A critical review of the validity of measuring stages of change in relation to exercise and moderate physical activity

Abstract

Many professionals are integrally involved in the promotion of exercise and physical activity, for specific therapeutic purposes, and with the aim of improving population health and quality of life. Design and evaluation of intervention strategies are frequently underpinned by the Transtheoretical Model, a process-oriented approach to behaviour change. One component of this model is the stage of change structure, which describes a person's behaviour in the context of a change process. It is frequently used to assess current levels of exercise or physical activity participation, and as a measure of change in behaviour following intervention. This paper discusses the importance of validity in the assessment of stages of change for exercise and physical activity. Various different scales exist and have been investigated for validity using comparisons with self-reported outcome measures and physiological markers of activity. Generally, comparative data provide evidence of stage hierarchies relating to both exercise and physical activity. However, this does not establish actual levels of activity represented by stage allocation, limiting its applicability. Further appropriately designed comparisons with objective measures are required if the stage of change structure is to be applied as a meaningful, accurate and sensitive tool for the measurement of physical activity and exercise.