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Table 3 Distributions of absolute- and relative strength measures

From: Screen-based sedentary behavior and associations with functional strength in 6–15 year-old children in the United States

 

Percentiles

Mean ± SE

Linear trend for difference across age groups (p-value)a

 

10

25

50

75

90

 

Absolute Strength

Grip (kg)b

Age Group

 

6-9 y

10

12

14

16

19

14.1 (13.7 –14.6)

<0.001

10-12 y

16

19

22

26

31

23.1 (22.2 – 23.9)

13-15 y

24

27

31

37

44

32.6 (31.3 – 33.8)

Full sample (6–15 y)

11

14

20

28

36

22.2 (21.5 – 22.9)

 

Leg Extensions (kg)c

6-9 y

8

12

17

22

27

17.7 (14.9 – 20.5)

 

10-12 y

12

22

30

36

44

29.1 (25.0 – 33.2)

<0.001

13-15 y

18

29

41

49

59

40.2 (33.6 – 46.8)

 

Full sample

(6–15 y)

11

16

24

37

48

27.7 (23.4 – 32.0)

 

Relative Strength

Grip (kg per kg of Body Weight)d

6-9 y

0.37

0.42

0.48

0.55

0.61

0.49 (0.47 – 0.50)

 

10-12 y

0.34

0.43

0.50

0.57

0.62

0.50 (0.49 – 0.51)

0.005

13-15 y

0.37

0.45

0.53

0.60

0.69

0.53 (0.51 – 0.55)

 

Full sample (6–15 y)

0.37

0.43

0.50

0.57

0.64

0.50 (0.50 – 0.51)

 

Leg Extensions (kg per kg of Body Weight)e

6-9 y

0.31

0.46

0.63

0.74

0.87

0.60 (0.51 – 0.70)

 

10-12 y

0.31

0.47

0.66

0.77

0.86

0.62 (0.54 – 0.70)

0.020

13-15 y

0.30

0.47

0.65

0.82

0.94

0.65 (0.54 – 0.75)

 

Full sample (6–15 y)

0.31

0.46

0.64

0.77

0.89

0.62 (0.53 – 0.71)

 

Plank (Seconds)f

6-9 y

15

28

51

72

104

56.9 (52.5 – 61.3)

 

10-12 y

19

38

64

92

127

69.7 (64.7 – 74.7)

<0.001

13-15 y

29

55

79

121

149

88.6 (80.3 – 96.9)

 

Full sample (6–15 y)

18

37

63

91

128

69.9 (66.1 – 73.6)

 

Pullups (Repetitions)g

     

% ≥ 1 (95 % CI)h

Mean (95 % CI)h

  

6-9 y

0

0.5

2.9

6.5

10.2

81 (77 – 86)

5.7 (5.3 – 6.0)

0.029

<0.001

10-12 y

0

0.6

3.5

7.6

11.9

80 (76 – 85)

6.7 (5.5 – 7.9)

13-15 y

0

0

4.7

10.1

19.5

74 (69 – 80)

9.6 (8.6 – 10.6)

Full sample (6–15 y)

0

0.4

3.4

8.0

13.0

79 (75 – 82)

7.0 (6.5 – 7.6)

  
  1. a Linear trends across the three age categories for absolute- and relative strength measures were tested using simple linear regression models accounting for the survey design of the 2012 NNYFS
  2. b Muscle strength was measured through a grip test using a handgrip dynamometer
  3. c A digital hand-held dynamometer was used to measure the knee extension force
  4. d Relative grip strength was estimated as a child’s grip strength divided by their body weight
  5. e Relative leg extension strength was estimated as a child’s leg strength divided by their body weight
  6. f A horizontal body position held with only the hands/forearms and toes touching the floor
  7. g Participants lay on their backs and used their arms to pull themselves up to a strap hanging down 8 inches from the center of the bar
  8. h Due to the large proportion of children that could not complete a modified pull-up, the analysis was conducted using two models: a logistic regression model to test a linear trend in the odds of being able to complete ≥1 modified pull-up with age, and a linear regression model to test a linear trend in the number of pull-ups with age among children that could complete 1 or more modified pull-ups