Anthropometric characteristics, including age, height, body weight, percentage fat (%) and maximal VO2 (VO2max), number of sports (n), training volume (hours/week), sleeping time in the school days and weekends (hours per night) and number of injuries (n) at baseline (13.4 years) and after 1 year (14.4 years)
| Variables at baseline and after 1 year/participants | 1* | 2 | 3 | 4 | 5 | 6* | Mean (SD) |
|---|---|---|---|---|---|---|---|
| Age (years) | 13.4 | 13.4 | 13.1 | 12.7 | 13.0 | 13.4 | 13.1 (0.3) |
| 14.4 | 14.4 | 14.1 | 13.7 | 14.0 | 14.4 | 14.1 (0.3) | |
| Height (cm) | 159 | 161 | 152 | 160 | 162 | 158 | |
| 160 | 168 | 160 | 167 | 168 | 162 | 164.6 (4.2) | |
| Weight (kg) | 50.5 | 53.5 | 45.8 | 47.3 | 53.2 | 44.8 | 49.2 (3.8) |
| 53.2 | 56.5 | 51.0 | 52.4 | 58.8 | 49.0 | 54.4 (3.2) | |
| Fat mass (%) | 16.8 | 24.0 | 8.4 | 10.3 | 16.8 | 9.2 | 14.3 (6.1) |
| 17.4 | 20.8 | 9.4 | 12.5 | 17.5 | 12.1 | 15.4 (4.5) | |
| VO2max (mL/kg/min) | 62.5 | 56.3 | 57.9 | 54.1 | 53.2 | 55.2 | 56.5 (3.4) |
| 64.8 | 59.4 | 56.8 | 54.8 | 49.2 | 53.9 | 57.0 (5.8) | |
| Number of sports (n) | 1 | 1 | 2 | 1 | 2 | 1 | nc |
| 1 | 1 | 2 | 1 | 2 | 1 | nc | |
| Training volume (hours/week) | 10 16 | 8 14 | 7 12 | 8 14 | 7 12 | 8 14 | 8.0 (0.8) 13.6 (1.7) |
| ST schooldays (hours per night) | 8.5 7.0 | 8 7.5 | 8.5 7.5 | 8 7.0 | 8.5 7.0 | 8.5 7.0 | 8.3 (0.3) 7.2 (0.3 |
| ST weekends (hours per night) | nm 10.5 | nm 10.0 | nm 10.0 | nm 10.5 | nm 10.5 | nm 9.5 | 10.3 (0.3) |
| Number of injuries (n) | 0 | 0 | 1 | 0 | 1 | 0 | Nc |
| 0 | 1 | 2 | 2 | 1 | 0 | Nc | |
| Age of menarche (years) | 11.5 | 14.2 | 13.2 | 13.6 | 13.1 | & | 13.1 (0.8) |
Results are given individually and with mean±SD. Age of menarche is given in the last row.*= not injured.
&, not reached menarche; nc, not calculated; nm, not measured at age 13 years; ST, sleeping time.