It is fairly common for individuals to engage in a variety
of exercise activities and at different rates of intensity. This can make it
challenging to evaluate just how much activity they are actually doing across
the week. Taking these activities and transforming them into a common value would
be great way to get a snap shot of the week’s activities which would be helpful
for tracking exercise habits and progress.
That common value is MET
minutes. Let’s review what a MET is. The metabolic equivalent of task
(MET), or simply metabolic equivalent, is a physiological measure
expressing the energy cost (or calories) of physical activities. One MET is the
energy equivalent expended by an individual while seated at rest. While
exercising, the MET equivalent is the energy expended compared to rest so MET
values indicate the intensity. An activity with a MET value of 5 means you are
expending 5 times the energy (number of calories) than you would at rest.
Okay so now that we are refreshed on what a MET is, what is
a MET minute? MET minutes are simply the time engaged in an activity with
consideration to the number of METs. So if you walked at a pace equivalent to 5
METs for 30 minutes it would be calculated as follows:
5 METs x 30 minutes =
150 MET minutes
MET minutes per week can also be calculated. If you
participated in this activity 5 days per week:
150 MET minutes per day X 5 days per week = 750 MET minutes
per week.
If you participated in this activity 3 days per week but
another activity 2 days per week that was equivalent to 6 METs for 20 minutes
you could tally the two together like this:
5 METs x 30 minutes = 150 MET minutes
6 METs x 20 minutes = 120 MET minutes
150 MET minutes x 3 days = 450 MET minutes
120 MET minutes x 2 days = 240 MET minutes
450 MET minutes + 240 MET minutes = 690 MET minutes per week
The most current Physical Activity Guidelines for
Americans suggest that there are substantial health benefits for adults
engaging in 500-1,000 MET minutes per week. These two examples, therefore, meet
the current recommendations.
The Guidelines
designate the following aerobic intensity categories based on MET levels.
·
Light-intensity aerobic activity = 1.1 to 2.9
METs
·
Moderate-intensity activity = 3.0 to 5.9 METs
·
Vigorous-intensity aerobic activity = 6.0 or
> METs
How do you know what MET value your physical activity is?
Many cardiovascular machines display the MET value of your
selected activity and intensity. You can also access the Compendium
of Physical Activities to find the MET value of a number of different
activities. The Compendium is quite comprehensive. You can select an activity
like walking and it provides the MET value for numerous different scenarios (over
50) like hiking with a back pack, race walking, or walking while doing house
work.
Beyond MET value though, many are interested in the number
of calories they are burning. An estimation of this can be calculated as well.
The equation used is listed below. Not that the bolded numbers 3.5 and 200 are both constants and do not change. You simply have to
provide the MET value of your activity and your weight in kilograms. To convert
your body weight in pounds to kilograms divide by 2.2.
_____MET Value x 3.5 x _____kg
body weight ÷ 200 = calories burned per minute.
For a 150 pound
person (68.2 kg) doing brisk walking (approximately 4 mph) for 150 minutes per
week at 5 METs the total calories burned would be 900.
5 METs x 3.5 x 68.2
kg ÷ 200 = 6 calories per minute
150 minutes each
week X 6 calories per minute = 900 calories burned per week.
For health benefits for most adults, the national guidelines
suggest burning 1,000 calories per week.
For weight loss and even greater health benefits an expenditure of 2,000
calories per week is suggested.
In summary, tracking volume of exercise can be challenging, especially when
including a variety of activities of different intensities and duration. For
the purpose of tracking progress and summaries of activities, both MET minutes
per week and MET calories per week can be useful in activity logging, in goal
setting and quite motivating.
Bushman, B. A. (2012). How can I use
METS to quantify the amount of aerobic exercise. ACSM's Health & Fitness
Journal, 16(No. 2), 5-7.