Last night I wanted to do my own little HR test, so I ran a fast 5K (8:02 pace, fast for me), which included a moderately fast 1st mile, a faster 2nd, and the 3rd included a couple sprints where I checked my max after each. My calculated max was 186 (220 – age). I hit 99% of that at 184. I plan to do this again in a week or so, but for now I guess I’m sticking with 186.
This all means that I need to focus on slowing down on my long runs. My “natural” pace has been putting me around 85%, so I’m going to have to throttle that back. I’m planning around 7.5 tomorrow, so we’ll see how it goes.