I ran today to stress test and get my max heart rate. 5.5% grade starting slow and building speed up to 9 mph when I couldn't go any further. I walked a bit after that to loosen my legs a bit but I was fairly shot and couldn't get any miles in after this.

Hopefully I can start training tomorrow with a more accurate max heart rate. I'll probably test this again outside once a reasonable day presents itself in a few weeks or so.