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Table 1 Characteristics for adolescent female football players at baseline and at the 1-year follow-up

From: Lifestyle characteristics in adolescent female football players: data from the Karolinska football Injury Cohort

 

Total cohort

(12–17 years)

Total cohort divided into age groups

Sub-cohort (12–17 years)a

Baseline versus Follow-Up

Effect Size

n

n = 419

12 years (n = 97)

13 years (n = 158)

14 years (n = 91)

15–17 years (n = 73)

Baseline (n = 286)

Follow-Up (n = 286)

P Value

Cohen’s d

Age, years

418

13.9 ± 1.1

12.7 ± 0.2

13.4 ± 0.3

14.5 ± 0.3

15.8 ± 0.6

13.9 ± 1.2

14.9 ± 1.6

  

Height, cm

417

163 ± 6.8

160 ± 6.4

161 ± 6.5

165 ± 5.7

168 ± 5.8

162.5 ± 6.8

165.5 ± 5.6

< 0.001

1.07

Body mass, kg

417

53 ± 9.0

48 ± 7.5

51 ± 7.7

57 ± 7.6

61 ± 7.6

53.2 ± 9.0

57.8 ± 7.7

< 0.001

1.08

Body mass index, kg/m2

416

20.1 ± 2.5

18.8 ± 2.2

19.6 ± 2.2

20.9 ± 2.4

21.8 ± 2.1

20.0 ± 2.5

21.1 ± 2.4

< 0.001

0.65

Menarche, n (%)

418

280 (67)

35 (36)

92 (58)

82 (90)

71 (97)

184 (64)

 

Age at menarche

416

12.4 ± 1.0

11.9 ± 0.9

12.3 ± 0.9

12.7 ± 1.1

12.6 ± 1.1

12.5 ± 1.1

 

Amenorrhea >3 monthsb, n (%)

412

46 (16)

4 (4)

17 (11)

9 (10)

16 (22)

    

Years playing organized football

417

7.0 ± 2.2

6.0 ± 1.9

6.3 ± 1.8

7.5 ± 1.8

9.2 ± 1.7

7.0 ± 2.2

 

Dominant leg, n (%)

419

         

 Right

 

399 (95)

95 (98)

149 (94)

87 (96)

68 (93)

270 (94)

 

 Left

 

17 (4)

2 (2)

8 (5)

4 (4)

3 (4)

13 (5)

 

 Both

 

3 (1)

0 (0)

1 (1)

0 (0)

2 (3)

3 (1)

 

Playing position, n (%)

414

       

0.466

 

 Goalkeeper

 

34 (8)

6 (6)

11 (7)

9 (10)

8 (11)

19 (7)

21 (7)

  

 Defender

 

130 (31)

37 (38)

45 (29)

25 (28)

23 (32)

85 (30)

95 (33)

  

 Midfielder

 

168 (41)

29 (30)

79 (51)

36 (40)

24 (33)

117 (42)

109 (38)

  

 Forward

 

82 (20)

25 (26)

21 (13)

19 (21)

17 (24)

61 (22)

59 (21)

  

Football matches/week, n

419

1.5 ± 0.6

1.6 ± 0.6

1.5 ± 0.6

1.4 ± 0.7

1.2 ± 0.6

1.5 ± 0.6

1.4 ± 0.7

0.387

–0.05

Football training h/week, n

419

5.0 ± 1.8

4.6 ± 1.5

5.0 ± 1.6

5.0 ± 1.7

5.4 ± 2.6

5.1 ± 1.9

5.1 ± 2.0

0.783

0.02

Other training with football team h/week

416

1.6 ± 1.4

1.4 ± 1.2

1.5 ± 1.3

1.5 ± 1.1

2.2 ± 1.8

1.7 ± 1.5

1.6 ± 1.2

0.365

–0.05

Injury prevention training, yes

419

320 (76)

77 (79)

121 (77)

65 (71)

57 (78)

223 (78)

199 (70)

0.011

 

Prevention times/week

400

2.5 ± 1.3

2.5 ± 1.2

2.7 ± 1.2

2.2 ± 1.2

2.4 ± 1.4

2.6 ± 1.3

2.9 ± 1.4

0.010

0.21

 1–2 times/week

 

157 (39)

36 (37)

48 (30)

39 (43)

34 (47)

107 (37)

70 (25)

  

 3–4 times/week

 

127 (32)

32 (33)

59 (37)

20 (22)

17 (23)

93 (33)

96 (34)

  

 >4 times/week

 

16 (4)

3 (3)

7 (4)

2 (2)

4 (5)

11 (4)

21 (7)

  

Training with older players in the previous 6 months

416

       

< 0.001

 

 Every week

 

70 (17)

11 (12)

16 (10)

16 (18)

27 (37)

52 (18)

24 (8)

  

 Few times/every month

 

28 (7)

2 (2)

12 (8)

4 (4)

10 (14)

18 (6)

37 (13)

  

 Few times previous 6 months

 

99 (24)

26 (27)

38 (24)

23 (25)

12 (16)

56 (20)

90 (32)

  

 Never

 

219 (53)

56 (59)

91 (58)

48 (53)

24 (33)

157 (56)

133 (47)

  

Match play with older players in the previous 6 months

418

       

0.509

 

 Every week

 

33 (8)

7 (7)

10 (6)

8 (9)

8 (11)

22 (8)

19 (7)

  

 Few times/every month

 

52 (12)

7 (7)

17 (11)

15 (16)

13 (18)

42 (15)

42 (15)

  

 Few times in the previous 6 months

 

124 (30)

29 (30)

46 (29)

25 (27)

24 (33)

79 (28)

92 (32)

  

 Never

 

209 (50)

54 (56)

84 (54)

43 (47)

28 (38)

142 (50)

133 (46)

  

Other training (not football), n (%)

418

135 (32)

33 (34)

55 (36)

23 (25)

23 (32)

90 (32)

85 (30)

0.615

 

Other training (not football), h/week

133

2.7 ± 2.0

2.5 ± 2.1

2.4 ± 1.7

2.7 ± 2.2

3.5 ± 2.4

2.8 ± 2.1

2.3 ± 1.5

0.002

−0.45

  1. Values are reported as means ± standard deviations or n (%). P values in bold type are significant. Effect size measured as Cohen’s d, where d = 0.2 indicates a small effect, d = 0.5 indicates a medium effect, and d = 0.8 indicates a large effect. The values regarding training/match are weekly averages of the preceding 6 months. –, data not collected
  2. aMissing value from 0–3 players for the different questions both at baseline and at follow-up 
  3. bThe question: If you menstruation has become regular, has your period stopped for more than 3 months in a row, or longer?