I just got my Vivoactive HR (SW 3.4) and immediately noticed that the Calorie Burned Counter was way off. I had a sedentary weekend with a 1 hr workout and it was showing 5200 - 5500 Calories burned. Digging into this a bit more I noticed that the activity calories logged said I had burned 2000-2600 Calories on each day walking which is not possible for 5200 to 5600 steps (More like 150 Calories). This all brought to light that the way Garmin is calculating calories is probably not correct and is double counting my BMR during the workouts. Since it is counting my steps as a walking workout starting at midnight till I go to sleep essentially my entire day is being double counted and accruing ridiculous calories burned on top of my BMR which is already included in my Total Calories.
The formula should look like:
Total Calories Burned = Basic Metabolic Rate + Net Calories Burned (Activity 1>X) + Net Calories Burned (Steps)
Instead I think it is calculating:
Total Calories Burned = Basic Metabolic Rate + Net Calories Burned (Activity 1>X) + Total Calories Burned (During Step)
Worse, it could be:
Total Calories Burned = Basic Metabolic Rate + Total Calories Burned (Activity 1>X) + Total Calories Burned (During Step)
This could be even worse with steps in a run double counting between the two activities but judging from Today's run I do not think this is the case.
This seems like a major oversight from Garmin and should be addressed quickly, though digging through the forums this appears to have been a problem back in 2014. This is more of a problem at Gyms that use the Total Calories Burned Counter on their machine in order to make their machine look like it burned more calories than others.
I've attached Graphs at the bottom collected from Garmin Connects own website. The Total Calories Graph, Blue = BMR and Red = Activies