3.3.2. Assessing and Developing Cardiorespiratory Fitness
Assessing Cardiorespiratory Fitness
To adequately prepare for starting a personal fitness program, it is important to first assess your current level of fitness. There are multiple methods for assessing a person’s level of fitness. Each of the walking/jogging assessments discussed here attempts to estimate a key physiological marker of the heart’s and lungs’ functioning capacity and maximal oxygen consumption. Maximal oxygen consumption, or VO2max, measures the body’s maximum ability to take in and utilize oxygen, which directly correlates to overall health and fitness. A good estimate of VO2max provides a one- time glance at a person’s health and fitness level and a baseline measurement for reassessment at future dates to gauge improvements.
Some of the most common walking/jogging assessments used to estimate VO2max include the 12-Minute Walk, 1.5-Mile Run/Walk Test, 3-Minute Step Test, and 1- Mile Walk Test. Unfortunately, these field assessments, although practical and inexpensive, only provide estimations. More accurate assessments require a lab- based VO2max test using equipment that measures the volume of oxygen and carbon dioxide being moved in and out of the air passages during exercise. Although this test is more accurate, the expense and availability make it impractical for most. Unlike the lab test, the field assessments are relatively cost free, user-friendly and require very little expertise to conduct or perform. In addition, the key point of the assessment is measuring differences rather than absolute values, and the field tests accurately meet that objective.
Information on how to safely perform these assessments will be provided at the end of this chapter.
Measuring Heart Rate
Those starting the VO2max assessments must first measure their heart rate, an important component used in the calculations.
Here is a video describing how to determine heart rate:
How to check your pulse
Creating a Plan To Develop Cardiorespiratory Fitness
Once the assessments have been completed, the next step is to develop a plan for maintaining or improving your current level of fitness. This fitness plan should include activities that are safe and adapted to meet your personal goals. Once these fitness goals have been identified, the principles of adaptation to change can be utilized to achieve those goals. These principles include specificity, targeting specific areas in a workout, and overload, the practice of increasing exertion as the body adapts to ensure continued gains in fitness levels. Specifically, you need to apply the FITT principle (Fitness, Intensity, Time, and Type) described in detail in the previous chapter, “Basic Fitness Principles and Exercise Habits”:
- frequency: 3–5 days per week for healthy adults.
- intensity: moderate to vigorous intensity, which equals 40–85% of heart rate reserve, or 55–90% of percentage of max heart rate. (More information about intensity will be provided later.)
- time/duration: 20–60 minutes per session or accumulation of 150 minutes per week. Sessions must be continuous for 10 minutes or more.
- type/mode: Use large muscle groups and exercises specific to cardiorespiratory exercise.
Click on the link below for ACSM’s latest recommendations on the quantity and quality of exercise for adults:
Measuring Intensity
Intensity may be the most important aspect of the FITT principle. Engaging in a “cardio” program that does not stress the CR system to the recommended levels will be ineffective. Engaging in a program that overstresses the system can lead to injury and pose unnecessary risks. So how do you know if you are in the right range?
Heart rate is one of the best ways to measure effort level. Walking and jogging increase a person’s heart rate. Based on the function of the heart, this is no surprise. The heart rate directly correlates with the amount of oxygen being taken in by the lungs. As activity increases in intensity, oxygen demands increase and so does heart rate.
Because of this relationship, heart rate can be used in the design of an effective walking and jogging program by creating target heart rate zones. Heart rate zones represent an intensity range—a low end heart rate and a high end rate—within which a person’s heart rate would fall during a walking or jogging session.
The first step in determining your target heart rate (THR), is to determine your maximum heart rate (MHR), both measured in beats per minute (bpm). Generally, MHR is estimated to be your age subtracted from 220 beats per minute. In other words, your heart rate should theoretically stop increasing once it reaches the calculated maximum. While helpful, it is not uncommon to see variances in the laboratory tested maximum heart rate versus the calculated method.
The next step in calculating THR is to calculate a specific percentage of your MHR. This is done using two different methods. Keep in mind, finding the THR is the objective in both methods, even though slightly different numbers are used.
The first method, called Max Heart Rate Method, is more commonly used.
Max Heart Rate Method
- Calculate MHR; MHR = 220 – age.
- Calculate high and low THR by plugging in a percentage range. In this example, 60 and 80% are being used.
MHR x .60 = THRLow
MHR x .80 =THRHigh - The resulting low and high THR numbers represent the range, or target intensity.
The target intensity signifies an optimal training zone for that particular walking or jogging session. By keeping the heart rate within that range, you will drive adaptation specific to that intensity. By using real, but random numbers, and plugging them into the above equation this becomes apparent.
Female, aged 20:
MHR = 220 -20
MHR = 200 bpm;
THRlow= 200 x .60
THRlow= 120 bpm
THRhigh=200 x .80
THRhigh= 160 bpm
THR=120-160bpm
To achieve her self-established goals, the female in the example above will need to stay within the range of 120 and 160 bpm. If her efforts are intense enough that she begins to exceed 160 bpm during her session, or easy enough that her heart rate falls below 120 bpm, she would need to change her intensity mid-session to get the optimal results.
The Karvonen Formula or Heart Rate Reserve Method
- Calculate MHR; MHR = 220 – age.
- Determine your resting heart rate (RHR).
- Find the heart rate reserve (HRR); HRR = MHR – RHR
- Calculate high and low THR by plugging in a percentage range and then adding in the RHR. In this example, 60 and 80% are being used. THRlow= HRR x .60 + RHR, THRhigh= HRR x .80 + RHR
- The resulting low and high THR numbers represent the range, or target intensity.
Clearly, the Karvonen formula requires a few more steps, specifically, the incorporation of the resting heart rate. Using the same female in the example above, along with a randomly selected RHR, the THR looks like this:
MHR=220–20 MHR = 200
RHR = 72 bpm (randomly selected)
HRR=MHR–RHR
HRR=200–72
HRR = 128
THRlow=HRR x 0.60+RHR
THRlow=128 x 0.60+72
THRlow= 149 bpm
THRhigh= HRR x 0.80 + RHR
THRhigh=128 x 0.80+72
THRhigh= 174 bpm
THR=149–174bpm
A comparison of the two methods, reveals that the low and high end of the Karvonen formula is much higher than the Max Heart Rate method, even though the exact same percentages have been used. If the female in this example used the Karvonen Formula, she would find herself at a much higher intensity, especially at the low end of the range (120 vs. 149 bpm). How can this be? Aren’t these formulas supposed to have the same objective?
While it is true that both equations are used to estimate a target heart rate range, only the Karvonen Formula takes into account the RHR, the lowest possible heart rate that can be measured for that individual. The Max Heart Rate method assumes the lowest heart rate possible is “0,” a number to be avoided if at all possible! Because of the difference between 0 and the maximum heart rate, the calculated percentages result in a much lower number. In terms of accuracy, the Karvonen method is superior. It simply is a better representation of true target ranges.
Other Ways To Determine Intensity
Since not everyone owns a heart rate monitor, other methods of determining exercise intensity have been developed. One particular method, called the rating of perceived exertion (RPE), uses subjective measurement to determine intensity. The method is as simple as asking the question, Overall, how hard do I feel I am working? The answer is given based on a scale of 6 to 20 with 6 being almost no effort and 20 being maximum effort. Studies have indicated that when subjects are asked to exercise at a moderate or heavy intensity level, subjects can accurately do so, even without seeing their heart rate. As a result, using the RPE scale can be an effective way of managing intensity.
The original RPE scale or Borg Scale, designed by Dr. Gunnar Borg, was developed to mimic generalized heart rate patterns. The starting and ending point of the scale are less intuitive than a typical scale of 1-10. By design, the 6 represents a resting heart rate of 60 bpm and the 20 an exercise heart rate of 200 bpm, a beat count someone might experience at maximum effort. Over time, a modified Borg Scale was developed using a simple 1– 10 scale, with 1 being resting effort and 10 being maximum effort. Even though the modified scale is more intuitive, the traditional scale is still used more frequently.
Walking and jogging not only benefit physical health, but many enjoy the social benefits realized by exercising with friends. When walking or jogging with friends, intensity can easily be measured by monitoring your ability to carry on a conversation. With the Talk Test, if you are only able to say short phrases or give one word responses when attempting to converse during an exercise session, this would suggest you are working at a high enough intensity that your breathing rate makes conversation difficult. Certainly, if you can speak in full sentences without getting winded, the intensity would be very light. Just like RPE, the Talk Test is yet another way to subjectively measure intensity, which can then be correlated with heart rates.
Terminology Checklist
Cardiorespiratory system: the term used to describe the relationship between the cardiovascular system (heart and blood vessels) and respiratory system (lungs).
Calorie: a term used to describe food energy. Scientifically, it is the amount of energy needed to raise one kilogram of water, 1 degree Celsius. More accurately, it is one kilocalorie.
Adenosine triphosphate (ATP): the basic unit of energy used by the cells.
Aerobic energy system: the term used to describe the way cells produce ATP. In this case, the cells require oxygen to assist in ATP production.
Mitochondria: the area (organelle) of the cell where ATP is produced.
Creatine phosphate: a compound found in the cells and used by the immediate energy system that can be used to produce ATP.
Non-oxidative energy system: a term used to describe the way cells produce ATP. In this case, cells do not require oxygen to produce ATP.
Glucose: the simplest form of sugars found in the blood.
Tidal volume: the amount of air measured during inspiration or expiration.
Diffusion capacity: the amount of air that is transferred from the lungs to the blood.
Arterial-vein difference (aVO2diff): the difference between the oxygen found in arterial blood and venous blood.
Principle of reversibility: the fitness principle describing how fitness is lost while detraining.
Maximal oxygen consumption (VO2max): the maximum amount of oxygen the body can take in and utilize.
Specificity: a fitness principle describing how fitness improvements or adaptations to exercise stress are specific to the type of training that is performed.
Overload: the fitness principle describing how adaption to exercise stress is driven by progressively increasing the workload during training.
Target heart rate (THR): a term describing heart rate zones that represent an intensity range—a low end heart rate and a high end rate—used as a guide for exercise intensity.
Max heart rate (MHR): the maximum number of beats per minute the heart can contract.
Resting Heart Rate (RHR): the minimum number of beats per minute the heart contracts.
Heart Rate Reserve (HRR): the difference between the maximum heart rate and the resting heart rate. This term is also used to describe a method for calculating target heart rate.
Rating of perceived exertion (RPE): a self-assessment used during exercise used to estimate the intensity of the work being performed. The scale used, called the Borg Scale, ranges from 6 to 20.
Talk-test: a self-assessment used during exercise to estimate the intensity of the work being performed. The assessment is based on the degree of breathlessness observed while attempting to talk during exercise.
