Table 2: Risk of bias summary: review authors' judgments about each risk of bias item for each included study.

Random sequence generationAllocation concealmentBlinding of participants and personnelBlinding of outcome assessmentIncomplete outcome dataSelective reportingOther bias
(selection bias)(selection bias)(performance bias)(detection bias)(attrition bias)(reporting bias)

Astin et al., 2003 [33]++?+++
Haak and Scott,2008 [34]???+++
Liu et al., 2012 [35]??++++
Lynch et al., 2012 [36]+??++++
Maddali Bongi et al., 2012 [37]++?++++
Mannerkorpi and Arndorw,2004 [39]???+++
Stephens et al., 2008 [38]++?+++

“+” means low risk, “−” means high risk, and “?” means unclear risk of bias.