Table 3.

The results of quality assessment of included studies.

Study	Items of quality assessment∗									Total (%)
	1	2	3	4	5	6	7	8	9
Kujala et al., 1994 [21]	1	0	1	1	1	1	1	1	0	77
Kujala et al., 1997 [28]	1	1	0	1	1	0	1	1	1	77
Burdorf et al., 1996 [33]	0	1	1	0	1	1	1	1	1	77
Nadler et al., 1998 [27]	0	1	1	1	0	0	0	1	0	44
Evans et al., 2005 [22]	1	1	1	1	0	0	1	1	0	66
Renkawitz et al., 2006 [32]	1	1	1	1	1	0	1	0	1	77
Hjelm et al., 2012 [31]	0	0	0	1	1	1	1	1	0	55

^∗The items are observable on Table 1.