Calories burned - Figuring out what to believe

JethroXP

I just finished my first workout with my new Polar FT7 Heart Rate Monitor. According to it, I burned 895 Calories walking 5 miles at a 4 MPH pace on a 5% incline. The MFP database tells me that effort was only good for 715 calories.

The difference between my HRM and MFP has me wondering which is closer to the truth. I was able to lose 75 pounds in six months going by the MFP database, and now I'm wondering if that rapid loss was because I was undercounting my calorie burn. I'm a bit confused, hoping someone can point me to a good resource for information.

scotty579

I also had my first run today with my Polar FT7 (correctly set up) showed 376 kcal whereas my BH Prisma M80 treadmill showed 270. The heart rate on the treadmill (that was reading from my Polar chest strap) also showed 30 bpm under around the 170 mark whereas it was only out by around 5-10 beats around the 120 bpm mark. No weight, age or height details were entered into the treadmill.

Do I go by Polar FT7 or treadmill? Did you set up your FT7 with all your user data correctly?

melaniecheeks

I'd keep in mind that both of them are estimates - do a plus or minus of 10% on each reading and you'll see they're not so different.

Personally, I'd go with the heart monitor.

JethroXP

I did set up the FT7 with all my personal data, and after seeing the results I even double checked, thinking maybe I had done something wrong like entering my weight in Kg instead of pounds, but it was all correct.

The treadmill was actually closer to the HRM value, 945 vs. 895. However the treadmill has no data about me, it doesn't know my gender, age, height, weight, or even heart rate, so I figured there was no way it could be accurate because it was just using default values, that's why I didn't mention it before, I never considered it a source of real information.

Also, just to clarify, the results I get from MFP aren't exactly from the MFP database. MFP didn't have an entry for Treadmill 4MPH and 5% incline, I got the initial value from the Sparkpeople.com database, entered it here, and MFP has been adjusting the value for me as I lost weight. I did that so long ago I had forgotten that it wasn't originally in MFP's database. Comparing again to the Sparkepeople database shows the same difference, so it's not really an issue with MFP.

I am inclined to believe the HRM as well, it was just very surprising to see such a big difference.

chickybuns

Maybe go somewhere inbetween the two. If you were losing weight quickly with MFP's ratings and you wish to continue, stick with those numbers. If you want to maintain, which your ticker looks that way, then go with the HRM. I use the bodybugg and I find that MFP is fairly close to that. However, I found talking to others the HRM often reads much higher than my bodybugg.

Vic303

I think the wide variances are partly accounted for by some programs adding in your base metabolic rate to things. I know Endomondo & sportstracker apps read VERY different from Strava for the same course (run concurrently on the phone). For MFP you also have to account for your perception of effort expended.

Personally I don't use Strava for calories burned, and between Endo, ST and MFP I tend to avreage their results as they are all fairly similar.

gstraub

I have had a slightly different (yet same) issue, I use the FT4 with chest strap and my gym has both treadmills and elliptical machines allow me to enter my age and weight. The machines sync and keep accurate BPM with my watch. Each of the machines show a significantly higher calories burned (100 or more) than my FT4. I usually go by my FT4 since it is constantly monitored by the chest strap. I figure if I go by the lower and get the benefit of the higher I have nothing to lose.

TrainingWithTonya

Do you consume caffeine? Are you on medications such as allergy or asthma medications that will increase your heart rate without exercise? If so, the HRM reading will be chemically elevated and will give an artificially high calorie burn reading.

The ACSM has a formula for figuring VO2 from walking and then you can convert the VO2 to Calories burned, so I'll plug your info into the formula for you to see what that comes up with. I'm going to base the weight for the final conversion to Calories on your ticker and get 172.5 pounds. Let me know if that is incorrect or redo the math yourself with the correct number.

V02 = (0.1 x S) + (1.8 x S x G) + 3.5 (S = speed in meters per minute, so mph will be multiplied by 26.8 to convert to m/min; G = % grade; the 3.5 at the end is the resting VO2)

VO2 = (0.1 x 4 x 26.8) + (1.8 x 4 x 26.8 x 0.05) + 3.5

VO2 = 10.72 + 9.648 + 3.5

VO2 = 23.868 ml/kg/min

METs = 23.868 / 3.5 = 6.819428571 METs

172.5 pounds / 2.2046 = 78.24548671 kilograms

78.24548671 x 6.819428571 x 0.0175 = 9.337816383 Calories per minute

Just realized after all that math that you didn't list the time you were walking on the treadmill. So, multiply the last number there by the number of minutes to get what would be their estimate. Remember, though that you have to subtract out 1 MET for the calories you would have burned just sitting around for that workout time. Which with your weight in kg would be 1.369296017 calories per minute. The HRM and treadmill probably wouldn't have subtracted that, which is why I did the calculation without subtracting it first so you could compare. I'm not sure how the Sparkpeople/MFP number was figured, so I can't say for sure with that one.

JethroXP

I have had a slightly different (yet same) issue, I use the FT4 with chest strap and my gym has both treadmills and elliptical machines allow me to enter my age and weight. The machines sync and keep accurate BPM with my watch. Each of the machines show a significantly higher calories burned (100 or more) than my FT4. I usually go by my FT4 since it is constantly monitored by the chest strap. I figure if I go by the lower and get the benefit of the higher I have nothing to lose.

My wife has the same issue, and she does the same thing you are doing for the same reason, better to be under and benefit unknowingly than be over and wonder why she isn't making progress.

sleepytexan

Sometimes I think people get overly riled up about figuring out their "exact" burns or claiming this way is better than that way. If you've lost 75 lbs, you're doing it right.

Everything is an estimate, especially what we eat when we don't prepare it ourselves. It's ok, just becoming aware of what you're eating in general vs. what you're burning in general is half the battle. (the other half, for most of us, is staying HONEST about what we're eating).

Congrats!

sleepytexan

Do you consume caffeine? Are you on medications such as allergy or asthma medications that will increase your heart rate without exercise? If so, the HRM reading will be chemically elevated and will give an artificially high calorie burn reading.

The ACSM has a formula for figuring VO2 from walking and then you can convert the VO2 to Calories burned, so I'll plug your info into the formula for you to see what that comes up with. I'm going to base the weight for the final conversion to Calories on your ticker and get 172.5 pounds. Let me know if that is incorrect or redo the math yourself with the correct number.

V02 = (0.1 x S) + (1.8 x S x G) + 3.5 (S = speed in meters per minute, so mph will be multiplied by 26.8 to convert to m/min; G = % grade; the 3.5 at the end is the resting VO2)

VO2 = (0.1 x 4 x 26.8) + (1.8 x 4 x 26.8 x 0.05) + 3.5

VO2 = 10.72 + 9.648 + 3.5

VO2 = 23.868 ml/kg/min

METs = 23.868 / 3.5 = 6.819428571 METs

172.5 pounds / 2.2046 = 78.24548671 kilograms

78.24548671 x 6.819428571 x 0.0175 = 9.337816383 Calories per minute

Just realized after all that math that you didn't list the time you were walking on the treadmill. So, multiply the last number there by the number of minutes to get what would be their estimate. Remember, though that you have to subtract out 1 MET for the calories you would have burned just sitting around for that workout time. Which with your weight in kg would be 1.369296017 calories per minute. The HRM and treadmill probably wouldn't have subtracted that, which is why I did the calculation without subtracting it first so you could compare. I'm not sure how the Sparkpeople/MFP number was figured, so I can't say for sure with that one.

Math!!! Aack! my head just exploded

JethroXP

Do you consume caffeine? Are you on medications such as allergy or asthma medications that will increase your heart rate without exercise? If so, the HRM reading will be chemically elevated and will give an artificially high calorie burn reading.

The ACSM has a formula for figuring VO2 from walking and then you can convert the VO2 to Calories burned, so I'll plug your info into the formula for you to see what that comes up with. I'm going to base the weight for the final conversion to Calories on your ticker and get 172.5 pounds. Let me know if that is incorrect or redo the math yourself with the correct number.

V02 = (0.1 x S) + (1.8 x S x G) + 3.5 (S = speed in meters per minute, so mph will be multiplied by 26.8 to convert to m/min; G = % grade; the 3.5 at the end is the resting VO2)

VO2 = (0.1 x 4 x 26.8) + (1.8 x 4 x 26.8 x 0.05) + 3.5

VO2 = 10.72 + 9.648 + 3.5

VO2 = 23.868 ml/kg/min

METs = 23.868 / 3.5 = 6.819428571 METs

172.5 pounds / 2.2046 = 78.24548671 kilograms

78.24548671 x 6.819428571 x 0.0175 = 9.337816383 Calories per minute

Just realized after all that math that you didn't list the time you were walking on the treadmill. So, multiply the last number there by the number of minutes to get what would be their estimate. Remember, though that you have to subtract out 1 MET for the calories you would have burned just sitting around for that workout time. Which with your weight in kg would be 1.369296017 calories per minute. The HRM and treadmill probably wouldn't have subtracted that, which is why I did the calculation without subtracting it first so you could compare. I'm not sure how the Sparkpeople/MFP number was figured, so I can't say for sure with that one.

I do drink two cups of coffee before going to the gym, but I don't take any medications. About how much of an artifical HR increase would that result in?

I do love math! Thanks for the formulas, this is great! I was on the treadmill for 75 minutes, walking at 4 MPH at a 5% incline. Using your numbers I get a very close match to the MFP numbers.

Today at the Gym, I used the niffty new Precor Adaptive Motion Trainer, which is a fancy new Elliptical that allows you to dynamically adjust your stride, and as a result keep your heart rate high. I did 65 minutes, averaged 166 BPM and hit a max of 181 BPM. I entered my age and weight into the machine, and it calculated 924 cals burned. My Polar FT7 HRM said 1098.

I asked a personal trainer at the Gym and her advice was "Short of hooking you up to an array of sensors like an astronaut, all of these devices are just giving you a best guess, so it's probably more important to just use the most consistent device which is likely to be your HRM, since you'll probably wear that regardless of which activity you do, including those where there is no other calorie measure."

Since the FT7 defualts to 220 - Age for HRMax, which for me is 178, and today I was able to actually hit 181, I think I'll try manual overriding the default HRMax to 181 as that will result in lower number for the calories burned since it is based on a percentage of HRMax.

And while I'm not trying to lose weight, just maintain, I plan to go by the calories burned as reported by my HRM monitor, knowing that they may be a bit high, but continue for the time being to run a 500 calorie daily deficit to see if that balances things out.

JethroXP

Sometimes I think people get overly riled up about figuring out their "exact" burns or claiming this way is better than that way. If you've lost 75 lbs, you're doing it right.

Everything is an estimate, especially what we eat when we don't prepare it ourselves. It's ok, just becoming aware of what you're eating in general vs. what you're burning in general is half the battle. (the other half, for most of us, is staying HONEST about what we're eating).

Congrats!

Thank you! Yes, I did lose 75 pounds in six months just going by the MFP estimates. Now that I'm in maintenance mode I've got a HRM and just trying to reconcile the differences. What you said makes perfect sense, its all just a best guess. And you are right, the key thing is remaining honest with yourself. I log everything that touches my lips, even the four leftover goldfish crackers from my kid's snack bowl (which once you start logging it you sort of gain the will power to avoid eating them in the first place).

TrainingWithTonya

Do you consume caffeine? Are you on medications such as allergy or asthma medications that will increase your heart rate without exercise? If so, the HRM reading will be chemically elevated and will give an artificially high calorie burn reading.

The ACSM has a formula for figuring VO2 from walking and then you can convert the VO2 to Calories burned, so I'll plug your info into the formula for you to see what that comes up with. I'm going to base the weight for the final conversion to Calories on your ticker and get 172.5 pounds. Let me know if that is incorrect or redo the math yourself with the correct number.

V02 = (0.1 x S) + (1.8 x S x G) + 3.5 (S = speed in meters per minute, so mph will be multiplied by 26.8 to convert to m/min; G = % grade; the 3.5 at the end is the resting VO2)

VO2 = (0.1 x 4 x 26.8) + (1.8 x 4 x 26.8 x 0.05) + 3.5

VO2 = 10.72 + 9.648 + 3.5

VO2 = 23.868 ml/kg/min

METs = 23.868 / 3.5 = 6.819428571 METs

172.5 pounds / 2.2046 = 78.24548671 kilograms

78.24548671 x 6.819428571 x 0.0175 = 9.337816383 Calories per minute

Just realized after all that math that you didn't list the time you were walking on the treadmill. So, multiply the last number there by the number of minutes to get what would be their estimate. Remember, though that you have to subtract out 1 MET for the calories you would have burned just sitting around for that workout time. Which with your weight in kg would be 1.369296017 calories per minute. The HRM and treadmill probably wouldn't have subtracted that, which is why I did the calculation without subtracting it first so you could compare. I'm not sure how the Sparkpeople/MFP number was figured, so I can't say for sure with that one.

I do drink two cups of coffee before going to the gym, but I don't take any medications. About how much of an artifical HR increase would that result in?

I do love math! Thanks for the formulas, this is great! I was on the treadmill for 75 minutes, walking at 4 MPH at a 5% incline. Using your numbers I get a very close match to the MFP numbers.

Today at the Gym, I used the niffty new Precor Adaptive Motion Trainer, which is a fancy new Elliptical that allows you to dynamically adjust your stride, and as a result keep your heart rate high. I did 65 minutes, averaged 166 BPM and hit a max of 181 BPM. I entered my age and weight into the machine, and it calculated 924 cals burned. My Polar FT7 HRM said 1098.

I asked a personal trainer at the Gym and her advice was "Short of hooking you up to an array of sensors like an astronaut, all of these devices are just giving you a best guess, so it's probably more important to just use the most consistent device which is likely to be your HRM, since you'll probably wear that regardless of which activity you do, including those where there is no other calorie measure."

Since the FT7 defualts to 220 - Age for HRMax, which for me is 178, and today I was able to actually hit 181, I think I'll try manual overriding the default HRMax to 181 as that will result in lower number for the calories burned since it is based on a percentage of HRMax.

And while I'm not trying to lose weight, just maintain, I plan to go by the calories burned as reported by my HRM monitor, knowing that they may be a bit high, but continue for the time being to run a 500 calorie daily deficit to see if that balances things out.

The response to caffeine varies from person to person, so I can't say for sure how much it is elevating your HR. But, you can test it. Take your resting heart rate one morning when you don't have to get up early, just after waking up but not after you've been startled awake. Take it before you even get out of bed. Then have someone bring you your normal coffee and lay in bed to drink it. Wait 15-30 minutes and take your heart rate again while still laying in bed doing nothing. It's not exact, but it is about as close as you can get to a HR response to the caffeine in a home test.

As for HR max, there is a new formula for the age predicted HR max. 206.9 - (0.67 x age) = HR Max I would use it and see if you get a more accurate number for you, because based on the fact that you can comfortably work at 181, I would say it isn't your max.

JethroXP

Thanks! Using that new formula I basically get the same number as the old one, 178 :-)

I wouldn't say I was "comfortable" at 181, I hit that by deliberately trying to see what my max heart rate was. I was only able to sustain that for about 45 seconds and my heart felt like it was pounding out of my chest. I was however able to comfortably sustain about 172-174 which I thought was odd, being so close to 181 yet it felt totally different. Today I could tell that yesterday's workout was pretty hard (some muscle soreness) so I tried to maintain 160-165 today, the hard part was not going above 165, I kept feeling like I was restraining myself from going faster, and indeed when my mind would drift for a minute or so and I'd look down at the HR display I was creeping up in the 167 range forcing me to slow down a bit to get it to drop.

I'll give myself a few days and then try to hit my HRMax again, just to see if it really is 181 or something higher. Also curious to try the coffee in bed test, probably give that a try this weekend.

As for my calorie count, I've gone ahead and changed the default HRMax on my HRM from 178 to 181, which should slightly reduce the number of calories burned that it reports.

TrainingWithTonya

Thanks! Using that new formula I basically get the same number as the old one, 178 :-)

I wouldn't say I was "comfortable" at 181, I hit that by deliberately trying to see what my max heart rate was. I was only able to sustain that for about 45 seconds and my heart felt like it was pounding out of my chest. I was however able to comfortably sustain about 172-174 which I thought was odd, being so close to 181 yet it felt totally different. Today I could tell that yesterday's workout was pretty hard (some muscle soreness) so I tried to maintain 160-165 today, the hard part was not going above 165, I kept feeling like I was restraining myself from going faster, and indeed when my mind would drift for a minute or so and I'd look down at the HR display I was creeping up in the 167 range forcing me to slow down a bit to get it to drop.

I'll give myself a few days and then try to hit my HRMax again, just to see if it really is 181 or something higher. Also curious to try the coffee in bed test, probably give that a try this weekend.

As for my calorie count, I've gone ahead and changed the default HRMax on my HRM from 178 to 181, which should slightly reduce the number of calories burned that it reports.

Well, remember that these formulas are just estimates. They aren't always accurate for people who are highly trained in cardiovascular endurance. There are tests that you can do to get a more accurate max heart rate, but I don't recommend doing them without the supervision of a professional just because off safety. Maybe you could call around to your local universities and see if they have an exercise science or exercise physiology program. If so, they may accept a volunteer to come in while the professor is teaching the students how to do those tests and give you the information gained in exchange for coming in during their class time to do it. Otherwise, one of those students will have to be the practice dummy of sorts and won't get to take notes on how to do the tests. I was the practice dummy in our class and felt like it took me longer to get all the info in my head because I wasn't able to observe it the first time so I had to practice more to get it all. So, sell it to them like that and maybe they'll do it for you at no charge. Otherwise, it can get expensive to have it done.