Well after 2 months stuck slow commuting on my mtb and riding the stationary bike I git kur on my toy. The paths were clear and it was cold enough that traffic was light. But when I tried my usual 3 hour 45 minute 100km my body soon informed me that jst because you don't gain weight stationary biking you lose condition anyway. It took 4 hours to go 100km and my legs are sure telling me about ut tonight. At least though my cardio was more than up to the task.
Just need to get my endurance back.