Targeted strength training is considered safe and effective and can counteract problems associated with the inactivity pandemic, as it promotes the development of muscle strength, bone density and metabolism, especially during childhood. However, children respond differently to exercise than adults and the physiological differences are not yet fully understood. Previous research shows that the increased muscle strength is mainly due to neuronal adaptations, as hormonal responses are lower in children and therefore may have less effect on muscle size. It is suspected that other mechanisms are involved, but these have not yet been identified. Furthermore, we know little about how physical activity, especially in pre-puberty, affects muscles during maturation. Therefore, there is an urgent need for a comprehensive study to understand the mechanisms of adaptation and their sustainability in order to develop more targeted prevention strategies.

In our study, we investigate neuromuscular, hormonal and structural adaptations after 20 weeks of strength training and their long-term effects over a period of 1.5 years. In this randomized study, we use state-of-the-art methods to assess the various adaptation mechanisms in detail, including strength, fatigue, muscle activation, hormonal responses, and muscle structure and size. This comprehensive study provides an in-depth understanding of the interplay of different adaptations, which has never been studied to this extent before. On this basis, future training programs can be developed based on evidence and adapted to the target groups. The long-term effect on children's health can be described and better supported.