The problem with heart rate monitors.

For those who love gadgets, heart rate monitors can be great motivational tools. For others who have trouble incorporating rest and recovery into their training, they can help them turn down the intensity, using lower target zones for recovery days. Some runners need to be reminded to keep an elevated heart rate for a sustained amount of time. Heart monitors can help them insure that their cardiovascular system is being challenged. And for the focused, competitive runner, a heart rate monitor is almost essential to get adequate results from lactic threshold training. (For tips see Bob Glovers articles in Running & Fit News May and June 1999.)

But for many other runners, heart monitors can complicate their running and distract them from the meditative potential of running. Even worse, heart monitors can cause anxiety for the runner who finds his heart rate climbing beyond a certain predetermined number. The American Running Association hears from many runners whose use of heart rate monitors has led them to believe that something must be wrong. If this happens, you need to sit back, regroup, and ask yourself "Why do I run?"

Do you run for fun, fitness, stress management or improved personal health and longevity? In a society pushing technology on us with cellular phones, computers, beepers, and fax machines, some of us may prefer less technological running. But if you are using a precision training tool, for precision training, you need a precise maximum heart rate.

What's Your Max?

This is the biggest challenge with using a heart rate monitor. The key is to start with an accurate number...which is harder than you may think. The most accurate way to find your Maximum Heart Rate is with a direct measurement in a fitness laboratory or with a maximum stress test conducted by your cardiologist. But these tests, although accurate, are quite expensive. The next best way to determine your Maximum Heart Rate is by conducting a series of running tests using your heart rate monitor for measurement (see Running & FitNews, June 1999).

By far the most common, least expensive, and least accurate method is to use one of the many formulas that calculate MHR based on your age. The most common formula determines MHR by subtracting your age from 220. A training target zone can then be calculated that is 70% to 85% of this Maximum Heart Rate (or 80% to 95% for more intense training).

For example, using this formula, a fifty-year-old runner would have a MHR of 170 and would aim for training heart rates between 120 and 145. But these are only estimates based on a very crude formula According to Running & FitNews, Editorial Board Member Jack Daniels, Ph.D., there are 50-year-olds who have been tested with MHRs in the 190s and 30-year-olds whose MHRs are measured at 148. Averages can be poor predictors of an actual value for an individual runner.

What Rate for Training?

An aerobic range where your body can continue to use oxygen without going into oxygen debt (the anaerobic state) is between 70% to 85% of your maximum heart rate. When you exceed this point, you become too breathless to carry on a conversation while you work out, and in fact, must cease in order to catch your breath. If you are running at a heart rate that is higher than your "predicted" target zone without feeling out of breath then the number you are using to estimate MHR is probably not accurate. (John D. McPhail, C.R.C., is the Senior Health Educator with the Michigan Public Health Institute's Resource Center for Cardiovascular Health and is an American Running Clinic Advisor.)

RELATED ARTICLE: Why are the Numbers Wrong?

* You've used a formula that hasn't given you an accurate number for your maximum heart rate.

* Profuse sweating or outside electronic interference can cause bad readings.

* Caffeine, cold medications that contain ephedrine/pseudoephedrine, excessive heat and humidity, or a recent blood donation can elevate your pulse rate.

* Some medications used to treat blood pressure or heart problems can cause the heart rate to remain lower than it would normally be.

* "Cardiac drift" in which the pulse may drift upwards by five to 15 beats, can occur late in a long run.

Sound Training Without the Numbers

Running gurus such as Dave Costill, Ph.D., and the late George Sheehan, M.D., agree that you can learn o "feel" the right exercise intensity for a workout using Ratings of Perceived Exertion. RPE is a scale developed to gauge exercise intensity by learning how to read subjective "cues" from your body. In fact, these subjective cues are likely to give you more valid information than any formula based on aggregate heart rates.

For example, when you breathlessly finish your second or third 50 meter interval your heart rate could be just about at your maximum. Your heart rate during a 5K race where you set a PR could be a good target for lactic threshold training. Your heart rate during long runs, where you can go on forever, could be the right rate for your recovery days or long runs. You can use your monitor to replicate these intensities in your training, or RPE. Your training pace effects your racing performance. Learn to associate rates with specific cues or performances, and begin to instinctively feel at what rate you should be working out.

Should You Be Worried? If you experience chest discomfort, difficulty breathing, an irregular pulse, dizziness with exertion or dizziness that persists more than a few minutes following exercise, see your doctor. A pulse that remains over 120 beats per minute for more than ten minutes after exercise is also a danger sign and should be investigated.