LLCJ wrote:
I'll be the one to ask the obvious question: Why were you wearing a HRM in a 5K race?
I know the question was directed at the OP, but I'll add: I run 20-25 road races a year. I wear my HR monitor in one or two of them. I specifically DON'T wear it in important races, because I don't want to be distracted by stray thoughts like "Jeez, I need to be working harder" and the like.
But a couple of times a year, often in the summer when I know I'm not going for PRs, I wear it in the service of science, hoping to discover something useful that can help me train even more effectively.
One June, for example, I ran a dead-flat 5-mile race in Grenada, Mississippi on the top of a dam. 82 degrees, sunny, and humid. I decided to go out with the leader, strong local master's guy, just for the hell of it. I ran 6:21, 7:06, 7:05, 7:07, 6:41. Basically what I discovered is that going out with the leader--running significantly faster than a pace I could possibly sustain--forces you to slow at a certain point, and when you slow to a manageable pace, it ends up being (in my case) something more like tempo pace, even though your HR is still at race pace. That was a useful discovery.