05.08.08
The Fitness Stress Test
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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
