Monitoring My Heart Rate

After about three weeks of daily running for fun, fitness, and health, I chanced upon an article in The (Baltimore) Sun, my local newspaper, "Work out smart, monitor your heart," which extolled the virtues of using a heart rate monitor. I went out and bought one, a Polar FS1, at the Sports Authority for $50.00. I have used it once. That was yesterday, today being my day off running. I was quite pleased with it.

Non-fitness nuts such as myself — until now — may not be aware that regular "training" exercise such as brisk walking, running, cycling, swimming, rowing, and so forth is going to do two things, over the long haul. It's going to make the large skeletal muscles of your body, such as those in your legs, arms, and shoulders, better able to take up oxygen from the blood. And it's going to strengthen your heart.

Your heart is a pump. It pumps blood through your body. When the blood goes through the lungs, it gives up carbon dioxide (CO2) and takes up oxygen (O2). Returning to the heart, the oxygenated blood is then sent out to the rest of the body, including the skeletal muscles. The muscles, when being worked, take O2 from the blood into their cells. The muscle cells use it to produce energy, with CO2, a waste product, being carried off by the blood. The CO2 goes to the heart and then to the lungs, which expel it with the next exhalation. More O2 is taken in the next time you inhale, and the cycle continues.

For running to be fun, this cycle should be done with a degree of efficiency. Problem One is that the skeletal muscles of a couch potato don't take up oxygen well. Problem Two is that the couch potato's heart, basically made of muscle itself, isn't all that efficient, either.

When large skeletal muscles are not in good condition, they can't use all the oxygen they receive fast enough to keep lactic acid from building up and causing that burning, fatigued feeling. Solution: regular "training" exercise.


When the heart is out of training, though, its "stroke volume" is too small. That is, the volume of blood it pushes out with each contraction is too low. Even if the muscles have been conditioned to utilize oxygen real fast, the heart can't deliver oxygenated blood to the muscles fast enough.

To compensate as best it can, the heart's rate of contraction, measured in beats per minute, rises.

You have a resting heart rate, which you can measure by taking your pulse for ten seconds just after you wake up in the morning, while you are still lying in bed. Take the number of beats and multiply by six, the number of ten-second intervals in a minute. (If you have a heart rate monitor, you can use it instead.)

That gives you a baseline heart rate. Any physical activity you do, however minor, will raise you heart rate, albeit temporarily. The heart rate (aka pulse rate) will change quite a bit, up and down, as you go about your daily business. But unless you exercise, it won't go high enough to give you a "training" effect.

"Training" in this context means exercising steadily enough for long enough (at least 30 minutes per workout) often enough (at least three or four times a week) to get your heart pumping at a rate high enough to increase its "stroke volume" over the long haul (say, three to six months, to get a major improvement).


What heart rate is high enough? You want to exercise hard enough to keep your heart rate in a range of, say, 60% to 90% of your maximum heart rate, as long as the exercise continues.

Note that the boundaries of this optimal, so-called "submaximal" range are cited differently by different authorities. The article I mentioned recommended a 50%-85% range, based on the book Fitness for Dummies. The important thing is that there is a "training" range, above that range which you usually achieve in your day-to-day activities, and below your maximum heart rate. You need to put your heart in that range for at least 30 minutes at least three or four times a week to boost its stroke volume, and thus its ability to cope with your workouts more efficiently.

How do you know what your maximum heart rate is, though? Short of taking a very rigorous stress test, most people use the formula "220 minus age" to estimate their maximum heart rate.

The idea here is that very young children's hearts can typically beat at up to 220 beats per minute when they, the kids, are maximally active. As we age, that maximum possible rate drops by about one beat a year. So a 57-year-old like me probably has a maximum heart rate (MHR) of 220 - 57, or 163 beats per minute (bpm).

That's a statistical average. If you test 100 individuals of my age, picked at random, their MHR might range from, say, 143 to 183. Your MHR might not be 220 minus your age. But statistically, it is probably very close.


So I bought a heart rate monitor to wear while I'm running and to tell me what my heart rate is from moment to moment, and also whether the rate is in my target range or not.

Basically, it consists of a transmitter which you strap to your chest, beneath the chest muscles/breasts, right next to the skin. It picks up your heartbeats through two flat electrodes that seem to be made of a plastic-like material. It transmits those beats to a wristwatch-like receiver, which displays your instantaneous heart rate and also whether or not it's in the target range, under it, or over it.

I initially started by asssuming my maximum heart rate to be that of a 60-year-old, since the math is easier with 220 - 60 = 160. That makes each 5% of the range equivalent to 8 bpm.

I figured originally on targeting a range of 60% (96 bpm) to 80% (128 bpm). But that proved unrealistic. My heart rate gets up close to the 128-bpm upper limit when I walk up the steep hill that I have to deal with to get to where I run! Then, when I run on level ground, I find that my rate goes up above 128 bpm right off the bat.

In fact, I find that a steady pattern of 50-paces-jogging/50-paces-walking keeps me in the 128-140 range. So I am upping my upper limit to 136 bpm, which is 85% of my estimated maximum, and I allow my heart rate to overshoot as high as 140, which is 87.5%.

Specifically, I run until the monitor reaches 136, which usually happens after 50-to-100 paces at a jog or trot. Then I start walking, and as I do, my heart rate at first overshoots for a few seconds: 137, 138, etc., sometimes going as high as 140 or 141. Then it starts to drop. When it reaches 130, I start running again. There may be a few seconds of "undershoot" — going as low as 128 — and then a steady climb back up to 136, when I again resume walking. And so on.


That seems to produce a "fun run." By that I mean a run (or run/walk) that does not make me feel like I want to stop. There's no thought of "how much longer?" Rather, it's "I know I'd better stop, but I don't really want to."

At the same time, I know from the heart rate monitor that I'm definitely getting a "training" effect. I'm not failing to push myself hard enough to do any good.

As far as I'm concerned, that's really where its at.