I guess the it’s the always irritating answer of…. it depends.

For me it I just try to be as sport specific as possible which is a recurring theme in these forums I have found.
In the spring I use the treadmill alot to get in shape for trail running (when I have to be indoors that is).
In the fall I have a big pack and go up and down my garage stairs. If it was a machine I think the step mill is the best answer but they are very expensive and not every gym has them.

The “star masters” with the rotating feet I think are the least specific and realistic. They can get your going for Z1 and Z2 but your legs aren’t getting the same workload. Better than nothing though.

Jake

To add another voice here, the stairmill is a great training tool. I’m a flat lander and as a result I’ve spent countless hours on them training with pack and with body weight. Last year my meniscus was messed up and I could run, but could hike on the stairmill and used it for ALL of the Z2 work as part of the fall training group in preparation for a successful trek of Kilimanjaro. Overall I’m a big fan for those that don’t have regular access to mountains.

This is not a knock on treadmills, but unless you have access to an incline trainer that goes above 15%, my strong preference for simulating mountains is the stairmill. Now if you are doing MTN running or something else, then maybe the treadmill is a better tool, but for Rainier I find the stairmill superior. Although when I first went up Rainier I trained with a treadmill and had a very successful summit. Consistency is very important, as is training for the pack weight.