Exercise Standards for Testing and Training

AHA Scientific Statement
Exercise Standards for Testing and Training
A Statement for Healthcare Professionals
From the American Heart Association
Gerald F. Fletcher, MD, Chair; Gary J. Balady, MD, Vice Chair; Ezra A. Amsterdam, MD;
Bernard Chaitman, MD; Robert Eckel, MD; Jerome Fleg, MD; Victor F. Froelicher, MD;
Arthur S. Leon, MD; Ileana L. Pin˜a, MD; Roxanne Rodney, MD;
Denise G. Simons-Morton, MD, PhD; Mark A. Williams, PhD; Terry Bazzarre, PhD
The purpose of this report is to provide revised standards (static), isotonic (dynamic or locomotory), and resistance (a
and guidelines for the exercise testing and training of
combination of isometric and isotonic).4,5 Isotonic exercise,
individuals who are free from clinical manifestations of
which is defined as a muscular contraction resulting in
cardiovascular disease and those with known cardiovascular
movement, primarily provides a volume load to the left
disease. These guidelines are intended for physicians, nurses,
ventricle, and the response is proportional to the size of the
exercise physiologists, specialists, technologists, and other
working muscle mass and the intensity of exercise. Isometric
healthcare professionals involved in exercise testing and
exercise is defined as a muscular contraction without move-
training of these populations. This report is in accord with the
ment (eg, handgrip) and imposes greater pressure than vol-
“Statement on Exercise” published by the American Heart
ume load on the left ventricle in relation to the body’s ability
Association (AHA).1
to supply oxygen. Cardiac output is not increased as much as
These guidelines are a revision of the 1995 standards of the
in isotonic exercise because increased resistance in active
AHA that addressed the issues of exercise testing and
muscle groups limits blood flow. Resistance exercise com-
training.2 An update of background, scientific rationale, and
bines both isometric and isotonic exercise (such as free
selected references is provided, and current issues of practical
weight lifting).
importance in the clinical use of these standards are consid-
ered. These guidelines are in accord with the American
Exercise Physiology
College of Cardiology (ACC)/AHA Guidelines for Exercise
In the early phases of exercise in the upright position, cardiac
Testing.3
output is increased by an augmentation in stroke volume
mediated through the use of the Frank-Starling mechanism
Exercise Testing
and heart rate; the increase in cardiac output in the latter
The Cardiovascular Response to Exercise
phases of exercise is primarily due to an increase in heart rate.
Exercise, a common physiological stress, can elicit cardio-
At fixed submaximal workloads below ventilatory threshold
vascular abnormalities that are not present at rest, and it can
in healthy persons, steady-state conditions are usually
be used to determine the adequacy of cardiac function.
reached within minutes after the onset of exercise; after this
Because exercise is only one of many stresses to which
occurs, heart rate, cardiac output, blood pressure, and pulmo-
humans can be exposed, it is more appropriate to call an
nary ventilation are maintained at reasonably constant levels.
exercise test exactly that and not a “stress test.” This is
During strenuous exertion, sympathetic discharge is maximal
particularly relevant considering the increased use of nonex-
and parasympathetic stimulation is withdrawn, resulting in
ercise stress tests.
vasoconstriction in most circulatory body systems, except for
that in exercising muscle and in the cerebral and coronary
Types of Exercise
circulations. As exercise progresses, skeletal muscle blood
Three types of muscular contraction or exercise can be
flow is increased, oxygen extraction increases as much as
applied as a stress to the cardiovascular system: isometric
3-fold, total calculated peripheral resistance decreases, and
The American Heart Association makes every effort to avoid any actual or potential conflicts of interest that may arise as a result of an outside
relationship or a personal, professional or business interest of a member of the writing panel. Specifically, all members of the writing group are required
to complete and submit a Disclosure Questionnaire showing all such relationships that might be perceived as real or potential conflicts of interest.
This statement was approved by the American Heart Association Science Advisory and Coordinating Committee in June 2001. A single reprint is
available by calling 800-242-8721 (US only) or writing the American Heart Association, Public Information, 7272 Greenville Ave, Dallas, TX
75231-4596. Ask for reprint No. 71-0210. To purchase additional reprints: up to 999 copies, call 800-611-6083 (US only) or fax 413-665-2671; 1000
or more copies, call 214-706-1466, fax 214-691-6342, or e-mail pubauth@heart.org. To make photocopies for personal or educational use, call the
Copyright Clearance Center, 978-750-8400.
(Circulation. 2001;104:1694-1740.)
© 2001 American Heart Association, Inc.
Circulation is available at http://www.circulationaha.org
1694

---

Fletcher et al
Exercise Standards for Testing and Training
1695
systolic blood pressure, mean arterial pressure, and pulse
TABLE 1.
Normal Values of Maximal Oxygen Uptake at
pressure usually increase. Diastolic blood pressure may
Different Ages
remain unchanged or decrease to a minimal degree. The
Age, y
Men
Women
pulmonary vascular bed can accommodate as much as a
20 –29
6-fold increase in cardiac output without a significant in-
mL kg 1 min 1
43 7.2
36 6.9
crease in pulmonary artery pressure. In normal subjects, this
is not a limiting determinant of peak exercise capacity.
METs
12
10
Cardiac output can increase as much as 4- to 6-fold above
30–39
basal levels during strenuous exertion in the upright position,
mL kg 1 min 1
42 7.0
34 6.2
depending on genetic endowment and level of training. In the
METs
12
10
postexercise phase, hemodynamics return to baseline within
40–49
minutes of termination. Vagal reactivation is an important
mL kg 1 min 1
40 7.2
32 6.2
cardiac deceleration mechanism after exercise; it is acceler-
METs
11
9
ated in well-trained athletes but may be blunted in decondi-
50–59
tioned and/or “medically ill” patients.
mL kg 1 min 1
36 7.1
29 5.4
Maximum Oxygen Uptake
METs
10
8
Oxygen uptake quickly increases when dynamic exercise is
60–69
begun or increased. During staged exercise testing, oxygen
mL kg 1 min 1
33 7.3
27 4.7
uptake usually remains relatively stable (steady state) after
METs
9
8
the second minute of each intensity of exercise below the
70–79
ventilatory threshold. Maximal oxygen consumption (V
˙ O2 max)
mL kg 1 min 1
29 7.3
27 5.8
is the greatest amount of oxygen a person can take in from
METs
8
8
inspired air while performing dynamic exercise involving a
large part of total muscle mass.6 It is considered the best
Values are expressed as mean SD. MET indicates metabolic equivalent or
3.5 mL O
measure of cardiovascular fitness and exercise capacity. V
˙ O
2
kg 1 min 1.
2 max
represents the amount of oxygen transported and used in
cellular metabolism. It is convenient to express oxygen
Heredity
There is a natural variation in V
˙ O
uptake in multiples of sitting/resting requirements. One met-
2 max that is related to genetic
factors.8,9
abolic equivalent (MET) is a unit of sitting/resting oxygen
uptake ( 3.5 mL of O2 per kilogram of body weight per
Cardiovascular Clinical Status
minute [mL · kg 1 · min 1]). V
˙ O2 max is influenced by age, sex,
V
˙ O2 max is affected by the degree of impairment caused by
exercise habits, heredity, and cardiovascular clinical status.
disease. It is difficult to accurately predict V
˙ O2 max from its
The ventilatory threshold is another measure of relative work
relation to exercise habits and age because of considerable
effort, and it represents the point at which ventilation abruptly
scatter and correlations that are generally low. Table 1 depicts
increases, despite linear increases in oxygen uptake and work
normal values for age. The nomogram shown in Figure 1
rate. In most cases, the ventilatory threshold is highly
expresses the concept of maximal METs predicted from peak
reproducible, although it may not be achieved or readily
treadmill workload by reflecting it in terms of that expected
identified in some patients, particularly those with very poor
for age in men, with 100% being normal.10
exercise capacity.7
V
˙ O2 max is equal to the product of maximum cardiac output
and maximum arteriovenous oxygen difference. Because
Age
cardiac output is equal to the product of stroke volume and
Maximum values of V
˙ O2 max occur between the ages of 15 and
heart rate and because stroke volume only increases to a
30 years and decrease progressively with age. At 60 years,
certain level, V
˙ O2 is directly related to heart rate. The
mean V
˙ O2 max in men is approximately two-thirds of that at 20
maximum arteriovenous V
˙ O2 difference (which increases with
years. The decline in V
˙ O2 max averages 8% to 10% per decade
exercise) during exercise has a physiological limit of 15% to
in both sedentary and athletic populations.6
17% volume; hence, if maximum effort is achieved, V
˙ O2 max
Sex
can be used to estimate maximum cardiac output.
A lower V
˙ O2 max in women is attributed to their smaller muscle
mass, lower hemoglobin and blood volume, and smaller
Myocardial Oxygen Uptake
Myocardial oxygen uptake is primarily determined by in-
stroke volume compared with men.
tramyocardial wall stress (ie, the product of left ventricular
Exercise Habits
[LV] pressure and volume, divided by LV wall thickness),
Physical activity has an important influence on V
˙ O2 max. After
contractility, and heart rate. Other, less important factors
3 weeks of bed rest, there is a 25% decrease in V
˙ O2 max in
include external work performed by the heart, the energy
healthy men. In moderately active young men, V
˙ O2 max is 12
necessary for activation, and the basal metabolism of the
METs, whereas individuals performing aerobic training such
myocardium.
as distance running can have a V
˙ O2 max as high as 18 to 24
Accurate measurement of myocardial oxygen uptake re-
METs (60 to 85 mL · kg 1 · min 1).
quires cardiac catheterization to obtain coronary arterial and

---

1696
Circulation
October 2, 2001
physical conditions, state of health, blood volume, sinus node
function, medications, and environment.
Arterial Blood Pressure Response
Systolic blood pressure rises with increasing dynamic work
as a result of increasing cardiac output, whereas diastolic
pressure usually remains about the same or moderately lower,
and it may be heard to zero in some normal subjects. Normal
values of maximum systolic blood pressure for men have
been defined and are directly related to age.
After maximum exercise, there is usually a decline in
systolic blood pressure, which normally reaches resting levels
within 6 minutes and often remains lower than pre-exercise
levels for several hours. When exercise is terminated
abruptly, some healthy persons have precipitous drops in
systolic blood pressure due to venous pooling and a delayed
immediate postexercise increase in systemic vascular resis-
tance to match the reduction in cardiac output. Figure 2 shows
the physiological response to submaximal and maximum
treadmill exercise on the basis of tests of
700 apparently
healthy men aged 25 to 54 years. Maximum rate-pressure
Figure 1. Nomogram based on age, METs, and activity status
product (heart rate systolic blood pressure) ranges from a
(sedentary vs active) that provides a percent of age-expected
exercise capacity in men. For example, a 60-year-old man with
tenth percentile value of 25 000 to a 90th percentile value of
a 3-MET capacity has 40% of the age-expected exercise
40 000.
capacity for sedentary men and 30% of that for active men.
Testing Procedures
venous oxygen content. Myocardial oxygen uptake can be
estimated during clinical exercise testing by the product of
Subject Preparation
Preparations for exercise testing include the following.
heart rate and systolic blood pressure, which is called the
double product or rate-pressure product. There is a linear
● The subject should be instructed not to eat or smoke for 3
relation between myocardial oxygen uptake and coronary
hours before the test. Water may be taken as needed at any
blood flow. During exercise, coronary blood flow increases
time. Subjects should dress appropriately for exercise,
as much as 5-fold above the resting value. A subject with
especially with regard to footwear. No unusual physical
obstructive coronary artery disease (CAD) often cannot
efforts should be performed for at least 12 hours before
maintain adequate coronary blood flow to the affected region
testing.
and supply the metabolic demands of the myocardium during
● When exercise testing is performed for diagnostic pur-
exercise; consequently, myocardial ischemia occurs. Myocar-
poses, withdrawal of medications may be considered be-
dial ischemia usually occurs at the same rate-pressure product
cause some drugs (especially
-blockers) attenuate the
rather than at the same external workload (eg, exercise test
exercise responses and limit the test interpretation. There
stage).
are no formal guidelines for tapering medications, but
rebound phenomena may occur with abrupt discontinuation
Heart Rate Response
of
-blockers in patients with a recent acute coronary
The immediate response of the cardiovascular system to
syndrome. However, most subjects are tested while taking
exercise is an increase in heart rate due to a decrease in vagal
their usual medications. Specific questioning is important
tone. This increase is followed by an increase in sympathetic
to determine which drugs have been taken so that the
outflow to the heart and systemic blood vessels. During
physician can be aware of possible electrolyte abnormali-
dynamic exercise, heart rate increases linearly with workload
ties and hemodynamic effects of cardioactive drugs.
and V
˙ O2. Heart rate will reach a steady state within minutes
● A brief history and physical examination should be per-
during low levels of exercise and at a constant work rate. As
formed to rule out contraindications (Table 2) to testing or
workload increases, the time necessary for the heart rate to
to detect important clinical signs such as a cardiac murmur,
stabilize will progressively lengthen.
gallop sounds, pulmonary “wheezing,” or rales. Subjects
The heart rate response to exercise is influenced by several
with a history of worsening unstable angina or decompen-
factors. There is a decline in mean maximum heart rate with
sated heart failure should not undergo exercise testing until
age11 that seems to be related to neural influences. Dynamic
their condition stabilizes. A cardiac physical examination
exercise increases heart rate more than isometric or resistance
should indicate which subjects have valvular or congenital
exercise. An accelerated heart rate response to standardized
heart disease. Because hemodynamic responses to exercise
workloads is observed after prolonged bed rest, indicating a
may be abnormal in such subjects, such subjects always
deconditioning response. Other factors that influence heart
warrant careful monitoring and, at times, may require early
rate include body position, type of dynamic exercise, certain
termination of testing. Special considerations should be

---

Fletcher et al
Exercise Standards for Testing and Training
1697
Figure 2. Normal response to progressive tread-
mill exercise in healthy subjects. bpm indicates
beats per minute. Reprinted with permission from
Froelicher VF. Exercise and the Heart: Clinical
Concepts. Chicago, Ill: Yearbook Medical Publish-
ers, Inc; 1987:102.
made for those with elevated blood pressure and aortic
● A resting standard 12-lead electrocardiogram (ECG)
stenosis.
should be obtained because it may differ from the resting
● If the indication for the testing is not clear, the subject
pre-exercise ECG. The “torso” ECG distorts the standard
should be questioned and the referring physician contacted.
ECG by shifting the axis to the right, increasing voltage in
the inferior lead group. This may cause a disappearance of
Q waves in a patient with a documented previous Q-wave
TABLE 2.
Absolute and Relative Contraindications to
inferior myocardial infarction (MI).
Exercise Testing
● Standing ECG and blood pressure should be recorded (in
Absolute
the sitting position with cycle ergometry) to determine
● Acute MI (within 2 days)
vasoregulatory abnormalities and positional changes, espe-
● High-risk unstable angina
cially ST-segment depression.
● Uncontrolled cardiac arrhythmias causing symptoms of hemodynamic
● A detailed explanation of the testing procedure should be
compromise
given that outlines risks and possible complications. The
● Active endocarditis
subject should be instructed on how to perform the test, and
● Symptomatic severe aortic stenosis
these instructions should include a demonstration. If mus-
● Decompensated symptomatic heart failure
culoskeletal or certain orthopedic limitations are a concern,
● Acute pulmonary embolus or pulmonary infarction
the testing protocol should be modified.
● Acute noncardiac disorder that may affect exercise performance or be
aggravated by exercise (eg, infection, renal failure, thyrotoxicosis)
Electrocardiographic Recording
● Acute myocarditis or pericarditis
Skin Preparation
● Physical disability that would preclude safe and adequate test
The most critical point of the electrode-amplifier recording
performance
system is the interface between electrode and skin. Removal
● Inability to obtain consent
of the superficial layer of skin significantly lowers its
Relative*
resistance, thus decreasing the signal-to-noise ratio. The areas
● Left main coronary stenosis or its equivalent
for electrode application are first shaved and then rubbed with
● Moderate stenotic valvular heart disease
alcohol-saturated gauze. After the skin dries, it is marked
with a felt-tipped pen and rubbed with a fine sandpaper or
● Electrolyte abnormalities
rough material. With these procedures, skin resistance should
● Tachyarrhythmias or bradyarrhythmias
be reduced to 5000
or less.
● Atrial fibrillation with uncontrolled ventricular rate
● Hypertrophic cardiomyopathy
Electrodes and Cables
● Mental impairment leading to inability to cooperate
Many electrodes are available for performing exercise testing.
● High-degree AV block
Silver plate or silver chloride crystal pellets are preferred
*Relative contraindications can be superseded if benefits outweigh risks of
because they have the lowest offset voltage. Care should be
exercise.
taken to assure that the electrode gel is moist.

---

1698
Circulation
October 2, 2001
Figure 3. Placement of 12-lead ECG
electrodes. RA indicates right arm; LA,
left arm; RL, right leg; and LL,
left leg.
Connecting cables between the electrodes and recorder
to generate average waveforms and make ECG measure-
should be light, flexible, and properly shielded. Most avail-
ments. The physician must compare the raw analog data with
able commercial exercise cables are constructed to lessen
computer-generated output to validate its accuracy. Computer
motion artifact. Cables generally have a life span of
1 year.
processing is not completely reliable because of software
They eventually become a source of both electrical interfer-
limitations in handling noise and inadequacy of the available
ence and discontinuity and must be replaced.
algorithms.
Multiple Leads
Equipment and Protocols
Because a high-quality standard 12-lead ECG with electrodes
For details regarding exercise testing equipment and exercise
placed on the limbs cannot be obtained during exercise, other
testing laboratories, the reader should refer to the AHA’s
electrode placements have been used. Electrode placement
“Guidelines for Clinical Exercise Testing Laboratories.”12
affects ST segment slope and amplitude. Various placements
Figure 4 illustrates the relation of METs to stages in the
do not result in comparable waveforms for analysis. For
various testing protocols. The treadmill and cycle ergometer
comparison with the standard resting 12-lead recording, arm
are now the most commonly used dynamic exercise testing
and leg electrodes should be moved to the wrists and ankles,
devices.
with the subject in the supine position. Differences can be
minimized by placing the arm electrodes as close to the
Cycle
shoulders as possible, placing the leg electrodes below the
Electrically braked cycles vary the resistance to the pedaling
umbilicus, and recording the resting ECG with the subject
speed (rate-independent ergometers), thereby permitting bet-
supine (Figure 3). Any modification of lead placement should
ter power output control, because it is common for subjects
be recorded on the tracing.
who are fatigued or unable to cooperate to decrease their
pedaling speed. The highest values of V
˙ O2 and heart rate are
Relative Sensitivity of Leads
obtained with pedaling speeds of 50 to 80 rpm. Cycles are
The lateral precordial leads (V4 through V6) are capable of
calibrated in kiloponds (kp) or watts (W); 1 W is equivalent
detecting 90% of all ST depression observed in multiple lead
to
6 kp-meters per minute (kpm/min). Because exercise on
systems. ST elevation (over non–Q-wave areas) is a rare but
a cycle ergometer is non–weight-bearing, kiloponds or watts
critical change due to transmural ischemia that occurs as
can be converted to oxygen uptake in milliliters per minute.
frequently in lead V2 and aVF as in V5.
METs are obtained by dividing V
˙ O2 in milliliters per minute
Recorders
by the product of body weight (in kg) 3.5. The number 3.5
There are many good recorders designed to capture high-
is the accepted value assigned to oxygen uptake while at rest
quality ECG data during exercise. Many use microprocessors
and is expressed as milliliters of O2 per kilogram of body

---

Fletcher et al
Exercise Standards for Testing and Training
1699
Figure 4. Relation of METs to stages in the various testing protocols. Functional class refers to New York Heart Association class; kpm
indicates kilopond-meters; MPH, miles per hour; and %GR, percent grade.
weight per minute. Figure 4 demonstrates the MET levels at
increasing loads and an adequate time interval in each level,
given work rates (kpm/min) of a cycle protocol for a 70-kg
and a recovery period. For cycle ergometry, the initial power
person.
output is usually 10 or 25 W (150 kpm/min), usually followed
The cycle ergometer is usually less expensive, occupies
by increases of 25 W every 2 or 3 minutes until end points are
less space, and is less noisy than a treadmill. Upper body
reached. If arm ergometry is substituted for cycle ergometry,
motion is usually reduced, making it easier to obtain blood
a similar protocol may be used, except that initial power
pressure measurements and to record the ECG. Care must be
output and incremental increases are lower. Two-minute
taken to prevent isometric or resistance exercise of the arms
stages are most popular with arm ergometry.13,14
while grasping the handlebars.
Several different treadmill protocols are in use and are
A major limitation to cycle ergometer testing is the
defined in Figure 4 according to treadmill speed, grade, stage
discomfort and fatigue of the quadriceps muscles. Leg fatigue
duration, and estimated METs. The advantages of the Bruce
in an inexperienced subject may cause him or her to stop
protocol are its use in many published studies and the value
before reaching a true V
˙ O2 max. Thus, V˙O2 max is 10% to 15%
of 3-minute stages to acquire submaximal data. Its disadvan-
lower in cycle versus treadmill testing in those not accus-
tages are large interstage increments in work that can make
tomed to cycling.
estimation of V
˙ O2 max less accurate and a fourth stage that can
Treadmill
be either run or walked, resulting in different oxygen costs.
The treadmill should have front and/or side rails to aid in
Some subjects are forced to stop exercising prematurely
subject stability. However, subjects should be encouraged not
because of musculoskeletal discomfort or an inability to
to tightly grasp the front or side rails because this action
tolerate the high workload increments. Initial zero or one-half
supports body weight and thus reduces the workload at any
stages (1.7 miles/hour at 0% and 5% grades) can be used for
given stage. It may be helpful if subjects remove their hands
subjects with compromised exercise capacities. The optimum
from the rails, close their fists, and place one finger on the
protocol for any test should last 6 to 12 minutes and should be
rails to maintain balance after they are accustomed to walking
adjusted to the subject’s needs.
on the treadmill. The treadmill should have both variable
Ramp protocols start the subject at a relatively low tread-
speed and grade capability and must be accurately calibrated.
mill speed, which is gradually increased until the patient has
Protocols
a good stride. The ramp angle of incline is progressively
Protocols for clinical exercise testing include an initial
increased at fixed intervals (ie, 10 to 60 seconds) starting at 0
warm-up (low load), progressive uninterrupted exercise with
grade, with the increase in grade calculated on the patient’s

---

1700
Circulation
October 2, 2001
estimated functional capacity such that the protocol will be
TABLE 3.
Complications Secondary to Exercise Tests
completed in 6 to 12 minutes. In this type of protocol, the rate
Cardiac
of work increases continuously, and steady states are not
● Bradyarrhythmias
reached. A limitation of ramp protocols is the requirement to
● Tachyarrhythmias
estimate functional capacity from an activity scale and adjust
the ramp accordingly. Occasionally underestimation or over-
● Acute coronary syndromes
estimation of functional capacity will result in an endurance
● Heart failure
test or in premature exercise termination. Exercise protocols
● Hypotension, syncope, and shock
should be individualized according to the type of subject
● Death
being tested. A 9-minute targeted ramp protocol that in-
Noncardiac
creases in small steps has many advantages, including more
● Musculoskeletal trauma
accurate estimates of MET level.15
● Soft-tissue injury
The 6-minute walk test is a functional test that can be used
Miscellaneous
to evaluate exercise capacity in patients with marked LV
● Severe fatigue (malaise), sometimes persisting for days; dizziness;
dysfunction or peripheral arterial occlusive disease who
fainting; body aches; delayed feelings of illness
cannot perform cycle ergometer or treadmill exercise. Pa-
tients are instructed to walk down a 100-foot corridor at their
own pace, attempting to cover as much ground as possible in
6 minutes. At the end of the 6-minute interval, the total
Exercise testing should be performed under the supervision
distance walked is determined and the symptoms experienced
of a physician who is appropriately trained to administer
by the patient are recorded. This type of protocol uses a
exercise tests. The physician should be responsible for
submaximal level of stress and thus correlates only modestly
ensuring that the exercise laboratory is properly equipped and
with V
˙
that exercise testing personnel are appropriately trained. The
O2 max.16 ECG monitoring is not routinely done with this
testing, thus limiting its diagnostic accuracy.
degree of subject supervision needed during a test can be
determined by the clinical status of the subject being tested.
Exercise Test Supervision and Interpretation
This determination is made by the physician or physician’s
Exercise testing should be conducted only by well-trained
designated staff member, who asks pertinent questions about
personnel with a sufficient knowledge of exercise physiology.
the subject’s medical history, performs a brief physical
Only technicians, physiologists, nurses, and physicians famil-
examination, and reviews the standard 12-lead ECG per-
iar with normal and abnormal responses during exercise can
formed immediately before testing. The physician should
recognize or prevent adverse events. Equipment, medications,
interpret data derived from testing and suggest further eval-
and personnel trained to provide advanced cardiopulmonary
uation or therapy. The physician or senior medical profes-
resuscitation (CPR) must be readily available. For details
sional conducting the test must be trained in advanced CPR.
regarding supervision and interpretation of exercise tests, the
A defibrillator and appropriate medications should also be
reader should refer to the ACC/AHA/American College of
immediately available.
Physicians’ “Clinical Competence Statement on Stress
The degree of supervision can be assigned to a properly
Testing.”17
trained nonphysician (ie, a nurse, physician assistant, or
Although exercise testing is considered a safe procedure,
exercise physiologist or specialist) for testing apparently
there are reports of acute MIs and deaths. Multiple surveys
healthy younger persons ( 40 years of age) and those with
confirm that as many as 10 MIs or deaths or both may be
stable chest pain syndromes. A physician should be immedi-
expected per 10 000 tests in those with CAD.18 Risk is greater
ately available during all exercise tests.
in the post-MI subject and in those being evaluated for
malignant ventricular arrhythmias. A review summarizing 8
Perceived Exertion
studies of estimates of sudden cardiac death during exercise
The subjective rating of the intensity of exertion perceived by
testing revealed rates from 0.0 (4 studies) to 5 per 100 000
the person exercising is generally a sound indicator of relative
tests.18 Table 3 lists 3 classes of complications secondary to
fatigue. Rather than using heart rate alone to clinically
exercise tests.
determine intensity of exercise, the 6 to 20 Borg scale of
Good clinical judgment should be foremost in deciding
perceived exertion19 is useful (Table 4). Special verbal and
indications and contraindications for exercise testing.3 Al-
written explanations about the rating of perceived exertion
though absolute contraindications are definitive, in selected
are available for subjects. Although there is some variation
cases with relative contraindications, even submaximal test-
among subjects in their actual rating of fatigue, they seem to
ing can provide valuable information. Table 2 lists absolute
rate consistently from test to test. Thus, the Borg scale can
and relative contraindications to exercise testing. In any
assist the clinician in judging the degree of fatigue reached
procedure with a risk of complications, the physician should
from one test to another and in correlating the level of fatigue
be certain that the subject understands the risks and benefits
during testing with that experienced during daily activities. In
of the test. Good physician-patient communication about
general, a Borg scale
18 indicates the patient has performed
testing is mandatory, and written informed consent should be
maximal exercise, and values
15 to 16 suggest that the
obtained.
anaerobic threshold has been exceeded.

---

Fletcher et al
Exercise Standards for Testing and Training
1701
TABLE 4.
Borg Scale for Rating Perceived Exertion
● Sustained ventricular tachycardia.
● Technical difficulties monitoring the ECG or systolic
20-Grade Scale
blood pressure.
6
● Subject’s request to stop.
7
Very, very light
8
Relative Indications
9
Very light
● ST or QRS changes such as excessive ST displacement
10
(horizontal or downsloping of
2 mm) or marked axis
11
Fairly light
shift.
12
● Drop in systolic blood pressure
10 mm Hg (persistently
13
Somewhat hard
below baseline). despite an increase in workload, in the
14
absence of other evidence of ischemia.
● Increasing chest pain.
15
Hard
● Fatigue, shortness of breath, wheezing, leg cramps, or
16
claudication.
17
Very hard
● Arrhythmias other than sustained ventricular tachycardia,
18
including multifocal ectopic, ventricular triplets, supraventric-
19
Very, very hard
ular tachycardia, heart block, or bradyarrhythmias.
20
● General appearance (see below).
The rating of perceived exertion scale. Reprinted with permission from
● Hypertensive response (systolic blood pressure
250 mm Hg
Borg.19
and/or diastolic blood pressure
115 mm Hg).
● Development of bundle-branch block that cannot be distin-
Anginal Scale
guished from ventricular tachycardia.
Levels of anginal discomfort in those with known or sus-
Postexercise Period
pected CAD are also excellent subjective end points. Table 5
Some abnormal responses occur only in recovery. If maxi-
details the 1 to 4 scale that is recommended.
mum sensitivity is to be achieved with an exercise test,
subjects should be supine in the postexercise period; how-
Indications for Terminating Exercise Testing
ever, for subject comfort, many health professionals prefer
Absolute Indications
the sitting position. A cool-down walk after the test can delay
or eliminate the appearance of ST-segment depression; how-
● ST-segment elevation ( 1.0 mm) in leads without Q waves
ever, the cool down may be indicated in some subjects,
(other than V1 or aVR).
whereas abrupt cessation of exercise is the norm for exercise
● Drop in systolic blood pressure
10 mm Hg (persistently
ECG studies. Monitoring should continue for 6 to 8 minutes
below baseline), despite an increase in workload, when
after exercise or until blood pressure, heart rate, and ST
accompanied by any other evidence of ischemia.
segments are approximate to baseline values. Approximately
● Moderate-to-severe angina (grade 3 to 4); Table 5 details
85% of subjects with abnormal responses manifest the abnor-
descriptions and grades for angina scale.
mality during exercise or within 5 to 6 minutes of recovery.
● Central nervous system symptoms (eg, ataxia, dizziness, or
An abnormal ECG response occurring only in the recovery
near syncope).
period is not unusual. Mechanical dysfunction and electro-
● Signs of poor perfusion (cyanosis or pallor).
physiological abnormalities in the ischemic ventricle after
exercise can persist for minutes to hours. Monitoring of blood
TABLE 5.
Four-Level Angina Scale for Exercise
pressure should continue during recovery because abnormal
Tolerance Testing*
responses may occur, particularly hypotension.
Description
Level
Interpretation
Onset of angina, mild but recognized as the usual angina-of-effort
1
pain or discomfort with which the subject is familiar
Clinical Responses
Same pain, moderately severe and definitely uncomfortable but
2
Symptoms
still tolerable
Typical anginal symptoms induced by the exercise test are
Severe anginal pain at a level that the subject will wish to stop
3
predictive of CAD and are even more predictive with asso-
exercising
ciated ST-segment depression. It is important to obtain a
Unbearable chest pain; the most severe pain the subject has felt
4
careful description of the discomfort from the subject to
ascertain that it is typical angina rather than nonischemic
*Angina criteria for stopping a symptom-limited exercise test is level 2
angina, approaching level 3. Data in Table are from Allred EN, Bleecker ER,
chest pain.
Chaitman BR, et al. Effects of carbon monoxide on myocardial ischemia.
Subject’s Appearance
Environ Health Perspect. 1991;91:89 –132 and Allred EN, Bleecker ER,
The subject’s general appearance is helpful in the clinical
Chaitman BR, et al. Short-term effects of carbon monoxide exposure on the
exercise performance of subjects with coronary artery disease. N Engl J Med.
assessment. A decrease in skin temperature, cool and light
1989;321:1426 –1432.
perspiration, and peripheral cyanosis during exercise can

---

1702
Circulation
October 2, 2001
indicate poor tissue perfusion due to inadequate cardiac
cardiac complications during exercise testing (for example,
output with secondary vasoconstriction. Such subjects should
serious arrhythmias), seems to be alleviated by coronary
not be encouraged to attempt greater workloads.
artery bypass grafting (CABG), and can occur in subjects
with CAD, valvular heart disease, or cardiomyopathy. Occa-
Physical Examination
sionally, subjects without clinically significant heart disease
Cardiac auscultation immediately after exercise can provide
will exhibit exercise-induced hypotension during exercise
information about ischemia-induced LV dysfunction. Gallop
related to dehydration, antihypertensive therapy, or prolonged
sounds or a precordial bulge can result from LV dysfunction.
strenuous exercise.
A new mitral regurgitant murmur suggests papillary muscle
dysfunction, which may be related to transitory myocardial
Heart Rate During Exercise
ischemia. It is preferable to have subjects lie supine after
Relatively rapid heart rate during submaximal exercise or
exercise testing and allow those who develop orthopnea to sit
recovery could be due to deconditioning, prolonged bed rest,
up. In addition, severe angina or ominous arrhythmias after
anemia, metabolic disorders, or any other condition that
exercise may be lessened by allowing the subject to sit up,
decreases vascular volume or peripheral resistance. This
because ischemia may be decreased due to lower LV wall
finding is relatively frequent soon after MI and CABG.
tension.
Relatively low heart rate at any point during submaximal
exercise could be due to exercise training, enhanced stroke
Exercise Capacity
volume, or drugs. The common use of
-blockers, which
Maximal work capacity in normal individuals is influenced
lower heart rate, limits the interpretation of the heart rate
by familiarization with the exercise test equipment, level of
response to exercise. Conditions that affect the sinus node can
training, and environmental conditions at the time of testing.
attenuate the normal response of heart rate during exercise
In estimating exercise capacity, the amount of work per-
testing. Chronotropic incompetence, which is defined as
formed in METs (or exercise stage achieved) should be the
either failure to achieve 85% of the age-predicted maximal
index measured and not the number of minutes of exercise.
heart rate or a low chronotropic index (heart rate adjusted to
Serial comparison of exercise capacity in individual patients
MET level), is associated with an increased mortality risk in
to assess significant interval change requires a careful exam-
patients with known cardiovascular disease.23
ination of the exercise protocol used during both tests,
cardioactive drug therapy and time of ingestion, systemic
Responses in Subjects With Normal Resting ECGs
blood pressure, and other conditions that might influence test
P Wave
performance. Each of these factors must be considered before
During exercise, P wave magnitude increases significantly in
attributing changes in functional capacity to progression of
inferior leads. There should be no significant changes in P
coronary heart disease or worsening of LV function.
wave duration.
A normal exercise capacity does not exclude severe LV
systolic dysfunction. Mechanisms proposed to explain a
PR Segment
normal work performance in these subjects include increased
The PR segment shortens and slopes downward in the inferior
peripheral oxygen extraction, preservation of stroke volume
leads during exercise. The decreasing slope has been attrib-
and chronotropic reserve, ability to tolerate elevated pulmo-
uted to atrial repolarization (the Ta wave) and can cause
nary wedge pressures without dyspnea, ventricular dilation,
false-positive ST depression in the inferior leads.
and increased levels of plasma norepinephrine at rest and
QRS Complex
during exercise. Many subjects with decreased ejection frac-
The Q wave shows very small changes from the resting
tions at rest can perform relatively normal levels of exercise,
values; however, it does become slightly more negative at
some without side effects, whereas others report increased
maximum exercise. Changes in median R wave amplitude are
fatigue for some time after the test.
noted near maximum effort. A sharp decrease in the R wave
Hemodynamic Responses
is observed in the lateral leads (V5) at maximum exercise and
into the first minute of recovery. In the lateral and vertical
Blood Pressure During Exercise
leads (V5 and aVF), the S wave becomes greater in depth
Blood pressure is dependent on cardiac output and peripheral
(more negative), showing a greater deflection at maximum
resistance. An inadequate rise or a fall in systolic blood
exercise, and then gradually returns to resting values in
pressure during exercise can occur. An inadequate rise in
recovery. As the R wave decreases in amplitude, the S wave
systolic blood pressure ( 20 to 30 mm Hg) or a drop can
increases in depth.
result from aortic outflow obstruction, severe LV dysfunc-
tion, myocardial ischemia, and certain types of drug therapy
J-Junction (J-Point) Depression
(ie, -blockers). In some subjects with CAD, higher levels of
The J junction (QRS end/ST beginning) is depressed in lateral
systolic blood pressure exceeding peak exercise values have
leads to a maximum depression at maximum exercise, then
been observed during the recovery phase.21 In most studies,
gradually returns toward pre-exercise values in recovery.
exercise-induced hypotension in association with other mea-
J-junction depression is more common in older patients.
sures of ischemia predicts a poor prognosis, with a positive
Subjects with resting J-junction elevation (early repolariza-
predictive value of 50% for left main or triple-vessel dis-
tion) may develop an isoelectric J junction with exercise; this
ease.22 Exercise-induced hypotension is also associated with
is a normal finding. The normal ST segment vector response

---

Fletcher et al
Exercise Standards for Testing and Training
1703
Figure 5. ST deviation assessment.
both to tachycardia and exercise is a shift rightward and
ischemic segments, the extent of the ischemic zone, previous
upward.
areas of myocardial necrosis, and location of the recording
electrodes (Figure 5). The standard criterion for this abnormal
T Wave
response is horizontal or downsloping ST segment depression
A gradual decrease in T wave amplitude is observed in all
of
0.10 mV (1 mm) for 80 ms. However, as shown in Figure
leads during early exercise. At maximum exercise, the T
5, other criteria have been considered. Downsloping ST
wave begins to increase, and at 1 minute into recovery, the
segment depression is a more specific change than horizontal
amplitude is equivalent to resting values in the lateral leads.
or upsloping depression. In the presence of marked baseline
U Wave
abnormalities, exercise-induced ST segment depression is
No significant changes are noted with exercise; however, U
less specific for myocardial ischemia. Other factors related to
waves may be difficult to identify at ventricular rates
130
the probability and severity of CAD include the degree, time
beats/min because of the close approximation of the T and P
of appearance, duration, and number of leads with ST
waves with the increased heart rate of exercise.
segment depression.
Severity of CAD is also related to the time of appearance
Abnormal Responses
of ischemic ST segment shifts. The lower the workload and
rate-pressure product at which it occurs, the worse the
ST Segment Changes
The ST level is measured relative to the P-Q junction because
prognosis and the more likely the presence of multivessel
the U-P segment during exercise is difficult to measure.
disease. The duration of ST depression in the recovery phase
Ideally, 3 consecutive beats in the same lead with a stable
is also related to the severity of CAD.
baseline should be identified and the average displacement
ST Segment Elevation
determined. The 3 key measurements are identification of the
Exercise-induced elevation may occur in an infarct territory
P-Q junction (isoelectric line), the J point (ie, J junction, QRS
where Q waves are present or in a noninfarct territory. The
end, and ST segment beginning), and 60 or 80 ms after the J
development of
0.10 mV of J-point elevation that is
point. At ventricular rates
130 beats/min, 60 ms after the J
persistently elevated ( 0.10 mV) at 60 ms after the J point in
junction is optimal to determine the extent of ST segment
3 consecutive beats with a stable baseline is considered an
displacement in patients with an upsloping ST segment slope.
abnormal response.
When the J point relative to the P-Q junction is depressed at
baseline, the net difference from the J junction determines the
ST Segment Elevation in Post-MI Patients With Q Waves
Prior MI is the most frequent cause of ST-segment elevation
magnitude of exercise-induced displacement. When the J
during exercise and seems to be related to the presence of
junction is elevated at rest (early repolarization) and progres-
severe hypokinetic or akinetic LV segmental wall motion.
sively becomes more depressed during exercise, the magni-
Approximately 30% of subjects with anterior MI and 15% of
tude of ST-segment displacement is determined from the P-Q
subjects with inferior MI tested early after MI demonstrate
junction and not from the resting elevated J junction.
exercise-induced ST segment elevation in Q-wave leads. The
Exercise-induced myocardial ischemia can result in 1 of the
changes may result in reciprocal ST-segment depression that
following 3 ST segment manifestations on the surface ECG:
simulates myocardial ischemia in other leads. However,
depression, elevation, or normalization (Figure 5).
ST-segment elevation and depression in the same test may
ST Segment Depression
indicate multivessel CAD. Myocardial imaging techniques
ST segment depression is the most common manifestation of
will help distinguish the concomitant presence of a new
exercise-induced myocardial ischemia. The ST segment de-
myocardial ischemic zone from reciprocal changes induced
pression represents electrical gradients caused by myocardial
by ST-segment elevation in Q-wave leads.

---