Table 3. Summary of risk of bias (high, low, unclear).

Study	Selection bias (risk on incomparable groups, due to sequence generation and allocation concealment)	Performance bias (blinding participants and therapists)	Detection bias (blinding outcome (assessors))	Attrition bias (incomplete outcome data)	Reporting bias (selective reporting)	Overall risk of bias
Henderson et al. (2007)	Unclear	High	Unclear	Unclear	Low	High
Sandmire et al. (2012)	Unclear	High	Unclear	Low	Low	High
Yu et al. (2016)	Unclear	High	Low	Low	Low	High