Apple Watch exercise calories burned are inconsistent in the same workout

Hi, I'm using an Apple Watch 8. I've noticed inconsistencies in the active calories during my workouts. A month ago I typically did 45 minutes of the indoor cycle workout and burned about 320 active calories. For the last 2 weeks, I've been doing outdoor walk exercise for 30-45 mins because my indoor bike was being repaired. For the last three days, I started doing the indoor bike exercise again and noticed that in the exact same 45-minute workout with the same intensity, my Apple Watch is recording closer to 450 active calories burned.

Does anyone have any idea why the watch is recording a higher active calorie burn for the same exercise?