Table 2. Risk of bias assessment using the Cochrane Collaboration’s tool.

First author	Random sequence generation	Allocation concealment	Blinding of participants and researchers	Blinding of outcome assessment	Incomplete outcome data	Selective reporting	Other bias
RCTs
Bang, 2014	+	-	-	-	+	+	+
Greulich, 2014	+	+	-	+	+	+	+
Greulich, 2014a	+	+	-	?	+	+	+
Hecksteden, 2013	+	+	-	+	+	+	+
Kim, 2015	-	-	-	-	+	+	+
Kim, 2016	?	-	-	-	+	+	+
Scharhag- Rosenberger, 2014	?	?	-	+	+	+	+
Huh, 2015	-	?	-	?	?	+	+
Nygaard, 2015	-	+	-	?	?	+	+
Tsuchiya, 2014	-	+	-	?	?	+	+
Tsuchiya, 2015	-	+	-	?	?	+	+
Tsuchiya, 2016	?	-	-	-	?	+	+
CTs
Aydin, 2013	-	-	-	-	?	+	+
Ijiri, 2015a	-	-	-	-	?	+	+
Kraemer, 2014	-	-	-	-	?	+	+
Miyamoto-Mikami, 2015	-	-	-	-	?	+	+
Norheim, 2014	-	-	-	?	?	+	+
Pekkala, 2013	-	-	-	-	?	+	+
Prestes, 2015	-	-	-	-	+	+	+
Timmons, 2012	-	-	-	-	?	+	+
SGS
Alvehus, 2014	-	-	-	-	?	+	+
Anastasilakis, 2014	-	-	-	-	?	+	+
Besse-Patin, 2014	-	-	-	-	?	+	+
Blüher, 2014	-	-	-	-	+	+	+
Boström, 2012	-	-	-	-	?	+	+
Camera, 2015	-	-	-	-	?	+	+
Comassi, 2015	-	-	-	-	+	+	+
Daskalopoulou, 2014	-	-	-	-	?	+	+
Ellefsen, 2014	-	-	-	-	?	+	+
Hew-Butler, 2015	-	-	-	-	+	+	+
Huh, 2012	-	-	-	-	?	+	+
Huh, 2014	-	-	-	-	?	+	+
Huh, 2014a	-	-	-	-	?	+	+
Khodadadi, 2014	-	-	-	-	?	+	+
Kurdiova, 2014	-	-	-	-	?	+	+
Lee, 2014	-	-	-	-	?	+	+
Löffler, 2015	-	-	-	-	?	+	+
Moraes, 2013	-	-	-	-	?	+	+
Murawska- Cialowicz, 2015	-	-	-	-	+	+	+
Moienneia, 2016	?	-	-	-	+	+	+
Palacios-González, 2015	-	-	-	-	?	+	+
Raschke, 2013	-	-	-	-	?	+	+
Scalzo, 2014	-	-	-	-	?	+	+
CSS
Al-Daghri, 2015	-	-	-	-	?	+	+
Hofmann, 2014	-	-	-	-	?	+	+
Ijiri, 2015b	-	-	-	-	?	+	+
Jedrychowski, 2015	-	-	-	-	?	+	+
Kwaśniewska, 2016	-	-	-	-	+	+	+
Lecker, 2012	-	-	-	-	?	+	+
Moreno, 2015	-	-	-	-	?	+	+
Palermo, 2015	-	-	-	-	?	+	+
Pardo, 2014	-	-	-	-	?	+	+

+: Low risk of bias; -: High risk of bias; ?: Unclear risk of bias; RCT: Randomised controlled trials; CT: Controlled trials; SGS: Single group design studies; CSS: Cross sectional studies.