Table 2: Risk of bias assessment of the included studies using the Cochrane Back Review Group risk of bias tool.

Author, yearBias
Selection bias:Performance bias:Attrition bias:Reporting bias:Detection bias:Total: (max. 12)a
Adequate random sequence generationAdequate allocation concealmentSimilar baseline characteristicsAdequate participant blindingAdequate provider blindingSimilar or no co-interventionsAcceptable complianceAcceptable and described drop-out rateInclusion of an intention-to-treat analysisNo selective outcome reportingAdequate outcome assessor blindingSimilar timing of outcome assessment

Afonso et al., 2011 [42]UnclearUnclearNoUnclearUnclearUnclearUnclearNoNoYesUnclearYes2
Carson et al., 2009 [43]YesYesYesUnclearUnclearYesYesYesYesYesYesYes10
Chattha et al., 2008 [44]YesUnclearYesNoNoUnclearYesYesNoNoUnclearYes5
Elavsky and McAuley, 2007 [45]YesUnclearNoUnclearUnclearUnclearYesYesNoNoYesYes5
Joshi et al., 2011 [46]YesYesYesUnclearUnclearUnclearYesYesNoYesUnclearYes7

aHigher scores indicate lower risk of bias.