METS

So a couple of weeks ago I was using wiifit plus, and the game popped up a little box that said "Hi were now using these things called METs to calculate the estimated number of calories you're burning during each activity.

Being the curious person I am, I immediately went, what the heck is a MET. So I poked around in the game and found an area that talked about them... but it basically retold me the same information. So I decided to do some research and this is what I found.

MET stands for Metabolic Equivalents, with 1 MET equal to 3.5 milliliter oxygen per kg of body weight per minute. It's a gauge of how hard your body is working, and thus by extension how much oxygen your body burns to release the energy you need to do said activity. The maximum amount of Oxygen your body can use is called your VO2 max.

At rest every human being is uses roughly 1 MET and your average middle aged man or woman has a peak MET output of 8 to 10. Right now that doesn't mean much so let me give you some examples.

Walking = about 3 METS
Hiking = 7 METS
Swimming at a moderate speed = 8 mets

The sustainable MET output for your average human is 60-80% of their maximum METs. At 80-100% output the activity is not able to be sustained for any significant length of time.
So that's the bad news. The good news is the more fit you are the higher your maximum METs and the longer you can sustain a given output. This is because the more fit you are the higher your VO2 max.

Lets take a quick look at VO2 max. This represents the capacity of your body to deliver oxygen to your cells and the ability of your cells to use that oxygen. In an unfit body, the cells make poor use of oxygen and the cardiovascular system doesn't supply enough oxygen to the muscles. Where as in an someone who's fit, a greater volume of oxygen is delivered to the cells and the cells are more efficient in their use of that oxygen. A normal VO2 max for a 20-29 year old male is 43-52 ml/kg/min where as a male soccer player age 22-28 by contrast, is able to use 54-64.

So how do you use all this to calculate calories burned? For that we use the equation 1MET = 1cal/kg/hr. But since we use lb in the US, we have to divide that by 2.2, since 1kg = 2.2lb. So for us its going to be 1MET = .45cal/lb/hr. There for a 200 lb person hiking at 7 METs for an Hour would burn an estimated 630 cal or about 10.5 cal/min.

Lets extrapolate this. If you burn 1MET at rest. That means a 200 lb person is burning 90 cal/hr sitting on their but, or a total of 2160 cal in a day by doing nothing. This explains why when you look at the back of any food product the daily allowed numbers are based on a 2000 cal diet. Because the average human will burn more then 2000 cal by simply living. So to not waste away to nothing, we must consume at least 2000 cal a day. Which in the US, isn't much of a problem.

If you want to know what the MET value's are for just about any activity you can imagine just follow this link. Take a look you might be surprised at how high some of the activities you enjoy are. Also if you want to read more about VO2 Max follow this link. and a link to some one of the pages on METs I looked at.

And now you know. :)