Roller skiing!
It’s terrifying to start, but I’ve found roller skiing to be a great, low-impact addition to my training this year. It’s made a big difference to how much volume I can handle.
When I feel my knees or hips start to protest from running, I put a few days in of roller skiing. If I keep roller skiing to 20-30% of total training time, I find I don’t have any knee or hip issues at all.