How are active calories calculated? Different results on same distance

In the last week I’ve done two 8 k walks, almost the same duration and speed, on the first I spent more than twice as many calories as on the second.
I also did a 4K walk this week that spent more calories than my second 8k walk.

this seems very strange.

The only difference in my metrics during this time is the lost 0,5 kg

0 mehmetozturk over 4 years ago

Heartrate?

0 subra over 4 years ago

As mehmetozturk already stated, HR is used for the calculation of the calories.

If you'd like to have a deeper look into the calculation

assets.firstbeat.com/.../white_paper_energy_expenditure_estimation.pdf

The SW for analyzing the activities is mostly developed by firstbeat.

0 Niklas over 4 years ago in reply to mehmetozturk

Was a difference of the average bpm of 10

0 Václav Koucký over 4 years ago

Compare the time spent in heart rate zones for both activities. Most likely it will show that during the activity with less calories burnt you will find more time spent on the anaerobic zone. Setting the zones correctly will give you a more relevant outcome.

Also note that time effects the energy burned somewhat: on the calories burnt during the activity there are both the BMR as well as "active" calories counted together. The reason is that the BMR calories are being burned regardless of the activity, so they are a part of the total energy burned.

0 Niklas over 4 years ago in reply to Václav Koucký

Thanks for the reply

what do you mean by ”Setting the zones correctly”?

feel like i’ve missed something here

0 Václav Koucký over 4 years ago in reply to Niklas

Hi Niklas, universally Garmin sets the heart rate zones based on the "universal" formula which says that the maximum heart rate is "220 -(your age)". The resulting figure is your max heart rate. But since we all are in a different condition you see that this can be very innacurate. The best way is to test the max heart rate. There are labs which would do it in a professional way but there is an amateur test everyone can conduct by himself.

1. Find a trail (flat or slightly uphill) some 400 - 600 m long, if you have the HRM band, put it on (the values measured by the watch can be innacurate, so in case you don't have the HRM you better count your heart rate the old "manual way)

2. Warm up by an easy run of some 800 - 1600 m

3. Run the 400 - 600 m trail as fast as you can and right after check your heart rate, calm down by an easy run of about 2 minutes

4. Run the 400 - 600 m trail as fast as you can and right after check your heart rate, calm down by an easy run of about 2 minutes

5. Run the 400 - 600 m trail as fast as you can and right after check your heart rate. This value should be your max heart rate.

Garmin works with 5 heart rate zones. In the basic distribution based on the max heart rate value the steps are (in %) 50-60, 60-70, 70-80, 80-90 and 90-100. These values can be adjusted in your Garmin Connect application when you tap the image of your watch on the top of the homescreen, then tap the User settings and there in the bottom the Configure heart rate zones (maybe it's slightly different wording as I have the app in Czech).

So provided you are more (or less...) fit than an average person of your age your heart rate zones might differ from the universal ones preset by Garmin yet you can adjust them to your fitness level based on the above described (or a sports lab conducted) test.