Characteristics of the healthy participants
| Characteristic | Whole group | Females | Males |
| Subjects n | 74 | 43 | 31 |
| Age yrs | 14.2±1.1 | 14.4±1.2 | 13.9±1.1 |
| Weight kg | 48.6±8.5 | 46.1±5.8 | 52.1±10.4 |
| Height cm | 159.4±7.2 | 156.7±4.7 | 163.2±8.3 |
| Body mass index | 19.1±2.6 | 18.7±2.0 | 19.5±3.3 |
| FEV1 % pred | 91.4±10.2 | 89.6±9.0 | 93.9±11.3 |
| Heart rate beats·min−1 | |||
| Difference at end of 6MWT | 60.3±22.2 | 58.8±24.3 | 62.4±19.0 |
| At end of 6MWT | 147.8±18.7 | 150.3±18.6 | 144.3±18.5 |
| Max. during treadmill test | 196.4±9.6 | 193.3±9.8 | 200.7±7.5 |
| 6MWD m | 659.8±58.1 | 637.4±38.6 | 691.0±66.3 |
| V′O2,max L·min−1 | 1675.1±425.3 | 1416.7±210.5 | 2033.5±386.9 |
Data are presented as mean±sd, unless otherwise stated. FEV1: forced expiratory volume in one second; % pred: per cent predicted; 6MWT: 6-min walk test; max.: maximum; 6MWD: 6-min walk distance; V′O2,max: maximum oxygen consumption at peak exercise on treadmill test.