Table 4 Descriptive data of study participants by trial arm at t0 and t1

Age (years)

149

8.4 ± 0.9

153

8.3 ± 1.3

136

9.1 ± 0.9

128

8.9 ± 1.3

Height (m)

149

1.3 ± 0.1

153

1.3 ± 0.1

136

1.4 ± 0.1

128

1.4 ± 0.1

Weight (kg)

149

32.6 ± 8.5

153

31.8 ± 8.8

136

35.5 ± 9.2

128

34.2 ± 9.6

Body-Mass-Index (kg/m²)

149

18.1 ± 3.4

153

17.7 ± 3.1

136

18.5 ± 3.5

128

17.9 ± 3.2

BMI category

Normal weight/underweight

87

58.4

93

60.8

77

56.6

78

60.9

Overweight/obese

62

41.6

60

39.2

59

43.4

50

39.1

Sex

Boys

78

52.3

86

56.2

73

53.7

72

56.3

Girls

71

47.7

67

43.8

63

46.3

56

43.8

Migration background

No migration background

57

38.3

49

32.0

49

36.0

46

35.9

One-sided migration background

25

16.8

30

19.6

23

16.9

22

17.2

Two-sided migration background

37

24.8

35

22.9

36

26.5

29

22.7

Missing

30

20.1

39

25.5

28

20.6

31

24.2

Highest parental education

Low

13

8.7

20

13.1

11

8.1

16

12.5

Medium

56

37.6

35

22.9

50

36.8

28

21.9

High

37

24.8

52

34.0

34

25.0

49

38.3

Missing

43

28.9

46

30.1

41

30.1

35

27.3

Physical fitness

6-min run (laps)

148

15.2 ± 2.4

150

16.3 ± 2.4

136

15.4 ± 2.6

128

15.9 ± 2.8

6-min run (distance in m)

148

820.2 ± 131.2

150

879.0 ± 129.8

136

830.5 ± 141.5

128

860.3 ± 150.7

6-min run z-score

148

93.3 ± 9.7

150

98.2 ± 10.6

136

92.0 ± 10.5

128

94.5 ± 10.7

Physical Activity¹

MVPA (min per day)

57

99.1 ± 32.9

76

104.7 ± 32.4

42

96.1 ± 29.4

60

128.9 ± 42.5

Meeting guideline (≥ 90 min of MVPA per day)

35

61.4

48

63.2

22

52.4

51

85.0

Not meeting guidelines (< 90 min of MVPA per day)

22

38.6

28

36.8

20

47.6

9

15.0