Table 1 Methodological quality assessment of included studies

Andrade et al. (2013) [39]

No

n = 10

Yes

100%

Yes

No

No

Andrade et al. (2011) [38]

No

n = 10

Yes

100%

Yes

No

No

Gebhardt et al. (2006) [37]

Yes

n = 31

Yes

88%

Yes

Yes

Yes

Hasvik et al. (2014) [21]

Yes

n = 118^a

Yes

95%

No

Yes

Yes

Jacobsen et al. (2013) [44]

Yes

n = 260^a

Yes

91%

Yes

Yes

Yes

Jacobsen et al. (2012) [43]

Yes

n = 258^a

Yes

89%

Yes

Yes

Yes

Karppinen et al. (2008) [29]

Yes

n = 153

Yes

97%

Yes

No

No

Moen et al. (2014) [31]

Yes

n = 252^a

Yes

91%

No

Yes

Yes

Olsen et al. (2012) [20]

Yes

n = 258^a

Yes

92%

Yes

Yes

Yes

Rut et al. (2014) [40]

Yes

n = 176

Yes

100%

Yes

Yes

No

Schistad et al. (2014) [42]

Yes

n = 108^a

Yes

90%

Yes

Yes

No

Schistad et al. (2014) [30]

Yes

n = 121^a

Yes

91%

No

No

No

Scuderi et al. (2009) [45]

No

n = 47

Yes

100%

Yes

No

No

Takeuchi et al. (2007) [41]

No

n = 27

Yes

100%

Yes

Yes

No

Tegeder et al. (2006) [24]

Yes

n = 168

Yes

88%

Yes

Yes

NA