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How Can You Determine Exercise Intensity?

Each training protocol within this book refers to "easy" or "moderate" intensity walks or runs throughout the week. It is critical that you understand what easy and moderate actually mean as well as how they feel in order to train appropriately. Two ways to determine exercise intensity are by calculating your target heart rate ranges and subjectively measuring your rating of perceived exertion while walking and running.

Measuring your heart rate during exercise provides an objective measure of your exercise intensity. Monitoring your heart rate is an excellent tool to determine more precisely how hard you are working so you can actually walk or run "easy" on your easy days and "moderate" on your moderate days. If you relate best to numbers and exact measurements, monitoring your heart rate may be a good option for you. However, you must realize that heart rates can vary daily based on sleep patterns, stress levels, hydration status, or the ingestion of medications. Therefore, it is best to use heart rate in combination with your rating of perceived exertion.

The rating of perceived exertion (RPE) is a psychophysical scale developed to have a high correlation with heart rates and other metabolic parameters. The RPE scale subjectively measures exercise intensity by using verbal expressions to evaluate the perception of effort during walking or running. The RPE scale is an excellent tool to use if you are not a numbers person or do not want to be bothered with monitoring your heart rate during exercise. Ideally, you will use the RPE scale in conjunction with heart rate monitoring during exercise. Using both methods will confirm you are walking or running at an appropriate intensity. For example, if you are completing an easy day of exercise and your heart rate is within your calculated easy range but it feels moderate or hard, this is an indication that you are tired and you need to decrease the intensity of your walk or run by slowing the pace. Another example might be that you are completing a moderate workout and your heart rate is within your moderate intensity range, but it feels easy. In this case, you might push the pace a little more to achieve a moderate level of perceived exertion.

The next section reviews how to establish your target heart rate ranges, explains how to use the rating of perceived exertion, and finally, discusses the relationship between heart rate, RPE, and walking or running pace.

How Can You Establish Your Target Heart Rate Ranges?

Determining and training within various heart rate ranges can help to improve fitness, enhance performance, and prevent injury and overtraining. The following formulas, collectively titled the Karvonen Formula developed by Dr. M. Karvonen, will lead you through the process of calculating your Target Heart Rate Ranges. Each protocol within this book refers to easy or moderate days of training, with all long workouts performed at an easy intensity. None of the protocols incorporate "hard" intensity workouts. For beginners, training at too high of an intensity can lead to injuries. You will calculate your "hard" heart rate range solely for the purpose of recognizing when you are working too hard and therefore need to slow down in order to decrease your exercise intensity.

Calculating your target heart rate ranges requires the knowledge of two variables: your maximum heart rate and your resting heart rate. Your maximum heart rate, or the greatest number of beats per minute your heart can pump during exercise, can be directly measured during a maximal effort treadmill test or through an estimation equation. The results of a treadmill test are extremely accurate; however, the test can be costly, time-intensive, and risky for some individuals. The estimation equation is quick and easy; however, the results have been shown to be highly variable as compared to actual measurements and therefore can be somewhat inaccurate. For beginners, using the maximum heart rate estimation equation will be sufficient in providing a ballpark figure to aim for during walking and running. If you choose to continue walking and running, and you desire more precise training heart rate ranges, you can inquire about scheduling a maximal effort treadmill test with your physician or fitness specialist.

The target heart rate range calculations use the maximum heart rate estimation equation and resting heart rate measurements. The only variable in the maximum heart rate range estimation equation is age. In general, as we age, our maximum heart rate will decline. For the target heart rate range calculation, you are also required to measure your resting heart rate on three separate occasions. Your resting heart rate is the number of times your heart beats per minute while at rest. It is best to take your resting heart rate first thing in the morning—before getting out of bed, having coffee, or going to the bathroom—by counting your pulse for one full minute. Your pulse can be found at your carotid artery in your neck, just off center, or on the inside of your wrist, just below your thumb, by using your two fore fingers. You should not use your thumb to measure your heart rate because it has a pulse of its own. After recording your resting heart rate for three days, take the average of the three measurements.

Use the following blanks to enter your numbers. If you are confused by any part of these Karvonen Formula calculations, refer to the sample calculations later in this chapter.

  1. Maximal Heart Rate (220 – your age) = _____

  2. Average of Resting Heart Rate for three days (taken first thing in the morning):

    Day 1 ____ Day 2 ____ Day 3 ____

    Average of 3 days = ____

  3. Maximal Heart Rate minus Average Resting Heart Rate = Heart Rate Reserve (HRR)

    ____ – ____ = (HRR)

  4. Training Intensity Range (Heart Rate Reserve x 50%–96%):


    (HRR x 0.50) = x 0.50 = beats/minute

    (HRR x 0.70) = x 0.70 = beats/minute


    (HRR x 0.75) = x 0.75 = beats/minute

    (HRR x 0.85) = x 0.85 = beats/minute


    (HRR x 0.86) = x 0.86 = beats/minute

    (HRR x 0.96) = x 0.96 = beats/minute

  5. Add the Average Resting Heart Rate to the Training Intensity Range to find your Target Heart Rate Range.


    ____ + ( ____ – ____ ) = ____ – ____ beats/minute


    ____ + ( ____ – ____ ) = ____ – ____ beats/minute


    ____ + ( ____ – ____ ) = ____ – ____ beats/minute

Sample Calculation

Susie is 45 years old.

  1. Maximal Heart Rate (220 – age) = 220 – 45 = 175

  2. Average of Resting Heart Rate for 3 days (taken first thing in the morning):

    Day 1 = 75 Day 2 = 72 Day 3 = 76

    Average of 3 days = 74 beats per minute

  3. Maximal Heart Rate minus Average Resting Heart Rate = Heart Rate Reserve (HRR)

    175 – 74 = 101 beats per minute

  4. Training Intensity Range (Heart Rate Reserve x 50%–96%):


    (HRR x 0.50) = 101 x 0.50 = 51 beats/minute

    (HRR x 0.70) = 101 x 0.70 = 71 beats/minute


    (HRR x 0.75) = 101 x 0.75 = 76 beats/minute

    (HRR x 0.85) = 101 x 0.85 = 86 beats/minute


    (HRR x 0.86) = 101 x 0.86 = 87 beats/minute

    (HRR x 0.96) = 101 x 0.96 = 97 beats/minute

  5. Add the Average Resting Heart Rate to the Training Intensity Range to find your Target Heart Rate Range.


    74 + (51–71) = 125–145 beats/minute


    74 + (76–86) = 150–160 beats/minute


    74 + (87–97) = 161–171 beats/minute

While walking or running, you can measure your heart rate by counting your pulse or wearing a heart rate monitor. Similar to measuring your resting rate heart, your pulse can be found at your carotid artery (neck) or your radial artery (wrist). The preferred location during exercise is at the radial artery. The reason for this preference is due to the presence of pressure receptors in your carotid artery. If too much pressure is applied to the neck while attempting to obtain an exercise heart rate, the body will sense an increased pressure in the arteries, causing a dilation of the blood vessels, which will decrease blood pressure and in turn possibly cause you to pass out. This is obviously not a desired result of taking your pulse while you are walking or running! Therefore, take your heart rate at your radial artery in your wrist. If counting your pulse is too challenging while you are exercising, consider purchasing a heart rate monitor. Wearing a heart rate monitor can make measuring your heart rate during exercise very easy and generally more accurate compared to counting your pulse with your fingers. Heart rate monitors can be purchased at most running/walking or sporting goods stores. For more information on heart rate monitors, see the following sidebar.

Running and Walking Training Gadgets—Heart Rate Monitors

Monitoring your heart rate provides an objective measurement of your effort level during walking and running, ensuring you are working hard enough but not too hard. It can be challenging to accurately measure your own heart rate while walking and running. Therefore, heart rate monitors are an excellent tool for beginners as well as advanced exercisers. All heart rate monitors will include a watch-like receiver and a chest strap that detects your heart rate and sends the information to the receiver. Your heart rate is displayed continuously during your exercise session. All descriptions are taken directly from the products' websites.

Polar Heart Rate Monitor—M32 model (http://www.polarusa.com)—The M32 model includes the OwnCal™ feature, which counts the calories and fat you burn during an exercise session. It also includes the new OwnZone™ feature, which automatically determines each day's target heart rate zone. The M32 is a moderately priced model providing the essential components for the first-time walker or runner.

Timex Heart Rate Monitor—1440 Sport Digital model (http://www.timex.com)—For walkers and runners looking for an easy-to-use and inexpensive heart rate monitor, the Timex 1440 Sport Digital Heart Rate Monitor is an excellent choice. This model provides the basic features of a heart rate monitor without the bells and whistles of other models. The heart rate monitor can also be used as a stopwatch, allowing for the correlation between heart rate and walking/running pace.

NIKE Heart Rate Monitor—Imara model (http://www.nike.com)—This NIKE heart rate monitor features a calorie counter and programmable heart rate ranges. A moderately priced monitor, the Imara model is marketed specifically to women. Men can check out the more advanced, as well as more expensive, Triax Elite model.

How Can You Use the Rating of Perceived Exertion Scale?

The Borg Rating of Perceived Exertion (RPE) scale is a subjective measurement of exercise intensity. The original scale asks you to rate yourself from 6 (very, very light) to 20 (very, very hard) based on how you feel physically during exercise. The original scale was designed to directly correlate with heart rates measurements. Adding a zero to the end of each number on the RPE scale provides the corresponding heart rate. For example, a rating of 8 on the RPE would approximate a heart rate of 80. Newer scales use a 0–10 rating scale which many people find easier to relate to when providing a subjective measurement of exertion. Either scale is considered valid and useful. First-time walkers and runners should strive for an 11 (fairly light) to 15 (hard) on the 6–20 scale during exercise.


Be careful to not work in the "hard" range of the RPE scale more than once a week during your training. To prevent injury and burnout, spend most of your time training in the "fairly light to somewhat hard" range of the RPE scale.

Use the RPE scale periodically during a walk or run to monitor your effort levels. Keep in mind when training for your first 5K, 10K, or half-marathon that a majority of your training should fall in the 11–13 range, with only a portion of one workout per week performed at a level of 14–15. Table 3.1 presents the Rating of Perceived Exertion Scale and the corresponding feelings in order to evaluate your exertion level during physical activity.

Table 3.1  Rating of Perceived Exertion During Activity


sitting (limited activity)


very, very light




very light




fairly light




somewhat hard








very hard




very, very hard


total fatigue (exhaustion)

Source: Borg GAV. Med Sci Sports Exerc 14:377-387, 1982. Noble B., Borg GAV, Jacobs I., Ceci R., Kaiser P. Med Sci Sports Exerc 15:523-528, 1983

Can Pace Be Used in Conjunction with Heart Rate and RPE to Measure Walking and Running Intensity?

Your pace during one workout may not be a valid indicator of intensity because of the many variables that influence pace such as hills, wind, temperature, and so on. However, most walkers and runners find that over time they can identify specific paces that feel "easy" and paces that feel "hard." For most of your training for the 5K, 10K, or half-marathon, you want to find a pace that feels in the easy-to-moderate range of intensity. You can experiment with various walking and running paces, while measuring your heart rate or RPE to identify your easy and moderate pace ranges. Refer to the following Running and Walking Gadgets sidebar for information on a gadget that can help you monitor your pace no matter where you are walking or running—a GPS monitor.


Set your goal for your 5K, 10K, or half-marathon finish time at a pace that you consider to be easy to moderate. The average pace you maintain for your long training walks and runs will give you a good indication of an appropriate pace for your race.

Figure 3.10 presents the total time to complete various distances from a 5K through a half-marathon for walkers and runners moving at a 6 minute per mile up to a 20 minute per mile pace. This chart is extremely useful for estimating your finish time for your 5K, 10K, or half-marathon goal race based on your current training pace.

Running and Walking Training Gadgets—GPS Monitors

If you prefer to train according to pace and perceived exertion levels, a GPS (Global Positioning System) monitor may be the gadget for you. GPS monitors use a network of global positioning satellites to precisely track the distance and pace you are walking or running anywhere in the world. This is an excellent tool for individuals who travel frequently or walk or run in areas without marked paths. Product description taken directly from the Timex website.

Timex® Ironman Triathlon® Speed + Distance System (http://www.timex.com)—The Timex GPS device will track your distance and speed, providing essential information for training by pace. In addition, this model has a lap counter, timer, and separate weekday and weekend alarms. This device is also part of the Timex® Bodylink™ System, which can be used to measure your heart rate during workouts and record all data to be downloaded and tracked over time.

Figure 3.10

Figure 3.10 Walk/Run pace chart.

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