Over the years, I've tried various fitness classes ranging from HIIT, dance cardio, and indoor cycling to lower impact workouts like Pilates and yoga, mixing in weightlifting and treadmill work at the ...

When elites like Kellyn Taylor—who trains in Flagstaff, Arizona—and Emma Coburn—who trains in Crested Butte, Colorado—work out at elevations around 6,000 to 8,000 feet above sea level, then you know ...