I recently got a heart rate monitor. It has really helped me pace myself, thereby increasing my distance. However, recently (last couple of weeks,) I have seen absolutely no gain, perhaps even a little loss, in my running time.

I've done a little reading on hill running, and interval training, but I still wonder what exactly the ideal heart rate is for both distance runs, and interval runs is. I'd say my heart rate for an average four mile run would be 174-176. If I go over 183, as soon as I slow down I have a strong urge to puke. Is 183 acceptable for interval runs?

One last question. Due to time constraints, and pure boredom of running, I like to do my push-ups during my runs. I'll run a quarter of a mile, stop for a sec and let my heart rate drop to 170, do one set of push-ups, then hop up and run another quarter of a mile. Am I slowing my running progress by interrupting my runs?

If anyone tells you what your ideal HR is without using a stress test, they do not know of what they speak. The common falacy is to use 220 - age = HR max. This formula will not work for a good number of people. A more accurate way to determine HR max is to use Karvonen's formula: X% = ((Max HR-Resting HR)*X/100)+Resting HR. Training zones are usually within 65 to 85% of this "adjusted" HR max.