Exercise stress testing
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EXERCISE STRESS TESTING
INTRODUCTION
► physical exercise:
- creates a functional overload of the organism which leads to a change in the
homeostasis of the organism in order to cover increased metabolic needs of the
working muscles
- most important systems affected: cardiovascular system and respiratory
system
- it is an activity that enhances or maintains physical fitness and overall health;
it is performed for strengthening muscles and the cardiovascular system, acquiring
athletic skills, weight loss or maintenance and for enjoyment
► exercise stress testing:
- even a low intensity physical activity will increase heavily the metabolic
demand of the organism
- by creating a functional overload of the cardiovascular and respiratory
systems one can show disorders that are hidden while resting
EVALUATING PHYSICAL STRESS CAPACITY
► best estimate is made by measuring oxygen consumption:
- might be measured using close circuit respiratory systems, but this is not
easily realized
- in everyday practice it is estimated by charts and nomograms
► metabolic equivalent:
- expresses the energy cost of physical activities as multiples of Resting
Metabolic Rate (RMR)
- by convention 1 MET is considered as the resting metabolic rate (RMR)
obtained during quiet sitting
- estimated: 1 MET = 3.5 ml O2 / kgbw / min
- MET values of physical activities range from 0.9 (sleeping) to 18 (running at
18 km/h)
Table no. 2. Average MET values during different physical activities.
Physical Activity
Light Intensity Activities
Sleeping
watching television
writing, desk work, typing
walking, less than 2.0 mph (3.2 km/h), level ground, strolling, very slow
Moderate Intensity Activities
bicycling, stationary, 50 watts, very light effort
bicycling, <10 mph (16 km/h), leisure, to work or for pleasure
bicycling, stationary, 100 watts, light effort
Vigorous Intensity Activities
jogging, general
calisthenics (e.g. pushups, sit-ups, pull-ups, jumping jacks)
running jogging, in place
MET
<3
0.9
1
1.8
2
3 to 6
3
4
5.5
>6
7
8
8
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► maximum oxygen consumption (VO2max):
- depends (even in healthy individuals) on the adaptation capacity of the
cardiovascular and respiratory systems to effort
- in healthy persons achieved at reaching the upper limit of cardiac minute
volume
- calculated using nomograms (modified Astrand-Ryhming nomogram)
- expressed as MET or ml O2 / kgbw / min
- must be compared with theoretical value:
VO2 max  45.8  (0.17  age)
► functional aerobic deficit (FAD) refers to the difference of calculated (real-time)
maximum oxygen consumption compared to theoretical maximum oxygen
consumption
- FAD between 0 - 25%: no reduction of effort capacity
- FAD between 25 - 50%: minor reduction of effort capacity
- FAD between 50 - 75%: moderate reduction of effort capacity
- FAD over 75%: major reduction of effort capacity
FAD =
VO 2 max theoretical - VO 2 max calculated
x 100
VO 2 max theoretical
CLASSIFICATION OF EXERCISE STRESS TESTING
► by effort intensity:
- maximal: testing done until maximum oxygen consumption is reached
- sub-maximal: testing done until 80-90% of maximum oxygen consumption is
reached
► by type of effort:
- rectangular - it uses the same level of effort throughout a determined period
of time. It does not lead to the same cardiovascular changes among subjects with
different effort capacities – those with poor physical condition might be overloaded,
those with excellent physical condition might be insufficiently tested.
- in steps - refers to a progressive increase of effort intensity, up to a target
level set by the effort capacity of the subject
Figure no. 91. Classification of exercise stress testing by type of effort.
Exercise stress testing
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HARVARD STEP TEST
It is a maximal test developed to test the athlete's cardiovascular system or to monitor its
development. It is based on measurement of the heart rate during recovery after an effort
► Method: subject steps up and down the gym steps with a rate of 30/min during 5
minutes. If subject cannot go on at this rate for 5 minutes, time duration is noted and
taken into account at reading of the result. Immediately after finishing the effort, pulse
rate is measured in 3 periods of 30 seconds:
- first 30 seconds, 0” – 30” - P1
- second 30 seconds, 1’00” – 1’30” - P2
- third 30 seconds, 2’00” – 2’30” - P3
Stop immediately if subject complains of chest pain, (occipital) headache, or
faintness during the exercise stress test!
► For calculating the result, the following formula is used:
Aptitude  index 
Time(sec)  100
( P1  P 2  P3)  2
► Interpret aptitude-index after the following data table:
- under 55 = poor physical condition
- between 55 – 79 = average physical condition
- between 80 – 89 = good physical condition
- over 90 = excellent physical condition
ASTRAND 6 MINUTE CYCLE TEST
It is a maximal test to determine indirectly the maximum oxygen consumption. Thus it helps
to assess maximum capacity of cardiovascular and respiratory systems.
► Method: subject undertakes a quantified effort (expressed in watts) that increases
the heart rate above 120/min. Subject pedals on the cycloergometer at 45rpm for 6
minutes at the chosen loading (120W/s for males and 100W/s for females).
Immediately after finishing, pulse rate is measured during the first 10 seconds
(subject is in standing position). Result is multiplied by 6 (calculated for one minute).
Test is inconclusive if subject cannot finish or does not achieve established heart rate.
Stop immediately if subject complains of chest pain, (occipital) headache, or
faintness during the exercise stress test!
Maximum oxygen consumption (VO2max) is read from Astrand nomogram
(expressed in liters/min, Figure no. 94). It is reported to the ideal weight calculated by
Lorentz’s formula:
Weight  Height (cm)  100 
Height  150
4
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Then maximum aerobic capacity (ml/min/kg) calculated:
MAC 
VO2 max
Weight
Using the following tables (Table no. 3 and Table no. 4), effort capacity is evaluated in
function of maximum oxygen consumption, gender and age.
Table no. 3. MAC for males.
AGE
(years)
20 - 29
30 - 39
40 - 49
50 - 59
60 - 69
Effort capacity
Very low
below 38
below 34
below 30
below 25
below 21
Low
39 - 43
35 - 39
31 - 35
26 - 31
22 - 26
Average
44 - 51
40 - 47
36 - 43
32 - 39
27 - 35
High
over 52
over 48
over 44
over 40
over 36
Table no. 4. MAC for females.
AGE
Effort capacity
(years)
Very low
Low
Average
High
20 - 29
below 28
29 - 34
35 - 43
over 44
30 - 39
below 27
28 - 33
34 - 41
over 42
40 - 49
below 25
26 - 31
32 - 40
over 41
50 - 65
below 21
22 - 28
29 - 36
over 37
RUFFIER TEST
It is a submaximal test, its objective being to monitor cardiovascular recovery of non-athletes
based on the measurement of heart rate during recovery.
► Method:
- measure heart rate while sitting (P1)
- execute 30 squats (genuflections)
- measure heart rate during the first 15 seconds after completing the exercise
(multiply by 4, P2) – patient is lying down
- measure heart rate after one minute rest (for 15 seconds, multiply by 4, P3)
- calculate Ruffier index
Ruffier 
( P 2  70)  ( P3  P1)
10
Stop immediately if subject complains of chest pain, (occipital) headache, or
faintness during the exercise stress test!
► Interpret data:
- 0-2.9 – good
- 3-6 – average
- over 6 – poor
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SCHELLONG II TEST
It is a submaximal test to monitor cardiovascular recovery of non-athletes. It is based on
measurement of heart rate and blood pressure during recovery after effort.
► Method:
- measure heart rate and blood pressure while standing
- subject does 30 squats (genuflections) than lies down
- measure heart rate and blood pressure during the first 15 seconds of every
minute for at least 4 minutes (until the recovery is complete)
Stop immediately if subject complains of chest pain, (occipital) headache, or
faintness during the exercise stress test!
► Interpret data (in healthy subjects)
- heart rate increases slightly (not exceeding 120/min)
- systolic BP increases by 15 - 20 mmHg
- diastolic BP does not change (or decreases slightly) – pulse pressure
increases
- recovery of pulse rate and BP in 2 - 3 minutes
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CARDIAC STRESS TESTING
► Principles: myocardial cells use almost exclusively oxygen, so there is a need of
immediate adjustment of cardiac circulation to metabolic requirements. Increase of
oxygen consumption during stress tests helps us to evaluate the coronary circulation.
Cardiac stress testing reflects indirectly arterial blood flow to the heart during physical
exercise; when compared to blood flow during rest and shows imbalances of blood
flow to the heart's left ventricular muscle tissue. This is assessed by recording ECG:
hypoxia creates disturbances in myocardial repolarization.
A
B
C
Figure no. 92. Methods to perform cardiac stress testing. A - gym-steps, B cycloergometer, C - treadmill
► It is a submaximal test: load increased until subject’s heart rate reaches to 85%
of maximum heart rate (this is the target heart rate). Maximum heart rate is supposed
to be associated with maximum cardiac minute volume.
Maximum heart rate  220  age
► Method:
- using treadmill, gym steps or cycloergometer
- measure heart rate, blood pressure, record a 12 lead ECG while resting
- subject carries out effort testing (e.g. on cycloergometer, increasing the load
by steps of 25 W at 2 minute intervals until reaching the target heart rate)
- monitor ECG and BP continuously during and for at least 10 minutes after
completing the test (until complete recovery)
- immediately stop test if positive criteria's were reached
Stop immediately if subject complains of chest pain, (occipital) headache, or
faintness during the exercise stress test!
► Reading: criteria that mark a positive cardiac stress test are as follows:
- Clinical criteria: chest pain similar to angina pectoris which is reproducible at
the same level of effort, sudden dizziness
- ECG criteria:
- changes in ST segment that can be:
- horizontal or descending ST depression with amplitude ≥1mm
and duration ≥ 0.08 seconds
- descending (junctional) ST depression with amplitude ≥ 2 mm
and duration ≥ 0.08 seconds
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- U wave becomes negative
- changes of T wave: it becomes negative during effort or it
“normalizes” (when it was negative during resting). These changes are not specific in
in the absence of SST or U -wave modifications.
- Arrhythmias: repetitive or multifocal ventricular extrasystoles,
paroxysmal supraventricular or ventricular tachycardia, which demand stopping the
test immediately. These changes are also less specific for diagnosis in lack of other
criteria.
Figure no. 93. ECG trace recorded during cardiac stress test on
cycloergometer with steps of 30W. Only leads V5 and V6 are shown. Note
the progressive depression of SST and also the inversion of T wave. As the
patient complained also of chest pains the test was regarded positive based
on ECG and clinical criteria.
- Hemodynamic criteria: based on multiplying the heart rate by the blood
pressure measured at the last step. This is the pressure-time index (PTI) and refers to
the heart’s oxygen consumption. The calculated value is compared with the theoretic
value which is computed after the following formula:
PTI theoretical  (364  age)  100
Result is expressed as the myocardial aerobic deficit (MAD):
MAD 
( PTI theoretical  PTI calculated )
 100
PTI theoretical
MAD is interpreted as:
- MAD = 0-20%: no/insignificant deficit
- MAD = 20-40%: minor deficit
- MAD = 40-60%: moderate deficit
- MAD > 60%: major deficit
Comparing the myocardic aerobic deficit to the functional aerobic deficit helps us
assess whether the functional deficit is due to the cardiac circulation suffering or not.
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Figure no. 94. Modified Astrand-Rhyming nomogram.