Characteristics of physical activity guidelines and their effect on adherence: a review of randomized trials.

Prescription characteristics and guidelines of recommended physical activity have been suggested as factors that may affect behavioural adherence; however, no review has critically appraised the current evidence. Thus, the purpose of this article was to review the effect of frequency, intensity, duration and mode on physical activity adherence and provide meta-analytical summaries of the findings. A total of 27 peer-reviewed studies met inclusion criteria and random-effects meta-analytical procedures, correcting for sampling bias, were employed where possible. Overall, results showed that the effect of physical activity guideline characteristics on behavioural adherence is not particularly robust as evidenced by a lack of unified findings and almost no evidence for the interaction among these factors (e.g. volume of activity and energy expenditure). Frequency (d = 0.08), intensity (d = 0.02), duration (d = 0.05) and mode of activity (ds = 0.03-0.10) showed generally null/trivial effects. Factors unrelated to the recommended guidelines may be of greater importance when considering behavioural adherence issues. Social cognitive, personality, and environmental or socioeconomic factors have amassed considerable evidence as correlates or determinants of physical activity, and health promoters may wish to consider these variables before basic physical activity characteristics.