| Content validity | Validation | |
---|---|---|---|
Participants (n = 9) | T0 Participants (n = 110) | T1 Participants (n = 69) | |
Age, mean ± SD, y | 13.4 ± 2.4 | 13.9 ± 2.6 | 13.7 ± 2.5 |
Sex, No. (%) | |||
 Female | 7 (78) | 60 (55) | 38 (51) |
 Male | 2 (22) | 50 (46) | 37 (49) |
BMI, mean ± SD, kg/m2 | 19.4 ± 2.3 | 18.3 ± 2.7 | 18.1 ± 2.8 |
Weekly participation in sports at a sports club, mean ± SD, h |  | 4.3 ± 3.1 | 4.0 ± 2.9 |
Weekly participation in sports without sports club, mean ± SD, h |  | 4.3 ± 4.3 | 4.0 ± 2.3 |
Days per week with at least 1 hour of physical activity, No. (%) | |||
 Almost never |  | 1 (1) | 0 (0) |
 1 day per week |  | 3 (3) | 3 (4) |
 2 days per week |  | 3 (3) | 2 (3) |
 3 days per week |  | 15 (14) | 9 (12) |
 4 days per week |  | 11 (10) | 5 (7) |
 5 days per week |  | 22 (20) | 15 (20) |
 6 days per week |  | 24 (22) | 18 (24) |
 Every day |  | 30 (27) | 22 (30) |
 Missing |  | 1 (1) | 1 (1) |
Competition level, No. (%) | |||
 Recreational |  | 34 (31) | 23 (32) |
 Regional |  | 64 (58) | 45 (63) |
 National |  | 5 (5) | 3 (4) |
 International/elite |  | 3 (3) | 1 (1) |
 Missing |  | 4 (4) | 3 (4) |