Measuring the body’s intensity level during exercise is vital to any fitness program. Regular exertion checks help to maximize the cardiovascular benefits of an activity and can provide a warning if a person is working too hard.
People should be able to perform exertion checks without interrupting the flow of their workout. The intensity of a workout is typically categorized as light, moderate or vigorous, based on the amount of energy or effort expended by a particular individual. Intensity can be measured in the following ways:
Talk test
Target heart rate
Perceived exertion scale (also called the Borg Rating of Perceived Exertion Scale)
Signs and symptoms
The talk test is a simple, but useful, method to determine if a person might be working out too hard. It is based on the ability to talk while exercising.
The most accurate method is to track the target heart rate. By staying within the target heart rate zone, a people are more likely to achieve their fitness goals. The most efficient way is to use a heart-rate monitor, which is an electronic device calibrated to keep someone within their target heart rate zone.
Without a heart-rate monitor, it is still possible for a person to utilize the target heart rate method by checking his or her heart rate manually. This does, however, require more time and attention than does the use of an electronic monitor.
The perceived exertion scale is based on what a person feels while exercising. This method is subjective, but it can provide a reasonable estimate of the actual heart rate during physical activity.
Signs and symptoms refer to certain responses of the body to exercise. There are certain signs and symptoms that indicate the body is operating at too high of an intensity level. If these signs and symptoms occur during exercise, the exercise should be stopped.
All of these methods are designed for both men and women.
An exercise program should not begin without first consulting the appropriate health professional.
Talk test
The talk test method of measuring exertion simply measures whether someone is able to sing or talk during exercise. While exercising at a light intensity level, a person should be able to sing while performing the workout.
While exercising at a moderate intensity level, people should be able to carry on a conversation comfortably. If they are too out of breath to carry on a conversation, they are exercising at a vigorous level and should reduce their intensity level. Follow this good rule of thumb for staying within an appropriate level of exertion: a person should be able to carry on a conversation, but should be working out hard enough that they don’t really want to talk.
Again, according to the parameters of the talk test, a person who is gasping and unable to talk has probably reached or exceeded his or her aerobic zone. The intensity of the workout may be too hard at this point and should be modified.
Target heart rate
Heart rate is generally accepted as the gold standard for measuring intensity during aerobic activities, such as running, swimming, cycling and so on. The target heart rate (also called the training heart rate) is a percentage of the estimated maximum heart rate and it varies based on the age of the person doing the exercise. It is the range in which a person can achieve the greatest cardiovascular benefit from aerobic exercise without “overdoing” it. Target heart rate is measured in beats per minute (bpm).
There is a low and a high range of the target heart rate. The recommended target heart rate zone for moderate-intensity physical activity should be 50 to 70 percent of maximum heart rate. Examples of moderate-intensity activities are walking briskly, pulling or carrying golf clubs, recreational swimming, pushing a powered lawn mower, playing tennis doubles, riding a bike 5 to 9 mph with few hills, washing and scrubbing the floors and weight lifting. This level of activity burns approximately 3.5 to 7 kcal per minute.
The generally accepted target heart rate zone for vigorous-intensity physical activity is considered to be 70 to 85 percent of the maximum heart rate. Examples of vigorous-intensity activities are running, jogging, race walking, swimming laps, pushing a hand-powered lawn mower, tennis singles, biking more than 10 mph or with steep hills, moving furniture and circuit training. This level of activity burns approximately 7 or more kcal per minute.
Simple math shows that equal amount of calories can be burned in less time with vigorous-intensity activities compared with lower-intensity activities. Staying within these parameters means a person is exercising within the desired target heart rate zone. Following the steps described below will help determine a person's maximum heart rate as well as his or her target heart rate zone during aerobic exercise.
First, find the maximum heart rate. Maximum heart rate (MHR) = 220 – age. For example, the MHR of a 50-year-old would be 170 beats per minute (bpm).
Multiply the MHR by 0.7 to get the low range of the target heart rate zone. For example, the low range for a 50-year-old is 119 bpm (170 x 0.7).
Multiply the MHR by 0.85 to get the high range. For example, a 50-year-old should not exceed a heart rate of 145 bpm (170 x 0.85).
To achieve cardiovascular benefits, a person should exercise for at least 20 minutes within his or her target heart rate zone. This is most efficiently done by using an electronic heart-rate monitor, which may be embedded in an exercise machine or worn separately by the exerciser.
If an electronic heart rate monitor is not available, a person can manually check his or her own heart rate by monitoring the radial pulse of one arm with the third and fourth fingers of the opposite arm. The radial pulse can be found by following the following steps:
Position one hand with the palm facing up toward the ceiling.
The pulse of the radial artery can be felt on the palm side of the wrist just below the base of the thumb. Get comfortable finding this pulse before beginning exercise so it is easy to find quickly while performing an activity.
Use the pads of the third and fourth fingers of one hand to feel the radial pulse of the opposite arm. This is important because the thumb and index finger have their own pulses, which can cause a miscount of the actual beats per minute.
When the radial pulse is found, use a clock with a second hand or a timer and begin counting beats. The first beat should be counted as “0” and the count should proceed from there (0...1...2...etc.).
Count the number of beats felt during a one-minute period of time. For a faster but slightly less accurate alternative, count the number of beats felt in 30 seconds and multiply that number times two, or count the number of beats felt in six seconds and multiply that number times 10 to estimate your heart rate.
Try to keep moving by marching in place while counting the pulse rate.
People unable to find their radial pulse can use the carotid pulse on the side of the neck located just below the angle of the lower jaw.
Apply only light pressure over the wrist or neck with the third and fourth fingers. Too much pressure over the pulse can lead to a miscount.
The maximum heart rate is a number used to help calculate the target heart rate zone. People should avoid reaching their maximum heart rate during aerobic exercise, nor should they exercise above 85 percent of this number.
Rate of perceived exertion
The rate of perceived exertion (RPE) scale is a tool that allows people to measure how they feel during aerobic or anaerobic exercise (e.g., their effort, strain, discomfort and/or fatigue). Formally, the scale is called the Borg rating of perceived exertion scale, named after Swedish psychologist Gunnar Borg.
The scale uses heart rate, breathing rate, sweating and muscle fatigue to measure how hard a person is exercising. The sensations felt correspond with numbers on the scale. For instance, if people estimate they are working out somewhat hard, that level of exertion corresponds with 12 to 13 on the scale – which is about 60 percent of their maximum heart rate.
The scale was originally designed to run from 6 to 20:
6 – no exertion
7
7.5 – extremely light exertion
8
9 – very light exertion (such as walking slowly at your own pace)
10
11 – light exertion
12
13 – somewhat hard (breathing and heart rate are up, but you can continue)
14
15 – hard (heavy)
16
17 – very hard (you have to push yourself to continue, and you feel tired)
18
19 – extremely hard (you are exercising at a new level)
20 – maximum exertion
Multiplying the exertion rating by 10 has been found to give a good approximation of the actual heart rate. For instance, if the perceived exertion rate is 15, and 15 x 10 = 150, then the heart rate should be about 150 beats per minute. However, this is only an approximation; the actual heart rate can vary widely depending on age, health and fitness level.
While the original Borg rate of perceived exertion scale is a relatively accurate and commonly used method of monitoring the intensity of aerobic activity, the 6 to 20 scale is sometimes difficult to recall in the midst of strenuous activity. For this reason, a revised version of the RPE scale has been developed. This revised version uses slightly different terminology and a 0-to-10 scale, which can be easier to follow. Both the 6-to-20 RPE scale and the 0-to-10 RPE scale correlate well to actual physiological exertion. The modified Borg RPE Scale runs as follows:
0 – nothing at all
0.5 – very, very weak
1 – very weak
2 – weak
3 - moderate
4 – somewhat strong
5 – strong
6
7 – very strong
8
9
10 – very, very strong
maximal
Metabolic Equivalent
The intensity of physical activity can also be estimated by using the metabolic equivalent (MET) scale. Metabolic equivalent is the ratio of the work metabolic rate to the resting metabolic rate. One MET equals the expenditure of 3.5 milliliters of oxygen a minute for each kilogram (2.2 pounds) of body weight. This approximates the energy cost of sitting quietly.
The harder the body works, the higher the MET level. For example, a 5 MET activity such as cleaning gutters uses about five times more energy than sitting still.
An extensive chart called "The Compendium for Physical Activities Tracking Guide" lists the METs used for hundreds of leisure, work, household and other activities, everything from dancing the mambo (3 METs) to making maple syrup (5 METs) to mowing a lawn (5.5 METs).
Moderate activities are broadly described as 3 to 6 METs, while vigorous activities are classified as greater than 6 METs. Many activities are broken down to detailed levels of exertion. For instance, bicycling 10 to 11.9 miles per hour (mph) uses 6 METs, and bicycling 16 to 19 mph uses 12 METs.
A physician may advise patients to avoid overexertion by limiting activity to a certain MET level. These individuals would be given a copy of the chart. The MET scale is used most often with patients who have heart conditions, which are common complications of diabetes.
Signs and symptoms
Angina and dyspnea (shortness of breath) are two critical signs and symptoms that indicate a person may be exercising at too high of an intensity level. Angina, or angina pectoris, refers to cardiac-related chest pain that can often radiate out into the left shoulder and down into the left arm. The pain of angina can radiate into the jaw, as well. Dyspnea refers to difficulty breathing. If either of these two signs and symptoms occurs, stop exercising immediately and immediately consult a health care provider.
Whatever method of monitoring exertion level during exercise is chosen, be comfortable with it before getting started with the activity. All of the methods are effective, but they do not work unless they are used correctly.
Questions for your doctor on exertion checks
Preparing questions in advance can help patients to have more meaningful discussions regarding their conditions. Patients may wish to ask their doctor the following questions related to exertion checks:
What exercise program do you recommend for me?
Should I consult a personal trainer? Can you recommend one?
What type of exertion check is best for my workout?
At what intensity should I start and how should I increase intensity?
How can I tell if I’m overdoing it?
Can overdoing it in my workout be dangerous for my health?
Could any of my medications interfere with my workout?
Is it safe to exercise at my usual intensity if I am pregnant?
What signs or symptoms should prompt me to stop my workout?
Are there any signs of symptoms I should report immediately to you if I experience them during my workout?
How much and what type of fluids should I be consuming before, during and after exercise?
