Download Functional diagnostics

COLLEGE OF PHYSICAL EDUCATION AND
SPORT PALESTRA
Functional diagnostics
Doc. MUDr. Zdenek Vilikus, CSc.
Prague 2012
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Content
1.
Spiroergometry.................................................................................................... 4
1.1. Definition ...................................................................................................... 4
1.2. Indication...................................................................................................... 4
1.2.1. Physical fitness ..................................................................................... 4
1.2.2. Prescription of physical activity ............................................................. 4
1.2.3. Choosing an appropriate sports discipline ............................................ 4
1.2.4. Prevention of health complications ....................................................... 5
1.2.5. Differential diagnostics of chest pain .................................................... 5
1.2.6. Evaluation of treatment effects ............................................................. 5
1.2.7. Revealing hidden disease ..................................................................... 5
1.2.8. Assessment terms ................................................................................ 6
1.3. Ergometers .................................................................................................. 6
1.3.1. Bicycle ergometer ................................................................................. 6
1.3.2. Running carpet, Tread-mill.................................................................... 7
1.3.3. Windlass ............................................................................................... 7
1.4. Methodology of spiroergometry implementation, load dosage ..................... 7
1.5. Analysis of exhaled air ................................................................................. 8
1.5.1. Scholander analyzer ............................................................................. 8
1.5.2. Interferometer ....................................................................................... 9
1.5.3. Continuous analyzers ........................................................................... 9
1.6. Correction of respiratory gases values ....................................................... 11
1.7. Calculation and evaluation of spiroergometric parameters ........................ 12
1.7.1. Heart rate, HR..................................................................................... 12
1.7.2. Performance (Wmax, Wmax.kg-1) ...................................................... 15
1.7.3. Pulmonary minute ventilation (Vmax, VE max) ................................... 16
1.7.4. Tidal volume (VT), respiratory rate (RF, fB) ........................................ 17
1.7.5. Oxygen consumption (VO2, V = volume) and carbon dioxide output
(VCO2) 17
1.7.6. Relative oxygen consumption (VO2 max.kg-1) ................................... 19
1.7.7. Stroke oxygen (VO2 max .RF-1; VO2 max . HR-1) ............................ 21
1.7.8. Ventilatory equivalent for oxygen and carbon dioxide (VEO2 max
VECO2 max) ..................................................................................................... 24
1.7.9. Respiratory quotient, ratio of respiratory gas exchange (R, RQ, RER
max)
26
1.8. Criteria of exertion...................................................................................... 27
1.9. Anaerobic threshold (ANT, stress threshold, lactate threshold) ................. 28
2. Diving reflex ...................................................................................................... 34
2.1. Diving reflex – principle and purpose ......................................................... 34
2.2. Neural path of diving reflex ........................................................................ 35
2.3. Methodology of diving reflex ...................................................................... 35
2.3.1. Hemodynamic changes during diving reflex ....................................... 35
2.3.2. Arrhythmia during diving reflex ........................................................... 35
1. SPIROERGOMETRY
Content of the chapter
Definition
Indication
Ergometers
Methodology of spiroergometry implementation, load dosage
1.1.
Definition
It is a method that determines aerobic cardiorespiratory fitness by analyzing
exhaled air at the maximum physical load of an organism. It is usually performed in a
laboratory, most frequently on an ergometer bicycle, less frequently on a treadmill.
It is the most comprehensive stress test out of all with the most detailed form of
examination of oxygen transport system.
1.2.
Indication
1.2.1. Physical fitness
The basic indication of spiroergometry in healthy athletes is measuring the
impact of training on physical fitness. Any change in training, environment, diet, loss
of training due to injury or illness, psychological stress, drug usage, change in a
biorhythm and other factors can affect athlete‘s fitness, both in a negative or a
positive way. An experienced coach is always interested in knowing whether a
particular intervention within training process changes athlete’s cardiorespiratory
fitness.
1.2.2. Prescription of physical activity
According to the results from spiroergometry a doctor can prescribe physical
activity most accurately. By prescribing physical activity we mean setting up an
optimal weekly training frequency, a duration of one training unit and mainly an
optimal intensity of training load, which will be effective for a particular athlete as it
will lead to a significant increase in physical fitness, but at the same time it will not
produce negative feelings or even overload or chronic overtraining. Regarding
patients, the load is often limited by the symptoms of their disease, most frequently
breathlessness, hypertonic reaction to the load, angina pectoris, ECG records, etc..
1.2.3. Choosing an appropriate sports discipline
Spiroergometry can help young athletes to choose the best sports discipline.
Maximum aerobic capacity (VO2 max) is crucial for good performance in endurance
sports. Subnormal values, on the other hand, indicate little chance of achieving good
performance in most sports disciplines – even in those that are not just pure
endurance. Disposition for aerobic physical fitness is to a certain degree inherited.
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Most authors (Cooper, Bouchard, Hollmann, Perusse, etc.) agree on the fact that
genetically inherited component comprises about 30%, while acquired fitness
component (susceptible to training) about 70%.
1.2.4. Prevention of health complications
Common clinical examination in resting conditions does not have to reveal
pathological changes; those are then often reflected in full extent during physical
activity. The most common pathological manifestations in younger people are cardiac
arrhythmias, whereas in people older than 40 years ischemic ECG and hypertonic
reaction to stress. Spiroergometry is implemented especially in individuals with
positive family history (coronary heart disease in parents under the age of 60,
dyslipidemia, cardiomyopathy, sudden death, arterial hypertension, etc.).
1.2.5. Differential diagnostics of chest pain
Spiroergometry, an integral part of stress ECG, is often implemented because
of differential diagnostics of chest pain. During that, it is important to distinguish a
pain related to angina pectoris from a pain that has a different origin - mostly coming
from back pain and spine, or from symptoms associated with neurotic disorders.
1.2.6. Evaluation of treatment effects
Thanks to spiroergometry we can see changes in patients‘ functional abilities
after treatment. Treatments can be conservative (medical, physical, remedial), as
well as radical - operational. Regarding medication (drugs), we usually examine
changes in maximum tolerated load after the implementation of nitrates, beta
blockers, hypotensives and antiarrhytmics. An implementation of beta-blockers in
healthy individuals leads to a reduction in maximum aerobic capacity due to the fact
that betablockers reduce inotropic and chronotropic reserves, to a reduction in
maximum minute cardiac output and maximum oxygen consumption and that
negatively affects maximum performance. In contrast, in cardiac patients who are
limited by ischemic heart disease, beta-blockers can paradoxically increase their
maximum tolerated load. That happens because the weakest link of the transport
system - the disparity between oxygen supply to myocardium and oxygen
consumption in myocardium – is strengthened. Medical reduction of myocardial
oxygen consumption leads to an increase of tolerated load and thus enhance
performance.
SA is also the most appropriate examination assessing medical effects after
surgery in for example patients with rheumatic valvular disease, who received an
implanted replacement. Follow-up examinations are usually done at the earliest 6
months after surgery. However, surgery itself is usually not enough to improve
patients’ functional state; an important part of a treatment is a subsequent physical
stimulation of the patient.
1.2.7. Revealing hidden disease
During stress testing it is also possible to detect some diseases that could idle
concealed for a long time during standard testing. Arterial hypertension has been
discussed above. Hypertonic response to stress usually manifests itself in resting
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conditions earlier than increased blood pressure. Similarly, it is possible to detect
latent ongoing ischemia, peripheral arterial disease, cardiac arrhythmias,
cardiomyopathy, etc..
1.2.8. Assessment terms
With spiroergometry it is possible to objectify patient’s functional disability. In
clinical medicine commonly used functional classification NYHA (according to the
New York Heart Association) is mainly based on anamnestic data, how a patient
tolerates different physical stress (with which degree of dyspnea), and therefore this
technique can contain subjective error. Weber classification based on spiroergometry
results may be critical when the Assessment Commission decides whether to admit a
patient the right to disability pension or not (Table 1).
Tab. 1 Functional classification of aerobic capacity (Weber et al., 1988)
Degree of malfunction
VO2max
[ml. min-1.kg-1]
A
Zero to low
> 20
B
Low to intermediate
16-20
C
Intermediate to high
10-15
D
High
6-9
E
Very high
<6
class
1.3.
Ergometers
There are more types of ergometers: bicycle ergometer, running carpet,
windlass ergometer, rowing ergometer, swimming pools with a flow, and others.
Each has its advantages and disadvantages.
1.3.1. Bicycle ergometer
Bicycle ergometers are used in our conditions most often. Its great advantage
is that even with a very intensive exercise upper body remains relatively stable and
thus does not disturb simultaneous ECG recording; it is possible to measure blood
pressure, take blood samples during exercise, etc. It is also advantageous that there
is a very low risk of injury during bicycle ergometry and that performance is
measured in standard physical units, in watts.
Its disadvantage is that it places great demands on lower body muscles. That
results in considerable local fatigue, which can be a performance limiting factor. It
can happen that the local muscle fatigue occurs even prior to the full use of
cardiorespiratory system. That results in VO2 max value misrepresentation because
the overload was not complete; then only VO2 submax was actually measured. For
such patient we can only establish VO2 max when we use a running carpet. Another
disadvantage of bicycle ergometers is that they do not allow us to achieve the
absolute highest VO2 max values; compared to a treadmill, reached values are
about 5-8% lower. It is therefore a system error caused by this type of ergometer. It
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is clear that two spiroergometry results are comparable only when we use the same
kind of ergometers.
1.3.2. Running carpet, Tread-mill
Tread-mills are most frequently used in USA. Their great advantage is that
lower and upper body muscles and trunk are dynamically burdened and thus the
system measurement error does not occur.
A disadvantage is that they do not allow us to simultaneously measure blood
pressure; there is also a significant interference of ECG recording caused by trunk
movements, which is transmitted to arm movements. Another disadvantage is a
higher risk of injury, higher cost and noisy operation.
1.3.3. Windlass
The percentage of muscle load during exercise on windlass ergometer is so
little that it is impossible to fully use the cardiorespiratory system. It is most frequently
used to determine fitness of handicapped patients (for example patients after lower
limb amputation or paraplegics).
1.4.
Methodology of spiroergometry implementation, load dosage
During spiroergometry examination it is important that the load is gradually
increased. First, patient has some time to warm up (sub maximum load). For the first
stage of sub maximum level we set a load of 1 W.kg-1 (i.e. about 65-85 W) in healthy
male non-athletes, whereas in female non-athletes about 0.75 W.kg-1 (i.e. about 4560 W). This stress level usually takes 4-6 minutes so the patient can reach a steady
state. The second stress level comes right after the first one without a break and for
men is Approximately 1.5 W.kg-1 (i.e. about 100-150 W), whereas for women 1.25 W
kg-1 (i.e. about 80-120 W) and again lasts 4-6 minutes. Warm up intensity should not
be too low so the transition to the maximum stress level is neither too sudden nor too
high, which prevents premature local lower body muscles fatigue.
A two minutes break during which legs recover best if the examined person
continues to pedal in a moderate resistance (20-40 W) follows. Use the break so the
patient can moisten his/her mouth (mouth breathing dries oral cavity) and ask
him/her about subjective effort he/she has to exert to manage the sub maximum
load. For the subjective evaluation use the Borg scale from 6 to 20. If the patient
during the second stage indicates subjective effort greater than 13 ("somewhat
heavy" load) on Borg scale, then we start the maximum stress level with the same
load with which we finished the sub maximum load, if it is lower than or equal to 13,
then we start the maximum stress level 0.25 to 0.50 W.kg-1 higher than where we
finished.
The maximum stress level that burdens circulatory and metabolic system
should last about 5-6 minutes. Not less than 3 minutes (maximum oxygen
consumption does not rise faster), but not longer than 8 minutes, so we avoid results
distortion due to local muscle fatigue. We can find accurate values of Wmax.kg-1 for
men respectively women of a certain age in tables. We set this intensity for the 5th
minute of maximum stress level and plan previous loads accordingly so the workload
increases evenly from the second sub maximum level.
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Example: Let’s create a stress protocol for a 42-year-old man who weighs 75
kg and spends 1 hour per week playing volleyball. Because of the low sport activity,
the first sub maximum load for him will be 75 W, the second 115 W. During the break
the patient indicates that his subjective stress perception on Borg scale is "mild"
(grade = 11). Therefore we start the maximum stress level at 135 W. According to
the tables, an appropriate maximum performance for Czech population of 42 years
old men is 3.2 W.kg-1, i.e. 240 W. We divide the difference of 240 W - 135 W = 105
W evenly into 4 subsequent minutes, i.e. Approximately 25 W/min; the maximum
stress level will therefore be as follows: 1 minute at 135 W; 2 minutes at 160 W; 3
minutes at 185 W; 4 minutes at 210 W; 5 minutes at 235 W.
According
to
this load
schedule we
can
create
an
appropriate stress protocol by which we can correctly measure about 90% of all
cases. When we examine a patient for the first time, it is always only an educated
guess at which we sometimes underestimate and sometimes overestimate
the patient. The basic scheme is adjusted according to experience; in particular we
must take into account participant’s sports history: which sport he/she engages in
(endurance vs. non-endurance), how often he/she trains, how long does a training
unit usually
lasts
and
what is
the
total weekly energy
expenditure during sports activity. A useful guide is a stress testing from past years.
There are other ways of load dosage. For example when we try to determine
anaerobic threshold, we implement a small regular increase in workload every
minute ("continuous" increase) without a break (and without a steady state).
1.5.
Analysis of exhaled air
1.5.1. Scholander analyzer
Scholander developer this method already in the 40th of the last century and
today it is one of the classic ways of measuring oxygen and carbon dioxide
concentration. It is based on a lengthy principle of chemical absorption. Despite of
that, this method have preserved a sense of irreplaceability because it allows an
absolute measurement of O2 and CO2 concentration, which means measurement
without comparison with a calibration gas of accurately known composition (as it is
for example in automatic analyzers). The principle of the method is the following: the
device consists of three interconnected glass chambers that are perfectly sealed
from external environment and act as connected vessels. The chambers are
separated from each other by pure mercury. The left chamber is filled with a solution
of O2 absorber, the right chamber with a solution of CO2 absorber. The middle
chamber is filled with a gas sample of unknown concentration, but accurately known
volume. An inclination of the tube to the left will cause a spillage of oxygen
absorption solution through mercury in the middle chamber, an absorption will occur
and a micro-screw will measure the loss of gas volume. The same can be done with
a CO2 absorption solution by inclining the system to the right. Again, we allow for the
absorption and measure the loss of gas. Then percentage volume of O2 and CO2
can easily be calculated. Accuracy of the method is high, it allows measurements of
hundredths percent. A disadvantage of this method is considerable amount of work
(especially the preparation of absorbent solutions) and time (one analysis takes 3060 minutes) involved and certain risk of working with a higher amount of toxic
mercury. Therefore it is not commonly used for each spiroergometric measurement,
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however, it is very useful for example when we need to control the concentrations of
calibration gases in pressure containers for longer storage.
1.5.2. Interferometer
Intereferometers (commercially manufactured by Zeiss, Jena) began to be
used for analysis of respiratory gases in the sixties. They are based on a physical
principle that rays of modified light (interference spectrum) is deviated from its
position and the magnitude of the deviation is directly proportional to gas
concentration through which interfering light passes. An examiner can see two
analogue spectra in an optical device. The bottom spectrum has a so-called zero
position set by the manufacturer. During an actual measurement we examine the
deviation of the upper spectrum from the zero position. First, we let the atmospheric
air to go through the device and using a micro screw we align both spectra exactly
below each other. Then, we switch the interferometer to oxygen analysis and the
upper range of the swing will deviate; using the micro screw we return the deviation
of the upper spectrum back to its original position so the two spectra correspond to
each other. The deviation from zero position is expressed by the number of divisions
that we had to turn by the micro screw. Then an examiner finds the oxygen
concentration difference against atmosphere in percents in specific tables. In other
words, he/she measures how many less % of oxygen is in the stale air in comparison
to atmosphere. The same procedure is repeated for carbon dioxide.
But how does the gas sample gets into the device? A patient puts a
mouthpiece with a hose leading to a switching system that is connected to a socalled Douglas Bag (a large solid plastic bag with a capacity of 200 l) in his/her
mouth. At an exact moment an examiner switches the expiratory path so the air gets
into the Douglas bag to which the patient exhales for exactly 60 seconds. After that
the examiner closes the bag and takes it to the interferometer. He/she sucks a
sample for the interferometer (about 500 ml) and examines it. Then he/she sucks the
rest of the air from the Douglas bag using a conventional vacuum through a gas
clock and thus measures pulmonary ventilation per minute (VATPS). For values
correction to standard conditions the examiner applies correctional factors BTPS and
STPD; its values can be found in the tables according to a current temperature and
atmospheric pressure in a functional laboratory. Finally, he/she calculates
spiroergometric parameters. (One analysis takes Approximately 15 minutes.) We
mention the whole process so students can imagine the method that was still
commonly used in the eighties.
1.5.3. Continuous analyzers
Continuous analyzers are used in our country since late seventies. Its big
advantage is that a measurement is conducted "on-line". Exhaled air is conducted to
a mixing container (mixing chamber) where the gases concentration becomes
balanced (at the beginning of exhalation it is different than at the end). The propeller
measuring pulmonary ventilation is placed in the system in front of a mixing
container. The propeller rotates faster with increasing ventilation; the number of its
revolutions is calibrated so it exactly matches a ventilation unit. The system
automatically does corrections of pulmonary ventilation according to the atmospheric
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temperature and pressure. An air sample is sucked from the mixing container into O2
and CO2 analyzer; an exhaled air then escapes freely into the atmosphere from the
opposite end of the mixing container.
Various oxygen analyzers are based on different principles. So-called Clark
oxygen sensor, a small cylinder with two electrodes, is often used. The first one is
silver and it is the outer case of the cylinder; the other one is a thin strip of gold
located along the lengthwise axis of the cylinder. The electrodes are charged with a
small DC voltage (0.6 V). The filling between the electrodes is made of special
conductive gel so there is no current between the electrodes. There is a gap with a
semi permeable membrane in the bottom base of the cylinder through which
molecular oxygen penetrating inside from the stale air. This oxygen in the gel is
gradually reduced to hydroxyl ion that has a negative charge and goes from a silver
cathode to a gold anode. The intensity of the current is directly proportional to the
oxygen concentration in exhaled air.
Carbon dioxide analyzers are based on various thermal conductivity of gases
(Spirolyt), but most frequently used is an infrared (IR) method. The principle of IR
sensors is based on the fact that carbon dioxide absorbs infrared light very well.
There are two IR beams of equal intensity in one analyzer. A cuvette through which
flows exhaled air is placed in one of them. The higher the CO2 concentration in
cuvette, the weaker the intensity of the IR beam. Every IR beam falls on a
hermetically sealed cell. The cells are separated from each other by a thin flexible
metal membrane. The cell to which falls the IR reference beam is heated more than
the other one. It also has a higher pressure than the other one and that causes the
membrane to convexly arch into the cooler cell. The membrane arch changes its
electrical properties (capacitance) and that is finally measured. Even thought during
the process light energy of IR beam changes to thermal energy, thermal to
mechanical and mechanical to electrical, the measurement is very accurate.
However, the measurement is not absolute as it is in Scholander analyzer. Automatic
continuous analyzers always measure the difference of concentrations between
exhaled gas and calibrating gas of exactly known concentrations of O2 and CO2.
Calibration gas mixture has a similar composition as exhaled air (typically 5% of
CO2, 15% of O2 in nitrogen) with a specifically set concentration (hundredth of a
volume percent) and is bought to order in specialized companies.
A great advantage of continuous analyzers is their speed (one analysis takes
only couple seconds), enabling on-line monitoring of spiroergometric indicators on a
computer screen that is part of the analyzer. Thus a practitioner can observe the
degree of participant’s activity not only according to heart rate, but also according to
pulmonary minute ventilation, oxygen consumption, ventilatory equivalent, and in
particular according to the current ratio of exhaled gases (ratio CO2/O2). The ratio of
exhaled gases is a very reliable indicator of participant‘s metabolic load. That allows
the athlete's/patient‘s physician to encourage him/her for even greater performance
in case the load if insufficient, or contrary to terminate the load, even though the
person being tested wants to continue and thus prevent the acute distress syndrome.
Note: Spirolyt is a widespread continuous analyzer whose common vision,
however, does not show numerical values of functional parameters as it shows only
a scatter plot of changing O2 and CO2 concentrations above atmospheric air. Only
manual measurement of these Graphs can give us the numerical values. Therefore,
10
this analysis is somewhat faster than analysis on interferometer, but it does not
render on-line results monitoring. Spirolyt’s considerable popularity for its accuracy,
reliability and low cost has induced some workplaces to technically perfect the
analyzers so they currently equal other modern device while the price remains very
reasonable.
Continuous analyzers are well suited for routine performance of a functional
laboratory; it is possible to examine lots of patients in a short period of time thanks to
the analysis speed and its possibility to immediately print the resultant values.
One disadvantage of continuous analyzers is their high price. An ideal
analyzer should be equipped with a software enabling a direct comparison of
measured results with appropriate values for people of the same age and sex. That
way it would be possible to provide a patient/athlete with measured data immediately
after the test. The examiner could give them a comparison of the obtained data with
reference data (either a percentage of particular values or predicted standard
deviations in "Z-score") and print a completed report of functional fitness tests.
However, these analyzers are not commercially manufactured yet.
1.6.
Correction of respiratory gases values
Exhaled air is a mixture of gases. Gases change their volume according to
surrounding physical conditions. The results obtained in various atmospheric
conditions (ATPS, Ambient Temperature, Pressure, Saturated; ambient =
surrounding) have to be converted to standard conditions if we want them to be
comparable. We use two factors for corrections.
Factors BTPS (Body Temperature, Pressure, Saturated)
Using this factor we correct measured pulmonary ventilation to 37°C (air
exhaled from our lungs actually has this temperature), and to barometric pressure of
1013 hPa at full saturation with water vapors (we actually exhale air that is this
moist). Factor BTPS is used as the final indicator for conversion of pulmonary minute
ventilation. According to the measured lab temperature and air pressure we find
functional values of BTPS factor in the tables and multiply it by measured pulmonary
ventilation (ATPS).
Example: We obtained a pulmonary minute ventilation (VE ATPS) of 105 l.min-1.
The barometric pressure in the laboratory was 986 hPa and the temperature reached
20°C during the examination. BTPS factor corresponding to these conditions is
according to the tables 1.103. Adjusted VE BTPS is therefore 105 x 1.103 l, which is
115.8 l. That is about 10% higher than the obtained value.
Factors STPD (Standard Temperature, Pressure, Dry)
Using this factor we correct the obtained pulmonary ventilation to standard
physical conditions: a temperature of 0°C and a pressure of dry gas equal to 1013
hPa. STPD factor is used to correct values of pulmonary minute ventilation
(intermediate step) so oxygen consumption can be calculated and serve as a final
indicator. According to the temperature and pressure measured in the functional lab,
11
we find STPD factor values in the tables and multiply them by the obtained
pulmonary ventilation values (ATPS).
Example: Measured lung ventilation (VE ATPS) was 105 l.min-1. STPD factor for
correction at 20°C and a barometric pressure of 986 hPa is according to the tables
0.886. The corrected ventilation (VE STPD) is 105 x 0.886 = 93.03 l. It is about 10%
less than the obtained value.
Modern analyzers of respiratory gases already correct values automatically, but a
doctor should know how the instrument obtained these values.
1.7.
Calculation and evaluation of spiroergometric parameters
To evaluate spiroergometric indicators, we used results obtained at the
International Biological Program (IBP) published by Seliger and colleagues in 1976.
Based on these results, we performed an actual calculation of regressions to obtain
appropriate values.
1.7.1. Heart rate, HR
We monitor HR continuously on a cardio tachometer, an ECG monitor or on a
monitor of a gas analyzer. ECG recording is performed in healthy athletes usually
during the second and the fourth minute of each sub maximum load, in patients
mostly during the last 10 seconds of each minute during the exercise and then during
the first, third, and fifth minute of recovery period. Newer ECG devices already record
the ECG curve and measured heart rate. For measurements that are more important
we also check for HR from the ECG recording using a special ruler.
Heart rate can also be monitored by palpation, or even listening, but with a risk
of error, which increases with increasing load (sounds caused by hyperventilation
disturb listening, patient’s movement interrupt palpate measurements).
a) HR evaluation during a sub maximum load
Athletes, mostly endurance athletes, have a significantly lower heart rate
during sub maximum exercise at comparable stress levels (loads). This phenomenon
is in trained individuals related primarily to higher vagotonia and later also to a higher
stroke volume (Qs, SV, Systolic Volume). The same stress level (load) is achieved at
the same energy output, which requires the same oxygen consumption, which
requires the same cardiac output per minute (Q, CO). However, different individuals
reach the same cardiac output per minute at different heart rates. That is because of
the adaptation of cardiovascular system to endurance training. Thanks to a better
ventricular wall plasticity, increased myocardial contractility and proportional cardiac
heart dilation, an endurance athlete covers required minute cardiac output with an
increased stroke volume and thus has a lower heart rate. Fitness measurement
using W170 is based on this principle (see below).
W170 (working capacity at 170 heartbeats)
12
Heart rate measurement at different stages of sub maximum load is used to
calculate power (W) at heart rate of 170 beats per min. This value can be determined
either by gradual slow load increase (Approximately by 10-20 W) every minute, until
170 beats per minute is reached. However, it can be also found indirectly from two or
better from three sub maximum load stages using an extrapolative method. (The
theoretical basis for this procedure is that up to 170 beats per minute we have a
linear heart rate increase.) A person that is being tested goes through three stress
(load) levels - each of them lasting three to six minutes to achieve a steady state
every time. Heart rate is measured during the last 10 seconds of each stage.
Obtained HR values are then recorded in a Graph. We get three points, through
which we draw a line. After that we draw another line at the intersection of the first
line with a horizontal line corresponding to HR of 170 beats per minute. The point of
intersection of the perpendicular to the x-axis corresponds to a working capacity at
170 beats per minute. People with lower heart rate have higher W170, thus they are
better adapted to stress (load).
Test W170 is performed routinely for every athlete under 40 years of age
within a regular preventive medical examination. Due to technical reasons it is
impossible to conduct a spiroergometric examination for every athlete. Test W170 is
used for an approximate determination of cardio respiratory fitness. Compared to
spiroergometry, it is certainly less accurate, but it saves time (10-15 minutes),
requires less personnel (1 nurse) and is less instrumentally demanding (1
ergometer); (spiroergometry: 45 minutes, 1 doctor + 1 nurse, ergometer + analyzer of
exhaled gases).
For better interindividual comparability we usually refer W170 values to 1 kg of
body weight. Simplified, we can say that men are around 2.5 W.kg-1, and women
around 1.75 W.kg-1. Reference values are relatively stable. Males reach their
maximum around 21 years and then slowly decline while women almost never
change. Stabilization of W170 values in people of higher age is probably caused by
their already lower heart rate reactivity to stress, which corresponds to an overall
declining trend of maximum heart rate due to their age.
The following equation is used for an accurate calculation of predicted W170
.kg-1 in men:
aged 11 to 20 years: y = - 0.0049.age2 + 0.1958.age + 0.76
aged 21 to 60 years: y = - 0.0137.age + 3.05
Indicators W 150, or even W 130 are used instead of W 170 in elderly.
b) Maximum heart rate
Graph 1 shows average values of maximum heart rate in Czech population.
Obviously, at young age HRmax reaches values that are close to 200 beats per
minute but that significantly decreases with age. For everyday practice and activities
such as running and others we can calculate reference values of HRmax according to
a simple formula 220-age, for cycling and bicycle ergometers 210-age, and that for
both men and women.
13
Graph 1
Dependence of heart rate on age at maximum load
(Vilikus, 1999 according to the results of IBP, Seliger et al.., 1976)
Note: conformity coefficient R2 between obtained and predicted values reaches high
values
For research purpose, it is necessary to use an exact calculation according to
the equation:
HRmax men = - 0.4635 . age + 202
HRmax women = - 0.5148 . age + 206
During maximal load - in contrast to sub maximal loads – there are no
significant differences in HRmax between trained and untrained individuals and the
differences between men and women are not significant either. However, it is true
that trained individuals compared to untrained, and men compared to women reach
their maximum heart rate with significantly higher load.
14
1.7.2. Performance (Wmax, Wmax.kg-1)
An athlete reaches a maximum performance on bicycle ergometer if we
properly measure out submaximal workload. Performance shows what kind of
power-endurance abilities an athlete has. Normal values of Wmax.kg-1 in sedentary
men are 3-4 W, in sedentary women 2.5 to 3.0 W; athletes reach around twice as
much, that is from 6.0 to 8.0 W. Cyclists are specifically trained for bicycle
ergometers. Some trained top track cyclists-sprinters can reach extremely high
values of Wmax.kg-1 around 10 W, which represents approximate absolute values of
700-800 W.
Graph 2
Dependence of performance on age at maximum load
(Vilikus, 1999 according to the results of IBP, Seliger et al., 1976)
Maximum performance linearly decreases with age since puberty (Figure 2) in
both men and women:
-1
Wmax.kg men = - 0.0374 . age + 4.77
-1
Wmax.kg women = - 0.0329 . age + 3.91
Weightlifters and bodybuilders with well developed lower limb muscles tend to
reach low values of Wmax.kg-1compared to cyclists. That is because their muscles
are not specifically trained for endurance load (they have majority of white muscle
fibers, particularly glycolytic muscle fibers IIB at the expense of white oxidative IIA).
Power athletes compared to cyclists reach significantly higher performance during
simple power loads (e.g. squat with a barbell on shoulders, leg-press).
15
1.7.3. Pulmonary minute ventilation (Vmax, VE max)
Values of trained and untrained athletes do not differ at sub maximal loads.
However, there will be significant differences once athletes get above their anaerobic
threshold and at maximal load. VE increases linearly up to the level of ANT, above
which it starts increasing faster and non-linearly.
Sedentary men during maximum load achieve ventilation of about 100 l.min-1,
sedentary women approximately 75 l.min-1. Top endurance athletes achieve
ventilation that is about twice as big, i.e. men 200 l.min-1, women approximately 150
l.min-1. Vmax decreases with increasing age. When we relate ventilation to one
kilogram of body weight, the decrease is linear from 12 to 60 years (Graph 3).
For exact calculation of the maximum pulmonary ventilation use the following
equation:
VEmax men = - 0.0105 . age + 1.775
VEmax women = - 0.00008 . age2 – 0.005 . age + 1.523
However, age differences are evident also in older people who have higher
values of pulmonary ventilation during the same wattage performance. This
demonstrates decrease in breathing economy caused by age. Pulmonary ventilation
in healthy people is usually not the limiting factor of performance. The limiting factor
is particularly the central circulatory system (heart). However, for some borderline
conditions and diseases (spastic bronchitis, chronic obstructive disease, bronchial
asthma, etc.), pulmonary ventilation can become a limiting factor in endurance
performance.
Graf 3 Dependence of pulmonary ventilation on age during maximum load
(Vilikus, 1999 according to the results of IBP, Seliger et al., 1976)
16
1.7.4. Tidal volume (VT), respiratory rate (RF, fB)
We calculate tidal volume so that we divide pulmonary minute ventilation by
breathing frequency: VT = VE / RF. According to the results of the International
Biological Program, athletes of both sexes have only slightly higher tidal volume than
sedentary people at maximum load. However, more important and statistically
significant are differences in breathing frequency (respiratory rate).
During exercise at lower intensity it increases mainly due to inhaled reserve
volume, at higher intensity due to expiratory reserve volume. Respiratory volume at
maximum load VTmax is about 50-60% of lung vital capacity (normally at rest it is
only about 15%). Therefore, VC is not completely used. That is because the changes
in placement of diaphragm during full inhalation or exhalation are already inefficient.
The respiratory muscles are strained in extreme positions because they must
overcome a big change of intrathoracic pressure while the change in lung volume is
already low. The other extreme, a very high respiratory rate would neither be
effective because an athlete would significantly increase ventilation within the dead
space in relation to alveolar ventilation. The most advantageous is a compromise
between VTmax and RFmax, when VTmax is about 50-60% of lung VC and RF
about 50 breaths per minute. Rash artificial interference to athlete‘s respiratory
stereotypes rather tend to harm and they usually do not increase performance.
RF is at low and medium intensity determined by the rhythm of the load and
habits and less by exercise intensity. The higher the load, the more DF depends on
its intensity.
Endurance athletes achieve higher lung ventilation per minute mainly due to
higher respiratory rate that moves during maximum around 50 breaths/min (in
sedentary individuals around 40 breaths/min). With age VTmax slightly increases at
the expense of lower RFmax
1.7.5. Oxygen consumption (VO2, V = volume) and carbon dioxide output
(VCO2)
Oxygen consumption in liters per minute can be calculated according to the
following formula:
VO2 [l] = (FIO2 - FEO2). VESTPD) / 100 [a]
FIO2 [%] respectively FEO2 [%] are so called fractions of inhaled respectively
exhaled oxygen expressed in percentages. Their difference, called oxygen deficit,
expresses by how much less volume percent of oxygen there is in the exhaled air
compared to the atmospheric air. Exhaled air during maximum exercise load
contains about 4-5 volume percent less oxygen (that is Approximately 16-17%) than
atmosphere (about 21%). Pulmonary ventilation adjusted by STPD factor is used, as
we already know, to calculate the oxygen consumption.
17
Similarly, we calculate carbon dioxide output per minute in liters according to
the formula:
[b]
VCO2 [l] = (FECO2 . VESTPD) / 100
The only difference is that the fraction of inhaled CO2 (FICO2) is so small
(0.03%) that it can be ignored in the calculation. There is about 5 percent more
carbon dioxide in exhaled air than in atmosphere.
Example: What was the oxygen consumption, when oxygen deficit in exhaled air
compared to the atmosphere was 4.61% and obtained minute ventilation was 75.5 l,
laboratory air temperature was 20°C and a barometric pressure was 999.7
hectopascals?
First we use the tables to find the correction factor value for given temperature
and barometric pressure: STPD = 0.898. Thus reduced ventilation is 75.5x0.898
= 67.8 liters. We insert the values to the formula [a]:
VO2 [l] = (4.61 x 67.8) / 100 = 3.12 l
Oxygen consumption (per minute) was 3.12 liters.
Oxygen consumption at submaximal loads depends linearly on absolute load.
Just at load that is close to vita maxima, VO2 recording becomes non-linear.
Therefore, at small and medium loads it is possible to estimate oxygen consumption
with good accuracy. For load of 100 W it is about 1.6 liter, for 200 W about 2.7 liters,
300 W about 3.8 liters and 400 W Approximately 4.9 l. This relationship, which can
be expressed with a simple equation (Graph 4), is true and almost independent of
age, gender or fitness. The only requirement is to maintain linearity, which is only
possible until we reach anaerobic threshold. Differences in oxygen consumption
among differently trained individuals show only above ANT and in a value of maximal
oxygen consumption.
Graph 4 Dependence of VO2 on performance
18
Maximum oxygen consumption (VO2max), maximal aerobic capacity, is the
most valuable indicator in assessing aerobic cardio-respiratory fitness. It shows the
ability of an organism to transport the highest amount of oxygen possible to working
muscles at maximum load. It is therefore a measure of maximum aerobic capacity of
an organism. Invasive catheteterized examination showed that VO2max value
correlated very closely with maximum cardiac output value (CO, cardiac output)
(Graph 5).
The Graph shows that there is a close relationship between VO2 max and
maximal minute cardiac output (COmax) and that different fitness levels and
adaptation to physical load can be expressed well by maximum oxygen consumption.
VO2 max and CO max of top athletes can be twice bigger than it is in non-athletes.
Graph 5 Relationship between VO2 max a CO max in individuals of various fitness
levels
1.7.6. Relative oxygen consumption (VO2 max.kg-1)
Among different individuals we can only compare values of VO2 max relative
to body weight. Values of peak VO2max.kg-1 are around 80 ml.min-1 (up to 100 ml.min1
!) for top endurance male athletes; in women of comparable age and fitness levels
are about ¼ lower than in men, that is, for top endurance female athletes about 60
ml.min-1 (up to 80 ml.min-1!).
19
Maximum oxygen consumption in athletes of various sports disciplines
depends on external factors, mainly on the proportion of endurance components in a
particular type of sport (Table 2).
Table 2 Values VO2 max .kg-1 [ml.min-1] in athletes of various sports disciplines
Macek and Vavra, 1988
sport
running – ski
running – endurance
cycling
competitive walk
running – sprint
swimming
rowing
gymnastics
weightlifting
non-athletes
Men
83
80
74
71
68
67
62
60
56
44
Women
64
61
59
57
51
55
50
52
39
Graph 6
Dependence of VO2 max kg-1 on age
(Vilikus, 1999 according to the results of IBP, Seliger et al., 1976)
Dependance of VO 2max.kg-1 on age
55
50
VO 2max .kg -1 = -0.691.age + 51.2
R2 = 0.99
VO 2max.kg-1 [ml.min -1]
45
40
35
30
VO 2max .kg -1 = -0.556.age + 40.7
R2 = 0.98
25
20
muži
15
ženy
59
55
51
47
43
39
35
31
27
23
20
18
16
14
12
10
Age [years]
VO2 max values per kg of body weight significantly decrease with age in both men
and women starting already at the age of 12 years (Graph 6). The decrease is
described best by linear equations:
VO2 max.kg-1 men = - 0.691 age + 51.2 [ml . min-1]
20
VO2 max.kg-1 women = - 0.556 age + 40.7 [ml . min-1]
1.7.7. Stroke oxygen (VO2 max .RF-1; VO2 max . HR-1)
It is the amount of oxygen from blood that is used for one heart beat. The value of
stroke oxygen is derived from Fick's equation:
VO2 = CO . (FaO2 – FvO2)
CO is Cardiac Output (minute heart dispensation) and expression (FaO2 FvO2) is an arterial-venous oxygen difference. AV difference is expressed in ml of O2
per 100 ml of blood and in resting conditions is Approximately 6 ml of O2/100 ml of
blood; at load that is close to maximum it is almost tripled and thus equal to about
16-18 ml of O2/100 ml of blood.
Example: What is the minute oxygen consumption in an individual at resting
conditions, when his cardiac output is 5 l.min-1? Inserting into Fick's equation we
get:
VO2 = 5000 [ml.min-1] . (6 [ml]/100 [ml]) = 300 [ml.min-1 ]
Resting oxygen consumption in this man is about 300 ml of oxygen per
minute. This oxygen consumption corresponds to one metabolic equivalent (1 MET).
We often express load intensity using multiples of METs, because it is convenient for
energy expenditure calculations: 1 MET corresponds to an expenditure of 1
kcal.kg.1.h-1.
In Fick’s equation we can substitute minute cardiac output by the product of
stroke oxygen and heart rate:
VO2 = Qs . RF . (FaO2 – FvO2) and then adjust it so the stroke oxygen
becomes independent:
VO2 / BF = Qs . (FaO2 – FvO2)
The equation shows that stroke oxygen will be higher with greater systolic
volume and arterio-venous difference. In exercise physiology and sports medicine
practice, stroke oxygen is used as a performance indicator of circulatory system.
Differences in cardio respiratory system performance can be differentiated thanks to
stroke oxygen already at sub maximal loads: the same energy expenditure is
required to achieve the same endurance performance, an organism reaches the
same energy expenditure at the same oxygen consumption, and the same oxygen
consumption is achieved with the same cardiac output per minute. However, different
individuals acquire the same CO with different stroke oxygen and different heart rate
frequency.
Vavra provides a good example (Table 3). Three different people will be tested
on a bicycle ergometer during exercise load at 200 W: an individual with cardiac
problems, a healthy non athlete and a well trained endurance athlete. During the load
of 200 W cardiac output reaches about 15 liters per minute:
21
Table 3
Hemodynamic indicators in patients with different fitness
(Macek and Vavra, 1988)
CO [ml.min-1]
cardiac problems
15000
non athlete
15000
endurance athlete 15000
Qs [ml]
60
90
150
BF [tepů.min-1]
250
165
100
note
unreal
high intensity
low intensity
A patient with cardiac problems, able to increase systolic volume only slightly,
should endure the load of 200 W for at most a few tens of seconds, he/she would
have to stop due to breathlessness. To reach minimal cardiac output of 15 l/min
he/she would need to increase RF to 250 beats/min, which is unreal. Healthy non
athlete would increase systolic volume to about 90 ml and to achieve the required
CO, he/she would have to get to HR of 165 beats/min. That load is real for him/her,
but is doable only with a considerable subjective effort. According to heart rate, it is
already a high exercise intensity. A trained endurance athlete with systolic volume of
150 ml would manage the load with HR of 100 beats/min, which for him/her
represents only a light cardiorespiratory load. In this example we demonstrated what
we all already know from experience: that the same absolute load means for people
at various fitness levels a significantly different relative load. And further, that systolic
volume is an essential factor for transport capacity of our circulatory system.
However, it is difficult to measure systolic volume during exercise. Invasive types of
measurements based on oxygen concentration measurements in venous and arterial
blood is out of the question. In turn, non-invasive methods such as respiratory gas
analyzers require equipment with a re-breathing circuit, which is very expensive.
However, magnitude of systolic volume can be estimated using stroke oxygen,
because these two parameters are closely correlated.
Common values of VO2 max . RF-1 in men – non athletes are approximately 15
ml/min, in women about 10 ml/min. A very well trained endurance athletes can reach
double of this value, that is men around 30 ml/min and women around 20 ml/min.
Looking at Graph 7, it is obvious that maximum stroke oxygen in men slightly
decreases with age according to the rational function:
VO2 max .RF-1 = - 0.0005 . age2 - 0.0167 . age + 17.3 [ml/min]
Stroke oxygen in women stays relatively stable in women:
VO 2
max
.RF-1 = - 0.0099 . age + 11.1 [ml/min]
Maximum stroke oxygen does not decrease with age as significantly as
VO2max.kg-1 (see Graph 7). That is again caused by a known phenomenon that heart
rate reactivity decreases with age.
Relationship between maximum stroke oxygen and VO2max.kg-1 in overweight
people, who almost always have reduced VO2max.kg-1, shows to what extent are low
fitness levels caused by excessive weight. Among athletes from various sports
22
disciplines, there are similar differences in VO2max.RF-1 as in VO2max.kg-1 (see Table
2).
Stroke oxygen evaluation can be disturbed by drug usage affecting heart rate,
especially beta-blockers. Stroke oxygen is after their usage artificially increased.
Graph 7 Changes in maximum stroke oxygen dependant on age
(Vilikus, 1999 according to the results of IBP, Seliger et al., 1976)
However, a short lapse of beta-blockers before a stress test in patients that
are taking them long-term would not make sense, because the prescription of
physical activity has to be done under the same conditions that correspond to
training conditions. Nonetheless, two stress tests for the same person with the same
drug dosage are already comparable.
23
1.7.8. Ventilatory equivalent for oxygen and carbon dioxide (VEO2 max VECO2
max)
Ventilatory equivalent for oxygen was defined by Anthony (5) as a number of
liters of air that a person must breathe so he/she consumes 1000 ml of oxygen.
Ventilatory equivalent is a measure of breathing economy and an indirect indicator of
alveolar-capillary membrane function. We calculate it according to the following:
VEO2 [liters] = VE BTPS [l] / VO2 STPD [l]
Ventilation is adjusted by the BTPS factor, and oxygen consumption by the
STPD factor. Some authors prefer to use reciprocal values of ventilatory equivalents
and call them ventilatory coefficients.
Graph 8A Dependence of ventilatory equivalent on age in young individuals
(Vilikus, 1999 according to the results of IBP, Seliger et al., 1976)
According to Seliger, normal values of a ventilatory equivalent move from
about 20 to 25. Ventilatory equivalent decreases at the beginning of submaximal
exercise. It is a sign of better oxygen utilization that is probably caused by expansion
24
of collaterals in pulmonary stream, which increases contact surface for oxygen.
Optimum oxygen utilization is for all age groups during exercise load around 100 W,
when we increase the load further, ventilatory equivalent increases as well, which
means worsening of breathing economy. It indicates that the transport system is able
to utilize a relatively smaller amount of oxygen from offered amount of air. One factor
that can limit O2 usage from inhaled air are mitochondria and activity of their active
oxidative enzymes.
Ventilatory equivalent increases with age until 37 years in men and women, on
the contrary from 37 years onwards it decreases (Graph 8 A, B). This phenomenon
can be explained as individuals at the age of 37 years have a relatively low oxygen
consumption and a relatively high ventilation. However, in people over 37, pulmonary
ventilation starts decreasing as well, which paradoxically improves their ventilatory
equivalent. A ventilatory equivalent of carbon dioxide has a similar course as the
ventilatory equivalent of oxygen.
Graph 8B Dependence of ventilatory equivalent on age in older individuals
(Vilikus, 1999 according to the results of IBP, Seliger et al., 1976)
25
1.7.9. Respiratory quotient, ratio of respiratory gas exchange (R, RQ, RER max)
Respiratory quotient is the ratio of exhaled CO2 to inhaled O2. To calculate R,
respectively RER, we use the ratio of gas volumes (or ratio of percentage change in
concentration of gases compared to atmosphere)
R = VCO2 / VO2
At resting conditions R depends on diet, especially in relation to three
nutritional components. If our diet consisted only of carbohydrates, R would be equal
to 1.00. If only of protein, R would be around 0.80 and if of fat, it would be about
0.70. Considering the fact that majority of our diet is mixed, R value is usually in a
range from 0.80 to 0.85.
Before starting a stress test, when we put a mask or a mouthpiece with a
valve to measure ventilation (and to get a sample of exhaled air) on participant’s
face, we often have to wait a few minutes before the athlete or patient calms down
than and adapts to unusual conditions. In some emotionally susceptible people it
may take even longer. Restless patients hyperventilate, which increases the value of
respiratory quotient, so R in these circumstances can reach values even above 1.00.
At submaximal loads, R value drops first because oxygen consumption in
working muscles increases, but ventilation responds little later. R begins to rise again
at higher intensities, when anaerobic energy release takes place. However, as
intensity increases, R values dependence on nutritional components decreases and
thus R changes rather according to the increasing concentration of lactic acid in
blood. Lactic acid is the main extracellular buffer system - bicarbonate - to form
unstable carbonic acid, which is decomposed into water and carbon dioxide. Further,
an individual exhales carbon dioxide in a higher concentration and thus R (RER)
increases. At higher loads we should not even use the term respiratory quotient, but
rather: the current ratio of respiratory gas exchange, RER (Respiratory Exchange
Ratio).
The ratio of respiratory gases, RER, is a reliable indicator of athlete’s
metabolic load during spiroergometry. It is important for test validity. If RER values
during exercise reach 1.00 and less, it is impossible to consider functional
parameters measurements to be maximal. (It's like we have measured temperature
before mercury column became stabilized; we would not actually know the
temperature.) To consider spiroergometry results valid, RER should reach values
ranging from 1.10 to 1.20, regardless of age, gender or fitness. In RER range of 1.05
to 1.10, it is unclear, whether the load was maximal and in range of 1.00 to 1.05, it is
very unlikely. RER value of 1.00 corresponds roughly to anaerobic threshold.
Only very few people can engage in larger loads than those that correspond to
RER of 1.20 and if that happens, we immediately terminate the test to avoid acute
overstrain or overwork.
Overstrain is manifested subjectively by weakness, dizziness, nausea,
objectively by paleness, decelerated reactions, impaired perception and decrease in
systolic pressure. Overwork means even bigger overstrain: breathlessness
accompanied by stridor, possible epistaxis, cramps, ashen paleness, lip cyanosis,
vomiting, poor movement coordination, collapse with nonexistent peripheral pulse
and unconsciousness.
26
1.8.
Criteria of exertion
Participant’s maximum performance is a very important condition for quality
spiroergometry. To assess athlete‘s performance and his/her exhaustion level, we
use several criteria that differ in accuracy and reliability.
Subjective criteria are considered the least reliable. An examined person
terminates the load when he/she feels "exhausted". However, that is a very
unreliable indicator because it is associated with participant’s motivation in a stress
test. A participant feels „exhausted", if his/her motivation is small, even though
according to objective indicators he/she is far from reaching full exhaustion.
Conversely, some highly motivated athletes refuse to terminate the test, even though
they express signs of overloading. Therefore, to refine the rating, Borg created a
subjective scale of perceived exertion (Table 4). To achieve maximal performance
(exhaustion), we have to reach at least level 16 ("heavy load" to "very difficult"). The
Borg scale starts at level 6 and ends at level 20, because multiplying the level by 10
Approximately equals to participant’s heart rate.
Table 4.Subjective scale of perceived exertion (RPE, Rate of Perceived
Exertion)
(Borg,1982)
degree
verbal interpretation HR beats.min-1
6
60
7 Very, very easy
70
8
80
9 Very easy
90
10
100
11 Easy
110
12
120
13 A bit difficult
130
14
140
15 Difficult
150
16
160
17 Very difficult
170
18
180
19 Very, very difficult
190
20 Maximal
200
Note: It is appropriate to use Borg scale also for prescription of physical activity
in patients, whose medication was changed or who cannot find their pulse
easily.
Before administering RPE, each patient should be instructed that he/she
should consider overall stress and fatigue perception, so he/she does not focus only
on individual factors such as leg pain, shortness of breath, load intensity, etc.
27
Objective criteria, spiroergometric indicators, are considered to be reliable: 1)
RER value (respiratory gas exchange ratio) between 1.10 - 1.20. 2) VO2 max. kg-1
value that reaches plateau and does not rise for at least 60 seconds. 3) Ventilation
equivalent for oxygen (VEO2) that reaches minimum value of 35 (which means that
the examined person has to ventilate at least 35 liters of air to consume 1 liter of O2).
Spiroergometric indicators are, similarly to biochemical parameters, very reliable.
Since we use continuous analyzers of exhaled air during stress tests, we can monitor
these parameters on the screen during the actual test - spiroergometry ("online"),
which enables complete exertion of examined individuals, while minimizing overload
risks.
1.9.
Anaerobic threshold (ANT, stress threshold, lactate threshold)
Definition
Anaerobic threshold is a short period of time during load increase, at which
our body achieves balance between lactate formation and removal. Upon further load
increase, blood lactate concentration already undergoes uncompensated rise. It is
the turning point between primarily aerobic and anaerobic coverage of energy bodily
requirements, see table 5.
Anaerobic threshold is the highest intensity of dynamic loads, at which lactic
acid isn’t accumulated in peripheral circulation, and which human body is able to
manage for a long term. Workload intensity with the anaerobic threshold is
somewhere between 60 to 90% of maximum, depending on the degree of adaptation
to endurance performance.
The importance of measuring anaerobic threshold
ANT was originally used only in sports at top level. Currently, we use stress
intensity at the level of anaerobic threshold for a wide range of people from athletes,
untrained healthy people, to sick people with cardiovascular and other diseases.
In healthy people, it is especially important as the most effective training
intensity for improving organism’s aerobic capacity. For sick people, it is important as
the upper limit of safe intensity, which, when exceeded, leads to rapid development
of metabolic acidosis..
Table 5 Overview of physiological workload intensity zones according to
hyperlactatemia
(According to Fořt, 1983, and Rotman, 1985)
La level
%VO2max
Zone
9-27 mmol/l
100 %
oxygen debt
4-9 mmol/l
<100 %
anaerobic zone
4 mmol/l
60-90 %
anaerobic threshold
60-90 %(x)
transition zone
2-4 mmol/l
2 mmol/l
50-70 %
(x)
aerobic threshold
Metabolism
uncompensated lactate acidosis
partial compensation of La acidosis
La production = La consumption
partially anaerobic
strictly aerobic energy production
28
(x)
values in the zones partially overlap, because % of VO2max depends on fitness
levels and is different for each individual; values do not overlap intra-individually
The use of anaerobic threshold in medicine
a) Examples of ANT use in current sports and sports medicine
ANT in sports medicine is most often used as an indicator of aerobic fitness (VO2
ANT) to determine the most effective training intensity and to diagnose syndrome of
chronic overtraining, because according to Omiya, the decrease in VO2 ANT is more
sensitive than the decrease in VO2 max). According to Bunce, VO2 ANT higher than
82.5% of VO2max is one of the prerequisites for successful international competitive
performance in triathlon. Training intensity at ANT has good health effects (fitness,
lipid spectrum, bone density) and is applicable also in healthy elderly aged 60-70
years, as well as in obese women. Endurance walking at the level of ANT enables
more effective prevention against the progression of postmenopausal osteoporosis
than walking below the ANT.
b) Examples of the use of ANT in contemporary cardiology
Klainman used ventilatory ANT for controlled prescription of physical activity in
patients with various severity of coronary heart disease. Anaerobic threshold was
used with very good results in stimulating the movement of patients with CHD also by
Coyle, Foster, Jensen and others. Many authors consider the measurement of
ventilatory ANT to be a useful indicator (independent of participants’ will) for
monitoring the aerobic capacity response to physical intervention in patients with
compensated chronic heart failure and for prescription of physical activity in patients
with hypertension, hyperlipidemia and diabetes.
c) Examples of ANT use in other medical disciplines
VO2 ANT is mostly used as a sensitive indicator of changes in cardio-respiratory
fitness before and after treatment, for example in patients with decompensated
hyperthyroidism after hormonal substitution, in dialysis patients with renal anemia
after erythropoietin treatment, etc.
Methodology for anaerobic threshold determination
a) invasive method using lactic curve
The most frequently used invasive method is so-called lactate threshold
established by the rise of lactic acid in blood. Lactate threshold is considered the
most accurate method, however, it is used rather for experiments than for routine
testing. An advantage is its relative accuracy, a disadvantage is its invasiveness. We
evenly increase exercise load on a bicycle ergometer (Approximately 15-30 W.min1
) and take blood samples from a fingertip at regular time intervals. Lactic acid
concentration is measured in each sample. After that we construct a Graph of
dependence of lactate concentration on performance load (Graph 9).
The Graph shows that lactic curve has Approximately exponential course. The
use of aerobic O2 is getting close to maximum during ANT exercise load; a human
29
body begins to produce energy rather in anaerobic way leading to a steeper rise of
lactatemia. This phenomenon appears at LA curve as a turning point, which
corresponds to the anaerobic threshold.
Graph 9. Determination of anaerobic threshold using lactate curve and heart
rate
A turning point of the lactate curve corresponds to the anaerobic threshold.
The anaerobic threshold in this case is set at the level of LA concentration that is 4.1
mmol-1, which corresponds to the power of 275 W and heart rate of 164 beats.min-1.
According to Conconiho, the turning point (anaerobic threshold) is also ATparent in
the heart rate curve.
Graphic design of anaerobic threshold - the exponential method (Graph 10)
First of all, we create a regressive exponential curve through all the points of
spiroergometric dependence; then we plot tangents of the exponential curve at the
initial (tp) and final (tk) loading point, and from the intersection of tangents (T)
construct the shortest possible join (s) with the exponential curve. Such a point on
the exponential curve, which is the closest to the intersection (P), is the point whose
coordinates correspond to the anaerobic threshold ANT.
Y-coordinate of ANT indicates lactate concentration at the level of ANT, Xcoordinate of ANT indicates loading intensity, which can be expressed in watts or for an athlete/patient best: as heart rate. Nowadays, it is very convenient to use a
software application such as for example a spreadsheet to create a structure and
determine ANT.
30
Heart rate at the threshold level (TFANT) is therefore athlete’s/patient‘s highest
endurance performance that he/she is able to handle. It is also the most effective
training intensity.
Graph 10. Determination of anaerobic threshold using Graphic design
Anaerobic threshold in this case is determined by Graphic design (for details see text).
b) Non-invasive method of „V-slope“
From non-invasive methods we mainly use ventilatory-respirometric
measurements. A ventilatory ANT methodology is based on a classical concept of
increased LA formation related to a non-linear increase in ventilation, which
preserves the maintenance of eucapnia by exhalation of CO2 formed by LA
bicarbonate buffering.
According to professional sources, the most widely used method for
ventilatory anaerobic threshold determination is the "V-slope" method. The method is
called the V-slope, because ANT is determined by the slope of two “volume curves”,
of exhaled gases. The essence of the V-slope method is a computer analysis of
VCO2 changes as a function of VO2 at continuously increasing exercise load. VO2 is
used here as an independent variable. The sudden change in VCO2 slope is then
reckoned to be the ANT (Figure 11).
Graph 11.
Determination of anaerobic threshold using the V-slope method
31
V-slope method of ANT determination is based on changes in VCO2 slope. The first turning
point corresponds to the aerobic threshold (AT), the second to anaerobic threshold (ANT)
itself. Respiratory gas exchange ratio RER then shortly after reaches the value of 1.0.
V-slope has the advantage of smaller variability in resulting values due to
smaller dependence of measured parameters on physiological fluctuation of
pulmonary ventilation. It is therefore more reliable than any other previous
ventilatory-respirometric method. The disadvantage of the V-slope method is that the
turning point is not always obvious, and that it requires expensive equipment
(analyzers).
There are usually two obvious turning points on the VCO2 curve (see Graph
11). The first one corresponds to so-called ANTI or aerobic threshold (AT), the
second one then is ANTII – the anaerobic threshold. The level of lactate at the
aerobic threshold is around 2.0 mmol.l-1, RER ranging from 0.80 to 0.95 and VO2 AT
around 50-60% of VO2 max. At the level of anaerobic threshold, lactate value is around
4.0 mmol.l-1, RER around 0.95 and VO2 ANT between 60-90% of VO2 max. Subjectively,
aerobic threshold is the transition from light to moderate load, anaerobic threshold is
generally perceived as a transition from heavy to very heavy loads.
c) Conconi test for ANT determination
Graph 9 illustrates the connection between ANT determined by a lactic and a
heart rate curve. An Italian physiologist Conconi discovered this relationship in early
eighties of the 20th century. Heart rate during increasing exercise load rises linearly
up to ANT and its increase slows down once it reaches it. An advantage of this
32
method is its non-invasiveness and low demands on equipment. Part of the
professional community criticizes the method for lower reliability.
Assessing fitness according to the course of lactate curve
Graph 12. Change of lactate curve after aerobic and anaerobic training
(Bunc, 1989)
a) Aerobic fitness
During regular endurance training with a predominance of aerobic load and
longer duration, changes in the course of lactate curve arise: these include shifting of
the ascending arm of the curve to the right; the shape or slope of the curve remain
unchanged (Graph 12).
b) Anaerobic fitness
During regular speed-endurance training at high intensity at the level of
anaerobic threshold, with a big part of anaerobic load and medium duration of
training units, there is a change in a lactate curve in a sense that the distance of the
ascending arm of the curve does not change, but the slope of the curve is smaller
and high lactate level in muscles is achieved later. Anaerobic fitness has improved
(Graph 12).
33
The reproducibility of ANT measurement
ANT results obtained by whatever method cannot be overestimated.
Processes of neurohumoral regulation during physical activity are so complex that
they cannot be fully described by just one curve. Neither lactate curve nor VCO2
curve display the result of only actual physical exercise. They are influenced (among
others) by previous training and nutritional composition of ingested food by an
athlete. Therefore, anaerobic threshold is not always fully reproducible.
2. DIVING REFLEX
2.1.
Diving reflex – principle and purpose
Diving reflex is a reflex associated with diving. It is one of the strongest
autonomous reflexes based on a combination of breath holding, water pressure
applied on eyeballs and especially cold stress affecting our face that evokes a
significant circulatory reaction: a sinusoidal bradycardia during which otherwise
hidden heart disease can appear. Simultaneously, there is a blood redistribution –
a selective vasoconstriction in upper and lower limbs associated with increased
blood pressure.
Diving is a very risky sport and that is why diving reflex is a required
component of preventive sport medicine examinations in divers. However, Kawakubo
34
recommends it also for hardy fellows, triathlete, distance swimmers, aquabellas,
water slalom racers, canoeists, windsurfers, and water skiers as a prevention of
heart failure, chamber fibrillation and other serious arrhythmias.
2.2.
Neural path of diving reflex
Panneton used muskrats and their anterograde transneural transport of
herpes simplex virus through anterograde ethmoidal nerve to show that afferent path
leads to the brain stem and spinal mesencephalic and spinal nucleus of the
trigeminal nerve through the trigeminal nerve and from there realigns to the vagus
nerve. Efferent paths lead impulses (modulated by wind, vasomotor and cardioinhibitory center) through the vagus nerve to the heart.
2.3.
Methodology of diving reflex
We place ECG electrodes on a person that is being tested; he/she inhales,
leans forward and immerse his/her face in a sink with cold water. We record ECG
throughout the whole process. In the methodology Lin recommends to immerse
forearms first (cold pressure test), then isolated lean forward, isolated apnea and
finally immerse the face or attach a bag (allows breathing) with a cold gel to the face
to distinguish to which maneuver is the examined person most sensitive. The
reproducibility of the test is greater when the water/gel temperature gets close to
zero. However, the water/gel temperature should rather be 8°-10°C to prevent
damage of patient's health. The test is performed until subjective maximum, however
apnea in men should last at least 1 minute, and in women 45 seconds. ECG can be
measured telemetrically (advantages: patient's mobility, safety, simplicity), on the
contrary a table ECG device allows to monitor more leads and thus diagnose more
precisely.
2.3.1. Hemodynamic changes during diving reflex
Diving reflex causes blood redistribution from limbs to chest, increases systolic
and diastolic blood pressure and peripheral vascular resistance, increases venous
return, central venous pressure, bradycardia occurs slowly (in 20-30%), stroke
volume usually increases, while cardiac output rather decreases (because unlike the
cold pressure test, during which is significantly activated only sympaticus, during
diving reflex is mainly activated vagus nerve).
2.3.2. Arrhythmia during diving reflex
Cinglova found various types of arrhythmia revealed thanks to diving reflex in
15-year-old swimmers: ventricular extrasystoles in 10%, supraventricular
extrasystoles in 3%, atrial rhythm in 3%, junctional rhythm in 6%, bottom junctional
rhythm in 3%, shifting pacemaker in 3%. According to our experience, percentage
representation has been similar, additionally several times we recorded also
sinoatrial block lasting longer than 3 seconds in adult men aged 18-45 years. The
most common arrhythmia was ventricular extrasystoles, whose severity (Table 6) is
evaluated according to Lown.
35
Table 6. Classification of severity of ventricular extrasystoles
(Lown, 1991, we use it as an assessment criterion for diving)
class
I
II
IIIa
IIIb
Iva
IVb
V
VES
monotopic, <30/min
monotopic, >30/min
polytopic
polytopic with affinity
in pairs
in bursts (3 and more)
phenomenon R on T
diving
allowed
further examination
diving prohibited
diving prohibited
diving prohibited
diving prohibited
diving prohibited
Diving cannot be allowed even when a heart attack (sinuous-atrial block) occurs
for a period longer than 3 seconds.
Diving reflex – mini-casuistry
Figure 1. ECG curve n. 1: sporadic SVES
Comment: man 23 years, apnea length 0 min 58 s, HR: 100/min ... 73/min … 42/min,
Sporadic SVES, still physiological curve, diving is permitted in full range
Figure 2. ECG curve n. 2: extreme bradycardia
36
Comment:
man 20 years, apnea 1 min 35 s, HR 92/min...131/min...25/min !
HR is gradually slowing down until extreme bradycardia
high irritation of autonomic nervous system, physiological curve
diving allowed in full range
37
Figure 3. ECG curve n. 3: nodal rhythm
Comment:
Man 18, apnea 1 min 18 s,... HR 89/min…98/min…37/min,
nodal rhythm 40/min (the shape of QRS has changed, duration of
0.10s), still physiological curve
diving allowed up to 6 m depth, organic disability not proved, after that
diving allowed in full range
Figure 4. ECG curve n. 4: sinus arrest
Comment:
Male 37 years, apnea for 1 min 15 s, HR 100/min…123/min...about
40/min,
5x supraventricular extrasystole, shifting pacemaker, sinoatrial block for 3 s,
38
pathological curve, organic disability has not been proved, despite of that
diving not allowed
39
Figure 5.
ECG curve n. 5: bottom junctional rhythm
Comment:
man 30 years, apnea for 1 min 42 s, HR 130/min…sinus for 44/min…
intermittent bottom junctional rhythm of 44/min (shape of the QRS
roughly changed, duration of 0.13 s; repolarization disorder in the form
of ST segment depression and pre-terminal negativity of T wave),
boundary curve, organic disability has not been proved, however diving
is limited up to 6 m of depth
40
Appendix 1
Compendium of selected human sports activities
(According to Ainsworth, 1993)
3.
Sport
Aerobics
Running
Running
Box
Skating
Cycling
Cycling
Cycling
Bicycle ergometer
Walking
Jogging
Judo
Lifting
Soccer
Soccer
Ski: cross-country
Ski: cross-country
Ski: downhill
Ski: downhill
Orienteer running
Swimming
Swimming
Squash
Table tennis
Tennis
Tennis
Windsurfing
Wrestle
characteristics
intensive
10 km/h
15 km/h
generally
generally
mountain bike
25 km/h
32 km/h
100 W
plateau, 6 km/h
generally
generally
generally
generally
competitively
generally
competitively
generally
competitively
generally
crawl easily
crawl fast
generally
generally
doubles
singles
generally
generally
METs
7,0
10,0
15,0
12,0
8,0
8,0
10,0
16,0
5,5
4,0
7,0
10,0
6,0
7,0
10,0
7,0
16,5
6,0
8,0
9,0
8,0
11,0
12,0
4,0
6,0
8,0
3,0
6,0
Appendix 2
List of used abbreviations
ANT
AT
ATPS
BTPS
anaerobic threshold, stress threshold, lactate threshold
aerobic threshold
correction factor to calculate gas volume (A=ambient)
correction factor to calculate gas volume (gas saturated with
water vapors)
CI
cardiac index (CO/m2)
CO
cardiac output
BF, fB
breathing frequency
ECG
electrocardiograph
FaO2
fraction of arterial O2
FEO2, FECO2
fraction of exhaled O2, CO2
FIO2, FICO2 fraction of inhaled O2, CO2
IBP
International Biological Program
IHD
ischemic heart disease
IM
myocardia infarction (heart attack)
VES
ventricular extrasystoles
LA
lactate, lactic acid
TSM
therapeutic sports medicine
MAT
mean arterial pressure
MET
metabolic equivalent (1 kcal/kg/hr)
MVC
maximal voluntary contraction
NYHA
functional classification according to New York Heart Association
Q
cardiac output
systolic volume
QS
R, RQ
respiratory quotient
RER
respiratory exchange ratio
RPE
Rate of Perceived Exertion
SI
stroke index (Qs/m2)
STPD
correction factor to calculate gas volume (dry gas – Standard,
Temperature, Pressure, Dry)
SV
systolic volume
HR
heart rate
DBP
diastolic blood pressure
SBP
systolic blood pressure
SMM
sports-medical monitoring
SM
sports medicine
VCO2
volume of released carbon dioxide
VECO2
ventilatory equivalent for carbon dioxide
VEO2
ventilatory equivalent for oxygen
VO2
volume of oxygen consumed
VO2.kg-1
consumption of oxygen per kg of body weight
VO2.BF-1 stroke oxygen
W170
work capacity at 170 beats