Timex HRM - Could it be wrong?

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dianaom
dianaom Posts: 5 Member
in Fitness and Exercise
Hey guys, it's my first post here, but i usually read other topics and have learned a lot from other people's experiences.
The thing is - I have a timex heart rate monitor, bought it 5 years ago and I use it constantly, when I go to the gym or for runs in the park. Normally when I exercise I burn about 700~800 kcal (1 hour high level exercise), and I consider it pretty exact, given the intensity of the workout. The problem was today - I took a 60' spinning class and kept checking my heart rate throughout the class (was trying to stay within the fat burning zone although I only achieved it for 20'), but in the end, the device indicated I had lost 1450 kcal during the workout! That simply cannot be right. It was intense, but not exausting, I felt fine the whole time. I changed the belt's battery not even a month ago, and the belt strap was well adjusted to my body. What do I do? Could this be a real number? Do I have to throw away my hrm and buy a new one? I'm lost here. Thanks for any help

Replies

  • BrianSharpe
    BrianSharpe Posts: 9,248 Member
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    I'd say the reading was wildly high, especially given that fact you were trying to stay in a low intensity zone (fat burning zone is around 50% maxHR and typically results in quite a low caloric expenditure when compared to higher intensities)
  • jlahorn
    jlahorn Posts: 377 Member
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    1. Yeah, definitely something wrong there. Try changing the battery - readings can get wonky when the battery starts to die. If that doesn't fix it, try contacting Timex.

    2. You probably don't actually want to be targeting the misleadingly-named "fat burning zone". It's called that because you burn a higher percentage of calories from fat when your heart rate is in that range, but you burn more TOTAL calories (including calories from fat) if you work harder.
  • hermann341
    hermann341 Posts: 443 Member
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    I've got the Timex Global Trainer and normally do 800 to 900 cal per hour in zone 3, so 1450 does seem bit high. I assume the spinning class didn't keep you at a steady heart rate, which my account for it.
  • hill8570
    hill8570 Posts: 1,466 Member
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    Since you've used this in the past, I'll assume you had the chest strap wet enough for good contact, and you'd think the battery in the strap was still good (you could check this by going for a bit of a run and see if it matches with prior experience).

    Since this was a class environment, my vote would be for interference -- either from other nearby HRMs or some other nearby radio frequency generator (such as fluorescent lights).
  • erickirb
    erickirb Posts: 12,293 Member
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    Timex HRM's are notorious for showing higher calorie burns than other branded HRMs. I would go with either Polar or Garmin, and pick one where you can change the max HR and V02Max inputs manually. Otherwise the HRM will not take into account increased fitness as you go along.
  • tycho_mx
    tycho_mx Posts: 426 Member
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    one more thing - calorie burn and HR are "mode dependant", because of the amount of muscles used, etc. Meaning that 150 HR running, cycling and skiing are not equivalent in calorie burn. They might be similar at the lower end, but as you go higher they become very different. Especially for cycling, since it's not load-bearing and only your legs move.

    I am a pretty fit, serious cyclist. I can ride 25 mi (40 km) in an hour - in fact, I did it yesterday. It burned exactly 1089 kJ of energy at 303 W for almost 59 minutes, which taking into account efficiency is about 1:1 with calories, so 1090. This was an absolute maximal effort - and your weight would not depend on it directly (as it would with running). I don't think anyone that is not a professional cyclist winning elite races can burn 1500 calories per hour riding a bike casually at zone 2 or 3. Seriously, that's massive power - 420 W. That's domestic elite levels.
  • Kevalicious99
    Kevalicious99 Posts: 1,131 Member
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    People here have this fixation with HRM's. Sorry they do one this .. measure your heart rate. The calorie calculation is just an estimate .. and can be very very very wrong.

    But .. time to move on. As you saw .. they are just someone's math calculation; Nothing more. They really cannot measure anything but your actual heart rate.

    For me the point of no return was when my Polar HRM said I burned 2000 cal from walking 3 hours.
  • erickirb
    erickirb Posts: 12,293 Member
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    People here have this fixation with HRM's. Sorry they do one this .. measure your heart rate. The calorie calculation is just an estimate .. and can be very very very wrong.

    But .. time to move on. As you saw .. they are just someone's math calculation; Nothing more. They really cannot measure anything but your actual heart rate.

    For me the point of no return was when my Polar HRM said I burned 2000 cal from walking 3 hours.

    Another thing to remember is that HRMs estimate total calories burned, which also includes what you would have burned had you not worked out (maintenance cals). which probably range from 1-1.75 cals/min.
  • dianaom
    dianaom Posts: 5 Member
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    Thank you all for sharing your opinions! I used it again today and the number appeared more normal... maybe it was really just interference. I'll keep an eye on this problem for a few weeks, and if the problem appears again than I guess i'm done with Timex. Thanks again everyone!
  • jimmabass
    jimmabass Posts: 6 Member
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    I have a Timex HRM - I find the heart rate to be accurate, but the calories burned to be horribly inaccurate. I've done some comparison with exercise machines, and other apps... I end up taking the reading, and dividing it by 2, and entering that.
  • dianaom
    dianaom Posts: 5 Member
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    I have a Timex HRM - I find the heart rate to be accurate, but the calories burned to be horribly inaccurate. I've done some comparison with exercise machines, and other apps... I end up taking the reading, and dividing it by 2, and entering that.

    I agree! that's what I do too.

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