Understanding the science behind cardio training and testing each individual independently is key to successful cardio programming.
To achieve optimal results, fitness enthusiasts must train at an intensity that is appropriate to their goals, current level of fitness and within the constraints of their health. Intensity is important because too low an intensity will not produce optimal results, while too high an intensity can lead to over-training and injury. To maximize training benefits, exercisers need practical and accurate approaches that fit their lifestyle. Workouts must be engaging, stimulating, motivating and results-orientated.
Cardiovascular training is a must for everyone. According to Ed Coyle, Ph.D., at the University of Texas, Austin, "If [your facility is] not conducting exercises testing with credible equipment and methods, [your members] will not get the desired results and [you may] lose your clients, if not kill them in the process."
To better understand cardio training, you will need to know the science behind it, and some practical applications. The principles presented in this article can be used in almost any training program.
Types of training
Moderate-intensity exercise is associated with many improvements in health-related variables. The improvement of endurance performance requires increases in qualities such as aerobic power and anaerobic threshold. To elicit positive changes in these qualities, a minimum intensity must be reached in training. Therefore, too low an intensity will lead to positive health benefits, but is unlikely to result in a change in endurance performance. On the other hand, a chronically high intensity with lack of sufficient recovery can lead to decreases in performance; this phenomenon is known as overtraining. A practical and accurate method for monitoring training intensity is required.
Like any combustion engine, the body uses oxygen and fuel to generate energy. The cardiovascular system delivers oxygen to the skeletal muscles, which then uses this oxygen to "burn" various fuels (carbohydrates and fat) to yield mechanical energy. A unique feature of the body is its ability to change in response to the demands placed on it. By working hard, the aerobic system is overloaded. During rest, the body adapts to make itself stronger. This is accomplished by improvements in cardiovascular and muscular function. The heart becomes stronger and more efficient, and the skeletal muscles become better at extracting oxygen from the bloodstream and excreting waste back into the bloodstream. Within muscle cells, the mitochondria boost their enzyme systems to oxidize fuels.
The science behind it
All of these changes occur over time. For improvement, the system must be continually overloaded. As an exerciser adapts, workouts should become more difficult. How is the right training level determined? Physiologists have discovered that the rate of oxygen "burned" in the muscles is the best measure of aerobic work. To determine this, exercisers use a treadmill, elliptical machine or cardio piece while the volume of inhaled and exhaled air is measured. Samples of exhaled air are periodically taken, and the oxygen concentration determined. The difference between the amounts of oxygen breathed in and out during the test is what the muscles have consumed to burn fuel. Also, the ratio of these substrates tell what the muscles have burned for fuel (carbohydrates and/or fat).
Equipment that does not measure both O2 in and CO2 out is inaccurate, and the resulting exercise prescription invalid and insignificant. The rate of oxygen consumption, in liters per minute, is called VO2. The test is performed at progressively harder levels until the individual "maxes out." The maximum rate of oxygen consumption is called the VO2max or VO2peak. VO2peak may not be practical in the health club environment.
With advances in software, a sub-max test can be delivered, and the software will extrapolate the VO2peak with extraordinary accuracy. Also, on the way to a sub-max, or VO2peak threshold, exercisers will pass through anaerobic threshold, which is another marker of cardiovascular fitness, and one that can be used to establish appropriate training zones for best and safe programming.
Anaerobic threshold (AT) represents how efficiently the muscles use oxygen to produce energy, or work. As such, AT represents the level of work the body can sustain over an extended period. When the body is called upon to perform above AT, lactic acid builds in the muscles, creating fatigue (the burning sensation felt), and the ability to continue to perform at this level is limited (a few seconds to a few minutes, depending on fitness level). Improving the anaerobic threshold is key to developing aerobic fitness. Generally speaking, an individual's AT may be between 52 and 95 percent of maximum heart rate. The more aerobically fit, the higher the AT.
Physiologically, in addition to burning fat in the aerobic zone, the body makes other, even more important, adaptations. Blood supply is increased through the new growth of blood vessels. This provides more nutrients to the working muscles, and helps take metabolic waste from the muscles. The mitochondria of the cells, where the energy production takes place, multiply up to 200 percent, providing a higher capacity for workload. The body also increases the level of hemoglobin and total blood volume. Oxygen in the blood is predominantly carried by hemoglobin, so with more hemoglobin, the working muscles get oxygen more efficiently. With the increase in blood volume, the cardiac muscle becomes larger, increasing the amount of blood pumped per heartbeat. This means a lower heart rate at rest, and more efficient recovery.The additional benefit of exercising at the appropriate intensity is increased lean mass. Muscle tissue burns, on average, 50 calories per hour per pound.
Research on VO2 has shown that there is a threshold below which no additional gains are achieved from aerobic exercise. For most people, this is a pace that allows for casual conversation during the workout, and is approximately 55 percent of VO2peak. Above this level, exercisers are sufficiently overloading the cardiovascular and muscular systems to bring about improvement. Related to this, group cycling is not beneficial if not performed properly. If participants exercise at too high an intensity for too long without sufficient recoveries, they become exhausted and don't lose any weight. They need to determine their "real" heart rate zones and adhere to them.
Gathering heart rate data
Methods for monitoring exercise intensity include the following:
* Using subjective ratings of perceived exertion
* Monitoring blood lactate levels
* Monitoring heart rate
* Monitoring O2 uptake
Interpretation of lactate data is difficult for the average recreational athlete or fitness center member. Subjective ratings of exertion have been used to monitor intensity, but several studies have shown that recreational athletes and those new to exercise judge intensity poorly with this method. Heart rate (HR), however, can be considered both an accurate and practical measurement of exercise intensity. It should be noted, though, that HR is not a direct measurement of exercise intensity. Heart rate is often used as a tool to estimate O2 consumed at a certain workload. There are factors, such as caffeine ingestion and dehydration, that can alter HR and affect its validity as an indicator of intensity.
Methods of monitoring HR are commonly used by endurance athletes as a measure of their training intensity, or as a pacing mechanism during competition. More recently, recreational exercisers are using HR monitors to regulate intensity with tremendous success in gaining fitness, reducing body fat and preventing injury. Youth fitness programs use HR to teach pacing and skill proficiency. Heart rate has been prescribed as a method for monitoring pre-competition emotional anxiety in weightlifters. Heart rate can be used to estimate energy expenditure in exercise lasting more than three minutes. This is due to the generally linear relationship between heart rate, power output and oxygen consumption. This relationship predicts that an increase in power output should be reflected in a proportional increase in HR.
Many methods can be used to measure HR. Commonly used methods include measurement of the pulse at the fingers or wrist, measurement of pulse pressure at the neck (carotid artery) or wrist (radial artery), measurement of opacity (how much light passes through) of the ear lobes and measurement of electrical activity of the heart at the chest.
The popularity of automated methods of recording HR has led to the inclusion of heart rate monitors on many pieces of aerobic fitness equipment. Studies conclude that the most valid and reliable system measures the electrical impulses of the heart at the chest. These systems commonly consist of a strap that is positioned just below the breast. Two electrodes lie on the inside of the strap, one on either side of the chest; they directly measure the interval between the "R" sections of the heart contraction. This method of monitoring HR is extremely accurate for men, women and children, as compared to an ECG reading. Other methods of recording HR may be unreliable; studies concluded that they might underestimate HR by up to 20 to 54 beats per minute.
As mentioned before, HR itself is not a direct indicator of exercise intensity. It is used to indicate intensity because it varies with exercise intensity. However, it can also be affected by a number of other factors, which include body position, hydration status and drugs (e.g.,beta blockers).
Using heart rate to determine intensity
Exercise shouldn't be based on distance, time or physical workload; it should be controlled by the degree of physical effort as measured by physiological signs, especially HR. Exercisers are less likely to cross the line between healthy exercise for aerobic fitness (a target heart rate of 55 to 90 percent maximum) and risky stressful exercise with a HR monitor. Training below minimum intensity level won't show much improvement in aerobic capacity. Above the 90 percent level, lactic acid will build up, resulting in decreased performance and susceptibility to injury.
Using the various formulas available for estimating HR max is fraught with error. Individuals do not have the same HR max, nor do they burn the same substrate for fuel at the same given HR intensity. (For example, Lance Armstrong's HR max using [220 age] is 186, when, in fact, his tested HRmax is 201.) There are in excess of 350 different formulas for determining HR max. The margin for error in several of the formulas is +/ 20. That could be catastrophic when setting up a cardio training program. Testing each individual is the key to successful cardio programming.
Designing exercise programs
See "Sample Workouts" for several examples of cardio workouts with different goals. Keep in mind that a successful end-result is dependent on the development of an aerobic base. The key components of an aerobic base include increasing the efficiency of the heart (stroke volume), increasing hemoglobin concentration (more oxygen transportation) and increasing muscle capillary density (better feeding system for the working muscles).
Key components of a successful weight-loss program include cardio work at the appropriate intensity, resistance training, appropriate calorie modulation and psychological readiness.
Based on goals, the HR zones in Figure 1 can be applied. Keep in mind that these zones can be further refined and narrowed as exercisers become more fit or desire to become competitive in their chosen activity.
Encourage cardio
The inclusion of innovative cardio programming can catalyze new growth opportunities within your facility. Not only will you have a better handle on members' exercise intensity, but you will create a whole new vertical revenue program. This way, your members are happy, and your bottom line is growing. Experience demonstrates a win/win scenario when appropriate, rational cardio programming is introduced, supported and optimized.
Why do cardio? Using an analogy from the automobile industry, it is simple: A person can have the best fuel (carbohydrates, supplements, etc.), most horsepower (bulging biceps/massive quads) and best body, but if the fuel pump or carburetor is missing, the person just sits there looking pretty. The heart is necessary to sustain life, but it can be a neglected component in fitness.
All too often, group exercise instructors focus on the choreography, music and fun aspects of their classes, with little consideration to intensity, duration and frequency of intensity. Following is how your instructors can help your group exercise participants get the maximum benefits for their hearts.
Help members become heart-strong
The inclusion of an appropriate cardio program for members is imperative to their overall success and longevity as members and humans.To achieve optimal results, fitness enthusiasts must train at intensities appropriate to their goals and current level of fitness, and within the constraints of their health. Intensity is important because too low an intensity will not produce optimal results, while too high an intensity can lead to overtraining, injury and even death.
Assessment and prescription for appropriate cardio training programs are important for all members. According to Ed Coyle at the University of Texas, Austin, "if you are not conducting exercise testing with credible equipment and methods, you will not get the desired results and lose the client, if not kill them in the process." (Coyle should know, since he has been testing and presenting results to Lance Armstrong since the cycler was 20 years old.)
Physical changes during cardio exercise
The body uses oxygen and fuel to generate energy. The cardiovascular system delivers oxygen to the skeletal muscles, which uses this oxygen to "burn" various fuels (carbohydrate and fat) to yield mechanical energy. A unique feature of the body is its ability to change in response to the demands placed on it. By working out hard, the aerobic system is overloaded. During rest, the body adapts, resulting in increased strength. This is accomplished by improvements in cardiovascular and muscular function, along with an improved transport system (like adding additional lanes to accommodate increases in traffic). The heart becomes stronger and more efficient, and the skeletal muscles become better at extracting oxygen from and excreting waste back into the bloodstream. Within muscle cells, the mitochondria boost their enzyme systems to oxidize fuels.
All of these changes occur slowly over time. For continued improvement, the system must be continually overloaded, and workouts become more difficult. How is the right training level determined? Physiologists have discovered that the rate of oxygen "burned" in the muscles is the best measure of aerobic work. Determining this used to require expensive equipment and specialized testing facilities. But now, basically, an individual runs on a treadmill, elliptical machine or cardio piece of choice while the volume of inhaled and exhaled air is measured. Samples of exhaled air are periodically taken, and the oxygen concentration determined. The difference between the amounts of oxygen breathed in and out during the test is what the muscles have consumed to burn fuel. Also, the ratio of these substrates will tell what the muscles have used for fuel (carbohydrates and/or fat).
VO2. Both the oxygen (O2) in and the carbon dioxide (CO2) out are critical to the process. Equipment that does not measure both O2 in and CO2 out is inaccurate, and the resulting exercise prescription invalid. The rate of oxygen consumption, in milliliters/kg body weight per minute, is called VO2. The test is performed at progressively harder levels until the individual "maxes out." The maximum rate of oxygen consumption is called the VO2 max or VO2 peak.
VO2 peak tests may not be practical in the fitness center environment. With advances in software, a sub-max test can be delivered, and the software will extrapolate the VO2 peak with extraordinary accuracy. Also, on the way to a sub-max or VO2 peak threshold, the client/member will pass through anaerobic threshold, which is another marker of cardiovascular fitness, and one that can be used to establish appropriate training zones for safe programming.
Anaerobic threshold. The anaerobic threshold (AT) represents how efficiently the muscles use oxygen to produce energy or work. As such, AT represents the level of work the body can sustain over an extended period. When the body is called upon to perform above AT, lactic acid builds in the muscles creating fatigue (the burning sensation felt), and the ability to continue at this level will be very limited (a few seconds to a few minutes, depending on the fitness level). Improving the anaerobic threshold is paramount to developing aerobic fitness. Generally speaking, AT may be between 52 and 95 percent of maximum heart rate. The more aerobically fit, the higher the AT.
Other physical changes. Physiologically, in addition to burning fat in the aerobic zone, the body makes other, even more important, adaptations. Blood supply is increased through the new growth of blood vessels. This provides more nutrients to the working muscles, and helps take metabolic wastes from the muscles. The mitochondria of the cells, where the energy production takes place, multiply up to 200 percent, providing a higher capacity for workload. The body also increases the level of hemoglobin and total blood volume. Oxygen in the blood is predominantly carried by hemoglobin, so with more hemoglobin, the working muscles will get the oxygen they need more efficiently. With the increase in blood volume, the cardiac muscle becomes stronger (primarily the left ventricle), increasing the amount of blood pumped per heartbeat. This means a lower heart rate at rest and more efficient recovery. The additional benefit of exercising at the appropriate intensity is increased lean mass. Muscle tissue burns, on average, 50 calories per hour per pound.
Moderation is key
Moderate-intensity exercise is associated with many improvements in health-related variables. The improvement of endurance performance requires increases in qualities such as aerobic power and anaerobic threshold. To elicit positive changes in these qualities, a minimum intensity must be reached in training. Therefore, too low an intensity may lead to positive health benefits, but is unlikely to result in a change in endurance performance. On the other hand, a chronically high intensity with lack of sufficient recovery can lead to decreases in performance; this is known as overtraining. Too high a heart rate too frequently has also been shown to cause irreversible cardiac muscle damage. A practical and accurate method for monitoring training intensity is required.
Monitoring methods
Research on VO2 has shown that there is a threshold below which no additional gains are achieved from aerobic exercise. For most people, this is a pace that allows for casual conversation during the workout, and is approximately 55 percent of VO2 peak. Above this level, an exerciser is sufficiently overloading the cardiovascular system and muscular systems to bring about improvement. A good example of this is group cycling. Many participants exercise at too high an intensity for too long without sufficient recoveries. Then they complain they are exhausted and don't lose any weight. They need to determine their "real" heart rate zones and adhere to them, regardless of the instructor's prodding.
Methods for monitoring intensity include use of subjective ratings of perceived exertion; monitoring blood lactate levels; monitoring heart rate; and monitoring O2 uptake during training.Interpretation of lactate data is difficult for the average recreational athlete. Subjective ratings of exertion have been used to monitor intensity, but several studies have shown that recreational athletes and those new to exercise judge intensity poorly with this method. Heart rate (HR), however, is both an accurate and practical measurement of exercise intensity. Heart rate is often used as a tool to estimate O2 consumed at a certain workload.
Heart rate. Heart rate can be used to estimate energy expenditure during exercise lasting more than three or four minutes. This is due to the generally linear relationship between heart rate, power output and oxygen consumption. This relationship predicts that an increase in power output should be reflected in a proportional increase in HR.
There are many methods used to measure HR. Commonly used methods include:
* Measurement of the pulse at the fingers or wrist
* Measurement of pulse pressure at the neck (carotid artery) or wrist (radial artery)
* Measurement of ear lobe opacity (how much light passes through)
* Measurement of electrical activity of the heart at the chest.
Studies conclude that the most valid and reliable system measures the electrical impulses of the heart at the chest (other methods might underestimate HR by up to 20 to 54 beats per minute). These systems commonly consist of a strap, which is positioned just below the breast. Two electrodes lie on the inside of the strap, one on either side of the chest; they directly measure the interval between the "R" sections of the heart contraction.
HR itself is not a direct indicator of exercise intensity. It is used to indicate intensity because it varies with exercise intensity. However, it can also be affected by a number of other factors. These include body position, hydration status and drugs (e.g.,caffeine, beta blockers).
Prescribing exercise
Exercise shouldn't be based on the distance traveled, the amount of time involved or the physical workload; it should be controlled by the degree of physical effort as measured by physiological signs, especially heart rate. Using the various formulas available for estimating max heart rate is fraught with error. Each member has his/her own unique maximum heart rate. Testing each individual is the key to successful cardio programming.
A successful end-result for an exercise program is dependent on the development of an aerobic base. The key components of the aerobic base are
* Increasing the efficiency of the heart (stroke volume)
* Increasing hemoglobin concentration (more oxygen transportation)
* Increased muscle capillary density (better feeding system for the working muscles).
The key components of a successful weight-loss program include cardio work at the appropriate intensity, resistance training, appropriate calorie modulation and psychological readiness.
Sample workouts
Following are several examples of cardio workouts with different goals.The speeds and times can be modified to fit the individual's ability to hold the heart rate, and for time available. As always, be conservative in the beginning stages, and include adequate warm-up, stretching and cool-downs. You may adjust these workouts for group cycling (change pace for resistance, hills, flats, sprints, etc.), group treadmill and combo group tread/bike class.
Fast walk. A fast walk uses approximately 325 calories. For this program, exercisers mix up faster sprints with slower recovery periods. Speedier walking calls more muscles into action -- specifically the butt, hips, abs and arms. With each step, have members roll from heel through the foot, then push down with the ball and toe into the next step. They should lean slightly forward from the hips. (See Table 1.)
Walk/run. With a walk/run workout, members use approximately 400 calories.Tossing short stints of running into the walk cranks up the intensity without too much stress. But if the extra impact makes members' joints ache, it is OK to power-walk the running intervals instead. Clients should run tall, but keep the upper body relaxed. Be sure they extend the back leg to lengthen their stride. They should avoid shuffling the feet, pick up their knees with each footstep and keep arms close to the body. (See Table 2.)
Hill pyramid. A hill workout uses about 325 calories. Walking or running up hills uses calories faster than walking on a flat surface because more effort is extracted in order to climb. With this gradual incline, there is plenty of time to adjust to the higher verticals. Keep a 4 mph (walking) or 5.5 to 6.5 mph (running) pace as the grade slowly increases. Be sure members keep their backs straight, then lean slightly into the incline. Encourage them to take quick short strides rather than long steps. They should lift their knees no higher than 6 inches for steep climbs. Decrease the incline if members' heels feel overstretched. (See Table 3.)
Group cycling. For a group cycling workout, have members perform a 10-minute warm-up at 55 to 60 percent maximum heart rate, or 30 beats below anaerobic threshold. Then, have them perform the following:
* Six times for 30 seconds each at 10 beats below anaerobic threshold; 30 seconds between each interval
*Three minutes at 20 beats below anaerobic threshold
*Six times for 15 seconds each at anaerobic threshold; recover 10 beats before next interval
*Three minutes at 20 beats below anaerobic threshold
*Two minutes at anaerobic threshold
*Six times for 10 seconds each at 90 percent max heart rate or 10 beats above anaerobic threshold
*Five minutes at anaerobic threshold
*Six times for 10 seconds each at 90 percent max heart rate, or 10 beats above anaerobic threshold
*Three minutes at anaerobic threshold
*Five minutes at 10 beats below anaerobic threshold
*Two minutes at 20 beats below anaerobic threshold
*Three minutes at 30 beats below anaerobic threshold
