Sudden drop calorie reading

I recently started rowing a lot, doing several workouts from intervals to long distance steady state. Since yesterday I experienced a sudden drop in the calorie measurement.

Today 5 feb I did a hard interval workout followed by a 30 min steady state row, I only burned 472 calories for 53 minutes! That with a training effect of 2,8.

For reference on 2 feb I did the exact same interval workout followed by a 15 min steady state row (so more easy than the 30 min I did today) Then I burned 627 calories in 40 minutes. So that is more calories for a less difficult workout.

I found another workout I did 29 jan with a training effect of 2,7 and similar time, that time I burned 727 calories. How is it possible the readings I get from today and yesterdays workout are so different?

0 trux over 1 year ago

4893563 said:
How is it possible the readings I get from today and yesterdays workout are so different?

It depends on your heart rate during the activity, on the 7-days Avg Resting HR, and also the HRV, and the respiratory rate have impact. So if those values differ, the Calories will differ too. Especially the Resting HR will have a huge impact, so have a look at https://connect.garmin.com/modern/report/60/wellness/last_seven_days, and compare the values on the concerned days.

0 4893563 over 1 year ago in reply to trux

The resting HR is exactly the same (47) on 29 jan and 5 feb

and my HRV on 29 jan is 63-106ms and on 5 feb 63-103ms

These values are the same, so I am still wondering were the change in measurement is coming from.

thanks for helping

0 trux over 1 year ago in reply to 4893563

Hard to tell without seeing the full details of both activities, including the graphs. If you share links to both activities, and make them public, perhaps we can find the clue.

0 4893563 over 1 year ago in reply to trux

So here is the activity of today (5 feb): https://connect.garmin.com/modern/activity/10448024574

similar activity (interval + steady state but less demanding and more calories burned) I did 2 feb: https://connect.garmin.com/modern/activity/10431906240

and the activity of 29 jan (same training effect and same time but this was without interval: https://connect.garmin.com/modern/activity/10402060224

0 4893563 over 1 year ago in reply to 4893563

In addition, when I first started rowing at the beginning of January the calorie measurement on the display of the machine were always lower than the measurement on my Garmin. Now suddenly since yesterday (workout of yesterday and today), this calorie measurement of the Garmin is lower than the measurement of the rower itself.

0 trux over 1 year ago in reply to 4893563

Frankly told, seeing the data, I'd expect the opposite ratio of burned Calories, too. One possibility for the discrepancy might perhaps be different accumulated EPOC from workouts in previous days, that increased the Energy Expenditure (EE) more at the later activity.

Another posibility is that the algorithm for the estimation of the EE during anaerobic effort is far less accurate than Garmin (resp. their Firstbeat branch) claim. They admit some a "slight underestimation" at a short anaerobic effort, but in your case the difference i Active Calories at comparable workouts is almost double, which is enormous.

This is what Firstbeat tells about the anaerobic effort in their whitepaper https://assets.firstbeat.com/firstbeat/uploads/2015/10/white_paper_energy_expenditure_estimation.pdf

The described EE-estimation estimates only the aerobic component of energy expenditure, which may cause slight underestimation of EE during short-term anaerobic activities lasting from few seconds to a couple of minutes. However, the underestimation is insignificant in measurements lasting longer than 2-3 minutes

I recommend you to contact the Support and asking them to look at it.