Crazy Calorie Burns While Using New HRM

enterdanger

Hi,

I got a garmin VivoFit with a chest strap for Christmas, so I'm totally new to the world of HRMs. I had been using whatever MFP or the machines at the gym calculated for calories burned. I've seen on the forums that usually those numbers are a little inflated so I asked for the HRM.

I've been surprised to see that my burn while using it is actually significantly higher than what MFP is calculating. I did do a little research and found I should find my v02 level, so I did. That didn't seem to change the burn numbers at all.

Yesterday, my average HR was 126 with max at 168, and Garmin logged this as 105 minutes with a 795 burn. Ok, I get that it was using the time from when I put on the strap and drove to the gym and the time until I got home and turned it off and while I was walking from one machine to the next at the gym so that could account for the 35 minute time difference.

I really did 15 minutes arc trainer (machine said 165 burned), 30 minutes circuit with step and 25 minutes on the treadmill at 3 incline and 3 mph (the machine said like 135 burned, I think). That is really 65 minutes and MFP estimated my burn right around 500 calories.

Anyone out there know what I'm doing wrong with the HRM. These burns it is calculating just seem crazy.

My stats are 36, 5'3" 190lbs, Female. I've been exercising 4-5 days a week for the last 6 months or so, mostly cardio.

Thanks.

TimothyFish

There are more things that can increase your heart rate than the amount of oxygen you use, so you can't rely on a HRM to give you an accurate calorie count.

MinnieInMaine

I think the answer is in your post. Don't put the strap on until you get to the gym. Or see if there is a way to stop/pause the reading so it's not calculating your drive time. The time walking between machines won't make that much of a difference so I wouldn't worry about that. Only have it running while you're at the gym.

WhatMeRunning

You'll be able to tell over time how accurate it is if you track all of your daily calories, your weight, and your calculated calorie expenditure from your HRM. Compare your actual weight loss over a couple weeks time against what it should have been based on your total calorie deficit during that time. If your ending weight does not match what it should have been, you can begin determining the percentage difference and you can adjust your HRM reading accordingly.

I did this when I got my HRM last June, because I thought the numbers reported from my runs at first were high. Compared to the calculations from MFP and Runkeeper my HRM seemed to be reporting a high number. Turns out it was pretty much spot on per the weight loss and calorie intake though.

The activity you do can affect accuracy of your HRM too. Most only work when you are in the cardio zones at higher heart rates (140+) and are less accurate at heart rates below this. For me, when running I tend to average around 135, so that might be part of it.

shadow2soul

Why did you put it in HR mode before you were actually working out?
Either:
1) Don't switch it to HR mode until you get to the gym. That way your activity time is just for your workout.
or
2) Don't put the HRM on until you get to the gym.

Mine gave me 356 for a 28 min workout (avg HR 172). However, I went in and adjusted it down to 268. I have never been comfortable logging the full calorie burn from my Plye HRM and I'm still skeptical with the Garmin HRM + VivoFit. Mostly I don't trust it because I know that it is only meant for steady state cardio and will be inaccurate outside of that. One of these days I might be brave enough to actually test the accuracy for a few weeks by not adjusting the calories burned, but for right now I'll stick with what I'm doing.

enterdanger

I live like a block from the gym so I go in my workout gear and don't change there at all. Once I put the strap on, it just starts calculating HR. I've recently discovered that if I hold the button on my vivofit I can turn the HR off. Otherwise, it calculates from the second you put it on.

shadow2soul

@enterdanger
Odd. Mine doesn't auto start. I have to push the button until my VivoFit shows " Heart " on the screen to start a HRM Activity.

enterdanger

Ok. Here is an update. I made sure the HRM was off until I went to the gym. I exercised for 50 minutes. The first 30 minutes I did the arc trainer on one of the hill programs at level 3. Machine estimated me at 360-ish for burn. Then I ran for 20 minutes at 5 mph (yes, I'm slow, but I'm a fat chick who can run over a mile without stopping, yay me!). The treadmill estimated my burn around 170. Total is 530. Garmin only captured the 50 minutes and gave me a 608 burn. My average bpm was 155 and my max was 175. I still don't understand the why I'm getting 2 number for % of max. One was 84% and the other was 95%.

Sorry for the run on paragraph. I love wearable tech, but I'm not convinced I can trust the numbers so only 1 beer tonight instead of the 2 I planned. lol

LTKeegan

Why do you think a machine that doesn't know your height and weight and probably isn't calibrated often would be more accurate than your HRM? What does MFP say for calorie burns. Also, is your HRM set to the right height/weight?

DavidMartinez2

The ARC trainer is pretty close to running, so you had 50 minutes of near continuous aerobic activity. 600 calories is a pretty decent estimate of your calorie burn.

shadow2soul

enterdanger wrote: »

Ok. Here is an update. I made sure the HRM was off until I went to the gym. I exercised for 50 minutes. The first 30 minutes I did the arc trainer on one of the hill programs at level 3. Machine estimated me at 360-ish for burn. Then I ran for 20 minutes at 5 mph (yes, I'm slow, but I'm a fat chick who can run over a mile without stopping, yay me!). The treadmill estimated my burn around 170. Total is 530. Garmin only captured the 50 minutes and gave me a 608 burn. My average bpm was 155 and my max was 175. I still don't understand the why I'm getting 2 number for % of max. One was 84% and the other was 95%.

Sorry for the run on paragraph. I love wearable tech, but I'm not convinced I can trust the numbers so only 1 beer tonight instead of the 2 I planned. lol

That calorie burn doesn't sound to outrageous.

I don't know where your looking at your information, but on the PC it tells me my Avg HR and what zone/% it was in as well as my Max HR and what zone/% it was in.

Cortelli

As others have said, HRMs aren't really calorie counters, but a proxy - so they are frequently off, moreso with some activites and less-so with others.

BUT - they are also generally attempting to count *all* the calories you burn. And if you were just sitting there, semi-comatose, in the afternoon on your couch, you burn some. Moving around a little, you burn more. It's important to understand the distinction between gross calories burned and net additional calories burned through deliberate exercise.

enterdanger

Thank you all for your responses and suggestions. I did make sure my height and weight are correct in Garmin Connect.

Shadow, thanks for explaining the percentages. I guess now I know why I'm always hungry. I thought it was just part of dieting but if my hrm numbers are correct I could eat a bit more. I feel like I just won the lottery.

I'll trust it for a couple weeks and see what my weight loss looks like.