HR Monitor vs. Trackers

27 Nov

For years, I have been working out without a legitimate heart rate monitor, besides my GPS watch I had for running that did track my calories (but was not based accurately on my weight or age). Instead, I relied on website trackers like Sparkpeople and Myfitnesspal to track calories burned.

For the most part, I figured they overestimated it by a bit. No better way to convince you to continue working out and using their site by posting bloated calorie burns. And, for the most part, it worked on me. I set my target at an unreal calorie burn number and would be thrilled when I hit that number week after week while only committing about 45 minutes per day.

An old friend of mine from high school is a personal trainer, and she frequently posts her daily calorie burns from her favorite workouts. She is a former fitness competitor, so her burn would be outstanding. But it mirrored mine. That was the first sign that something may be up, and that the number I was tracking was more than just inflated.

I started poking around online on how sites like these determined calorie burns. All the websites and trackers I would use had vast databases of workouts. Check out sparkpeople’s! Finally, I found a site that gives a vague method from

We begin with the amount of calories you burn currently (for calculations assume 12 calories burned per pound for women and 15 calories burned per pound for men). Add the amount of calories burned by your exercise (with walking, you burn .30 x your weight by walking 3 to 4 miles per hour).

But, what if I dont give my all that day (like today when I was feeling a bit off?). Or, what if my instructor was lazy and gave us a pretty easy workout compared to her normal thigh burner? These numbers cannot be same for me (who is admittedly overweight) compared to the girl who spends her life working in fitness.

So, on a whim and fueled by Black Friday, I bought myself a Polar FT4. Polar is the leader in heart rate monitors for fitness. (I will review the watch itself later after I get a good solid week with it.) That being said, I figured that a million users and a ton of friends using it couldn’t be wrong for this experiment.

Here’s my hypothesis: Trackers like Sparkpeople and Dailyfitnesspal, despite being set for my weight, height, gender, and age, would overestimate my calorie burn for a 1/2 hour kettlebell class by over 100 calories. It would be about 20-30 calories off on my 20 minute hill climb treadmill walk (moderate pace, but first thing in the morning).

Experiment: I brought the watch today for my 6am workout. As normal, I started out with some stretching and walking around the gym. Obviously, my heart was pretty much in a good base rate when I started since I literally rolled out of bed.

I start my Tuesdays with a light walk on the treadmill since there is no 6am class. I pick a typical 20 minute, scripted hill work with the max speed at 3.5 and the max hill at 7.0. No cool down. I feel pretty decent, no sweat just yet. Here are the results:

  • Treadmill reading: 158 calories
  • Sparkpeople reading: 192 calories
  • Myfitnesspal reading: 175 calories
  • WW activity points: 1
  • POLAR READING: 135 calories

So, the treadmill was the closest estimator. To be fair to it, it did not have a heart rate hand holder, so if you use that, it may be even closer. My beloved Sparkpeople, where I do most of my fitness tracking was WAY off by 60 calories. To give you a better idea, to actually get to 192 calories at the rate I was at, I would have to work out around 8 more minutes, or near half of my planned 20 minute workout.

After hopping off (and cleaning down) the treadmill, I head straight to my kettlebell class. This is one of my favorite classes because I’ve seen significant improvement in my form and strength. The teacher is also great and gives us a variety of sets. She starts the class with a version of kettlebell swings, moves to lunges and squats, gets a couple of core, and then 2 or 3 sets of arms and shoulders. No rest between the :45 sets, and we repeat each round 3 times with a 2 minute rest between the rounds. We then do about 3 challenging core sets.

Today, I used a medium set (17lbs), a heavy set (22lbs), and one small one for the lunges on the last round (12lbs). This is about typical, if not a bit heavier for me.

Here is the readout for my 30 minute class:

  • Sparkpeople: 600 calories
  • Myfitnesspal apparently doesn’t list kettlebell in their cardio or strength, so this is out. But, I am guessing that they would estimate it around 20 cals/minute = around 600.
  • WW activity points: 4
  • POLAR READING: 249 calories. 

In other words, according to my HR monitor, I didn’t even burn HALF of the calories I believed I had before today. Pretty disappointing, to be honest. I felt defeated walking out of the gym.

Am I going to give up on the class because of this reading? NO! This class, even if it is less effective in burning calories than I had originally believed, still works me up in to a good sweat, and I leave feeling stronger and more fit. Believe me, that’s half the battle.

Moral of the story: You can track and track all you want on WW, myfitnesspal, sparkpeople, etc., but there are so many other factors that determine your burn besides the pre-calculated nonsense or whatever comes out from holding on to a heart rate grip.

Just like the annoying State Farm, dont trust what you read on the internet!

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