Stages of motivational readiness for physical activity: a comparison of different algorithms of classification.

Objective: The aim of this study was to compare two approaches to classify individuals into stages of motivational readiness for physical activity and test which one was better explained by attitude and perceived behavioural control, as defined by Ajzen (1991).

Design: A survey of 20,430 respondents from a population-based sample.

Methods: The relevant variables were assessed in a self-administered questionnaire. The cluster approach consisted of combining both intention and behaviour in order to determine clusters of individuals; such clusters correspond to different stages of motivational readiness. The stage of change (SC) approach consisted of grouping the same individuals by using the SC variable of the Transtheoretical Model (TTM).

Results: The SC and cluster-solution approaches were replicated across four subsamples of the total number of respondents. Attitude and perceived behavioural control were more strongly associated with stage membership derived from four-cluster solution than with stage membership in the five categories assessed by the SC method.

Conclusion: Stage of motivational readiness for physical activity, and possibly for other health-related behaviours, may usefully be characterized when both recent past behaviour and intention in the near future are simultaneously and explicitly taken into consideration.