I too am a flatlander prepping for a fall 10K hunt. Been on the weights and bike, you guys have me interested in StairMaster. Question - I have a knee with worn maniscus from too much running over the years, and it limits what I can do. Is StairMaster hard or easy on knees?
I've had two knee surgeries, end result is that almost all the cartilage behind my right kneecap is gone, and I'm missing about 70% of both the medial and lateral meniscus in my right knee. The stairmaster is my go-to for gym cardio, I love not having to deal with the impact of coming downhill.
It'll help get you in shape, but it's not the same as being outside.
Good luck.