Mets, calorie burns (number nerdery thread)

yirara

How good are METs for for estimating calorie burns? Can anyone help me understand this?

The compendium of physical activity mentions: 3.5METs, walking, 2.8 to 3.2 mph, level, moderate pace, firm surface

The following equation gets cited regularly:
METs* weight in kg * 3.5 * minutes - oxygen intake in ml
previous equation / 1000 = oxygen intake in l
Result * 5kal per litre = calorie use.

Or in short
METs* weight in kg * 3.5 * minutes/200
(btw, is this gross or net calories?)

So for a 65 kg person, walking 3 miles in 1 hour this would be:
3.5 * 65 * 3.5 * 60/200 = 239kcal.

Using weight (lbs) * distance (miles) * 0.3 (often cited here) I get 128kcal, nearly half.

I don't have own reliable data for walking, but for running weight (lbs) * distance (miles) * 0.64 (also often cited) seems to be a perfect fit for me, while METs would overstate calories burned. Or do METs only work for athletes with a much higher oxygen intake or under other circumstances?

Thanks.

NorthCascades

METs is completely useless for me on a bike. Intensity is changing constantly. Which subjective label best describes the three hours I did? There were hills, there were sprints, there were times I coasted with the wind at my back.

yirara

NorthCascades wrote: »

METs is completely useless for me on a bike. Intensity is changing constantly. Which subjective label best describes the three hours I did? There were hills, there were sprints, there were times I coasted with the wind at my back.

Yes, there are mets for different kinds of cycling I guess, as there is for walking or running.

If we assume steady state, uniform terrain then why is there still such a big difference?

sijomial

Remember that the common walking and running formulae given on here are net not gross estimates.

A problem with much of the MFP database taken from the Compendium of Physical Activities which are gross METs.

Azdak

A MET is a shorthand way of expressing oxygen uptake. Oxygen uptake is the standard measurement of aerobic intensity (and calories burned). The Compendium is a collection of MET values for a large number of activities. The MET values are gathered from research studies. The authors of the Compendium state in the preface that they do not evaluate the research studies for either quality or accuracy. So the accuracy of the reported MET values varies quite a bit.

You are over complicating the equation for using METs to estimate calorie burn.

To determine calories burned per hour, multiply the MET value of the activity times body weight in kilograms. If your workout is less than an hour, multiply that number by the fraction of an hour worked (e.g. by 75% if you worked 45 minutes)

The MET values seen in various tables are *gross* values, not net. To estimate net calories, subtract 1 MET before multiplying METs x body weight.

Normally, MET values are based on continuous activity, not intervals or any stop and start workout.

NorthCascades

yirara wrote: »

NorthCascades wrote: »

METs is completely useless for me on a bike. Intensity is changing constantly. Which subjective label best describes the three hours I did? There were hills, there were sprints, there were times I coasted with the wind at my back.

Yes, there are mets for different kinds of cycling I guess, as there is for walking or running.

If we assume steady state, uniform terrain then why is there still such a big difference?

Because that assumption doesn't hold water. Cycling (outdoors) is never a steady state. Even minor changes in wind (speed or direction), in pavement quality, undulations, traffic, etc, all work together to keep cycling from being a steady state activity.

If you graph what METs you're riding at every second, I guarantee it will jump around like a seismometer in an earthquake.

yirara

sijomial wrote: »

Remember that the common walking and running formulae given on here are net not gross estimates.

A problem with much of the MFP database taken from the Compendium of Physical Activities which are gross METs.

Yes, I assumed that METs are goss. Still the often cited walking and running equations don't quite work at least for me.

yirara

Azdak wrote: »

A MET is a shorthand way of expressing oxygen uptake. Oxygen uptake is the standard measurement of aerobic intensity (and calories burned). The Compendium is a collection of MET values for a large number of activities. The MET values are gathered from research studies. The authors of the Compendium state in the preface that they do not evaluate the research studies for either quality or accuracy. So the accuracy of the reported MET values varies quite a bit.

You are over complicating the equation for using METs to estimate calorie burn.

To determine calories burned per hour, multiply the MET value of the activity times body weight in kilograms. If your workout is less than an hour, multiply that number by the fraction of an hour worked (e.g. by 75% if you worked 45 minutes)

The MET values seen in various tables are *gross* values, not net. To estimate net calories, subtract 1 MET before multiplying METs x body weight.

Normally, MET values are based on continuous activity, not intervals or any stop and start workout.

Ok, so lets say 3.5 Mets for walking * 60kg = 250kcal for an hour walking of about 3 miles per hour if assuming net (thus 2.5 mets). That seems closer indeed. Thanks.