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Physical activity and exercise

Physical activity and exercise
A woman picking peppers in a lush green field.

It’s easy to think of physical activity as something you do in your leisure time, such as going for a walk, or taking part in a sport. However, there are many ways of accumulating physical activity throughout the day. These can include occupational related activities such as manual labour, domestic chores such as gardening, hoovering, and cleaning, and active modes of transport such as cycling or walking to the shops.

In this article, we look at what the terms physical activity and exercise mean.

Physical activity is defined as “any bodily movement produced by skeletal muscles that results in energy expenditure” (Caspersen et al., 1985). The American College of Sports Medicine go one step further to define it as “Any bodily movement produced by skeletal muscles that results in energy expenditure above resting levels” (ACSM 2011).

Exercise is a sub-set of physical activity. That is to say:

All exercise can be considered physical activity, but not all physical activity can be considered exercise.

Exercise is characterised by being planned, structured and repetitive, and is carried out for the purpose of improving or maintaining physical fitness or health.

Cardiorespiratory fitness is different again. Although it is related to physical activity and exercise it is not the same and is generally defined as the ability of the circulatory and respiratory systems to supply oxygen to skeletal muscle during aerobic exercise.

Metabolic Equivalent of Task (METS) Measurement

Both physical activity and exercise can vary in intensity. The intensity of an activity is important as it can determine whether physiological changes will happen in response to the activity undertaken. Physical activities are generally classed as being of light, moderate, or vigorous intensity, and for health benefits, moderate to vigorous intensity physical activity is recommended. These intensities are measured in a unit called METS which means metabolic equivalents.

  • 1 MET is equal to the amount of energy you expend when you are at rest, relaxed and not moving. Consider this an anchor point. MET values for exercise are expressed as multiples of this figure.
  • Light intensity activity is an activity which results in an energy expenditure of up to 3 times the energy you expend at rest (up to 3 METS) and is generally more than 1.5 METS.
  • Moderate intensity is considered to be an activity that requires 3 to 6 times resting energy expenditure levels. In other words 3-6 METS.
  • Vigorous intensity activities are those that require greater than 6 METS. As metabolic equivalents are a ratio they have no unit.

It can be hard to decipher how many METS you are expending when being physically active. To help us determine how intense common activities are, in general, a compendium of physical activities was developed by Ainsworth et al (2011). The figures in this compendium are taken from studies where possible; however, there are so many different types of activities that some had to be estimated. This image shows some MET values for common home and sporting activities.

Graphic showing common MET values for home and sporting activities.( Common MET values for home and sporting activities. (Click to expand)

Take a look at this compendium of physical activities website, and in the comments section below:

  • Consider some common physical activities you do each week, and using the website or the above graph, list the MET value for them.
  • Would these physical activities be considered a form of exercise?
© Trinity College Dublin
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