When you run a marathon or an Ironman or Half Ironman (or the run leg of any triathlon), how do you choose your run pacing in hills? How do you adjust your target times and run paces for the hills you do encounter? There are a number of courses with hills early in the run, where you can realistically destroy your race by going way too hard too early. The (now cancelled) New York City Ironman was an obvious example, as it had a giant uphill in the first mile of the run.
You are trying to run steady splits (same pace every mile) for a triathlon or a marathon, but then you find a huge hill. Clearly, holding your target min/mile pace is silly-this will be difficult to impossible up a steep enough hill, and even if you can do it, your HR will go nuts and you will be exhausted. The answer is you keep either your perceived exertion (PE) or your HR basically steady. If you were doing a HR of 152 along the flats before the big hill, do whatever pace up the hill keeps you at around the same HR. I suggest letting your HR climb by about 5 bpm, but no more up the hill. This means that a lot of people will pass you going a lot faster uphill- this is OK, they are the ones being silly. You wouldn't randomly sprint for half a mile in the first half of a marathon, so why should you hammer as hard as you can up the hill?
I think the best calculator I have found is at this site, and my favorite calculator they have is this excel file, which lets you choose target paces for different courses based on your times or target times on other courses.
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