I took the riders I was leading into an introductory club ride last night on hills. It was only a few of us (five total) and two of them struggled a bit more on hills (it's very hilly going pretty much anywhere around our club's base). They were eager to improve. So I took them on one of my favorite recovery drill: slow racing up a hill.

The goal of the "slow race" is to go up the hill as slow as you can, keeping your heart rate as low as you can. Remember it's recovery day. I don't think there are many physiological benefits to be reaped from this exercise, but there are many psychological ones. First, you learn to control your heart rate and not to let it shoot through the roof as soon as you hit the hill. Second, you realize that hills don't have to be painful and that you can actually spin up them, all the while gossiping with your girlfriends. Third, I'd say that the speed you loose is less than the energy you're saving. What I mean by that is that it's not THAT much slower. So, returning to #1, you realize that controlling your heart rate on a climb is do-able and possibly more efficient than dying out there 'working hard' at 95% of your max heart rate.

So, to come back to your question: sometimes I'll do intervals and my heart rate will shoot to 200 and more going up a hill (I'm 28 but as the thread pointed above shows the equations for heart rate are all pretty wrong). On purpose. Recovering from that effort is what makes my heart stronger. Other times I'll go very slowly. On purpose. My heart doesn't really care but my mind gets stronger out of it. Doing this, I have learned to control my heart rate on hills I will not climb at much more than, say, 175-180 so I don't need to have a lot of time to recover once I'm at the top. Still on a club ride on a tough day I may be working hard not to loose the pack and my heart rate will go well beyond 200 and I'll struggle for a while after the top of the hill just to keep up on the flats. But that situation happens to me less and less often now...

Enjoy those hills! Sorry for giving such a contorted answer!