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The ABC's of HRM

2000 Jim Fiore, all rights reserved

(A slightly modified version of this article originally appeared in SpliTimes issues 14/8, August, 2000 and 14/9, September, 2000)

Maybe you've heard of Heart Rate Monitoring (HRM). Maybe you think it's only for hard-core enthusiasts or folks with money to burn. Maybe you think it's too confusing or complicated to be useful for you. Well, maybe it's time to take another look!

In this article I'm going to pare down HRM to its fundamentals and show you how it can benefit you even if you never want to set foot on a track to do "speed work". I'm also going to point out a few practical considerations and popular misconceptions. Much of the material here is a distillation of a number of books, including Training Lactate Pulse-Rate by Peter Janssen and Daniels' Running Formula by Jack Daniels, mixed with several years of my own experience.

First off, what can HRM do for you? The basic idea is one of optimal training. In other words, you do the most efficient workouts for a given goal while minimizing the possibility of overtraining or injury. If you're into racing, HRM is right up your alley. If you hate racing, look at HRM as a way of insuring fitness with minimal fatigue and injury.

At its most basic, a heart rate monitor simply tells you how fast your heart is beating. Generally, you wear a transmitter (a thin plastic and elastic belt) around your chest. The readout is worn like a wristwatch. Basic units can be had for under $50. You can pay over $200 for units that include interval timers, computer upload capability, and other fancy hoo-haa's.

OK, so you put one of these things on and you see your heart rate in beats per minute (BPM). So what? In order to make use of the monitor you need to have some idea of what your heart rate needs to be in order to accomplish a specific running goal. There are four basic training zones established by your heart rate. Each zone is used for a different purpose. Different coaches use different names for these zones. For example, some folks might call the first one "the aerobic zone" while someone else might just call it "zone 1". Names aside, the important thing to remember is that the four zones are defined as percentages of your maximum heart rate (HRmax). HRmax is as fast as your heart can beat; that's it, the pedal's to the metal and there ain't no more. The tricky part is that everyone's HRmax is different. It generally declines with age. A standard formula to predict HRmax in males is 220 minus age. Thus, a 40 year old runner has a predicted HRmax of 180. For persons that have been working out continually for many years, 205 minus half of their age seems to be a little more accurate (our 40 year old now has a predicted HRmax of 185). Women will be about 5 BPM higher than men. These formulas can be off by as much as 10 to 30 beats in normal people, so they're not particularly accurate. A better way of determining your HRmax is to perform a test. There are many such tests. The safest (and most expensive) is to go to your doctor and get a cardiac stress test on a treadmill. For reasonably fit folks, the simplest test that I have seen is the all-out mile. Basically, you go to a track and run an even-paced hard mile (i.e., mile race pace), pulling out all the stops for the last 200 meters. When you cross the line, look at your monitor. That's your HRmax. Note that HRmax by itself doesn't tell you much about your fitness. It's quite possible to have an HRmax that's 20 BPM lower than another person whom you regularly beat in races.

Now that you have your HRmax, the four zones can be defined in beats per minute (BPM). The first zone is the aerobic zone and spans the range of about 60 to 75% of HRmax. Thus, if your HRmax is 180 BPM, the aerobic range spans from about 108 to 135 BPM. This is the zone you use for most of your runs. It is sometimes referred to as "conversational pace" or "easy pace", in that you should be about able to talk to a fellow runner while running this fast, without gasping for air. In this zone, the heart rate monitor helps you to reign in any tendency to get carried away and pick up the pace. After all, what's the point of an easy run if it's not easy? If you're into fitness running, this is where you want to run. You'll get the most aerobic impact with the least injury potential.

The second zone is at your lactate threshold pace and corresponds to about 85 to 90% of HRmax. This is the pace at which you perform tempo runs. A typical tempo run lasts about 20 minutes with 10 minutes of warm-up and cool-down on either end. This is pretty fast running (a little slower than 10k race pace). The nice thing about the monitor here is that you'll know that you're working hard enough to gain benefits, but not so hard that you'll be risking injury or overtraining. Casual racers might consider a tempo run once a week or so. They can do wonders for your 10k times.

The third zone is used for interval pace running and corresponds to about 98% of HRmax. Interval pace running is hard running and usually involves repeated bouts in the range of 400 to 1200 meters with equally long (in time) rest periods. If you don't care about racing, then you can forget about this zone. The advantage of the monitor in this zone is that it keeps you from going "full tilt". Going faster will not produce superior results, it will only overstress your body.

The fourth zone involves any pace that hits 100% of HRmax. This includes sprint work. Note that this is, by definition, anaerobic training. Your heart cannot supply the blood and oxygen needed by the working muscles for very long, and you will soon be forced to slow down. A monitor isn't going to be of much use in this zone.

There is a fifth zone used by folks training for marathons. These runs are often called marathon pace or steady state runs and fall between the easy and lactate threshold paces (around 80% of HRmax). The monitor is beneficial here in that it helps you to learn how to maintain an even pace for long periods.

The preceding is a gentle introduction into heart rate monitoring. There are some practical things to be aware of though.

1. Don't be a slave to your monitor. If your calculated tempo pace heart rate is 140 BPM, you don't have to run at EXACTLY 140 BPM. Even if you do this on a treadmill at a constant speed, you will notice that your heart rate will fluctuate by several BPM. The key here is AVERAGE, especially on easy runs.

2. Your HRmax will fluctuate with the weather. This is known as cardiac drift. In hot weather, you should lower your target heart rates somewhat.

3. Your HRmax will fluctuate with altitude. At higher altitudes, there's less oxygen, so your heart has to beat faster for the same amount of work. For constant intensity workouts, you'll need to adjust your target heart rates upwards at altitude ("altitude" usually means at least 4000-5000 feet).

4. Your HRmax will fluctuate with your hydration. As you run, you sweat and lose fluid. This makes your heart beat faster for the same work output. Thus, on long runs, it is normal for your heart rate to increase, so make sure that you stay well hydrated to counteract this tendency.

5. HRmax depends on the activity. The value you get while running is not necessarily the same as you would get for, say, bicycling or swimming. If you're really into cross-training, you may want to perform HRmax tests for each activity. If you plan on hitting the pool, make sure that your monitor is guaranteed waterproof!

6. HRmax depends on you! You might be over-tired one day, and that can spoil these nice percentages! If a workout that you've done before is just killing you, forget what the monitor says and take an easy day.

In summary, heart rate monitoring can be used to guide the effort of your workouts to get the biggest return on your investment of time while minimizing injury potential. A key element is obtaining your HRmax. Easy runs should produce about 60 to 75% of HRmax and tempo runs should come in around 85 to 90% of HRmax. Heart rate monitoring is not foolproof and BPM values can shift due to such factors as weather, altitude, type of activity, and hydration. Use heart rate monitoring as a guide rather than as an iron rule.

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