If you have ever tried heart rate training, you may know that it is the most humbling, ego-less type of run training there is. It can be extremely mental.

If you haven’t, let me put it into perspective. My PR for a 5K is about 25 minutes. That was a recent PR and I could still likely run that if I got out there and pushed. Prior heart rate training, my long training runs were at around a 10:30 min/mi. Not anything speedy, but I ...