Importance of frequency, intensity, time and type (FITT) in physical activity assessment for epidemiological research.

Physical activity is a multi-faceted behaviour comprised of several components: frequency, intensity, time and type (FITT). Despite this understanding, there is currently a lack of knowledge regarding how the individual components of FITT influence chronic diseases. This is partly due to the tendency for researchers to focus on intensity via obtaining accurate measurements of energy expenditure. Although energy expenditure is an important consideration in the assessment of physical activity, it is only one component. Accordingly, future studies examining the association between physical activity and disease risk would benefit from examining all the components of FITT. Considering that all the components of FITT are modifiable, knowing their independent or combined influence on risk may provide valuable insight for future prevention interventions.