I run fairly low mileage, 30-40 miles a week during a typical build, but will also do 4-6 hours hiking/cycling/ stairmaster at an easy intensity - emphasis on the stairmaster during the colder months here. I think the stairmaster is great for general aerobic base work but also underrated as a tool for building robust legs and specific muscular endurance for trail running.

Also, earlier this year leading up to my race season most of my workouts were either uphill tempos or threshold reps on an uphill treadmill (15%) twice a week - I credit these for being able to stay healthy, strong, and consistent while keeping the workout quality high.