[Scott Johnston]

Mike:

Great questions and I am preparing an in-depth article that will touch on these subjects. But here is my take on what you experienced.

First let me say that pacing in an event eating many hours is much harder than pacing in a short race.  In a 1okm race if you are running a few seconds/km too fast you will feel it in within a few minutes and the feedback will tel you to slow down before too much damage is done.  So you get almost immediate feedback about your pacing.  In an ultra the effort should be so easy for you in most of the race that you will be tempted to push too hard in the early stages.  But, a pacing mistake of say 1min/km in the early stages will not make itself known until hours later, late in the race when it may force you to slow by many minutes/km.

Its sounds like you might have done just that kind of mistake in the 100k race. But the heat complicates things a great deal.  It might make you feel a little better to know that even the top pros I coach see a steady drop in HR during the race.  For instance: a 1 hour 17% climb early at UTMB HR can be 150 at an RPE of say 5.  A similar 18% climb late in the race might only see a HR max of 130 and have an RPE of 7 or 8.

In the 48mile pacing you probably were not as jacked up and excited so controlled the pace better.  Any we can’t discount the cooler conditions.  The HR decline is again quite normal.

I hope this helps,

Scott