How is Exercise Actually Measured?

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. When we say physiological change, we mean a change in how your body works – such as the blood pumping around it or changes in muscle fibres. At a really base level, it’s the reason for exercise – to improve your body’s function.

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 Equivalent of Task. A brief overview:

• 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 specific unit. This means 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 has been developed.

The figures in this compendium are taken from studies where possible, but there are so many different types of activities that some had to be estimated. If you’re really into your health & fitness and want to think about your exercise in terms of METs, this can be a good place to start.