BodyMedia vs. Polar HRM: my love/hate relationship triangle

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Swimgoddess
Swimgoddess Posts: 711 Member
in Fitness and Exercise
So I've been using my Polar FT7 HRM for about 18 months now. I ALWAYS tried to eat all my exercise calories back. Well lo and behold, last week I sat down and analyzed 82 weeks of data. LOTS of data; everything from the obvious averages (weight for the week, net intake, gross intake, calories burned, minutes worked out, macro breakdowns) to the obscure (sodium intake, where I'm at in my cycle, whether or not I had personal trainer assistance, my calipered body-fat, etc). I am an Excel spreadsheet geek and a bit of a control freak. In the past year, I've gained about 20lbs. Now, my body composition didn't go to total ****. I was 151lbs and 18.5% body-fat (7pt skinfold) in August 2011, at last measurement (Sept. 10th) I was 165lbs and 21.9% body-fat. Started hitting the gym a lot and crept up another 7 or so lbs before I went crazy on the Excel thing and figured out the primary culprit/trend.

-The more I worked out at the gym (HRM measured and logged activities), and the more calories I logged as burned off the HRM, then subsequently "ate back" to make net, the more weight I gained.

So either a.) I needed to lay the heck off the gym to lose weight or b.) my HRM was seriously overestimating my burns and I either need a new device / need to stop eating back all my HRM calories burned. I went with the latter. I picked up my BodyMedia Fit Link last week.

So far, the discrepancies haven't been that bad while wearing both. The BodyMedia registers burns anywhere from 78%-118% of the HRM. That's been doing primarily cardio though as I know to get back to the weight and body composition I want, some lean mass needs to be simutaneously sacrificed at the altar along with the fat mass (*gasp* commence "flaming"). I want to look more Gorgo from 300 than Xena Warrior Princess.

Anyway, here's the comparison between the two on an easy loping C25K Week 3 Day 3 "run" with my 11 year old son:

HRM: 201 calories burned in 30 minutes; 121 bpm average, 157 bpm max
BodyMedia Fit: 243 calories burned in 30 minutes; 6.1 average METs

My bread-and-butter / go-to exercise though is circuit weight training or strength training with supersets. It's what got me from 26% BF to 20% BF in Spring of 2011 in about 6 weeks (pre-HRM usage). Cardio and strength rolled into one, very time efficient slot. Before anyone jumps on me for it, YES, I change things up... a lot. I did that for about 40 minutes today between warmup (5min elliptical) and cooldown (15min treadmill 4.5 incline 3.4mph). Here's the comparison.

HRM: 708 calories burned in 60 minutes; 160 bpm average, 180 bpm max
BodyMedia Fit: 270 calories burned in 60 minutes; 3.5 average METs. :noway:

WHAT... THE... F&#%... I only burned TWENTY-SEVEN calories more in a FULL HOUR at 40 bpm average and 23 bpm max OVER my C25K jog for only 30 minutes??? Something is NOT adding up.

Now I know just going by my HRM is not the answer... that's what caused the pounds to pile up in the first place. But the BodyMedia Fit readings while circuit weight training CAN'T be right - look at my bpms! Compared with the easy C25K workout, something is definitely off. What to do?

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  • Swimgoddess
    Swimgoddess Posts: 711 Member
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    On a positive note: I've consistently dropped about .2lbs A DAY since I started with the BodyMedia. I've been only logging the BodyMedia burns, just noting the bpm info from the HRM, and rejecting the synced BodyMedia "adjustments" in MFP. Working backward from my last known body-fat % on my current weight using Katch-McArdle and my average burn (maintenance) from BMF, my TDEE was 1.35 last week. Not quite Lightly Active, but not quite Sedentary either.

    It's a HUGE step to get on the scale and not be suprised anymore because I know what my surplus/deficit was from the previous day. On my lazy days, BMF has me burning around 1900 calories, on my active days it's upwards of 2400. This is why having a set net in MFP never worked consistently for me, even as I adjusted for weight & body composition changes.
  • flisafakto
    flisafakto Posts: 143 Member
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    Bump! I've been considering the BM Fit Link. I've been using a HRM for exercise calories and setting my net goal at my BMR and that has just not worked well for me the past few months! My BMR is pretty low because I'm very short and have a crazy high body fat %.
  • onefitwahine
    onefitwahine Posts: 2
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    I've been using BM Fit Link for quite some time now and just recently noticed that I only less than 500 for one hour of HIIT bootcamp but other people using different tracking equipment lose 800+ calories. I just bought a Polar FT7 to keep better track of the calories I burn during strenght training since I do a majority of that. Plus I'm tired of wearing an armband all day every day!
  • Swimgoddess
    Swimgoddess Posts: 711 Member
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    I've been using BM Fit Link for quite some time now and just recently noticed that I only less than 500 for one hour of HIIT bootcamp but other people using different tracking equipment lose 800+ calories. I just bought a Polar FT7 to keep better track of the calories I burn during strenght training since I do a majority of that. Plus I'm tired of wearing an armband all day every day!

    Why? Polar FT7s have up to 33% inaccuracies in females (<8% for males) when tested against state-of-the-art New Leaf. Besides, Garmin has a couple models designed to work WITH BodyMedia. That's my next purchase I think :D

    On another note, with the negative adjustments being introduced, I'm going to start accepting the BodyMedia adjustments in MFP and leaving them in place. It's especially critical on my lower activity days.
  • tbear358
    tbear358 Posts: 41 Member
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    I wrote a blog post about this very same thing. I was a diehard Polar fan and even after I got the BMF, I was wearing both devices. Then I was like....why?? After about a week, the discrepancies weren't that bad, less than 100 cals apart on circuit training and just a miniscule difference on cardio. So I ditched the HRM. The BMF has completely changed my life.

    However, I do have a question. I just linked my BMF and MFP today and I am utterly confused. I used to log my food in MFP, then log the total calories into BMF. My goal was a 500-cal deficit, usually eat 1500 and burn 2000.

    Now I have no idea what I'm doing lol. I like the idea of having my food tracked all in one place, but what do I do if I don't want to earn back any calories? I just want to know what I consumed and what I burned. Do I just delete the BodyMedia calorie adjustment?
  • auroranflash
    auroranflash Posts: 3,569 Member
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    It's either an overestimation of calories burnt or underestimation of calorie intake, or a combination of the two. People are notoriously bad at estimating calories, myself included. I always log slightly less than my HRM says I burned and slightly more for any calories I'm estimating.
  • DavPul
    DavPul Posts: 61,406 Member
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    Now I know just going by my HRM is not the answer...

    There were a whole lot of words in the original post but this was the only sentence you needed
    On a positive note: I've consistently dropped about .2lbs A DAY since I started working out and eating in a deficit

    fixed your post
  • mcanavan05
    mcanavan05 Posts: 210 Member
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    Following as I'm thinking of getting BM link band.. see costco is selling it with free 12mo subscription for 120.
  • triggsta
    triggsta Posts: 140
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    Well, I don't eat my calories back period. Do you think that rather than assuming that your BodyMedia Fit is the more accurate of the two that rather you shouldn't be eating all those calories back in the first place? That you were just eating too much to lose weight (or maintain) from the beginning and that just the less food you're eating now is causing you to lose weight?

    I bought a HRM but just the Polar Wearlink+ Bluetooth. Haven't gotten it yet, but hoping not to get the same results I'm hearing on this thread with them.
  • omma_to_3
    omma_to_3 Posts: 3,265 Member
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    HRMs are not meant to be used while strength training. They work for cardio and cardio only. Its not surprising that it was way overestimating your calories on weight training and was pretty comparable to your BM for actual cardio.

    I've been using my HRM for EVERY cardio workout since I got it in January or February of this year. In that time, I have lost about 35 lbs which is exactly what I expected. I eat pretty much all of my exercise calories back, though about half way through the year I started subtracting my BMR calories from my HRM calories burned number. So, if my HRM says I burned 680 calories in an hour of running, I only record about 610 because my BMR burns about 70 calories per hour.
  • HulkDiesel77
    HulkDiesel77 Posts: 219 Member
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    I guess I can chime in here. I have lost a ton of weight and the one thing I know for sure, at least for me that is, when I eat my calories I burn I don't lose weight! I have a friend of mine that has a PhD. and she told me over and over that not eating your workout calories is not that important unless you are trying to build muscle. She also said that it is important to eat my calorioes that I am alotted for the day but dont worry about eating the calories burned. I gotta say she was right on. Oh and FYI she also said you can't put your body into starvation mode until your body fat % is around 10% or less (I thought this to be interesting)
  • UpEarly
    UpEarly Posts: 2,555 Member
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    I noticed HUGE discrepancies between the calorie burn on my HRM (Polar FT4) as compared to my BodyMedia Fit. My BodyMedia numbers seemed really low compared to my Polar numbers. BUT... at the end of the day, if I added my Polar number to my MFP base number I got a much lower TDEE than I did from using my BMF number.

    For example... after an hour of hiking, my Polar might say I burned 515 calories. I add that to my sedentary MFP base of 1670 for an estimated TDEE of 2185.

    But, if I just wear my BodyMedia - the TDEE for this same day with the same activities would come out closer to 2,500 calories, even though it might say I only burned 320 calories in the hour I hiked.

    When I used my Polar+MFP numbers, I lost weight faster than I "should" have. I also continued to lose weight beyond my goal weight (which I didn't really want to do). When I eat closer to my BMF number, I am more easily able to maintain my weight.

    This tells me that my BodyMedia is probably pretty accurate at determining my TDEE... even though it's saying I burn fewer calories during my actual workout.
  • escloflowneCHANGED
    escloflowneCHANGED Posts: 3,038 Member
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    I had the exact opposite results from you! I had my Polar and it was working but figured the BMF would be more accurate because it was on all day.My BMF would tell me I burned 260 calories while my Polar told me 600 calories so I stuck with the BMF... in the 2 months I used it I lost barely anything because I wasn't eating enough because the BMF underestimate burned calories like you wouldn't believe. I switched back to my HRM numbers and started eating at least 300-500 calories more per day and started losing 2lbs a week again.

    I bike ride where my HR was in the 140-160 range for 30 minutes would give about 400 calories burned on my HRM but only 150 calories burned on my BMF, turns out BMF doesn't work well with bike exercises or on a treadmill or elliptical. If I would jog/run/walk outside the HRM and BMF were within 30 calories each time.

    The body media fit is a great tool for people just starting out who don't do a lot of exercise or just walk as a primary source of exercise but once you get somewhat fit and start lifting and doing Hiit or using gym machines it becomes very inaccurate.
  • UpEarly
    UpEarly Posts: 2,555 Member
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    The body media fit is a great tool for people just starting out who don't do a lot of exercise or just walk as a primary source of exercise but once you get somewhat fit and start lifting and doing Hiit or using gym machines it becomes very inaccurate.

    I disagree.

    I consider myself to be extremely fit. I do HIIT, I lift, I can hike 25 miles in a day. I still find it to be very accurate for me.
  • DavPul
    DavPul Posts: 61,406 Member
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    The body media fit is a great tool for people just starting out who don't do a lot of exercise or just walk as a primary source of exercise but once you get somewhat fit and start lifting and doing Hiit or using gym machines it becomes very inaccurate.

    I disagree.

    I consider myself to be extremely fit. I do HIIT, I lift, I can hike 25 miles in a day. I still find it to be very accurate for me.

    based on what? you have had the results independently verified or you just have a hunch that it's "very accurate"
  • jofjltncb6
    jofjltncb6 Posts: 34,415 Member
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    Now I know just going by my HRM is not the answer...

    There were a whole lot of words in the original post but this was the only sentence you needed
    On a positive note: I've consistently dropped about .2lbs A DAY since I started working out and eating in a deficit

    fixed your post

    ^Lies!

    A HRM is the One True Way to precisely measure calories burned for all activities. All. Always. Exactly.
  • heybales
    heybales Posts: 18,842 Member
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    Do you have your HRM at least setup as accurately as it could be?

    And are you only using the calorie burns when it is an accurate tool?

    Steady-state aerobic is it.

    Anaerobic HIIT and lifting will be inflated values.

    Incorrectly setup HRM stats could have the intended use off too.

    The FT7 doesn't allow the biggest stat that could effect burn - VO2max. You are fitter, and while some efficiency of movement now, your lower HR doesn't mean you are burning less, but really about the same.

    Confirm your stats using the spreadsheet linked in this post - the HRM tab.
    You got stats from past burns and avgHR for a sessions probably, compare to the calorie burn using a Polar funded study formula that actually incorporates the VO2max and HRmax and such at the bottom of the tab.

    http://www.myfitnesspal.com/topics/show/750920-spreadsheet-for-bmr-tdee-deficit-macro-calcs-hrm-zones

    Then correct your HRM for at least the HRmax stat, and may have to change your height to get the calculated VO2max which you can't see to work properly.

    And for ultimate test of your HRM to see how far off it has been, or after correcting HRmax it still is.

    http://www.myfitnesspal.com/topics/show/774337-how-to-test-hrm-for-how-accurate-calorie-burn-is
  • tbear358
    tbear358 Posts: 41 Member
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    The body media fit is a great tool for people just starting out who don't do a lot of exercise or just walk as a primary source of exercise but once you get somewhat fit and start lifting and doing Hiit or using gym machines it becomes very inaccurate.

    Strongly disagree. I am very fit and active, burning about 2600 cals a day and starting out with only 10 pounds to lose. I lost all 10 consistently, 1 pound a week as I had set forth. I alternate cardio and strength days and still found it to be pretty accurate. Accurate enough for it to work as I wanted and expected it to. You don't have to think about a lot of things...just eat what you want and burn 500 more calories than you eat.
  • UpEarly
    UpEarly Posts: 2,555 Member
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    based on what? you have had the results independently verified or you just have a hunch that it's "very accurate"

    It's based on empirical evidence -- the the fact that I've been able to maintain my weight based on the number my BodyMedia produces. I have used my BodyMedia consistently over a nine month period. If it wasn't accurate, I would either be gaining or losing weight. When I eat close to the number I see on my BodyMedia, my weight stays stable. Since when is observation and measurement considered to be equitable to a 'hunch'?

    I also never said it was accurate for everybody. My direct quote was I still find it to be very accurate for me.

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