When I first purchased my treadmill in the summer of 2022, I chose the NordicTrack Commercial 1750 for two specific reasons: In addition to the incline capability you can find on most treadmills on the market, it had a decline capability that would allow me to train specifically for the Boston Marathon the following spring. Later, I used it to train for and set a new personal record at the Revel Big Cottonwood Half Marathon in Utah, which is part of a race series known for providing an aggressive downhill course. This summer, however, I’ve found myself doing the majority of my running (which is five days a week in total, with most weeks covering more than 40 miles) on the treadmill to train for the Chicago Marathon and go after a new personal best. I’ve found myself drawn to the Chicago Marathon for years (especially after spectating in person) but always said I would never do it because it would require completing the peak of training in the worst of Houston’s brutally hot and humid summer .…