From evidence on physical activity and the HBM (for example, Biddle and Ashford 1988;
Lindsay-Reid and Osborn 1980), it appears that the optimistic conclusions of Janz and
Becker (1984) and, to a certain extent the low but significant effect sizes reported in
Harrison et al.’s (1992) meta-analysis, do not necessarily hold true for physical activity.
Although isolated variables, such as barriers, may relate to some physical activity behav-iours, the model as a whole has been relatively unsuccessful in predicting the adoption and/or maintenance of physical activity and exercise. Indeed, it could be argued that there is greater support for beliefs about health concerns and worries from the HBM predicting non-participation. For example, some people may believe that exercise will cause more harm than good, with such beliefs often based on myths and stereotyping.
that prospective studies had significantly smaller effect sizes than retrospective ones, thus further weakening the case in favour of the HBM.