I am entered in a trail run that has lots of elevation changes and obviously terrain will be far slower than a road race.
I have never run trails before.
I estimate the run will take ~ 3 hours.
Since I have no idea of how to pace it based on how I would normally do it for min/mile what would you suggest for HR?
I am 40 and my max HR is quite high at 192 so I was thinking 165 or so for most of the run and then last 2 miles ramp up to max?
What's the distance and vert? I would suggest doing some trail running if you can. Pace and time goes out of the window until you're comfortable on the trails.
HR will go up and down with the terrain even at the same effort, if you try to manage 165 HR on a long downhill you will blow out your legs (or at least I would). I suggest going by effort, for me that is going to feel similar to the effort level of a road marathon. So on every uphill etc I'd be checking in every min or so to make sure it's an effort i could realistically sustain if the entire race was that uphill, for 3 hours straight. And just finding a relaxed flow on the downhills
Didn't you already post this question?
It's a trail run leave the electric stuff at home, enjoy the scenery and push the pace.
You should break up the race into a segment for each major climb.
For example a 13 mile course that has 3500 feet of climbing can be broken down to 6 sections.
1. Mile 0-2: 1000 feet
2. Mile 2-4: -1000 feet
3. Mile 4-6: 1500 feet
4. Mile 6-8: -1000 feet
5. Mile 8-10: +1000 feet
6. Mile 10-13: -1500 feet
Uphills are going to be a measure of your cardiovascular fitness and downhills will be a measure of your focus, stability muscles, and agility.
For this made up race you should plan for 3 major efforts. Section 1, 3, and 5. You should not finish each section completely gassed but you can expect that your HR will go back down during the downhill and it will feel like a little break.
Section 3 is going to be an absolute ball-buster anything above +500 feet/mile is intense and in extra steep spots (1000 ft/mile) power walking can actually be faster and more efficient than running.
Additionally it might be a good idea to finish section 5 at max heart rate since the final downhill will carry you home.
Another thing to think about is sometimes downhills have a maximum speed they can be run due to switchbacks, rocks, roots, and downed trees.
Mountain races are essentially multiple mini races with downhill rests in between. Attack on the uphill and lock in on the downhill.
It is not uncommon to see people on short races with extreme vert have paces between 15:00-5:00 minutes throughout the race.