Table 2. Assessment of risk of bias according to Cochrane Collaboration bias assessment tool. References Random sequence generation (Selection bias) Allocation concealment (Selection bias) Blinding of participants and personnel (Performance bias) Blinding of outcome assessment (Detection bias): Self-reported outcomes Blinding of outcome assessment (Detection bias): Objective measures Incomplete outcome data (Attrition bias) Selective reporting (Reporting bias) Other bias Shaver, 1970 + + - + + + + - Shaver, 1975 + + - + + + + - Komi et al., 1978 + ? - + + - + - Shields et al., 1999 + + - + + + + - Munn et al., 2005 + + - + + + + - Farthing et al., 2005 + + + + + ? + + Lagerquist et al., 2006 + ? - + + + + - Fimland et al., 2009 + ? + + + + + - Magnus et al., 2014 + + - + + - + - Lepley & Palmieri-Smith, 2014 + + - + + + + -