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Sudden change in active calories

I do the same commute cycling multiple times per week. I use a Garmin 820 with a chest strap HRM. Over the last year or so I have had a consistent 400 active calorie burn (+/- about 20 calories depending on wind/loading/traffic lights etc.). Suddenly (the last month) I am now getting a consistent 220 calories for the same route at the same speed and approx the same heart rate range. This also isn’t a change from ‘total’ to ‘active’ calories.

What could have changed? I haven’t messed with my settings, changed weight/had a birthday etc. The change happened in early/mid Nov.

The previous 400-ish calorie active rate was a little low relative to other devices (but that’s standard Garmin). The low value means that, flat out hill climbing at threshold, I’m now doing about 15 active calories a mile. I weigh 15-stone. Even on a nice bike I should be at 25-30 active calories per mile.

0 nickdodo over 2 years ago

I think the Calories are a bit of a guess by Garmin unless you have a power meter. I suppose it uses an algorithm involving weight and HR. Has is your HR consistent with previous rides? Maybe they changed the algorithm, although that's unlikely.

Sorry I can't help as I use a power meter so don't have the estimated calories.

Nick

0 6152514 over 2 years ago in reply to nickdodo

Heart Rates absolutely consistent for the rides. If it had been a sudden drop in recorded HR then I’d understand it. As it is, the same HR profile (from the same HR monitor) is giving hugely different values. The power level for the rides isn’t different either (nor is Strava’s Relative Effort); just the Garmin active calories.

I’m really not inclined to put a power meter on my bash-around commuter bikes and the setup I had up until the end of October seemed to be close enough.