The selection of talents in junior sports is strongly influenced by the current physical conditions of the athletes. However, the physical abilities, for example in junior football, are largely dependent on the maturation and show a high degree of variability during puberty. For example, the maturity status in an U14 football team fluctuates by up to 5 years between early and late developed players. It is necessary to include the maturation in junior sports in selections in order to give all athletes the same chance of selection regardless of their maturity status. This will make selections fairer and the promotion of athletes with the highest potential will be better implemented. Bone age is considered to be an objective indicator of the maturation. For this purpose, a practicable and preferably radiation-free method for determining bone age is needed. A new medical device promises to determine bone age based on ultrasound technology. This now offers the chance to switch to a significantly less stressful technique. The aim of the study is to determine the quality criteria (validity and reliability) of this new method in order to decide whether the current gold standard of the X-ray method could be replaced by a less stressful method.

Inclusion Criteria:

• Age between 10-18
• healthy
• voluntary participation
• consent of the participant or legal representative to participate in the project
• active in a sports club

Exclusion Criteria:

• pregnancy