My exercise routine includes a treadmill with between 4 and 5mph workouts. The fitness app on the Apple Watch recommends I calibrate it with an outdoor walk/run. I've read several articles about it, but am still confused by something. If I walk outside, I know I will not keep a constant 4mph pace, it will actually be much slower and it's in loops around my neighborhood, not some straight run in the park. Will calibrating at a slower speed really help it become that much more accurate for indoor walks/runs on a treadmill? What are you experiences with calibrating vs non calibration and treadmill workouts.