Hi everyone: So I have been tracking my MTB cycling workouts for a long time with multiple smartwatches before getting the Apple Watch ultra. I know quite well my usual metrics, including HR, distance, speed, elevation and calories expended of course. Son now I’ve seen the ultra consistently underestimating my calores burned when on (and only on that mode to be precise) outdoor cycle mode 
except for me second to last workout when I thought the problem had been fixed, but unfortunately it isn’t so. The difference is more than 50% so it quite concerning. What it’s very odd is that I compared the one workout that did calculate my calories more accurately with my latest workout which I intentionally made it very similar as in distance elevation terrain etc (and made sure that on all my workouts my info on the health app was accurate, weight height etc) and you can see in the graphs of both these workouts how similar my HR was, the time the distance everything… but on one workout I burned 675 active calories 1:16mn and the other only 441 1:25min.
here are the pictures to support my claim.
