I'm looking but can't really find anything that shows what I am refering too. I wish I had a powertap on my mountain bike, that would really show it. On my graph my heart rate stays pretty consistant, what it doesn't show is that my power output actually goes down for a period of time when I am suffering because I didn't warm up properly.

At the start of a race it is pretty normal for my heart rate to go from 80 bpm at the starting line to 180 a minute later when I am trying to be one of the first three into the singletrack. If you don't have a decent warm up prior to this spike your body isn't going to react in a good way. That is why the warm up is so important.

What sucks is that in our series you have to stand around 15 - 20 minutes prior to the start for the racer meeting and the staggered starts. During this time you have some time to cool down.