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health of a person’s cardiorespiratory system is critical to their ability to engage
in physical activity and exercise and can be assessed through a process called spirometry.
Spirometry uses a spirometer to measure the airflow into and out of the lungs, including
measurements of the following:
• Maximum voluntary ventilation: the volume of air breathed out in a specified time
with maximum effort
• Vital capacity: the greatest volume of air that can be expelled from the lungs after
taking the deepest possible breath
• Tidal volume: the lung volume representing the normal volume of air displaced
between normal inhalation and exhalation when extra effort is not applied
• Total lung capacity: the volume of the lungs when fully inflated
• Residual volume: the volume of air remaining in the lungs after maximum exhalation
Figure 11.1 Spirometer
SPIROMETER:
An apparatus for measuring
the volume of air inspired
and expired by the lungs.
TIDAL VOLUME:
The lung volume
representing the normal
volume of air displaced
between normal inhalation
and exhalation when extra
effort is not applied.
VITAL CAPACITY:
The greatest volume of air
that can be expelled from
the lungs after taking the
deepest possible breath.
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CHAPTER 11 | Concepts of Cardiovascular Exercise
VITAL CAPACITY
The vital capacity of the lungs is the greatest volume of air that can be expelled from
the lungs after taking the deepest possible breath. Using a spirometer, vital capacity is
measured by how much air is exhaled after a person breathes in as much air as possible.
Vital capacity measures the functional portion of a person’s lungs and, for healthy adults,
typically measures around 3,000 to 5,000 mL, depending on age, sex, height, and mass. Low
vital capacity (generally below 3 liters [L] or 3,000 mL) is generally a symptom or a sign of a
respiratory problem or disease.
The average adult has a normal breathing rate of 12 breaths per minute. A conditioned athlete
may breathe as much as 20 times their vital capacity over one minute, while a deconditioned
person may not even reach 10 times their vital capacity in one minute. However, aerobic
exercise can improve vital capacity by strengthening the muscles involved in respiration and
increasing the efficiency of the lungs.
TIDAL VOLUME
The tidal volume is the lung volume representing the normal volume of air displaced between
normal inhalation and exhalation when extra effort is not applied. This means it is a measure
of how much air moves into and out of someone’s lungs while at rest. On average, tidal
volume is about 10 percent of a person’s vital capacity.
People with larger bodies have larger lungs than those of smaller stature, which also means
they may have a higher natural tidal volume. Although this value will be different among
people of varying body size, an average adult tidal volume is about one-half of a liter (500 mL)
per breath in healthy males and slightly less (approximately 400 mL) per breath in healthy
females.
The following factors influence tidal volume and vital capacity:
• Age: Lungs are at their maximum capacity during early adulthood and decline with
age.
• Sex: Female reproductive hormones lower aerobic power and pulmonary function.
• Body size: Smaller bodies naturally have smaller lung capacity.
• Physical conditioning: Lung capacity improves (up to about 15 percent) with frequent
aerobic exercise.
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During exercise, tidal volume typically increases as breathing becomes deeper. This allows the
lungs to take in more oxygen and expel more carbon dioxide. However, tidal volume does reach
a plateau based on exercise intensity. During low- to moderate-intensity exercise, research
has shown that the increase in tidal volume and breathing rate is roughly proportionate to the
exercise intensity. However, at higher intensity efforts, a plateau in tidal volume is reached,
and the only way to increase respiration is to increase the number of breaths per minute.
MINUTE VENTILATION
The total amount of air entering the lungs over the course of one minute is called the minute
ventilation. This cardiorespiratory measurement is directly related to a person’s tidal volume
and is calculated as:
Minute ventilation (MV) = respiratory rate × tidal volume (TD)
where the respiratory rate describes how many breaths the person takes per minute.
The average adult has a minute ventilation of about 6 L per minute. During exercise, tidal volume
and breathing rate increase to supply working cells more effectively with oxygen for metabolism
and to remove waste products. Thus, minute ventilation also increases. The average healthy
adult’s breathing rate increases to 35 to 45 breaths per minute based on intensity during exercise
as their tidal volume also increases. Research has shown that healthy adults typically have a
minute ventilation of approximately 100 L during heavy exercise. Well-conditioned clients can have
a minute ventilation of up to 160 L during maximum-effort exercise.
Unconditioned people, those with chronic health conditions that affect the lungs directly
or the surrounding structures, and people with neuromuscular diseases that progressively
weaken the muscles involved in respiration may have reduced minute ventilation. These
physical conditions can also cause the body to become reliant on muscles outside those
typically used for respiration (e.g., the abdominals), and these people may have shallow,
rapid, or labored breathing. For a fitness professional, this is important to recognize because
it can affect a client’s ability to breathe adequately during physical activity, and the intensity
or effort may need to be adjusted.
VO2 MAX
A person’s VO2 max is a calculation of how much oxygen the body can use during intense exercise
(V, volume; O2, oxygen). The more oxygen the body can use during exercise, the more cellular
energy can be produced to fuel that exercise. Recent research has shown that although VO2 max
is partially predetermined by genetics, it may also be increased with appropriate training.
MINUTE VENTILATION:
The total amount of air
entering the lungs over the
course of one minute.
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CHAPTER 11 | Concepts of Cardiovascular Exercise
VO2 max is measured as the volume of milliliters of oxygen consumed per kilogram of body
weight per minute (mL/kg/min) and is most accurately calculated in a laboratory setting. The
Astrand-Rhyming Cycle Ergometer Test uses a bicycle to measure all-out efforts under a strict
protocol. While this is not conducted in most fitness settings (some facilities do have the
proper equipment and trained staff), the Rockport Walk Test (RWT) is often executed more
easily. This assessment requires a one-mile walk on a treadmill as fast as possible and has
been found to be relatively accurate for the estimation of VO2 max in adults aged 20 to 69.
With the Rockport Walk Test, VO2 max is calculated as:
Estimated VO2 max (mL/kg/min) = 132.853 – (0.0769 × body weight [lb]) – (0.3877 × age)
+ (6.3150 × sex) – (3.2649 × RWT time in minutes and hundredths) – (0.1565 × 1 – HR)
where age is in full years (no fractions), the sex variable is zero (0) for females and one (1)
for males, and the HR is the beats per minute taken at the end of the mile assessment. The
mile walk time is written in minutes and hundredths. For example, a time of 10:30 is 10.5
minutes, or a time of 11:15 is 11.25 minutes.
This estimation has been found to have an error margin of +/– 5, so the result should
account for this margin of error. For example, a VO2 max calculation of 35 mL/kg/min would
estimate between 30 and 40 mL/kg/min.
Some research has shown a link between heart rate and a person’s subjective RPE and VO2
max. Specifically, heart rate during activity can be used to estimate the VO2 max in many
clients. A general, though less accurate, calculation of VO2 max considers estimated
maximum heart rate and resting heart rate (RHR).
VO2 max = 15.3 × (max heart rate / resting heart rate)
where maximum heart rate is calculated as 220 minus age and resting heart rate is beats
per minute at rest (or the number of heartbeats at rest for 30 seconds multiplied by 2).
The norms for VO2 max also consider sex. It is important to understand that these calculations
are merely estimations unless completed under laboratory supervision, but the overall results
can be improved with cardiorespiratory training. For consistency, whichever method is used to
estimate VO2 max initially should be repeated for future evaluations.

METABOLIC EQUIVALENT (MET)
The MET is the measure of the ratio of expended energy to the person’s mass while performing
physical activity. This measure considers the metabolic rate at rest and the metabolic rate
required to support an activity. One (1) MET is equal to a person’s metabolic rate when at
rest. One (1) MET is approximately 3.5 mL of oxygen consumed per kilogram of body weight
and is calculated as:
1 MET = weight (kg) × 3.5 mL
For example, a 150-pound person (68.04 kg) would have a 1 MET of 68.04 kg × 3.5 mL =
238.14 mL of oxygen per minute.
A MET value of four would mean this person is using four times the amount of oxygen and
has a metabolic rate four times that of their metabolic rate at rest. Energy expenditure can
vary by age and fitness level, but for most healthy adults, MET values can be helpful in
exercise planning and as a gauge for the effort being put forth during activity.
Several activities have been calculated in METs for the average adult. The approximation of METs
can be used to estimate the number of Calories burned during each activity for an individual.

The Caloric value of an activity can be estimated using the MET value for the activity, body
weight in kilograms, and the following formula:
Calories burned per minute = (activity METs × 3.5 × bodyweight [kg]) / 200
For example, consider the 150-pound person again. Their weight in kilograms is 68.04 kg,
and they are walking at a very brisk pace with a MET value of 6.3.
Calories per minute = (6.3 × 3.5 × 68.04kg) / 200
= (1500.282) / 200
= 7.5 Calories per minute
7.5 Calories per minute × 60 minutes = approximately 450 Calories burned per hour
during this activity.
LACTATE THRESHOLD
Another means for calculating the efficiency of the cardiorespiratory system is the lactate
threshold. Lactate is a by-product of metabolism that is produced by blood cells, the brain,
and muscle tissue. It is used to supply the cells with energy when there is a lack of oxygen
or when normal cellular metabolism is disrupted. Lactate is a fuel, not a waste product.
However, the threshold where lactate builds up in the tissues faster than it can be cleared is
an important indicator of cardiorespiratory endurance performance and can be improved with
cardiorespiratory training.
The measure of the lactate threshold measures the maximum effort or intensity a person
can maintain for an extended time with minimal effect on blood lactate levels. This requires
a blood draw to measure blood lactate levels, which makes it accurate but not necessarily
practical in a fitness setting. Lactate threshold is often expressed as approximately 75
percent of VO2 max or 85 percent of the maximum heart rate for the average person and can
vary based on fitness level.
VENTILATORY THRESHOLD
Closely related to the lactate threshold is the ventilatory threshold (VT). This measure tracks
changes in carbon dioxide extraction, oxygen consumption, and breathing rate and volume.
Ventilatory threshold represents the lactate threshold—the level of intensity where blood
lactate accumulates faster than it can be cleared from the body—and it causes a person to
breathe faster (increase their breathing rate) to consume more oxygen and expel more carbon
LACTATE THRESHOLD:
The maximum effort or
intensity an individual can
maintain for an extended
time with minimal effect on
blood lactate levels.
VENTILATORY
THRESHOLD (VT):
The threshold where
ventilation increases faster
than the volume of oxygen.
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CHAPTER 11 | Concepts of Cardiovascular Exercise
dioxide. It is measured with a breathing mask or based on observable breathing rates as
opposed to the blood draw needed to accurately measure lactate thresholds.
For the average adult, the ventilatory threshold is at exercise intensities between 50 and 75
percent of maximum. An unconditioned client will reach their ventilatory thresholds at lower
physical intensities than a trained one. For example, walking may elevate an unconditioned
client’s breathing rate, while someone who has been training for a while may need to be
running at a seven-mile-per-hour pace to elevate their breathing rate.
It is also related to VO2 max in that ventilatory thresholds occur before maximum oxygen
uptake. Ventilatory threshold 1 (VT1) occurs when the breathing rate begins to increase
during activity, and ventilatory threshold 2 (VT2) is at a relatively high-intensity effort when the
person is out of breath. When someone achieves their VO2 max, they will no longer be able
to continue their exercise or activity.
rest
VT1
VT2
VO2 Max
exercise needs to
conclude due to
exhaustion
breathing increased to
point where person is
out of breath
breathing begins to
increase
Maxiumum
Figure 11.2 Ventilatory Thresholds and VO2 Max
MAXIMUM HEART RATE
Maximum heart rate is the maximum beats per minute someone’s heart can achieve during
activity, and it is a measure that is estimated to help determine exercise intensity for
cardiorespiratory training. Testing to determine a client’s actual maximum heart rate requires
the client to work at maximum capacity, which is not practical for a fitness setting. However,
an estimation of maximum heart rate is commonly found using the following formula:
Maximum heart rate (HRmax) = 220 – age
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where age is in whole years. While commonly used to estimate maximum heart rate, this
formula has a margin of error of +/– 10 to 15 beats.
There is great variability by client and age on actual heart rate maximums. For example,
a well-conditioned client will likely have a higher maximum heart rate and a lower resting
heart rate because their cardiorespiratory system is more conditioned and efficient and can
handle more work than an unconditioned client. With that in mind, a fitness professional can
estimate a client’s heart rate and corresponding heart rate zones, but this formula should
not be used as an absolute.
HEART RATE ZONES
The heart rate is a key indicator for exercise intensity and is used by fitness professionals to
prescribe intensity and evaluate fitness levels. There are five heart rate zones that generally
correspond with exercise intensities. Each zone represents a range of the percentage of
maximum heart rate and an RPE. As with the maximum heart rate estimation, heart rate
zones are also estimations and can vary based on the training status, health condition, age,
and body size of the client.
Zone 1 is a very light intensity and equates to 50 to 60 percent of maximum heart rate and
an RPE of 1 to 2. Examples of zone 1 activities include a warm-up, a cooldown, and a slow
walking pace. This zone can be used to slightly elevate the heart rate, promote physical
recovery, and promote optimal metabolism. Activities in zone 1 can be sustained for extended
periods.
Zone 2 is a light intensity and equates to 61 to 70 percent of maximum heart rate and an
RPE of 3 to 4 (easy). Lightweight resistance training, a light jog, or walking up a flight of
stairs would fall into zone 2 cardiorespiratory intensity. Breathing at this intensity is light,
and the client may begin to sweat. Training in this zone can improve both muscular and
cardiorespiratory endurance and can be sustained for extended periods.
Zone 3 is a moderate training intensity and equates to 71 to 80 percent of maximum heart rate
and an RPE of 5 to 6 (moderate). Breathing may begin to deepen with moderate sweating in this
zone. Based on the percentage of maximum heart rate, training in zone 3 is generally still aerobic,
and aerobic fitness can be improved. Hiking, a moderate jog, and moderate-paced resistance
training are generally zone 3 activities that can elicit this level of heart rate response.
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CHAPTER 11 | Concepts of Cardiovascular Exercise
Zone 4 is generally moving into anaerobic exercise and is a challenging intensity. Training in
this zone equates to 81 to 90 percent of maximum heart rate and an RPE of 7 to 8 (hard).
Training in zone 4 can only persist for moderate amounts of time and elicits feelings of
physical fatigue and heavy breathing to the point that the client cannot carry on a conversation.
For example, running at a five-kilometer run pace, cardiorespiratory interval training, or
resistance training intervals would fall into zone 4. Training in this heart rate zone can promote
anaerobic fitness improvements and improve performance capacity.
The final heart rate zone is zone 5. Zone 5 is maximum effort and equates to 91 to 100
percent of maximum heart rate with an RPE of 9 to 10 (very hard). This intensity can only be
maintained for short durations, and it will feel like an all-out effort. Training in this zone can
improve athletic performance, fast-twitch muscle fiber development, and sprint speeds. Not
all clients will need to reach this heart rate zone. However, unconditioned clients may reach
this zone and RPE at lower heart rates than estimated, while more conditioned clients will
see the opposite effect.
ZONE 1 • 50-60% Max HR
Very light activity, such as warm-up/cooldown
ZONE 2 • 61--70% Max HR
Light activity, such as slow-paced jogging, walking
up a flight of stairs, lightweight low resistance
ZONE 3 • 71--80% Max HR
Moderate activity that increases aerobic endurance,
such as moderate jogging, cycling, or rowing
ZONE 4 • 81--90% Max HR
Hard anaerobic activity, such as high rep ball slams,
boxing, or heavy weight lifting
ZONE 5 • 91--100% Max HR
Extreme hard maximum exertion activity, such as
sprinting. All out effort!
Figure 11.3 Heart Rate Zones
To calculate the beats per minute that equate to each heart rate zone during cardiorespiratory
fitness prescription, a client’s maximum heart rate will be multiplied by the high and low
ranges of each zone. For example, consider a 35-year-old client.
ANAEROBIC EXERCISE:
Short-duration muscle
contractions that break
down glucose without using
oxygen.
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HRmax = 220 – 35 = 185 beats per minute
Zone 1: 185 bpm × 0.50 = 92 bpm
185 bpm × 0.60 = 111 bpm
Zone 1 = 92 to 111 beats per minute
Zone 2: 185 bpm × 0.61 = 113 bpm
185 bpm × 0.70 = 129 bpm
Zone 2 = 113 to 129 beats per minute
Zone 3: 185 bpm × 0.71 = 131 bpm
185 bpm × 0.80 = 148 bpm
Zone 3 = 131 to 148 beats per minute
Zone 4: 185 bpm × 0.81 = 149 bpm
185 bpm × 0.90 = 166 bpm
Zone 4 = 149 to 166 beats per minute
Zone 5: 185 bpm × 0.91 = 168 bpm
185 bpm × 1.0 = 185 bpm
Zone 5 = 168 to 185 beats per minute
Again, these heart rate beats per minute are not absolute but can provide general guidance
as to where the client’s heart rate needs to be to achieve the desired cardiorespiratory
training effect.
HEART RATE RESERVE AND TARGET HEART RATE (THR)
Heart rate reserve (HRR) calculates the difference between a person’s estimated maximum
heart rate and their resting heart rate. It is a metric that can be tracked and improved as the
resting heart rate decreases with cardiorespiratory conditioning. A fitness professional can
use this formula to calculate HRR:
HRR = HRmax – HRrest
HEART RATE RESERVE
(HRR):
Maximum heart rate minus
resting heart rate.
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CHAPTER 11 | Concepts of Cardiovascular Exercise
HRR can also be used to calculate a client’s THR. THR is the desired heart rate to be
achieved based on the desired exercise intensity, and this measure also considers the
person’s maximum and resting heart rates. THR can be calculated with the Karvonen formula
as follows:
THR = ([HRmax – HRrest] × desired intensity) + HRrest
Consider the 35-year-old client again with a resting heart rate of 55 beats per minute. If the
trainer would like them to work at 80 percent training intensity, their THR would be calculated
as follows:
HRmax = 220 – 35 (age) = 185 bpm
HRR = 185 bpm – 55 bpm (resting) = 130
THR = ([HRR] × 0.80 [intensity]) + 55 (resting)
 = (130 × 0.80) + 55
 = 104 + 55
THR = 159 bpm for 80 percent exercise intensity