Is it me or my heart rate monitor??

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SillyFitMe
SillyFitMe Posts: 130 Member
in Fitness and Exercise
I bought my HRM a few months ago. The first time I wore it, it clocked me as having burned 400 calories during one, hour long session of P90X Plyometrics. Over the last 3 months, the calories burned for Plyo has been steadily going down. Now, it says I am barely burning 200 calories for the same exercises and level of exertion (which is pretty high).

I can tell my cardio fitness has imporved over the last 3 months because Plyometrics is easier and my heart rate rarely gets above 155 when it used to spike in the 170's. So my question is....do you burn less calories as you become used to a particular work-out routine and you become more fit? Or is my heart rate monitor just a piece of poo??
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Replies

  • Swibbels01
    Swibbels01 Posts: 47 Member
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    your heart rate isnt as fast now that your body is getting used to the cardio you have been giving it. Your heart isnt working as hard to pump blood now that its getting healthier. Keep it up!
  • stephanne82
    stephanne82 Posts: 58 Member
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    I have noticed the first couple of times I do a new workout, my calorie burn and heart rate is a lot higher. As my body gets used to that particular workout, the calorie burn goes down by sometimes 100 - 150 calories per workout and my average heartrate is lower. So I would say it is not your HRM, it is just your body getting more fit. I hope that helps. :happy:
  • SillyFitMe
    SillyFitMe Posts: 130 Member
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    Does heart rate directly correlate with calories burned? I understand the more fit you get, your heart doesn't have to work as hard however, based on a consistent level of exertion (judged by how exhausted, sweaty and tired I am-which hasn't changed) I FEEL like I am burning 400 calories and certainly not less than 200. I am just convinced its impossible to burn 170 calories for an hour of P90X ploymetics.
  • stephanne82
    stephanne82 Posts: 58 Member
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    The HRM calculates your calorie burn based on your heart rate. For example if you are doing strength training you will not have a high calorie burn compared to doing steady cardio, but you will burn more calories hours after your strength training workout. Also, as you lose weight the calorie burn will be lower.
  • SillyFitMe
    SillyFitMe Posts: 130 Member
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    Thanks ladies. I know in the back of mind that everything you are saying is correct. Something just isn't adding up though. I have actually gained 5 lbs since November so I feel like I should be burning more! Ha!
  • BrawlerBella
    BrawlerBella Posts: 400 Member
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    Hi there. What kind of HRM do you own? Maybe a battery replacement is needed or your personal settings may have gotten skewed during a workout?
  • SillyFitMe
    SillyFitMe Posts: 130 Member
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    I iave a Garmin Forerunner 110. I was thinking it could be a battery issue as well. Although it is only a few months old. I checked the settings and they are correct. I even added my 5 extra pounds.
  • jacksonpt
    jacksonpt Posts: 10,413 Member
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    Does heart rate directly correlate with calories burned? I understand the more fit you get, your heart doesn't have to work as hard however, based on a consistent level of exertion (judged by how exhausted, sweaty and tired I am-which hasn't changed) I FEEL like I am burning 400 calories and certainly not less than 200. I am just convinced its impossible to burn 170 calories for an hour of P90X ploymetics.

    It correlates direction because the HRM uses it as part of the calculation for cals burned, but in the real world it doesn't necessarily correlate. Cals burned is based on cellular activity, which basically comes down to oxygen exchange. Since machines, MFP, HRMs, etc don't no O2 exchange, they estimate based on HR.
  • ejwme
    ejwme Posts: 318
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    Congradulations! You've become highly efficient at your chosen form of exercise (quite a trick with that particular kind, I understand). Sadly, this means you'll burn fewer calories doing it. Happily, if those 5 added pounds are muscle (very likely), your base metabolic rate will be higher. If you change things up slightly - do thing out of order, confuse your body (and mind slightly), you'll likely see a higher heart rate and calorie burn. Sounds like it's time for a different HIIT workout.
  • _reno_
    _reno_ Posts: 87 Member
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    Something seems off. 200 Calories for Plyo can't be right. granted i am a 180 lb male, but I burned 900 -1000 calories doing plyo.

    Perhaps the calculations in your heart rate monitor are off.
    For example http://www.shapesense.com/fitness-exercise/calculators/heart-rate-based-calorie-burn-calculator.aspx

    Says 400+ calories for a 100 lb female for 1 hour with an average heart rate of 120 BPM.
  • SillyFitMe
    SillyFitMe Posts: 130 Member
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    I wish the entire 5 lbs were muscle but sadly I think it's made more of Moscato, fudge, and holiday cookies. ;)
    Thanks jacksonpt. Good to know about the O2 exchange. Even without the oxygen metric though, it shows a change and like ejwe said, maybe it's just time to switch things up a bit! Thanks guys!!
  • SillyFitMe
    SillyFitMe Posts: 130 Member
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    Ah hah Reno, I knew it!!! I am 134 lb, 38 year-old, female who really pushes during P90X and I just can't believe I'm only getting 200 calories out of plyo!
  • Madmom04
    Madmom04 Posts: 10
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    Could your heartrate be getting so high that the monitor is not registering it right? I tried to use mine when I did a weightlifting session and I would look at the monitor and it said heartrate error, or something like that. It's definitely a HRM error. You are most definitely burning more that 200c.
  • SillyFitMe
    SillyFitMe Posts: 130 Member
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    @ twindish. No, I don't think so. The few times I saw my heart rate get over 190 I distinctly remember how I felt physically. Nauseous and "woosie." Although I do push myself, I haven't had any of those uber intense workout sessions lately.
  • johnnlinda
    johnnlinda Posts: 69
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    I have gone through a few hrm. My last one was only a few months. I have learned a few things. The battery if low will display incorrect numbers. Also make sure you are wiping down the strap everyday. It gets a sweat buildup and that can give you a incorrect reading. There is no way you are only burning 200 calories. Even if you have obtained a higher fitness level, you know after doing these workouts for so long how many calories you are burning. I know each of my workout burns, so I know when my hrm is messed up. It wont change that much, no matter how fit you are. Try a different workout and see if it is still low.
  • Chainbreaker
    Chainbreaker Posts: 124 Member
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    Are the settings for weight, age, etc all currently up to date? If you have changed the battery in the computer they may have reset to the default.

    Are you still pushing yourself as hard or have you maybe backed off for some reason? There is a big difference in the effect between an effort of 90% and closer to 100% when it comes to plyo.

    Was the P90x your first go at plyometrics? Having taught plyo classes for years I can attest that new participants, or those returning after long lay offs, had signifigantly higher heart rates than those consistently participating. Combined with the fact that standard HRM is designed for steady state cardio then the spikes that come from activities like plyo may affect the immediate accuracy...especially in that introduction stage. Also, as you have adjusted to plyo training your hr likely drops off much more between sets.
  • heybales
    heybales Posts: 18,842 Member
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    Here's the problem.

    Say you did a treadmill first time walking at set fast pace, time, and set weight. Burned 500 calories according to HRM, and avgHR reached 170.

    3 months later same pace, time, and lets say you lost weight but are wearing a weight vest so the same weight. AHR now reached 150 because you are more cardiovascularly fit, meaning you have improved your VO2max, and HRM says you burned 300 calories now.

    You actually burned the same amount of energy (your efficiency walking didn't improve any), but since you are more fit, meaning you can move the same amount of required oxygen to burn fuel with less heart beats, your HRM assumes you didn't actually work as hard. So it gives you less calories burned.

    Any HRM that does not have a VO2max stat that is either tested for or allows entry of is assuming it and calculating it based on weight and height and age, the stats it does have.

    And those 3 things could easily stay the same, and yet you could have started exercising and improved your VO2max pretty well.

    But as far as the HRM is concerned assuming that stat - you are same fitness level, but lower HR means you worked less.

    So ya, inaccuracies will appear.

    In addition for this type of workout, you can easily have gotten more efficient with the work, so you actually aren't burning as much energy.
    Or the first times doing the workout, related to that efficiency, so got much hotter, and HR was elevated merely to help with cooling. So not high because of energy burn, high for that reason, so it was inflated readings to begin with.
    Or you always started the class after 3 cups of coffee and had elevated HR from the caffeine effect.

    Here's the other problem with plyo - that's mainly anaerobic.

    HRM calorie burn formulas are only valid for steady-state aerobic exercise, meaning same HR for 3-5 minutes.

    Lifting, intervals, plyo, P90X, your HR is all over the place. And being more fit allows faster Heart Rate Recovery, so it drops faster. To the HRM, that will register as less calories burned, even if you are getting up to the same high HR.

    So whole bunch of reasons why it will be off even using it for valid aerobic exercise, and even more reasons why it was invalid in the first place for these types of exercises.
  • heybales
    heybales Posts: 18,842 Member
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    I iave a Garmin Forerunner 110. I was thinking it could be a battery issue as well. Although it is only a few months old. I checked the settings and they are correct. I even added my 5 extra pounds.

    So you can upload the data and look at more than avgHR and maxHR, you can look at the readings for the whole session.

    If you've been using it the whole time, go compare the HR charts. Same MHR may be reached, but AHR is down. Or maybe the MHR is higher, but you recover faster to lower HR, so the AHR appears the same. That's actually a better workout.
  • mdcoug
    mdcoug Posts: 397 Member
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    While it certainly makes sense for calories burned to go down as you increase your fitness, 200 cals for 60 min. of plyometrics is definitely too low IMO. Are you sure it's registering the entire time? Make sure your chest strap is tight. That WAS my biggest issue when I had originally started losing weight, my chest strap started to get loose and slide down, messing with the reading. Check your batteries too.
  • heybales
    heybales Posts: 18,842 Member
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    I iave a Garmin Forerunner 110. I was thinking it could be a battery issue as well. Although it is only a few months old. I checked the settings and they are correct. I even added my 5 extra pounds.

    I just confirmed that HRM - very good one actually, better than the Polar's.

    It is a model using Firstbeat algorithms, and they keep track of your exercise amount to help decide what your VO2max is.

    So first workouts were totally based on default values, until it tweaked itself for you.

    It also estimates your breathing amount based on changes in HR between breathing in and out.
    So actually it has much less inflated calorie burns from inflated HR's based on heat or stress or whatever, because if your breathing rate doesn't go up along with HR, it knows there was a difference.

    It is also more accurate for anaerobic stuff, because again based on breathing rates, it knows what high HR's were likely anaerobic, and just doesn't count them in the calorie burn estimate at all.

    So actually, I used Garmin with same Firstbeat, comparing to a Polar FT7 for intervals and anaerobic stuff.
    Intervals was indeed 1/2 to 1/3 what the Polar reported, and was indeed lower than you might think, and that is valid.

    Now, your HR not getting as high means you haven't improved your muscles the same rate as you have improved your aerobic system. Meaning you can't push your HR as high now.

    And eating at a deficit, it will likely stay that way until you can at least eat at maintenance so body can really start building new muscle and making big improvements.

    I'm suggesting your initial burns were inflated because default values were being used, and the estimates have improved because it knows you better.

    2 points to confirm on the settings though, HRmax and the question about Lifetime athlete. Both have an influence on estimating calories burned.

    If you want more info on the Garmin setup, or how to possible tweak it for something more accurate, see the Garmin tab in this spreadsheet. And actually the HRM tab too, for another possible estimate of VO2max.
    Link for spreadsheet near the bottom.

    http://www.myfitnesspal.com/topics/show/813720-spreadsheet-bmr-tdee-deficit-macro-calcs-hrm-zones

    Here's info on what they are doing.

    http://www.myfitnesspal.com/topics/show/577664-garmin-hrm-setup-improved-calorie-estimates

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