Polar FT4 - Calorie/Zone Accuracy (Please Help!)

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parallelle
parallelle Posts: 2
in Fitness and Exercise
I have a question about my FT4 product. I am a 37 year old female weighing 250lbs. My resting HR appears to range from 80-90. I find that my calories burned on the watch are significantly lower than when I manually enter stats on the polar personal trainer site.

For example, my FT4 showed that I burned 197 calories in yesterday's workout. The duration of my workout was 00:30:53. I was "In Zone" 00:19:02. My zone is manually set to 135-175. And my maximum HR is set about 5bpm higher at 200. I manually changed my bpm and zone range percentage because I could never stay "in zone." I was always too high! For this workout my average HR was 144bpm and my maximum was 183bpm. (I'm now beginning to understand that because my goal is to burn fat, I shouldn't have done this!)

When I went to manually enter my stats in Polar Personal Trainer site (because I cannot download the program, I'm using an iPad), I entered my duration (00:30:53), my HR average (144), and my HR max (183). The site then fills in my calories burned in the box below, which was 526. If my watch is reading that I burned 197 calories, why does the site give such a huge burned calories reading? Which is more accurate?

Also, I am looking for my correct fat burning zone as I am a beginner to working out. As mentioned above, the FT4 sets a zone that is hard to maintain because when I'm working hard with cardio activities my HR is rather high (average often over 165). Any advice on zone setting? What is the most effective/accurate way to find my zone? Do I burn more calories "in zone"?

I am following a "clean eating" plan to the T. I'm trying to burn at minimum 400 calories a day, so accuracy is important to me. I greatly appreciate any advice!!!

Replies

  • cantfail
    cantfail Posts: 169 Member
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    Over 500 calories for a 30 minute workout? That doesn't seem right at all. I am not familiar with the Polar Personal Trainer site and I guess I'm not understanding why you are entering average and max heart rate there. Your watch that is actually measuring your heart rate is going to be more accurate than a number based on a calculations.

    IMO the total calories expended is way more important than how much time you spend in any particular zone. Yes, you may burn a higher percentage of fat at a lower zone, but your total calorie output is lower than if you work little harder. It's pretty much a wash if you ask me.
  • SecretAgent27
    SecretAgent27 Posts: 57 Member
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    It seems to me that the settings on either the watch or the site in regards to sex, height, or weight (or activity for the site) have to be off in order to get that kind of disparity.

    I tried the website a couple of times but never used it. I went back to see what it said for today's workout. My watch said I burned 733 calories and the site said 767. Not too much of a disparity. Actually, the site initially said 850 but then I remembered it still had my old weight so I changed it and got the more accurate result. You have to make sure to update both when you lose weight. Also make sure both have the same information if you want to see similar estimations of calories burned.

    I don't know if changing the "zone" affecting anything but changing the Max HR will. It's hard to know exactly what your Max HR is without having a professional test you. But a general rule of thumb is to take your age and subtract if from 220. I'm 33 so mine would be 187. The most I've been able to get mine up to (during a 5K race) is 180. I'm thinking 200 might be a bit high.

    If you have your Max HR set higher than your actual max HR, then the monitor will interpret you as working at a lower intensity since you're further away from your max HR. For example, if you average 140 and your max HR is set to 180 then it thinks that you're working at 78% your max HR, whereas if you have your max HR set to 200 then it thinks that you're working at 70% your max HR. So setting your max HR higher will make the monitor calculate fewer calories burned.

    I just tested my workout today with my overall Max HR (not just for today) set at 200 and it changed that 767 calories burned to 682.

    Regardless, cantfail is right. The website makes some assumptions based on your average and max HR for a given workout. The HR monitor tracks your HR and calculates calories burned on a moment to moment basis. So there's going to be some disparity, but the more accurate result is going to come from the monitor.

    Regarding the "fat burning zone" vs other zones, I don't worry about it. You use both fat and glycogen(carbs) for energy when you run. Which one doesn't really matter with regards to weight loss. When you go and eat later, you're going to replenish whatever energy stores you depleted during your workout (and you'll always have fat stores). And actually, whatever kind of energy you burn during the workout, you end up burning more of the other kind after the workout. So if you primarily burn fat during the workout, you're going to use more glycogen for energy afterwards and vice versa. It all evens out. So there's really no point in actively trying to burn one over the other.

    You're going to burn more calories at a higher HR. The problem with a higher HR is that you can't go as long before you have to stop. And it's harder to recover from, making tomorrow's workout harder. The longer you can go, the more calories you'll be able to burn in a workout. So a benefit of a lower HR is that while you may be burning fewer calories on a per minute basis, you can go longer and burn more calories overall. I can run for 25 minutes at a pretty high intensity, with an average HR of 175, and burn about 475 calories. Or I can run slower for 90 minutes, keeping my HR in the 140s to 150s, and burn 1,400-1,600 calories.
  • parallelle
    parallelle Posts: 2
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    Sorry for the delay. Thank you both so much for your replies! That helped so much! I am just going to focus on what my device puts out. The highest my HR has gone is 194 (during my first mile jog!), which occurred a couple of days ago. Would you suggest that I put that as my max HR and let the watch decide the zones (as opposed to manually entering them?).

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