BodyMedia vs. HRM...HELP!

significance

I've had a BodyMedia Link for a week now, and while I am going to go with its estimates for a couple of months at least, I don't really trust it. Some observations:

* I have a standing desk at work and find it a little disconcerting to see that standing while working apparently burns calories at about the same rate as sleeping. Various online sources suggest that sleeping should be 1.0 METS and standing, 2.0 METS: BodyMedia gives me 0.9 to 1.0 for sleeping, 1.0 to 1.1 for standing, typing. (Today, it says 1.0 for both).

* If I stand while moving my arms a little more (I spent two hours yesterday standing at a table, sorting and pricing books for a charity bookfair), BodyMedia does give me 2.0 METS on average.

* Most of my exercise is riding my bike, and I find that though my cycling is usually vigorous by the "breath" rule of thumb (i.e. it's vigorous if you couldn't hold a conversation at the same time), it never shows as more than "moderate" according to BodyMedia. Online sources suggest that on average, cycling at the pace I do should be about 6.5 METS, but BodyMedia says it's 3.5 to 4.0. It's likely that my burn for cycling is less than it would be for most people, since cycling has been my main physical activity for many years and my body must be used to it -- but that still seems too low. People suggest putting it on your calf when cycling, but that seems certain to yield an over-estimate.

* Routine activity like sauntering down a hill while chatting with colleagues shows up as more energetic (higher METS) than cycling, and every time I walk up a short flight of stairs (without getting the slightest bit out of breath), it appears as "vigorous" activity.

* Cycling in the morning apparently consistently burns more than cycling at the same pace over the same route in the afternoon: I suspect this comes down to the heat flux measurement, as the air is about 15C here in the morning, but has been 35C in the afternoon.

* Despite all this (and despite cycling for 2 hours a day and standing for 9 hours a day), my daily total energy burn according to BodyMedia is only 10% lower than I had been estimating using the MyFitnessPal tools -- probably because it counts all those short walks about the office building that I wasn't counting before. And MyFitnessPal seems about right, going by my rate of weight loss.

bikinibeliever

I can only add, I find my bodymedia incredibly accurate. Having said that, I don't bike. Why not give them a call and see what they say about biking, and the suggestion to wear it on your leg.

significance

I can only add, I find my bodymedia incredibly accurate. Having said that, I don't bike. Why not give them a call and see what they say about biking, and the suggestion to wear it on your leg.

Their official advice is to wear it as normal when on a road bike. They acknowledge that it is more accurate for some activities than others, but say that for most people, it should average out to 90% accurate across all your activities for the day.

snelson1966

bump, thanks for all the info

karlml

The HRM will obviously be the best sensor for determinig caloric expenditure, however it is not the sensor that calculate caloric burn, but the software that is used with it. There are big differences and you will notice it if you use Polar H7 HRM with 2 different iPhone apps running at the same time. I noticed a 20% difference for the exact same acticvity (I had several apps logging the same activity at the same time). This is becuase the algorithms are generally different in each app. Also you have to remember to subtract your Basal Metabolic Rate, but that is the same with all the apps I know of.

Bodymedia is a toy and I have never seen it used in any independent peer review academic/medical study. Always go with the HRM.