That's exactly the sort of HR trace I'd expect from a race - sharp rise at the start and, even though you feel like you are tiring, because you are (sub-consciously?) working harder, higher HR towards the end.
Looks like a v. good HR trace to me :)
If you reach max. surely you'll explode!? - isn't the idea to run a race at as near to Lactate Threshold as possible, for as long as possible, therefore achieving a fast even pace where you should be able to maintain without exhaustion?
I don't know - you'll need to ask someone like Paul M. how it's suppose to work?