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Table 1 Characteristics of preschool (2- < 6 years) and school (6–10 years) children, stratified by sex

From: Impact of physical activity, sedentary behaviour and muscle strength on bone stiffness in 2–10-year-old children-cross-sectional results from the IDEFICS study

  Preschool children (2- < 6 years) Primary school children (6–10 years)
  Boys Girls All Boys Girls All
  Mean ± SD Mean ± SD Mean ± SD Mean ± SD Mean ± SD Mean ± SD
Number 804 708 1512 1409 1544 2953
Age (years) 4.4 ± 0.9 4.5 ± 0.9 4.4 ± 0.9 8.1 ± 1.2 8.1 ± 1.2 8.1 ± 1.2
Anthropometric measures       
 Bone stiffness index 79.3 ± 14.6 79.8 ± 15.5 79.5 ± 15.0 82.1 ± 12.5 80.5 ± 11.7 81.3 ± 12.1
 Body height (cm) 116.0 ± 9.8 114.7 ± 9.4 115.4 ± 9.7 135.2 ± 9.0 134.7 ± 9.1 135.0 ± 9.0
 Body weight (kg) 21.8 ± 5.4 21.1 ± 4.9 21.5 ± 5.2 32.5 ± 8.7 32.1 ± 8.3 32.3 ± 8.5
 Fat-free mass (kg) 15.7 ± 3.6 13.9 ± 3.3 14.9 ± 3.6 23.1 ± 4.1 21.3 ± 4.0 22.2 ± 4.1
Objectively measured PA and sedentary behaviours     
 Sedentary time (hours/day) 4.4 ± 1.5 4.5 ± 1.4 4.4 ± 1.5 5.6 ± 1.5 5.7 ± 1.5 5.7 ± 1.5
 Light PA (hours/day) 6.4 ± 1.0 6.4 ± 1.0 6.4 ± 1.0 5.8 ± 1.1 5.8 ± 1.1 5.8 ± 1.1
 Moderate PA (min/day) 38 ± 18 29 ± 14 34 ± 17 39 ± 19 29 ± 14 34 ± 17
 Vigorous PA (min/day) 7 ± 7 6 ± 5 6 ± 6 9 ± 8 7 ± 6 8 ± 7
 Moderate-to-vigorous PA (min/day) 45 ± 23 35 ± 18 40 ± 21 48 ± 25 36 ± 18 42 ± 23
 PA levels (cpm) 653 ± 171 586 ± 147 622 ± 164 579 ± 169 507 ± 139 541 ± 158
 Wearing time (average hours/day) 11.6 ± 1.7 11.4 ± 1.7 11.5 ± 1.7 12.2 ± 1.7 12.1 ± 1.7 12.2 ± 1.7
Measures of muscle strength      
 Jumping distance (cm)     121 ± 25 114 ± 25 117 ± 25
 Handgrip strength (kg)     14.4 ± 3.9 13.2 ± 3.5 13.8 ± 3.7
Potential confounding lifestyle factors      
 Dairy products (frequency/week) 22 ± 12 21 ± 11 21 ± 12 20 ± 12 19 ± 12 20 ± 12
 Daylight duration (hours/week) 11.0 ± 2.8 10.8 ± 2.6 10.9 ± 2.7 10.8 ± 2.6 10.7 ± 2.6 10.7 ± 2.6
Reported PA and sedentary behaviours
 Continuous variables
 Leisure time PA (hours/week) 17.8 ± 10.0 17.6 ± 9.8 17.7 ± 9.9 18.9 ± 9.8 17.2 ± 9.7 18.0 ± 9.8
 Screen time (hours/week) 12.2 ± 7.0 10.6 ± 6.3 11.4 ± 6.7 15.2 ± 8.1 13.3 ± 7.2 14.2 ± 7.7
Categorical variable N (%) N (%) N (%) N (%) N (%) N (%)
 High-to-moderate WBE 182 (22.6) 222 (31.4) 404 (26.7) 822 (58.3) 817 (52.9) 1639 (55.5)
 No-impact WBE / no exercise 622 (77.4) 486 (68.6) 1108 (73.3) 587 (41.7) 727 (47.1) 1314 (44.5)
  1. cpm average counts per minute, N number, PA physical activity, WBE weight-bearing exercises, SD standard deviation