Whereas participatory forms of research have achieved recognition in several fields including education, social work, management and community development, participatory approaches in health research are relatively new. Health research is largely dominated by the biomedical model, which follows a positivist paradigm consistent with the natural sciences, thus privileging experimental designs and quantitative data. The focus is on acquiring an “objective” knowledge that is influenced neither by the particular context in which the data is collected, nor by the particularities of the lives of the study participants. Through various means related to design, data collection and statistical analysis, traditional health researchers seek to isolate and measure specific causal mechanisms and intervention effects as precisely as possible. The knowledge thus generated is sorted hierarchically into “classes of evidence” according to the principles of Evidenced-Based Medicine (EBM), with the results of experimental studies being judged as providing the strongest proof for mechanisms of disease causation and for the efficacy of interventions to ameliorate health problems.