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ABSTRACT
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.
Key words: Motor activity; chronic disease; epidemiology
La traduction du résumé se trouve à la fin de l'article. Can J Public Health 2011;102(4):174-75.
Mots clés : activité motrice; maladie chronique; épidémiologie
Physical activity is defined as any bodily movement produced by the skeletal muscles that results in energy expenditure beyond resting expenditure.1 Although this definition refers to both voluntary and involuntary movements, the assessment of physical activity is more commonly concerned with voluntary movement of the skeletal muscles. This is a multidimensional and complex behaviour that encompasses four components (FITT): frequency (of individual sessions), intensity (rate of energy expenditure), time (duration of an individual session), and the type of activity involved.2 Despite the understanding that physical activity is a multi-faceted behaviour, there is currently a lack of knowledge regarding how the individual components of FITT influence chronic diseases. This is partially a result of the tendency for researchers to focus predominantly on factors that are amenable to objective measurements, which in recent physical activity research has translated into a focus on obtaining accurate measurements of energy expenditure.
Energy expenditure is a complex concept that is a result of multiple factors including posture, voluntary and involuntary physical activity, resting metabolic rate, and the thermic effect of feeding (the energy required in the digestion and absorption of food).3 Although energy expenditure is an important consideration in the assessment of physical activity, the methods used to produce accurate measurements cannot distinguish between the individual components of FITT. Considering that these four components are all modifiable, knowing...