Tough day for intervals

Today's workout:

Intervals (50 minutes on the stairclimber --

five sets of 2:00 at zone 2; 8:00 at zone 4)

Today was interval day, the workout I dread most each week. I really do believe in the value of interval training, otherwise I would replace these ass-kicking workouts with something else. They take a lot out of me and always have, even at the beginning when I was working on staying in zone 4 for just two minutes at a time. But I can feel that my stamina has increased and my running pace has improved over the past fews months -- I think that's due in large part to the interval training. Plus, there's nothing like pushing myself that hard and succeeding. I love the end of an interval workout more than anything, when I finally step off the machine and know that I have another full week before the next one. Everything I've read says that I'd be better off doing two sessions of interval training per week, but I just can't make myself do it.

So what is interval training? It's going back and forth between levels of exertion. At its most basic, it can be alternating between jogging and sprinting: two minutes of jogging, two minutes of sprinting, repeat. But because I've had an EMR (exercise metabolic rate) test, my intervals get to be a little more scientific. My EMR results gave me a range of heart rate zones to work out in. The higher the heart rate the more calories burned, obviously -- but our bodies burn more calories from stored fat when we work out at a lower heart rate. (That's why people often hear that they're working out too hard -- if your heart rate is too high while you're exercising, you're not burning calories from stored fat, you're burning them from carbs in your bloodstream. That means that your workout isn't taking fat off your body -- and that you'll hit the proverbial wall when your body runs out of those on-demand carbs.)

The idea behind intervals is to increase the upper end of the range of heart rates in which the body is burning calories from stored fat. And, probably, to get used to working out at high heart rates without feeling like you're going to die. I had my EMR last fall and I'm still building on the interval training program I began just afterward. I started out doing two minutes at zone 2 (which, for me, is 144-156 beats per minute), followed by two minutes at zone 4 (165-173 beats per minute). I did that for three sets. Each week I added another set, until I was doing eight sets altogether. Then I went back to three sets, but increased my time in zone 4 to three minutes. After I'd worked up to eight sets of that, I started repeated the whole process with four minutes in zone 4. See where this is going? So, after about nine months, I'm up to five sets of eight minutes in zone 4 (the two minutes in zone 2 always stays the same). The woman who administered my test, the super smart and helpful Izette at Real Rehab in Greenwood, told me that ideally I'd work up to three sets of 10 minutes in zone 4.

At five sets of eight minutes in that zone, I feel like I'm getting close -- but I also feel like I'm approaching my limit. To stay on my (self-imposed) schedule, I should have done six sets today; I did five last week. But I could feel that I was pushing myself really hard -- I got the chills along my arms that are my body's signal that I'm about at my limit, and that was just three sets in. Plus, I was running the risk of being late to pick up C from daycamp. So I cut myself some slack and repeated the same schedule from last week. I still worked my ass off, something I had to remind myself of several times after I left the gym. I always feel guilty if I sense that I've slacked somehow in my workouts. I need a little dose of perspective to remind myself that I'm still working super hard.

I definitely think these last few steps toward the ultimate goal of three sets of 10 minutes in zone 4 will be challenging, and I want to remind myself that I can take my achieving it. It's OK to repeat a workout if I feel like I'm working too hard. But I also know I'm going to get there, and it's going to feel so good when I do. Hopefully by then I'll have enough money to spring for another EMR so I can see what all these months of training have done for my base (the range of heart rates in which I burn calories from stored fat).

Holy crap, what a long post. I'd like to close by saying three things:

• I hope I'm not totally talking out of my ass about all this heart rate/calorie burn stuff. Obviously, my understanding is rudimentary but I'm pretty sure I'm getting at least the gist of it right.

• Needless to say, I'm using a heart rate monitor for my interval workouts. Truth be told, I use mine for four of the six cardio workouts I do each week. I only skip it on my runs, when my plan is to generally stay in zone 2; I rely on my breathing to tell me if I'm working out too hard. After months of wearing the monitor, I've gotten pretty good at assessing if I'm in the correct zone. I didn't think I'd ever get used to wearing the monitor, but now I don't give it a second thought. And I love having something to pay attention to while I'm working out; it helps occupy my mind and makes the time go faster. My monitor is made by Polar and has far more functions than I actually use, but it's really reliable and the watch strap is pink and kind of cute.

• After much experimentation, I've been doing my intervals on the stairclimber for the past few months. The aforementioned smart Izette told me I could do them any way I wanted, outside on my own or in the gym on a machine -- treadmill, elliptical, stairclimber, whatever. For me, it doesn't matter how I get to the heart rates I'm working toward, just as long as I get there. If I was a star athlete trying to compete in a certain event, I'm sure it would be a different story. I started out doing my intervals on the treadmill but found after a few months that I was running too hard; the high impact was starting to give me shinsplints. So I tried them on the elliptical trainer, on the treadmill using incline instead of speed to increase my exertion, and on the stairclimber. To be brutally honest, I stayed with the stairclimber because I feel like it gets me into zone 4 with the least amount of agony. Every once in a while, especially if my legs are sore from a big run or workout, I'll try doing intervals on the elliptical again -- but it feels way harder, so I always go back to the stairs.