The Fitness Stress Test
Author: Brian D. Johnston
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It is recommended that adults over the age 35, who never
have exercised before, obtain medical clearance. This is
necessary for the protection of the individual’s health and
from any fitness professional’s legal perspective. Also, the
questionnaire consent/waiver form in Appendix A should be
completed for further legal protection and for the medical
doctor's perusal.
VALUE OF A STRESS TEST
A stress test should be completed by all mature adults and
individuals age 35 or older who are sedentary. Individuals
who possess one or several coronary risk factors, such as
high HDLs, a smoker, high BP, or if the individual has not
seen a physician within the last 5 years should undertake a
stress test.
A stress test becomes even more crucial for those over 65
as it is difficult to determine the over 65's tolerance for
activity. It also is necessary to determine presence or
absence of myocardial ischemia (a temporary deficiency of
blood supply to the heart caused by an obstruction), either
prior to an exercise program, while in relatively good health,
or as a post-coronary test to indicate damage levels and a
therapeutic program. A stress test is not a substitute for
complete history and yearly physical examinations, but it is a
viable test that can pick up on problems that would preclude
a person's participation in an exercise program or indicate
required modification of a program in accordance with
physical problems.
Fitness professionals or physicians should explain in
advance to the individual to be tested what is involved. This
helps to increase motivation and for the individual to
exercise for longer and with less anxiety. The individual will
need to:
-Wear proper clothing (tracksuit) and comfortable running or
walking shoes.
-Refrain from eating for 2-3 hours prior to the test, so that
digestion does not interfere with optimal blood flow.
-Refrain from smoking for at least 1-2 hours, since smoking
can impair cardiovascular capacity.
WHAT OCCURS
The stress test conducted by the physician can be
performed with a motorized treadmill, bicycle or arm
ergometer. Often if the individual suffers from lower body
maladies, or if a return to work after an illness involves
strenuous upper body activity, the arm ergometer may be
used to produce a more accurate test.
The stress test is designed to challenge the body to a safe
but necessary level to reveal irregularities that are unlikely to
show when at rest. Usually an undiagnosed heart disease
appears only during vigorous exercise. The narrowed
coronary arteries may supply enough blood to the resting
individual, but, as oxygen needs rise, electrocardiographic
abnormalities indicate a problem. The physician will look
for evidence of ischemia and its effects in rhythm
disturbances (tachyarrhythmias or bradyarrhythmias), aortic
and mitral valve disease, significant hypertension, and
myocardial disease.
The stress test usually will not take more than 10 minutes.
Exercise for longer will measure endurance rather than
aerobic capacity (VO2max). During any physical activity, the
body responds as follows:
-Heart rate increases
-Systolic BP increases
-Diastolic BP remains the same or decreases
-Cardiac output increases
-Systemic vascular resistance decreases
-Coronary blood flow increases
-Myocardial O2 demand increases
The client is tested at 85-90% of predicted maximal heart
rate, although some doctors do not advance the test this far
as they feel it is unnecessary to do so – usually as a safety
precaution. Doctors even may stop the test once the client
reaches his or her target heart rate. There is one serious
drawback to this approach. There is variability in maximal
heart rate of individuals within each specific age group. For
example, the predicted heart rate of a 60-year old at 85%
maximum heart rate is approximately 132 bpm. Because
there is a standard deviation, some individuals being in
better health and others in worse health for any age group,
or at least less tolerant to exercise strain, it is possible that
some people may have a maximal heart rate well above or
below 132 bpm. If an individual's heart rate is above or
below the age-specific level, the result will be unreliable in
that it is difficult to determine the safety or severity of the test.
The strain may not be enough, or too much. Therefore, it is
necessary for the physician to motivate the client safely to
his or her limits to determine the proposed intensity of the
exercise program, and for the client, or the client’s personal
trainer, to know at what level the body was stressed
sufficiently.
VO2max is another important consideration of the stress
test and this correlates well with physical fitness at least in
a cardiorespiratory and cardiovascular sense. The amount
of oxygen consumed by the myocardium is dependent on
oxygen demand: heart rate, contractility, and wall tension.
The individual will exercise until the oxygen demand by the
myocardial cells exceeds the ability of the stenotic coronary
artery to deliver oxygen. In other words, exercise continues
until the coronary reserve has been exhausted. At this point,
ischemia is induced and exercise must be terminated.
During the exercise test, if the individual experiences
pectoral angina, intense dyspnea or unusual changes on
the electrocardiogram, or significant rhythm change due to a
heart block or ventricular disturbance, an unsupervised
exercise program may be contraindicated.
The test may be stopped for reasons other than reaching a
VO2max upper threshold or having chest discomfort;
fatigue, dyspnea, and musculoskeletal problems may
cause the mature adult to discontinue exercise. The test
also will be terminated if the blood pressure drops as the
work increases. Blood pressure is recorded before the test,
at an exercise peak, and at recovery. Diastolic BP should
remain constant, but could increase slightly because of
anxiety. It then could decrease once the test begins.
Systolic BP usually increases by 60+/-25 mm Hg in males
50-64 years of age, and by 40+/-20 mm Hg in women in the
same age group. For example, if the systolic BP fails to
increase, or initially increases then drops by more than 20
mm Hg during exercise, then it may indicate severe left
ventricular dysfunction. Should the systolic blood pressure
fall more than 30mm Hg, then an unsupervised exercise
program may be contraindicated.
Sometimes the stress test shows heart complications
when, in fact, extrinsic factors are responsible, and this will
cause a false-positive result. These include:
-Hypertension
-Fasting
-Drug use (e.g., antidepressants) - the physician will take
into account the effects of any medication the individual may
be taking
-Malfunctioning ECG recording equipment
-And a host of other minor heart complications that should
not stop an individual from participating in an exercise
program.
It will be up to the physician to remove the causative agent
and re-test the patient. This especially is necessary to
discover if the patient is asymptomatic or has the potential
for a high exercise capacity. A false-negative test resulting
from an extrinsic factor is even more disturbing as this
would indicate failure to diagnose the presence of abnormal
coronary arteries. It then is up to the physician to rely on
other test procedures and for the individual or the fitness
professional to monitor progress carefully and to supply the
physician with any information in regard to physical difficulty
during exercise.
If the test is performed properly, and there is a negative ECG
response to exercise, the test does not indicate coronary
disease necessarily. Rather, it implies a risk factor that
must be taken into consideration when an exercise program
is created, and that there must be close monitoring of the
individual’s health and fitness level.
CONTRAINDICATIONS FOR A STRESS TEST
-Acute myocardial infarction (heart attack)
-Uncontrolled congestive heart failure
-Acute inflammatory cardiac disease, e.g., active rheumatic
heart disease, myocarditis
-Acute asthma or pneumonia
-Blood pressure greater than 240/120 mm Hg and
uncontrolled
-Acute renal (kidney) disease
Brian D. Johnston is the Director of Education and President of the I.A.R.T. fitness certification and education institute. He has written over 12 books and is a contributing author to the Merck Medical Manual. An international lecturer, Mr. Johnston wears many hats in the fitness and health industries, and can be reached at info@ExerciseCertification.com. Visit his site at www.ExerciseCertification.com for more free articles.