I've noticed that recently the calorie calculations have changed significantly for my running activities.
Here is a treadmill run from 4/11 with a duration of 55 minutes, an average HR of 153 and an average pace of 7:15 that shows 831 calories burned.
Here is a treadmill run from 5/6 with a duration of 56 minutes, an average HR of 152 and an average pace of 7:39 that shows 1,011 calories burned
I update my weight in GC regularly, but it hasn't changed by more than a kg in between the two activities.
I did change the calculation of HR zones from %Max to %LT, which resulted in Zone 5 going down by about 5 bpm (i.e., it now looks like I am exerting myself much more for the same effort). I'm not sure if GC tracks historical HR Zones within each activity, but the zones show as the same for each of the cited activities above.
Historically, I'm used to seeing calories burned within the range of the first activity. Is this 20% change related only to the change of my HR zones, or is there something else that is impacting it?
I looked at the Firstbeat site and they mention that calorie burned is derived from HR, respiration rate, and "algorithm". FWIW, I am using an armband oHRM, which does not provide reliable HRV data, but I've been using this same HRM for years.