I've always seen running as just my mistress while lifting weights is my wife but with gyms closed, I've been spending more time with the mistress. I've been running for about 2.5 years and have averaged about 8 mpw during that time. In April and May I have been logging closer to 20 mpw and breaking all of my records. I have turned my focused now to my mile time and have made four attempts in the past two weeks. I ran 5:34 twice then 5:28 and finally 5:26, all at the track. I am noticing that my heart rate starts very slow, though and I think is holding me back. During all of these all-out miles, my heart only gets up to 165 with an average of 155. I have been doing this with zero warmup because I was under the impression that it was best to use as little energy as possible before going for a PR. I'm just wondering what's up with the slow heart rate during an all-out activity and what I can do to get it to start faster.