I've heard that intervals are the way to go when doing cardio. Anyone else heard this? My water aerobics instructor uses them. I've been using them on the treadmill, kind of like the couch potato runner's program. Today I walked at 4.0 for 3 minutes, then ran at 5.3 for 2 min. I checked the heartrate monitor after I was done with the running interval, and once my heartrate was 163. My target heartrate is 135 at the maximum end. On the chart, I noticed that my heartrate at 163 was about 85% of what a 25 year old should have--I'm 52.
I'm just curious if it's "bad" to work at that high of a heartrate? I know the purpose of intervals is to push your heartrate up for short periods of time, but I'm wondering exactly how high? I feel okay, by the way, and have no heart problems that I know of. I passed my stress test a couple of years ago with flying colors. If I keep doing this, will my heartrate eventually go down when I do the intervals so that I can run for longer periods of time?
I have noticed that my resting heartrate has gone from 66 to 60. In fact, when I went to the doctor's office a while ago, the nurse said, oh, you have a runner's heartrate. Huh??? Since I don't really run, and I've still got 19-27 lbs. to lose (depending on where I set my final goal), I was rather startled.

In running, as the C25K program, I think it's the best way to work up to running. I used it in 2000, and it really worked. 
