Evaluation of Selected Genetic, Physiological and Environmental Factors to Support the Development of Elite Male Youth Football Players

Time-loss injury incidence disrupts access to developmental opportunities for elite male youth footballers. Interindividual genetic variations influence musculoskeletal injury susceptibility along with environmental factors and biological processes of growth and maturation. Greater understanding of these factors and how they may influence each other could inform targeted and individualised training programmes to support the long-term development of elite footballers. The aims of this research were to evaluate and explore the current applicability of selected genetic, physiological and environmental factors to inform support for the long-term development of elite male youth footballers. Initial scoping of literature highlighted injury prevention as the most ethically appropriate and practically meaningful area to apply genetic information to inform support of long-term elite footballer development at this time. A systematic review and meta-analysis of candidate gene association studies with fracture risk in physically active participants was completed to identify candidate genes for subsequent analysis along with existent literature. The influence of growth and maturation on injuries in elite male football were then explored to identify physiological factors which could mediate the influence of genetic variants on injury susceptibility. The association between candidate genes (COL1A1, COL1A2, COL5A1, ACTN3, ESR1, MMP3, ACE, VDR, and GDF5) and tissue-specific injury incidence in elite male youth footballers were then explored to identify genotypes which influence injury risk. Finally, growth, maturation, loading exposure, and tissue-specific total genotype injury risk score were combined to explore how different risk categories influence injury incidence, and which could inform targeted interventions to reduce injury risk in elite male youth football. The research contributed to current knowledge with the following findings: identifying a potential sex-specific influence of the COL1A1 (rs1800012) T allele on fracture risk in young physically active females from the extant literature; highlighting that growth rate alone appears unable to sensitively identify individuals at increased risk of injury when measured every 3-12 weeks, unlike previous research using longer measurements, which may have observed spurious relationships with maturational processes occurring alongside growth; detecting significant genetic associations between the MMP3 (rs679620) and VDR (rs2228570) SNPs with non-contact injury, and the COL1A2 (rs412777) variant with fracture risk (p ≤ 0.01); observing that when incorporating growth rate and loading exposure into a risk model, COL1A1 (rs1800012) T allele carriers and those experiencing rapid growth (>0.6 cm.m-1) were associated with significantly greater risk of apophysitis injury (p ≤ 0.03). These findings contribute towards the long-term goal of supporting elite male youth footballers to achieve their potential with genetically informed individualised training programmes.