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Getting your personalized calorie burn formula

Calculating for steady-state and non-steady-state aerobic cardio.

As always, explanation for understanding, then method. So looks long, but it's easy 30 min test.

First, notice this is not for anaerobic, so not for lifting or most intervals that go up in to anaerobic range, though it could help the latter be a tad more accurate.

Why distinction between steady-state (same HR for 2-4 min) and non-steady-state aerobic (HR bouncing all over the place)?
Because HRM's use a formula that is only for steady-state aerobic.
When you increase a workload (say pace) your HR initially goes up to say X. Then it drifts back down to say X-8 in 2-4 min. So X-8 is the HR really needed for that workload, X was actually inflated.
And what if you stop the workout and stand, how long before the HR drops to X-60 that is actually needed for just standing? That's obvious it was therefore inflated the whole time it was dropping.
What if your workout was nothing but changing workloads? The HR would be elevated the entire time above what it really needed to be. If elevated HR always seen by HRM, elevated calorie burn is result.

Second, why a personal formula, doesn't the HRM know my required stats to calculate accurate calorie burn?

Uh, no. Even if you have a HRM that has a self-test and stat for VO2max, and trying to estimate HRmax better, there are still several assumptions.
Your BMI (height and weight) is compared to range of fit to unfit (gender and age), to calculate VO2max (in cheaper Polar's), and combined with resting HR to calculate VO2max (in better Polar's).
Even if you enter in lab tested stats for those, an assumption is made between where your VO2max occurs compared to HRmax, and where you go anaerobic compared to your HRmax.

Third, can this be accurate?

Well, the formula for walking and running flat between certain speed ranges has been found to be within 4% of lab measured calorie burn. That is very accurate. Some slight incline is still more accurate that HRM.

The amount of calorie burn per minute has been found to be a straight line function between what is called HR-Flex point (where exercise level and need for more Oxygen for fuel burning starts, about 90 bpm) and your anaerobic line (where exercise is producing enough lactic acid muscles will soon lose ability to stay at that level and carb is total fuel source because not enough oxygen to keep burning fat). About 5 other studies in this study referenced for that point.

Traditionally you'd get a VO2max test and all the data, see what you burned at all the HR's as it went up, and create your own best fit trend line from 90 to anaerobic, and that would be your calorie burn formula (remember y=mx+b for defining a line on a graph).

This method uses that walking and jogging formula to skip the whole need for that test for purpose of calorie burn.

Because of the way the test is done, you can actually see what the inflated HR is right after the pace/incline is changed, but then keep doing the same workload to see what the HR lowers to for steady-state calculation.
If you do workouts that are always changing the workload and HR is all over the place, you use that formula meant for inflated HR.
If you do steady state cardio with HR pretty much the same with perhaps extended times up and down, you use that formula.

Here's how to do the test.
You'll need a treadmill that reports speed and % incline or grade, NOT degrees. (unless you convert first)
You'll need HRM that reports instant HR. For use of your personal formula later, you'll need time of workout and avgHR during the workout session.
You'll need Google Sheets or Excel to use your stats and get your results.
A notepad or something to record your HR on, and for notes on what speed and incline to use.
An idea of how high your HR can go for a good 5 min, higher the better, just want it in the aerobic zone, not dying in anaerobic, should feel like you could keep going for much longer than 5 min from breathing (though joints may not like it).

It would be best to pretest during some warmups for regular exercise to know about what speeds and inclines get you near goal HR. You want 4 data points of HR with decent separation, 100 bpm as desired minimum.
100 - 105 - 110 - 115 is NOT good.
100 - 115 - 130 - 145 is good. Or couple near the top if what you figure is aerobic range, like 150 - 165. But keep 100.
Record what speed and incline got you there. This can be done over several workouts, just test it out and note it.
While you could increase incline while walking steeper and steeper, the less incline the more accurate. So if 4 mph 2% incline is first level, then you'll need to start jogging at 0% whatever speed for next level.

You do not need to hit an exact HR, just close to a spread out range. Better to know what speed and incline you need to use to get close to it.

Get the spreadsheet to see what I'm talking about. Notice the walk/run, speed, and grade is used on next link. My sample data from last VO2max test should be deleted in yellow cells.

The cal/min will be obtained from this calculator. Try to keep walking speeds between 2-4 mph, running 4-6.3 mph, less incline the better for accuracy.

Real test. Just use the treadmill timer for this.
1 - Do a 10 min warmup walk, getting speed such the HR is steady at 90 by the end.
2 - Increase speed/incline to Level 1 that will hopefully get you near 100.
3 - Within 15-30 sec of change note the HR right then, unless it keeps going up.
4 - After 4:30 min note the HR then, it should be lowest then.
5 - At 5 min change speed/incline to next level.
6 - You get the idea, repeat steps 3-5 for all 4 levels, and 8 different HR's. Keep them separate.

Confirm you used the walk or run and speed and incline and correct the spreadsheet entry, enter the HR stat in each section.
Take the stats for that level to the calculator above, get your clothed weight (unless you did it naked with no shoes) with Gross goal option, and use 1000 min as time. Now the results for calorie burn you can move that decimal point over 3 places for better accuracy. So 3852 becomes 3.852 cal/min to put in spreadsheet in both sections.
The treadmill specs of test are merely there for future reference.
As weight lowers, what should happen to pace to keep the same HR, even without increasing fitness? Correct, faster.
What should happen to fitness even if weight and HR doesn't change? Correct, faster.
So you'll want to redo test if cardio fitness is still improving or weight is dropping, as it will change calorie burn for given HR.

So there are fields to actually put in your avgHR and time of workout, and you'll get back gross calorie burn. Use that if replacing Fitbit stats for better accuracy. Use net if doing MFP method of eating back, which takes out your maintenance burn already accounted for. Don't use one for the other, wrong way.

And displayed is your personal calorie burn formula that you can just use with a calculator. Notice if the final number is plus a negative which could happen, in other words subtract.

Graph is there for visual on how straight the line is. Variance may look big, but easily with 5% still.

And the correct formula can be used for any aerobic cardio that fits. Doesn't have to be running and walking.
This does not remove from possibility other reasons for elevated HR that would invalidate the formula to some degree of accuracy, like that double-espresso, or medication, or dehydrated, or 100 F, ect.
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