Garmin HRM setup, improved calorie estimates

heybales

More fun with math Topic!
So in doing some research, happened upon the fact that select Garmin models make use of the services of Firstbeat, which provides some Training Effect for workouts, and calorie burn estimates.

Firstbeat used a study for estimating VO2max which is used in their energy expenditure calculations.

That study came up with two VO2max formulas, one based on BMI, and one on BodyFat% - guess which one was more accurate?
Guess which one the HRM uses?
Even Polar's VO2max self test uses this theory along with resting HR test. Not sure if they use the actual formula though, but info on that in another Topic post coming.

So, if you know your bodyfat%, there is no place to enter that into the HRM, besides which it only uses the BMI formula. But you can fudge your height in the HRM so that the BMI formula results in the more correct VO2max figure. Of course if you have a tested VO2max figure, might as well correct for that use too, since no place to manually enter it, in which place skip the BF% estimate and just use your tested figure below.

Links at bottom for this info.

What I found interesting, is the study formula was even more accurate than submaximal tests for VO2max.
That being said, a real lab or self test to max heart rate which also has a VO2max estimate from it is better. My own VO2max tested was 54.0, this formula gave 45. For 1hr workout at good HR, that is only a difference of 50 calories. Not huge, but if the only reason you have the HRM is calorie burn estimate, well, there ya go.
http://www.myfitnesspal.com/topics/show/466973-i-want-to-test-for-my-max-heart-rate-vo2-max

So MaxHR would be a great correction too, and even if not tested for, another formula may be more correct. If in use you have EVER seen a peak HR higher than the max HR figure, yours is probably 5 higer than that. Some of these estimates of MHR are nice because they take into account your resting HR or athletic time, calculator at bottom for all results. http://www.brianmac.co.uk/maxhr.htm

Those 2 values, max HR and VO2max, have a great bearing on calorie estimates, and sadly women are all over the place for that. Men not so bad a potential.
http://www.myfitnesspal.com/topics/show/459580-polar-hrm-calorie-burn-estimate-accuracy-study

Which models use this VO2max estimate? Garmin Forerunner 110 / 210 / 310XT / 405CX / 410 / 610 / 910XT, Edge 500 / 800

How do I correct this, what info do I need?
gender, age, weight, height, BMI, bodyfat%, physical activity rating below - calculator, re-reading skills.

BMI estimates are everywhere. MFP - Tools - BMI Calc is easiest since they have your current stats.

Bodyfat% avg can be obtained here. Measure in the morning after hydration levels are normal, read description of locations correctly. 5% range is acceptable for use in this formula. Keep this figure, useful in so many things, like BMR Calc.
http://www.gymgoal.com/dtool_fat.html

Now you need your Physical Activity Rating (PAR). PAR is whole number from 0 to 7.
Select the number that best describes your overall level of physical activity for the previous 6 MONTHS (be honest, but don't short change yourself):

Does not participate regularly in programmed recreation, sport, or physical activity.
0 - Avoids walking or exercise (for example, always uses elevators, drives whenever possible instead of walking).
1 - Walks for pleasure, routinely uses stairs, occasionally exercises sufficiently to cause heavy breathing or perspiration.
Participates regularly in recreation or work requiring modest physical activity (such as golf, horseback riding, calisthenics, gymnastics, table tennis, bowling, weight lifting, or yard work).
2 - 10–60 minutes per week
3 - Over 1 hour per week
Participates regularly in heavy physical exercise (such as running or jogging, swimming, cycling, rowing, skipping rope, running in place) or engages in vigorous aerobic type activity (such as tennis, basketball, or handball).
4 - Runs less than 1 mile per week or spends less than 30 minutes per week in comparable physical activity.
5 - Runs 1–5 miles per week or spends 30–60 minutes per week in comparable physical activity.
6 - Runs 5–10 miles per week or spends 1–3 hours per week in comparable physical activity.
7 - Runs more than 10 miles per week or spends more than 3 hours per week in comparable physical activity.

So, you first want to compare the results, you might not actually be that far off between the BMI and BF% formulas. BF% is whole number, ie 40% is NOT 0.40, but 40 in formula. Most calculators handle multiply before add/minus correctly, so just go straight across.
BMI VO2max = 56.363 + (1.921 * PAR) – (0.381 * Age) – (0.754 * BMI) + (10.987 * Gender 0 female or 1 male)

BF% VO2max = 50.513 + (1.589 * PAR) – (0.289 * Age) – (0.522 * BF%) + (5.863 * Gender 0 female or 1 male)

Is the difference enough to you to correct? Now that you have two VO2max figures, test out a workout with both and see if the difference matters to you. 50 calories/hr may not matter to you, or you may have a bigger difference.
http://www.braydenwm.com/calburn.htm

Oh, how does your VO2max figure compare to others and what is it?
http://www.brianmac.co.uk/vo2max.htm

So, how to correct the height in the BMI stat so the BMI formula results in the same VO2max as the BF% one?

adjusted BMI = (56.363 - BF% VO2max + (1.921 * PAR) - (0.381 * Age) + (10.987 * Gender 0 female or 1 male)) / 0.754

adjusted height inches = squareroot (weight lbs / adjusted BMI * 703)
adjusted height meters = sqr (weight kg / adjusted BMI)

So that adjusted height is what you would put into the Garmin stats, so that it calculates a more accurate VO2max for use in calorie estimates. Use your manual for that location - usually Settings - User Profile.
The accuracy of the above formula is poor if your VO2max is 55 or greater, so great reason to actually test and correct if estimate is near that and you are very fit.

Since I have a tested VO2max of 54.0 I cannot enter into the HRM, I too can adjust the height so the BMI formula will result in my figure. 95 inches, wow am I tall. Just use your tested figure in place of the BF% VO2max in formula above. And I guess my 54 shows why the formula resulted in 45-46, accuracy starts going down as you approach 55. So if you ended up at 45, might be worth doing real test.

Firstbeat whitepaper on energy expenditure -
http://www.firstbeat.fi/consumers/heart-rate-monitors/firstbeat-intelligence-in-heart-rate-monitors#energyexpenditure

Study. "Appropriate for 96% of the population". "Accuracy ... with all but subjects with VO2peak >= 55 ml/kg/min".
http://www.ncbi.nlm.nih.gov/pubmed/2287267

Formula and PAR table spelled out -
http://www.topendsports.com/testing/tests/non-exercise.htm

Masterdo

Bump, will read after my exam today...

ATT949

Thanks for the posting. I'll dig into it over the weekend.

VO2 of 54…I'd love to have that! I just calced mine and my values are 41 and 43.

I'm getting mine tested on a treadmill next week — it will be interesting to see how that number compares the the formulas that you've cited.

Excellent info.


[Edit]
Just checked my copy of Daniels‘ Running Formula and a VO2 of 42 gives me an HM time of 1:46:27 and a marathon time of 3:40.

I wasn't able to run the Surf City Marathon this year because of my calf injury but I stopped in at the Expo to pick up my "$100 shirt". They had a list up there of timing brackets - what pace groups get what numbers.

I saw the 1:46 group and said to Debbie "That's the group I'm going to be in next year."

If I tape out at 42 +/- on the machine next week, I might have a shot at that!

FishingFan123

Bump (only so I can save this topic in my settings). Thx for the info!

heybales

Bump (only so I can save this topic in my settings). Thx for the info!

And there is a more recent study that obtained even more accuracy.

Find the study link, and easier to use calculator in the spreadsheet linked to in this topic.

http://www.myfitnesspal.com/topics/show/677905-spreadsheet-for-bmr-tdee-deficit-calc-macro-calc-hrm

DPernet

bump