I’m new to using a wearable as a monitor for my progress during training and I’m confused with the calculation of calories burned during different activities. Last week I went for a walk and on the same day for a ride on my Tacx Neo T2. For both events, I used my MARQ Athlete to register the results. During my walk of 5,67 km in 55 minutes (about 6 km/h, which is not an extraordinary pace) I burned 501 kcal. This seems to be as expected, according to sites where you can calculate the amount of calories burned for a specific activity (by entering activity, pace, length and weight). The strange thing is that for my ride, the amount of calories burned appears to be completely off; during a ride of 46 minutes with an average pace of 27,2 km/h with some hills along the way that pushed me to the limits, I apparently only burned 473 kcal (and the Tacx came to appr. the same amount). However, according to the same sites I used for calculation the calories burned during my walk, the amount should be about doubled. At first, I thought it might have something to do with the HRM being connected to both devices.
Next day, I went for another walk (13,5 km), again using the MARQ athlete, but also using my old watch (an Apple Watch) on the other wrist. Besides some differences that somehow surprised me (different distance (200 meters total difference) and completely different split times per km), the amount of kcal really surprised me. The MARQ again matched the sites I checked before, but the Apple Watch was completely of, showing only half the amount.
Just to get a complete picture, I went for a short ride on the Tacx again the day after that. This time, I disconnected both the HRM and the Tacx from the MARQ, using the pulse HR. Again both showed about the same amount of kcal burned, but still they both were off, comparing it to the sites I use.
Can somebody explain where my error in thinking lies? I just cannot believe that going for a vigorous ride on the bike burns the same amount of kcal when comparing it to a walk...