The Importance of Correctly Defining Physical Activity
Over the last fifty years, there has been substantial evidence to support the importance of frequent participation in physical activity for the maintenance of good health and protection from chronic disease. Physical activity guidelines have been produced by expert panels worldwide, however without a clear picture of what constitutes physical activity these appear a little confusing for some to interpret.
For the lay public, the term physical activity is an easily digestible word, for most of the lay public it is regarded as a behaviour that increases heart rate and induces perspiration. However we only have to look at recent data showing the public misconception on the health benefits of moderate physical activity (O’Donovan & Shave, 2007) to see that policy makers and practitioners alike have a responsibility to clearly define physical activity. Physical activity is a complex phenomenon that can be quantified by a number of dimensions which include frequency (of participation in), duration (i.e. for how long) and intensity (how hard) e.g. 30 minutes of moderate intensity physical activity on three days per week. In addition it can also be considered in relation to the type or mode of activity e.g. Running vs. Cycling (Corder et al., 2008).
Let us start with a simple definition, the most accepted being that physical activity is ‘any bodily movement produced by skeletal muscle that results in energy expenditure’ (Caspersen et al., 1985). Yes that is any bodily movement, anything from waving a friend goodbye and walking up the stairs to cycling up the notorious local hill- all of these actions result in the expenditure of energy. However, physical activity is an umbrella term and can be further broken down into different types, broadly these include: leisure-time physical activity (LTPA) and occupational physical activity (OPA). LTPA is a broad term to describe a number of activities in which one participates in during their free time. These include exercise programs, as well as walking, gardening, dancing, sport etc. The common denominator here is that these activities result in substantial increase in energy expenditure, above what we would observe when at rest- although the intensity and duration can vary greatly between types of LTPA (Howley, 2001)
Occupational physical activity (OPA) however, concerns any activity that is associated with the performance of a job; examples might include walking, hauling, lifting, pushing, carpentry, shovelling, and packing boxes. Finally we must not forget exercise (or exercise training) which many wrongly use interchangeably with physical activity. Exercise is a subcategory of LTPA in which planned, structured, and repetitive bodily movements are performed to improve or maintain one or more components of physical fitness- this can include aerobic endurance training and resistance training (Howley, 2001).
In this brief review of physical activity terminology it is quite salient how convoluted the term physical activity is. It is therefore imperative that clinicians, policy makers, exercise scientists and exercise practioners alike are well informed as to what exactly constitutes physical activity, and how it can be clearly and concisely expressed for the benefit of the lay public.
Caspersen, C.J., Powell, K.E., & Christenson, G.M. (1985). Physical activity, exercise and physical fitness: definitions and distinctions for health-related research. Public Health Rep, 100, 126-131.
Corder, K., Ekelund, U., Steele, R.M., Wareham, N.J., & Brage, S. (2008). Assessment of physical activity in youth. Journal of Applied Physiology, 105, 977-987.
Howley, E.T. (2001). Type of activity: resistance, aerobic, and leisure versus occupational physical activity. Medicine & Science in Sports and Exercise, 33(6), 364-369.
O’ Donavon, G. & Shave, R. (2007). British adults views on the health benefits of moderate and vigorous activity. Preventive Medicine, 45(6), 432-5.