Table 1 Number of measurements and number of players per age group and maturity status.

			Longitudinal data set Number of measurements			Control group (1-measurement)
Age	Maturity status	3	4	5	Total measurements
11 years	Late	0	4	2	6	2
	On Time	3	7	13	23	4
	Early	0	2	9	11	2
	Total	3	13	24	40	8
12 years	Late	0	4	5	9	2
	On Time	3	12	18	33	4
	Early	1	2	12	15	3
	Total	4	18	35	57	9
13 years	Late	1	5	5	11	2
	On Time	7	17	24	48	5
	Early	3	5	16	24	3
	Total	11	27	45	83	10
14 years	Late	1	5	5	11	1
	On Time	4	17	24	45	6
	Early	3	5	16	24	3
	Total	8	27	45	80	10
15 years	Late	1	1	5	7	1
	On Time	4	10	24	38	6
	Early	2	3	16	21	1
	Total	7	14	45	66	8
16 years	Late	0	1	3	4	0
	On Time	0	5	11	16	3
	Early	0	3	7	10	1
	Total	0	9	21	30	4
17 years	Late	0	0	0	0	0
	On Time	0	0	6	6	2
	Early	0	0	4	4	1
	Total	0	0	10	10	3
Number of measurements		33	108	225	366	52
Number of players		11	27	45	83	52
	Late	1	5	5	11	8
	On Time	7	17	24	48	30
	Early	3	5	16	24	14