Ambit's Calories Burned Summaries: Valid or Invalid?

[srwilson]

Hi, I just got back from a short run, I did it with the Ambit, set up with my weight of 70kg and it shows I burned about 400kcal on 10.5km. Well... I did the 10.5km in 49', with an indicated average of 143bpm and an easy pace of 4'40"/km. Without big math it's easy to see that my Ambit is way off regarding calories counts (and also distance measuring, but that's another topic). A 70kg man who runs 10.5km should roughly burn around 600 to 630kcal, any runnner with a little of experience knows it. Therefore my Ambit indicates about 40% less than the actual burning figure... Is there anything, beside altitude, that does it right?

Hi cfimarco, I'm curious what you have set for your Activity Level and MaxHR and how you determined what to use.

It looks like Suunto has revamped their math a bit according to their product Q&A page. Here is their response to someone questioning why they were seeing a 25% reduction in PTE and burned Calories in the Ambit vs. the T3.

"The differences are due to different algorithms. The Suunto Ambit uses an updated algorithm compared to the t3 to calculate the results."

I think for the formula Suunto is using to be accurate it is dependent on accurate MaxHR and Activity Levels settings. I think that is what they are using along with Weight and Heart Rate to calculate the VO2 and Energy numbers. (Compare by overlay the ‘VO2’ and ‘Energy’ graphs on Movescount… same graph different numbers)

I’m not so sure the other programs I’ve used in the past use Activity Levels (a way to determine approx. VO2Max #) and I’m pretty sure if they used MaxHR it was derived by the old ‘220 – Age’ formula, which is crap for a lot of folks me including. So I think we may have been conditioned to expect bigger numbers by lumping folks together in big buckets. So maybe a swing of 40% is not out of line when people are group as such.

Their numbers did and do look suspect, but I can’t say that they are wrong because I just don’t know. I can only make comparisons at this point. I'm certainly not an expert so...

Anyway, the ‘Activity Level’, is just their way of getting a MET value and for a A.L. of 7 I believe they use 12.7 METs in their formula (as seen on the same page you set the slider on) or 44.45 VO2Max [MET= VO2max (ml/kg/min)/3.5].

So what this tells me is, if you know your VO2Max or MET number, bump the Activity Level indicator up or down to match your number and not worry with their definitions, and you might be closer to actual. Their Activity Level definitions are there because most people do not know what a MET or VO2Max is.

Of course all this depends on their mathematical model being correct too. I was just hoping that someone in the know could shed some light on this so we could feel a little better about grabbing that 2^nd or 3^rd beer!!!

Take care!!

[Clevor]

A bike ride I just posted returned a Calorie Burned value of 675 Kcal. Using all the same info/data and using the with VO2max formula above I get a total calorie burned value of 1210 Kcal. The Ambit calculates 44% less burned calories for the same exercise! That’s a significant difference if you ask me.

On that ride, how long did you bike in hours, and what was the distance? Was it flat or any climbing?

I have a Sigma advanced cyclometer on my road bike so I can tell you if it's in the ballpark to that. But amount of calories burned always turns out disappointing. On a 3-hr ride, my Sigma says I burn anywhere from 1700 to 2300 calories depending if it's flat or if there are climbs. I could wear my Ambit for rides to compare but it's too bulky for road cycling.

Yesterday I did a 30 minute run up some 6-12% grades, climbing 292 ft. according to the Ambit, and I only burned 383 calories! Although half the run was downhill when I turned around and backtracked. I don't think it accounted for the heat and humidity of running at noon, although that might be reflected in the heart rate or respiration(?).

[pjc3]

Just did a short run with the Quest and Ambit off the same HR belt. Exact same HR values and graphs. Same biometric data.
Quest 474 Kcal vs Ambit 432.

[cfimarco]

Srwilson wrote:
Hi cfimarco, I'm curious what you have set for your Activity Level and MaxHR and how you determined what to use.
-----------------
Hi, thanks for your post, I set up my activity level at 7.5, that's honestly what I have been doing in the past year. (It would have been set at 7 in the past, but thanks to the economy's crisis I have more time for training
I set my rest HR at 40 (it's 36/38 but I set it up with 40) and I set my max HR as 185. Sometimes I go over 185, but not in summertime. I use to reach an higher HR in winter, when the air is colder and more dense. Somehow in summertime, when the air is muggy and less dense I can't get much higher HR.
I don't know if it's just me or is common, anyhow my timings on the same track reflect that, showing better performances when the temperature gets below 20°C
I see there is too much math involved in this Ambit and sometimes too much math means that it gets more complicated and less accurate than it should be. I wouldn't care if the calories count was off by 10% or the distance measured was off by 0.1%, but to me 40% off on calories and an average of 1.6% off on distance measured is too much to call it a modern and precise training instrument...
Beside, the lack of laps indication on the watch itself really bother me

[cfimarco]

One more thing about calories:
It seems to me that an easy way to estimate calories burned during running activities, (flat or almost flat terrain) when a calculator or an HR monitor is not available is the following:
(Weight x km) - 10%

Example:
Runner is 70kg
He runs 10km
70 x 10 = 700 - 10% = 630
Calories burned: 630kcal

May be is not the most accurate way to compute it, but surely more accurate than Ambit's computing

[srwilson]

On that ride, how long did you bike in hours, and what was the distance? Was it flat or any climbing?

Clevor, That particular ride was 1.3 hours, 20.5 miles, around 500ft of climb. = 675 cals burned.

While your checking , Yesterday I had a 1.76 hour, 26.5 mile, 1050 feet climb ride = 880 cal burned.

The Ambit does use Heart Rate for sure in their cal burned calculations. You can see the correlation in the graphs.

I think maybe the big difference between Suunto and other computations of calories burned is that they claim they have and can display calorie consumption in 'Real Time'. A person can monitor their workout and know just when they've accomplished their calorie burn goal.

To do this they would need to use whatever personal data that is in the watch (static stuff), add that to the incoming data from the exercises every second (dynamic stuff), and then add it all up in the end for an exercise total.

So my question is:
Is 'Real Time' Computing of calories burned more accurate? Hmmmm....

Thanks for running the numbers! I'm interested in the outcome!

[eeun]

Srwilson wrote:
Hi cfimarco, I'm curious what you have set for your Activity Level and MaxHR and how you determined what to use.
-----------------
Hi, thanks for your post, I set up my activity level at 7.5, that's honestly what I have been doing in the past year. (It would have been set at 7 in the past, but thanks to the economy's crisis I have more time for training
I set my rest HR at 40 (it's 36/38 but I set it up with 40) and I set my max HR as 185. Sometimes I go over 185, but not in summertime. I use to reach an higher HR in winter, when the air is colder and more dense. Somehow in summertime, when the air is muggy and less dense I can't get much higher HR.
I don't know if it's just me or is common, anyhow my timings on the same track reflect that, showing better performances when the temperature gets below 20°C
I see there is too much math involved in this Ambit and sometimes too much math means that it gets more complicated and less accurate than it should be. I wouldn't care if the calories count was off by 10% or the distance measured was off by 0.1%, but to me 40% off on calories and an average of 1.6% off on distance measured is too much to call it a modern and precise training instrument...
Beside, the lack of laps indication on the watch itself really bother me

I'm no expert but surely your resting and max heart rates are specifically..... what they are and both are measurable. Mine are 48 and 169 respectively and I never go below - or above either. I would have said the Suunto 'kit' compared to the Polar HRM I previously used is reading 10% to 15% higher calorie burn though the HR readings remain the same as the Polar at resting and max.

[cfimarco]

I'm no expert but surely your resting and max heart rates are specifically..... what they are and both are measurable. Mine are 48 and 169 respectively and I never go below - or above either.

Well... I guess none of us has always the same rest HR and max HR. There are too many factors involved. For my profession I have to take an EKG every six months (rest HR) and it never shows the same results. Sometimes it shows 38bpm, other times 44bpm. Even when I am at home, in relax, without the little stress given by a doctor and his machine, my rest HR is never the same. It depends what I did the previous days, how much training, sleeping, working, etc. Same for the max HR. Beside, it's not a matter of 10% difference on rest and/or max HR that could give such a silly result on calories burned by the Ambit. Once again, on flat terrain a runner usually burns roughly his weight in kg x distance in km - 10%, not almost half of that as shown by my Ambit
My unit shows that running at around 150bpm average, on a distance equivalent to about 1/3 of a marathon, I burn just over 600kcal. That's funny, as I wrote previously with this average I would burn less than 2000kcal on a 3h marathon, which is impossible. Man, I wish I could! (With the same settings the Garmin FR610 shows much more realistics data, therefore is not a matter of wrong settings)

[Lost-again]

Ok, looking at your general formula ( kg x km) - 10% , I have checked back over the last 10 moves I have made and guess what, your formula is really close, within 20 kcal over 5 & 10k. My only conclusion is you have something really screwy going on or not all your settings are correct (weight/activity etc.) or your HR belt/ Ambit is not working correctly.

[cfimarco]

I'm glad you agree that the easy formula works, I found it easy to use, since doesn't need big math to be done and it's accurate enough to me. (I'm not much interested on diets, I have been pretty much the same weight in the past 30 years, plus or minus a couple of kg's, but I like recording most data of my runs)
Regarding my Ambit's settings, I don't think there is anything wrong, I used the same basic settings I have on the Garmin FR610 (which is about right) and a index of 7 on the training index on Movescount. I guess something is wrong with the unit when it computes the calories, not the belt or the receiver, since it shows a very accurate rest reading.
I will forget calories burned and I will use it just to have an idea of my average HR and peak HR during the exercises for a while, then I will give it back and I will keep using just the FR610.