Systematic reviews fulfil a vital role in modern medicine.1 However, the results of systematic reviews are only as valid as the studies they include.2 Pooling flawed, or biased, results from different studies can compromise the credibility of systematic review findings. Bias is a systematic deviation from the truth in the results of a research study that can manifest due to limitations in study design, conduct, or analysis.3
The results of sport and exercise medicine research, like results in other fields, are vulnerable to bias.4 It is important that systematic review authors assess for bias in a way that enables a judgement about whether a review outcome is at risk of bias due to methodological limitations in included studies. This two-part education primer focuses on how systematic review authors can perform and interpret risk of bias assessments to avoid misleading systematic review conclusions. In this editorial, we introduce the concept of risk of bias, and the principles of assessing risk of bias.