So, my quesion is, when you are talking about "intervals", what kind of intervals are you talking about? From all the reading I've done, there are obviously wildly different definitions of what an "interval" is as far as training use goes.
I read the stub thread about the 2 x 20 tests, and it sounded interesting because I've never done something like that before. A little background, I'm 46, 6'2" and about 225 lbs. Doing the math with the funky formulae, I estimate my max HR at about 185 bpm. So, for this 2 x 20, I aimed for a 170bpm mark for the two 20 min sessions. The first session was hard because I'm a little slow to warm up, and don't feel liek I get in my groove for about the first 20 mins. After the 5 min recovery, the next 20 min at 170 bpm felt pretty good, I was working hard, but still had gas in the tank. In a couple weeks, I'll try it again at 175. I'm looking for the formulae now, that converts that 170bpm figure into some sort of performance measure. The link on the 2 x 20 post doesn't work anymore - the company has redone their site, or doesn't give out the freebies anymore.
That 2 x 20 test was hard, but the way I've trained, it isn't what I'd call an interval. When I do anything up to 4 min intervals, they hurt, a lot. Legs and lungs and my HR is 180 to 190bpm. I thought that was the principal behind intervals, shocking the system and getting it out of its comfort zone? I've done a couple 40km TTs, but quite a few 15km TTs, and for the 15k runs, I'm flat out for the duration (~20 mins) at 180 to 190bpm. I thought that was the point fo the shorter time trials, to go flat out? I don't mind the intervals, in fact, I sort of enjoy/fear them. The discomfort is definitely way up the scale, but the sense of satisfaction, and the feel of my legs and chest lets me know that I've sure as hell been working, and hopefully making my system adapt.
So, when people are talking about 10 to 30 minute "intervals", what % of max heart rate are they actually talking about? I don't have a power meter, so that's why I'm referring to HR.