Why am I finding it so easy to run in HR zone 2 but find it so difficult to maintain zone 2 on the bike. I’m good for maybe 1 to 1.5 hour but after that , nope. I’m following a half distance training program which requires up to 4 hours zone 2. I’ve tried high revs low power and low revs grinding. Just can’t maintain 128 +
Running at HR 150 all day long. Any advice ?