Physical activity measurements and characteristics (Mean (SD) of study participants included in the analysis at the four time points)
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| Boys | Girls | ||||||
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Age 7 (n=217) |
Age 9 (n=209) |
Age 12 (n=176) |
Age 15 (n=131) |
Age 7 (n=214) |
Age 9 (n=219) |
Age 12 (n=209) |
Age 15 (n=147) | |
| Age (years) | 7.5 (0.5) | 9.3 (0.4) | 12.5 (0.3) | 15.2 (0.4) | 7.5 (0.4) | 9.3 (0.4) | 12.5 (0.3) | 15.2 (0.4) |
| Anthropometry |
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| Height (cm) | 125.5 (5.7) | 135.9 (6.3) | 154.2 (8.7) | 171.6 (8.1) | 124.7 (5.8) | 135.4 (6.3) | 155.2 (7.3) | 163.0 (6.2) |
| Weight (kg) | 26.5 (5.5) | 33.0 (7.2) | 48.3 (11.8 | 63.4 (14.5) | 26.7 (5.9) | 33.8 (7.7) | 51.0 (12.4) | 61.8 (14.4) |
| BMI (kg/m2) | 16.7 (2.4) | 17.7 (2.8) | 20.1 (3.7) | 21.4 (4.0) | 17.1 (2.6) | 18.3 (3.0) | 21.0 (4.0) | 23.2 (4.6) |
| BMI z-score | 0.4 (1.2) | 0.5 (1.2)† | 0.7 (1.2)†‡ | 0.5 (1.3)§ | 0.4 (1.1) | 0.6 (1.1)† | 0.7 (1.1)†‡ | 0.8 (1.1)†‡ |
| Fat mass (kg) | 6.5 (3.2) | 8.7 (5.0) | 12.0 (8.4) | 14.2 (10.6) | 6.3 (3.6) | 9.2 (5.0) | 14.2 (8.6 | 21.8 (11.5) |
| Accelerometer data |
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| Wear time (min/day) | 672 (74.5) | 673 (77.6) | 712 (87.6 | 725 (88.4) | 667 (70.9) | 671 (75.6) | 718 (82.8) | 720 (87.2) |
| Days worn | 6.4 (1.0) | 5.9 (1.3) | 5.8 (1.4 | 5.3 (1.6) | 6.2 (1.2) | 5.9 (1.3) | 5.7 (1.5) | 5.4 (1.7) |
| Total physical activity (cpm)¶ | 780 (223)‡§* | 715 (192))§* | 558 (189)* | 482 (154) | 746 (222)‡§ | 653 (193)§* | 469 (191)§* | 400 (156) |
| MVPA (min/day)¶ | 75.5 (25.5)‡§* | 70.0 (23.9)§* | 60.3 (24.4)* | 51.4 (22.4) | 63.4 (20.9‡§* | 56.4 (19.8)§* | 47.4 (20.9)* | 41.0 (16.8) |
BMI, body mass index; cpm, accelerometer counts per min, a measure of the total amount of physical activity (light intensity physical activity and MVPA combined); MVPA, moderate-to-vigorous intensity physical activity, adjusted for season (winter vs summer) at age 15 years
†, significantly higher than age 7 years; ‡, significantly higher than age 9 years; §, significantly higher than age 12 years; ¶, Estimated marginal means derived from linear mixed model analysis; *, significantly higher than age 15 years.