The Essential Properties of Yoga Questionnaire: Development and Methods.

Yoga interventions have considerable heterogeneity, are multi-dimensional, and may impact health in different ways. However, most research reports regarding the effects of yoga on health and wellbeing do not adequately describe the components of the yoga interventions being used. Thus, drawing comparisons across studies or understanding the relative effects of specific aspects of a yoga intervention are rarely possible. To address this problem, we created the Essential Properties of Yoga Questionnaire (EPYQ) Project, an NCCAM-funded set of studies to develop a translational tool for yoga researchers. Here we describe the methods and developmental processes used in the EPYQ Project in detail. The project consists of four main phases. Phase I was designed to gain a comprehensive understanding of the relevant aspects of yoga by conducting a comprehensive systematic literature review and conducting focus groups with stakeholders including a wide variety of yoga teachers and students. In Phase II, a pool of potential questionnaire items was developed for the prototypic questionnaire using information from Phase I. Cognitive interviews were conducted with the preliminary EPYQ items to assess the perceived clarity, meaning, and importance of each item. In Phase III, the prototypic questionnaire was administered to two large samples of yoga students and instructors. Military personnel and veterans who practiced or taught yoga (n = 329) were recruited to participate. Factor analysis and item response theory were used to identify factors and select the final questionnaire items. Phase IV is ongoing and will collect reliability and validity data on the final instrument. Results are expected to be available in 2016. The EPYQ will provide an objective tool for describing the amount of various components of yoga interventions, eventually allowing researchers to link specific yoga components to health benefits, and facilitating the design of yoga interventions for specific health conditions.