I'm one of those people who can run 7:00 pace for a half marathon, can put in "MP" runs at 7:30 - 7:40 (which is where the calculators would put me), but hasn't managed to hold better than 8:00s on race day.  I prefer shorter, faster races. 

I wear a HR monitor and have learned a lot from attending to my HR at various paces, in various temperatures and humidities, and at various points on various length runs.

Forget about hewing to a preestablished MP in training:  that's where I come down.  We know that a good marathon is run about 5% slower than your lactate threshold.  And we know that a good half marathondepending on whether you're a 60 minute HMer or a 1:30 HMeris run right at your LT and a bit above it over the final 5K.

So learn to distinguish those two (critically) different levels.  Explore the terrain of various high aerobic paces.  I managed to hit an average HR of 173 in a marathon last December, but I've learned in training that 168-170 FEELS like MP HR.  That makes sense:  during the final 6 miles of the marathon, my HR naturally elevated to something like my threshold177-180 or so.  HM effort, if not HM pace.  <br /><br />Does this make sense?  We do sometimes make things too complicated, struggling to control what can't finally be fully controlled.  It's good to ask questions and process knowledge, but it's also finally important to learn how to listen deeply to your own body.  HR monitors can help that process, but it's important, too, to learn how to put them aside.  <br /><br />If you establish a MP prior to the race and then try to hold to it, you may indeed have a peak experience and run your best race, but I'd also suggest that you're as likely to run a bad or disappointing or subpar race that bears no relationship to the race you actually had in your legs.  Listening hard is the keyand, of course, race experience. 

The marathon is a beast. Be crafty. Don't overthink. Stay in control early on. There's plenty of time to be a hero later on--if it's in you to do that. But it may turn out that a conservative early pace was in fact not conservative at all; it may turn out to have been slightly overoptimistic.

[http://This message has been edited by KudzuRunner (edited Aug-31-2007).|http://This message has been edited by KudzuRunner (edited Aug-31-2007).]