"I share my office with one other person and the noise on my treadmill is not too loud...my office companion does not seem to mind it at all. When I am taking breaks or have to be at a "sit down" desk I offer up the treadmill for them…"
"Wow, 7 miles on your first day is good... or maybe if your feet are sore, it's too much.
So listen to your feet/body and do what you can. Our bodies become stronger by a balance of pushing them slightly and then rest, then push, then…"