Individualization in elite sports: optimizing strength for sports performance and performance development Reichert, Lukas

Muscular strength plays a decisive role in elite sports. Studies indicate that increased strength is associated with a lower risk of injury and better sports performance as well as better overall performance development. Practitioners therefore aim to increase athletes' strength levels strength and power training. Several studies describe how training should be structured to increase strength, but such descriptions are often generic. However, studies indicate that adaptations to strength training differs between individual athletes, requiring an individualized approach. The individual factors that contribute to interindividual adaptation to strength training have not yet been sufficiently researched. Therefore, this dissertation adopts an individualization approach. It is assumed that an individual's response to strength training is affected by various individual factors (e.g., genetics, nutrition), as well as the interaction between these factors and environmental factors (e.g., the actual training). Against this backdrop, a conceptual individualization model was developed to theoretically embed individual factors. This model structures and guides the studies in this thesis. The studies are described in three scientific articles and comprise the majority of this dissertation. The first study examines a sport-specific diagnostic of upper-body strength, while the second study investigates the relationship between individual genetic profiles and power performance in elite athletes. The third study, which is literaturebased, ad-dresses the extent to which genetics might inform individualized strength training recommendations or overall performance development and describes how genetic information is handled in an elite sports project (‘in:prove’). All studies focus on sports in which strength and power performance plays a decisive role, such as volleyball, ice hockey, and gymnastics. Methodologically, this dissertation considers both traditional exercise science (e.g., motor performance diagnostics) as well as multidisciplinary sports science methods (e.g., genetic analyses). Study 1 develops and evaluates a sport-specific diagnostic tool for assessing upperbody strength. The results suggest that the developed diagnostic tool is a valid and reliable method for measuring upperbody strength specifically for game sport athletes. This tool is a valuable addition to performance diagnostics, particularly in sports where upperbody strength is important, as it enables individualized training prescriptions. Study 2 examines the relationship between individual genetic profiles and power performance in elite athletes. The results show that the individual genetic profile (including specific polymor-phisms in different genes) accounts for approximately 10% of power performance in elite male and female athletes. Accordingly, other person-related and environmental factors account for 90% of the variance in power performance. The third study, a narrative review, describes the extent to which genetics might provide indications for individualized, genetics-based strength training recommendations. However, the analysis indicates that evidence in this area is currently limited, emphasizing the need for further experimental research. Thus, this third research paper provides a conceptual basis for further investigations into individual factors in the context of training adaptations to strength training. The dissertation concludes with a summary of the results, theoretical considerations, and practical implications. It is discussed how future research could benefit from the theoretical approach and results of this work, as well as from additional experimental investigations.