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Metabolic equivalents. Combining moderate with vigorous activities
This page will help you answer the question "How many mets should I burn during the week for health benefits to ensue?" "Moderate intensity" activities as defined by the ACSM/AHA are those activities that cause you to work at between 3.0 and 6.0 METs. Similarly, "vigorous intensity" activities are activities that cause you to work at more than 6.0 METs. The advantage in utilizing metabolic equivalents to assign intensity levels is that MET values have been determined for over 500 physical activities. Simply look up your favourite activity to see the value of metabolic equivalents it represents: This is simple enough but the trouble occurs when you want to combine moderate and vigorous activities throughout your week. So here is a fairly broad albeit, acceptable method of calculating the possible combinations of moderate and vigorous activities: Generally, the total amount of activity performed over a week is a function of its intensity, duration, and frequency (i.e., how hard you work, for how long, and how many times each week). Here’s the trick: to meet the minimum recommendation for physical activity, you will need to accumulate approximately 450 to 750 MET per minute per week, expressed as: 450 to 750 MET·min·wk This is how it works... Looking through the list of Compendium of Physical Activities, we find that walking on a flat, hard surface at 3.0 mph represents 3.3 METs. Therefore, this qualifies as a moderately intense activity and as such, you would need to engage in this activity 5 days a week for a minimum of 30 minutes each day to meet the minimum activity requirements. If you did this, you would accumulate 3.3 METs per minute for 30 minutes, or 99 METs a day (i.e., 3.3 METs x 30 min = 99 MET·min) for 5 days, or a total of 495 METs (i.e., 99 MET·min x 5 days = 495 MET·min·wk). Since you are between 450 to 750 METs per week, you can assume you have met the minimum requirements recommended. On the other hand, the Compendium of Physical Activities lists jogging on a similar surface at 5 mph, as expending 8.0 METs. Any activity over 6.0 METs represents a vigorously intense activity and as such, you would need to engage in this activity 3 days a week for a minimum of 20 minutes each day to meet the minimum activity requirements. Following the same approach, we can calculate your MET weekly expenditure level as: 8.0 METs x 20 min per day x 3 days = 480 MET·min·wk This too, falls between the 450 to 750 METs per week recommendation, and therefore, you can also assume you have met the minimum requirements recommended. To combine your activities then, you simply follow this approach to calculate your weekly metabolic equivalents expenditure level, and aim for a range of 450 to 750 MET·min·wk to meet the minimum recommended physical activity requirements. Let’s follow a typical example to facilitate our understanding of how to use metabolic equivalents when combining activities. Suppose you wanted to combine moderate with vigorous activities during your week. You want to walk AND jog throughout the week. How many days of walking and how many days of jogging will you need to meet the metabolic equivalents required? Will walking 2 days for 30 minutes and jogging 2 days for 20 minutes suffice? Here’s how to find out... Walking at 3.3 METs for 30 minutes on 2 days will equal 198 METs, i.e., -3.3 METs x 30 min per day x 2 days = 198 MET·min·wk Jogging at 8.0 METs for 20 minutes on 2 days will equal 320 METs, i.e., -8.0 METs x 20 min per day x 2 days = 320 MET·min·wk Your total MET activity level on all four days will therefore equal 518 METs, i.e., -198 + 320 = 518 MET·min·wk Because your activity level falls within the 450 to 750 MET range, the answer is Yes. You can combine walking and jogging in this way to meet your minimum weekly physical activity requirements. Of course, walking 1 day for 60 minutes and jogging 1 day for 40 minutes will also accomplish your minimum goal requirement. Can you see that? (3.3 METs x 60 min) + (8.0 METs x 40 min) = 198 + 320 = 518 MET·min·wk ...Whether you would want to do it this way or not is another matter entirely, but mathematically speaking you would still accumulate 518 METs. Beginners should start at the lower end of the range nearer to 450 METs weekly. Build up slowly and progress gradually to the higher end of the range as your fitness improves. Remember also that these are just 'minimum' activity recommendations. Engaging in larger amounts of physical activity, including more activity performed at vigorous intensities, are postulated to provide additional health benefits.
You'll soon be on your way to physical fitness. But before starting an exercise program, consider where your best chances for success lie. Will you be joining a health club or will you be working out from home? Perhaps the first thing to think about is your temperament and nature. Which are you more suited for? Weigh your options carefully. Discover both the advantages and drawbacks to working out from home. This is the topic of our next discussion...
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