Intervention arm (n = 31)

Control arm (n = 15)

N (%) or Mean SD

N (%) or Mean SD

Club

Tennis

17

(54.8%)

0

(0%)

Kendo

14

(45.2%)

0

(0%)

Handball

0

(0%)

9

(60.0%)

Athletics

0

(0%)

6

(40.0%)

Male

18

(58.1%)

12

(80.0%)

Age (years)

20.5

1.4

20.7

1.4

Grade

1st

9

(29.0%)

7

(46.7%)

2nd

6

(19.4%)

1

(6.7%)

3rd

10

(32.3%)

2

(13.3%)

4th

4

(12.9%)

5

(33.3%)

5th

2

(6.5%)

0

(0%)

6th

0

(0%)

0

(0%)

Sports history

Same kind of club (years)

5.0

4.6

3.3

3.1

Including other kinds (years)

9.7

4.8

7.1

5.5