# Ambit's Calories Burned Summaries: Valid or Invalid?



## srwilson (Jun 16, 2012)

I have seen in several different places where individuals have been questioning the validity of the Ambit's calculation of calories burned for an exercise/move. Cimarco, here on this forum, has also made comments that the figures are unrealistic. At this point I would have to agree. The calculated summaries do seem unrealistic based on my previous experience with other programs and known excepted formulas used to determining calories burned using Heart Rate, Age, Time, Weight and VO2max numbers.

Here is a standard formula used by several websites that calculate burned calories for an exercise. _(Google: Heart Rate Based Burned Calories Calculators)_
*
Using VO2max:*

_Men: C/min = (-59.3954 + (-36.3781 + 0.271 x age + 0.394 x weight + 0.404 x VO2max + 0.634 x HR))/4.184
Women: C/min = (-59.3954 + (0.274 x age + 0.103 x weight + 0.380 x VO2max + 0.450 x HR)) / 4.184

*Without VO2max:*

Men: C/min = (-55.0969 + 0.6309 x HR + 0.1988 x weight + 0.2017 x age) / 4.184
Women: C/min = (-20.4022 + 0.4472 x HR - 0.1263 x weight + 0.074 x age) / 4.184

where weight is in kilograms and C stands for Kcals. _

This work was published in the Journal of Sports Sciences on 01-Mar-05
Here is a link to the published paper: http://www.braydenwm.com/cal_vs_hr_ref_paper.pdf

Here is my real Life Example: 
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. This would seem to suggest that someone has completely missed the boat with their science and/or calculations. Also with this magnitude of difference I'd think there should be some papers floating about refuting the formulas previously submitted to the Journal of Sports Sciences on the subject. However, I can't find any such papers.

Does anyone have information on how the Ambit calculates calories burned? If so, can you share that with us? 
Has anyone brought this up with Suunto and gotten a reply? I'd be interested in what they had to say if you would be willing to share.

Thanks!!!


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## Lost-again (Feb 24, 2012)

Unfortunately I can't add anything on the formulas, but I can confirm that tha Ambit agrees roughly with my t3d on cals burnt. The only other comparison I have is with a friend on a very long difficult walk over several mountains in the English lake district. I had the T3 and he was using a Polar, we both recorded 6500 cal for the day. The only conclusion I can draw is that the calculation is in alignment with competitors.


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## eeun (May 31, 2012)

I switched from a Polar to a T6D in february this year and added an Ambit in May. The Ambit and T6D seem to be in 'sync' but both show higher calorie burn than the Polar which as it's not working I can't directly compare. Suffice to say I was working flat out or so I thought when using the Polar and buying 660 to 700 calories, I regularly burn 800/900 with the Suunto's. Maybe I'm working harder but my fitness has improved too so I'd expect the calorie burn to drop. This is not definitive of course and I cannot run the two (Polar vs either Suuntos) under scientific conditions. I do have my suspicions though. I guess it doesn't matter that much as I have the same point of reference.


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## Lost-again (Feb 24, 2012)

Not sure but think it is linked to the Activity level, if you increase the activity level I think the Cals recorded drops? I think I have observed this, but I have not experimented.


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## srwilson (Jun 16, 2012)

Lost-again said:


> Not sure but think it is linked to the Activity level, if you increase the activity level I think the Cals recorded drops? I think I have observed this, but I have not experimented.


Lost-again, 
I would think your thinking is correct; they use activity levels in their formula, somehow. I'm thinking it's the same idea as using a person's VO2max numbers like in the formula I previously posted. Efficiency absolutely plays a part. The more fit the more efficient. The more efficient the less you burn for the same activity. Make sense to me.

I'm now thinking that the numbers being displayed on the watch and on Movescount are Net calories burned, not Gross calories burned. I'm pretty sure the formula I've used produces a Gross number and not a Net number. So, if that be true, then the Ambit's numbers would naturally be smaller in comparison.

I've posted the Gross/Net question on their Movescount Facebook page, but I'll be surprised if I get an answer.

Going back to the Activity Level setting; I've noticed that this variable cannot be set on the watch itself. If it is used in the watch to determine calories burned it has to be set by Movescount. The only values you can set on the watch itself are Weight and MaxHR. I find this a little strange since Activity Level is more likely to change than MaxHR. Resting HR would also be an indicator of fitness, but you can't change it either on the watch. So I'm just not sure how or what they use.

I spent a little time looking at the XML to see if anything jumped out at me, but so far not that much. Here is what I came away with so far. 
In the xml file I see a Sum Value for Energy, _<Energy>1272787.2</Energy>_, and for me that value X 0.238845896627496 (static value) will give me the kcal value in the watch and Movescount. I would guess this to be the same for everyone. Someone else can check that out if you like.

At first I thought this Energy number was the sum of all the Energy Consumption values, _<EnergyConsumption>76.758</EnergyConsumption>, _taken ever second. It's close but there seems to be another component that is added and that component seems to change with the exercise. So I haven't quite figured that out yet. Maybe someone has gotten much further on this and if you want to share I'd be interested in what you have.

I wonder if they use the Activity Type in anyway. Hmmmm&#8230;

Oh well, I guess it really doesn't matter in the grand scheme of things, and I guess should be looked at as a relative thing.


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## or_watching (Nov 13, 2008)

srwilson said:


> Oh well, I guess it really doesn't matter in the grand scheme of things, and I guess should be looked at as a relative thing.


Not totally arbitrary...I divide by 218, and round up, to figure out how many beers I get to drink.


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## pjc3 (Mar 26, 2012)

srwilson said:


> Oh well, I guess it really doesn't matter in the grand scheme of things, and I guess should be looked at as a relative thing.


You are pretty well right with the last statement. As long as Suunto's methods are reproducible it should be a useful tool regarding the intensity of exercise to compare sessions. The absolute number is a bit contrived but comparing the numbers is potentially useful.

Once I get home I will do a session with the Quest, T6, T3 and Ambit all concurrently and report back. Unfortunately my Polar no longer works (and hence my initial swap to Suunto)


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## srwilson (Jun 16, 2012)

or_watching said:


> Not totally arbitrary...I divide by 218, and round up, to figure out how many beers I get to drink.


I like the way you think!


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## Lost-again (Feb 24, 2012)

Out of interest, my Cal reading is only normally a few points off the value on my Nordic Track Treadmill, which has no input parameters such as weight, age etc. it's just a generic setup.


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## cfimarco (Jun 30, 2012)

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?


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## srwilson (Jun 16, 2012)

cfimarco said:


> 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&#8230; 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[SUP]nd[/SUP] or 3[SUP]rd[/SUP] beer!!!;-)

Take care!!


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## Clevor (Sep 20, 2010)

srwilson said:


> 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(?).


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## pjc3 (Mar 26, 2012)

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.


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## cfimarco (Jun 30, 2012)

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:-(


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## cfimarco (Jun 30, 2012)

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


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## srwilson (Jun 16, 2012)

Clevor said:


> 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.... :think:

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


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## eeun (May 31, 2012)

cfimarco said:


> 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'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.


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## cfimarco (Jun 30, 2012)

eeun said:


> 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)


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## Lost-again (Feb 24, 2012)

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.


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## cfimarco (Jun 30, 2012)

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.


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## eeun (May 31, 2012)

cfimarco said:


> 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.


I believe you are answering your own point here. Many factors affect the heart rates we see on a day to day and exercise to exercise basis but we're rarely seeing true RHR and MHR. To measure your *true* RHR there is some guidance you must follow and that involves things like when you last exercised, how much recovery you have had, time of day, lack of illness, being relaxed etc etc. True RHR can lowered with improved fitness over time but it is possible to establish a pretty stable base line.

To measure your true MHR you need to build up your HR over a short period doing something intense like hill interval sprints or similar and if performed correctly it is possible to determine your *true* MHR pretty accurately. You will rarely see this in exercise (my MHR is 169 and I regularly see 163-167 at peak exercise) unless really going for it and of course it's not possible to sustain those level for long.

There's loads of info available on both subjects via google though as always caveat emptor as some advice is incorrect.


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## pjc3 (Mar 26, 2012)

eeun said:


> There's loads of info available on both subjects via google though as always caveat emptor as some advice is incorrect.


You are so right......unfortunately much is written (on many topics) which are for the "lay-person" and the truth is often missing. Just because it is "common knowledge" does not make it correct.


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## Clevor (Sep 20, 2010)

srwilson said:


> 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 numbers do look a little low. On my most relaxed 3-hr rides, I'd maybe go 35 miles with little climbing, mainly criss-crossing short farm roads, and I'd burn 1700 calories. It also depends on how you climbed the elevation gained: steady 6-7% grades or short stretches of double digit grades. They say the pros can burn up to 7000 calories in a day, but that's in a 5-6 hr training ride.

I always say while I'm jogging: it's easier to NOT eat that Big Mac I ate yesterday, if I want to lose weight. Hell, you can jog 3-4 miles at a 10 minute/mile rate, and barely burn off the calories for the french fries. And that doesn't even include the Big Mac and the Coke!


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## srwilson (Jun 16, 2012)

Just a quick update.

I had asked Suunto if the calories were a net or gross calculation and if they had any info to share on how they did the calculations. Here is their reply.

"The calorie consumption is basically all calories consumed since the log start. We hope to release more documentation about the calorie consumption in the future."

​So maybe one day...​

​


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## jimmijames73 (Jun 29, 2012)

I wish Suunto would be more upfront with the methods it uses to calculate calories, track distances, etc, so we could understand the limitations or shortcomings of the parameters provided.


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## pjc3 (Mar 26, 2012)

Quest vs Ambit: Trail running. 1Hr45min.

Quest: Av HR 147bpm; Kcal 1517; PTE 3.9; Recovery time 33Hrs
Ambit: Av HR 148bmp; Kcal 1118; PTE 3.7; Recovery time 39Hrs


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## PaulR7 (Mar 30, 2012)

pjc3 said:


> Quest vs Ambit: Trail running. 1Hr45min.
> 
> Quest: Av HR 147bpm; Kcal 1517; PTE 3.9; Recovery time 33Hrs
> Ambit: Av HR 148bmp; Kcal 1118; PTE 3.7; Recovery time 39Hrs


It would be really interesting to know Suunto response to this, calories aside, Lower PTE = Higher recovery time? This concerns me, as they are the 2 values that are most important to me post training run. Thanks for testing & posting the results.


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## matamua (Aug 10, 2012)

I've actually been wondering the opposite. I did a 4.25mi run today with my t3c. I was up in the 160-170s for most of it, and it spit out 913kcal as my expenditure. I have a hard time believing it. I've used a t1 and t3 and the results are similar between the two (probably use the same calculations). If anything, I feel like it's too high.

When I'm actually in shape (not currently) I can plan on roughly 600kcal for a 1hr mountainbike ride with my hr at 160ish for most of the duration. I use it primarily to gauge what I can splurge on after exercising.

I've tried calculating on two different treadmills (different models and brands) with my weight inputted, and it's always paradoxically a higher HR on the treadmill and fewer calories burned. That confuses me. I'd say it's on the order of 15-20% variation in the calorie department and 10bpm at any given time. The calories on the treadmill today were at 700ish with the t3c at 913. 

So I guess I'll just choose what to believe. When I'm trying to convince my wife that I'm really exercising, and that my gut bomb dinner choice is justifiable, I'll pick the big number. When I'm being conservative and wondering why in the world I'm not losing weight, I'll take 20% off.


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## eeun (May 31, 2012)

PaulR7 said:


> It would be really interesting to know Suunto response to this, calories aside, Lower PTE = Higher recovery time? This concerns me, as they are the 2 values that are most important to me post training run. Thanks for testing & posting the results.


I run a T6D and Ambit and see the same time, same HR data but vastly different calories/energy between the devices. as you say, PTE and other calculated data is inconsistent across devices and before and after upload. Suunto are aware and have acknowledged the inconsistencies and they say they are looking into this and will make whatever changes they feel are appropriate. However it's been on their radar for months and is as this point unresolved. I'm not convinced they will do anything dramatic that will eradicate this issue. I may be wrong.

I tend to use the T6D for all gym work such as spin as I like to be able to pair with the non ANT+ gym machines for HR data and use the Ambit for all outdoor GPS exercise. This way I do get some consistency though I am sceptical on the accuracy of any calculated figures which I see are different in Strava, Garmin Connct and Movescount.


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