of our first experimental study (Chapter Three) were to compare the frequency and durations of powerful actions during competitive English Premier League [under 18 (U18) and under 21 (U21)] elite youth soccer matches using a novel soccer specific powerful action (SSPA) notational analysis coding system. We found that while elite soccer match-play requires players to perform powerful actions in multiple directions [68 horizontal accelerations (in the horizontal-forward or mediolateral directions), eight sprints, and six vertical jumps (three bilateral and three unilateral)], horizontal accelerations of short duration ( A (rs6265), COL5A1 C>T (rs12722), and COL2A1 C>T (rs2070739)] played a role in determining elite youth soccer player status, and speed and power capabilities, in ESP and CON at different stages of maturation. We found that ACTN3 R- and BDNF G-allele frequencies were more frequent in post-PHV compared to pre-PHV ESP. Moreover, while the COL2A1 CC genotype was associated with greater horizontal power and faster 20 m sprint performance, BDNF GG genotype appears to positively influence 20 m sprint performance during the pre-PHV period only. Overall, our findings illustrate that elite soccer may require different genetic profiles before and after maturation, and genetic screening could be included in talent identification criteria to help predict maximal power and sprint potential in ESP. In summary, we devised a muscular power assessment battery that measured independent power qualities and could discriminate between U18 and U21 ESP and NSP. Our subsequent analysis showed that the physiological factors underpinning unilateral CMJ performance were direction-specific, and UV and UH CMJ capabilities were underpinned by separate neuromuscular and tendon properties, and should be assessed and developed, independently in U18 and U21 ESP. We then recruited a larger cohort of ESP and CON, at different stages of maturation, and demonstrated that muscular power was important for elite soccer performance at mid and post-PHV, but not pre-PHV. Finally, we showed that genetic profiles of ESP differed between pre- and post-PHV, and that certain gene variants [COL2A1 C>T (rs2070739), BDNF G>A (rs6265)] were associated with specific power and speed capabilities in ESP. Overall, our studies provide novel information that could have significant implications on soccer-associated power related talent identification and training intervention strategies in elite youth soccer academies.