I have been running for almost a month now. I do two 1 hour runs(~10km - mileage) per week and I run to maintain my bone density instead of going to the gym which is shut as of now. I really feel much better off the bike after I started running.
My FTP is 302W which puts me at 4.1w/kg. I have completed sweetspot base low volume 1, sweetspot base low volume two and I am currently in the 6th week of short power build low volume. Before I started running, I used to do endurance rides on those days which I currently run. Those endurance rides would be 1 hours and 30 minutes to 2 hours in length. My heart rate while running at an endurance pace is more than 150bpm which is 10bpm higher than my heart rate at my power zone 2. The question is, will I loose my biking fitness if I continue the runs. I plan to do a 2h30m to 3 hour endurance ride every week. I also have no issues completing the planned workouts. They are getting tougher as I am nearing the end of my short power build as each workout is taking a lot out of me. I have never done any anaerobic capacity training before so that is why I am probably saying this lol