I have just bought a S21 Ultra and a Watch 3 4G. I have been a FitBit user for many years and I am having difficulty working out the data presented from Samsung Health particularly in relation to calories. As an example yesterday I had two walks which auto-recorded in Samsung Health and also on my FitBit. The steps and distance measured were close enough matches on the Samsung and FitBit. Both devices are correctly set for age, weight, height, stride etc.
On the Samsung Health app:
Under steps I recorded 17542 steps, 13.48Km and 733 kcal.
Under exercise I first recorded 6432 steps, 4.81km and 193 kcal, and the second exercise 7777 steps, 6.14km and 170 kcal.
For the whole day, 172 mins active time, 13.37 km, total burnt calories 1949 kcal and 500 kcal burnt by activity.
The above equates to a BMR of 1648 which is correct by calculation.
What I don't understand is how Samsung Health says I have used 733 kcal in steps but only 500 kcal burnt by activity?
I am also concerned is how Samsung gives my total burnt calories as 1949 kcal and Fitbit 2902 kcal?
Today I measured a walking exercise using Samsung Watch and Phone, Fitbit HRM and Fitbit pedometer. All were close on steps, time and distance. The calorie results were very different.
Samsung Health Phone walking exercise auto recognised: 408 kcal
Samsung Health Watch walking exercise auto recognised: 233 kcal
Fitbit HRM: 736 kcal
Fitbit pedometer: 623 kcal
Walk was 7.7km, 87 minutes on a hard surface altitude variation 30m which calculates to about 430 kcal.
After wearing three different fitness monitors for the past week, varying the parameters in my profile and analysing the data, it seems that Samsung Health using watch data is miscalculating the calories burnt in activity. I have also analysed data from my wife on the same activity. The watch does seem to be making reasonably accurate measurements of steps, distance and heart rates. As a start the Samsung BMR calculation appears to use the Revised Harris-Benedict Equation. It also appears that it basically works on an algorithm that bases the burnt by activity calories on weight, height, time, distance and heart rate. It is in the heart rate part where I think it goes wrong.
Samsung Health calorific measurements using the watch appear to work on the nominal heart rate during activity when it should be working on the difference between resting heart rate and the activity heart rate. I have a very low resting heart rate and when I am walking at 5kph on the flat my active heart rate is below 70bpm which Samsung Health on the watch sees as barely active and using few calories. The fact that my heart rate is raised by 30bpm is not seen as the level of activity it should.
Samsung Health on another Samsung phone not synched to the watch sees the activity derived from the GPS phone movement and my profile as a more realistic figure compared to that from the watch measuring heart rate, albeit slightly on the high side. This is close to the calories shown in the Steps (as opposed to Active time and Exercise) part of Samsung Health using the watch. This is also more in line with other fitness trackers including a Fitbit HRM. I assume that the data assumptions used in my calculations, albeit a little old, based on the metabolic equivalent of tasks taken from the Compendium of Physical Activities are reasonably correct.
From what I understand after talking to the reps is that heart rate is used to calculate calorie activity when activity includes walking /running but doesn't with any other activity type. I tried the walking and it seems pretty accurate but any other workout you will find it's most likely off as it uses an algorithm to calculate the calorie activity
Yes it seems to be the case with walking but for me the calculation does not like my low heart rate. It works for my wife with a "normal" heart rate. Walking is my main need (and golf).
Looking further at my exercises according to the Samsung Health App, I spend 24% of my time in Heart Rate Zone 1 and the rest does not even reach that. Zone 1 starts at double my resting heart rate. No wonder it is not recording calorie burn correctly. I have raised this as an error with Samsung but it seems that either the app needs customisable heart rate zones, the capability of working these out from measurements rather than assumptions, or I need an alternate app that can do this.
Here today are screenshots of the same walking exercise captured on a Watch3 with a Samsung S21U and also captured on a Samsung S7E. The watch only records half the calories estimated by the S7 phone. Steps and distance are similar.
For the past two weeks my Watch3 has never recorded more than a total calorie burn of 1950Kcal in a day and I have done a minimum of a 10,000 step brisk walk plus another 2-3000 steps of movement every day. Both my Fitbits are recording around 2500Kcal per day. I am about 1.82m and 80Kg.
Something is very wrong with the Health app calculations as the watch sensor data seems correct.