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scubapro.com
HEARTRATE MEASUREMENT FOR
BETTER WORKLOAD ASSESSMENT
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03 - Heart rate measurement during diving
04 - How the heart rate is measured
05 - Resting heart rate - how is it influenced?
06 - Cardiac output, blood pressure and workload
09 - Influence of body position on the heart rate
10 - Change of heart rate through breathing
11 - Heart rate when in apnea
12 - Fluid balance and heart rate
13 - Heartbeat - heat and cold
14 - Why does excitement make the heart race?
14 - Heart rate training indicator
15 - Fitness training and training tips
18 - Glossary
TABLE OF CONTENTS
The heart rate is an important indicator
for arising stress. This has been known
for a long time. The sports industry has
reacted to this and is offering an array of
products for ambitious athletes to analyze
and evaluate their training. Whether
a passionate recreational athlete, a
professional marathon runner or a healthconscious retiree – today a heart rate meter
is almost a standard piece of equipment.
So why not use this technology in diving as
well? With the aid of a heart rate monitor
you can keep an eye on the heartbeat
underwater as well and are thereby able to
make your dives even safer. By monitoring
the heart rate, the workload can be
better assessed and the diver can react
to heightened stress in a timely manner.
Furthermore, by measuring the heart rate
you can specifically train to increase your
endurance in advance.
Since increased exertion while diving
in deep water increases circulation
and this in turn increases the nitrogen
uptake, the heart rate can also be used
to calculate decompression times even
more accurately and make diving even
safer. That’s why the SCUBAPRO computers
don’t just show depth, no-stop times and
the decompression schedule but also
continuously inform the underwater athlete
about his or her own heart rate, i.e. his or her
personal stress, which in turn is factored in
when calculating other dive parameters.
However, there are several factors to
consider when using the heart rate while
diving. This booklet will help you to better
understand the background and thereby
draw the right conclusions from the heart
rate behaviors measured. That way,
you’ll be able to make optimal use of this
innovative technology integrated in most
SCUBAPRO computers.
To make this fitness booklet easy and
quick to use and to make the contents as
readily understandable as possible, the
table of contents consists of frequently
asked questions with regard to heart rate,
fitness and diving. This way, any interested
diver only needs to take a quick glance at
the table of contents in order to find the
chapter that contains the answer to his or
her question.
Listen to your heart!
Written by:
Dr. Uwe Hoffmann
Dr. Tobias Dräger and
Jörn Kießler (editor)
INTRODUCTION
3
HEART RATE MEASUREMENT
DURING DIVING
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What exactly is the resting heart rate and
how is it influenced? The resting heart rate is
the heart rate a person has when he or she is
not exerting himself or herself. To determine
its reliably, the resting heart rate should
always be measured under comparable
conditions. Important factors are timing
– usually it is determined in the morning
five minutes after waking up – and body
position. Ideally, the person should remain
lying down in bed during the measurement.
The most reliable results are delivered by
a heart rate monitor in this case as well.
If none is available, you can also count
the heartbeats for 20 seconds and then
extrapolate this to one minute, i.e. multiply
the number by three. However, if you count
the heart rate yourself you should keep in
mind that even counting will influence the
heart rate. The important thing is that the
method of measurement should always be
the same.
On the one hand, the resting heart rate
measured provides you with a value to easily
compare yourself to others. However, the
role of the resting heart rate as an indicator
for the overall workload is much more
important. For exertion both underwater and
on the surface, the resting heart rate serves
as a point of reference in order to assess and
classify acute stress.
Of course, not everyone has the same heart
rate since every person is different. And it’s
exactly these differences that influence the
respective heart rates. For example, age,
body height (not just body position) and the
size of the heart are just three characteristics
that explain the differences between the
values of different individuals. For example,
past exertions on the previous day, diet,
fluid intake, time of day, ambient conditions
(temperature, humidity, altitude), and body
position are all factors that influence the
HEART RATE
5
RESTING HEART RATE HOW IS IT INFLUENCED?
There are many ways to measure the
heart rate. As an amateur, you can feel
the heart rate on the lower arm artery or
on the carotid artery, for example, and
count it for a set amount of time – usually
15 seconds. You can also hear a heartbeat
when putting your ear to another person’s
chest. In medical practice the heart rate is
usually captured by a electrocardiogram
(ECG). Every heartbeat produces a
measurable electrical signal. Using at least
two electrodes, one on each side of the
heart, this signal can be measured from the
exterior of the body.
Many heart rate monitors used in sports
apply this technique and incorporate such
electrodes into chest straps. The electronic
devices inside the chest strap search for
the electrical impulse every heartbeat
produces. The registered impulse is
transmitted as a signal to the receiver, e.g. a
heart rate monitor, and then analyzed. For
this application it is essential that the two
electrodes remain in contact with the chest
at all times.
WHILE DIVING
And that’s exactly the measuring principles
used by SCUBAPRO computers as well.
With a waterproof chest strap featuring
two electrodes, the electrical impulse
of the heartbeat can also be captured
underwater.
However, the data is not sent to a simple
heart rate monitor but to the dive computer.
And the computer does exactly the
same thing a heart rate monitor does, for
example, while someone is jogging: it shows
the heart rate the diver is experiencing a
that moment. Of course, it also stores the
data, so that after the dive it is possible
to reconstruct exactly at what point the
workload was especially high or especially
low. One special feature of SCUBAPRO
computers with which no regular heart rate
monitor or traditional dive computer can
compete, is that the diver’s heart rate is
factored into the calculation of the no-stop,
decompression and ascent times. Instead
of relying on a single algorithm, current
personal data is utilized.
To this end, SCUBAPRO computers display
the median heart rate over a set period
of time, e.g. every four seconds. Using this
technique, it is possible to capture the heart
rate at rest and during physical exertion
easily and without much disruption to the
person concerned.
HEART RATE
4
HOW THE HEART
RATE IS MEASURED
Heart rate measurement under
water using the chest strap
heart rate. But also acute changes have
an impact on the resting heart rate. For
example, breathing always plays a role with
regard to the level of the resting heart rate. It
influences the heart rate through its impact
on the blood supply and drainage to and
from the heart.
Among other things, an elevated respiratory
rate – due to excitement for example – also
increases the heart rate. After an exertion,
the heart rate of an endurance-trained
person drops back down to its base level
more quickly than the heart rate of an
untrained person.
WHILE DIVING
The resting heart rate indicates “the lowest
limit” that a diver could reach. Certainly,
no dive is started at the “true” resting heart
rate, since putting on the gear alone is often
strenuous enough to boost it.
200
150
100
50
HF
-2 -1 0 1 2 3 Time
Untrained Trained
Return to base heart rate
dependent on training status
Exertion Recovery
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HEART RATE
7
The heart is embedded between the two
lungs and works like a displacement pump:
blood is valve-controlled and sucked in
through the superior and inferior caval vein
via the right heart side , loaded with new
oxygen via the lung, and discharged again
through the large body artery (aorta) via the
left side of the heart.
For the body, the heart rate is really a
secondary factor. There is no place for the
body to capture the heart rate directly.
Similar to a gas pedal in a car, the optimal
heart rate at any given time is determined by
other factors. For example, you would never
drive full speed at rush hour in the city. Nor
would a driver ever crawl along an empty
highway at 20 miles per hour. So, just like the
traffic conditions determine the speed of a
car, supplying the tissue – in particular with
oxygen – is central to the organism. If the
tissue is using up a lot of oxygen, the heart
steps on the gas to pump a certain amount
of blood per unit of time through the tissue.
Therefore, the critical factor is the cardiac
output, that is to say the amount of blood
that is pumped through the body within one
minute of time, for example.
A second factor is the distribution of blood
within the body. This is measured by the
HEART RATE
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CARDIAC OUTPUT, BLOOD PRESSURE
AND WORKLOAD
An Emergency situation is communicated
to the body by sensors and the central
nervous system. In particular, information
from the central organs, like the brain itself, is
processed. Two compensation mechanisms
are possible:
Locally, better circulation can be
achieved by opening the arterial vessels,
i.e. the body provides the blood with
supply channels that are as large as
possible. To use the car metaphor again:
the body clears the highway for the blood.
This way, it can get to the undersupplied
areas quickly.
Centrally, cardiac output can be ramped
up by increasing the stroke volume and/
or heart rate: the body steps on the gas.
A special measure for the interaction
between local circulation and cardiac
output is the arterial blood pressure. It
determines how fast the blood flows
and therefore how fast substances are
transported back and forth. If the arterial
vessels are dilated and offer less flow
resistance, the cardiac output needs to be
raised to maintain the blood pressure – the
heart rate increases.
If the blood pressure is high, that is if the
vessels are constricted, it’s the other way
around. In this case, the heart rate is
lowered. Keeping these facts in mind, it is
worthwhile to take a closer look at how the
cardiovascular system reacts to increased
muscle activity. Because here, a special
case comes into effect.
MUSCLE ACTIVITY
When muscles are flexed they depress
the nearby vessels, which increases the
vessel resistance. This should lead to an
excessive increase in blood pressure, so the
heart rate should actually slow down as a
result. However, just the opposite happens
because the physical activity triggers
complex processes in the brain, which lead
blood pressure, which can be determined
by the organism based on how much the
vessels are stretched.
The way the system works couldn’t be easier.
As soon as there are signs of insufficient
circulation, compensation mechanisms
are put into action. The body reacts to the
imminent undersupply.
Diagram: Cardiopulmonary
System
to changes in blood pressure. The metabolic
process caused by the contraction, the
metabolites produced and the heightened
impact of the sympathetic nervous system
lead to further changes that cause the
heart rate to increase. Because when the
performance level increases the active
muscles must be supplied with more blood.
Nutrients and especially oxygen have to be
delivered in larger quantities, metabolites,
especially lactic acid and carbon dioxide,
as well as heat have to be removed. This
requires an increased cardiac output.
As the stroke volume ( meaning the amount
of blood that is pumped through the heart
by a heartbeat ) limits the ability to increase
the cardiac output, the greater need is
mainly met by the heart rate. The rule of
thumb is: the heart rate rises proportionally
to the metabolism.
Aortic arch
If the workload is high, more
oxygen needs to be transported
to the muscles, so the vessels are
dilated
In combination with the maximum heart
rate, you can at least define the range within
which the heart rate fluctuates. This way, just
one glance at a SCUBAPRO computer will tell
you how high your level of exertion currently
is, based on completely objective criteria.
Keep in mind however that, particularly
while in the water, it is conceivable that a
heart rate below the actual resting heart
rate can temporarily occur. Why? Simply
because basic environmental variables
change and affect the body when you
plunge into the water. The sum of the effects
described below makes the heart rate slow
down underwater.
This slowdown needs to be considered
when interpreting the changes in heart rate.
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HEART RATE
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HEART RATE
8
Let’s use the car metaphor again. In a car
(blood) certain passengers (oxygen and
metabolites) are to be quickly transported to
the requested location (muscles). Because
the car can only be enlarged to a limited
extent (limited stroke volume) and therefore
can only accommodate a limited number
of passengers, the pilot (heart) has to drive
more often and therefore steps on the gas
(heart rate). Responsible for the reaction
to such changes –(that cannot only be
caused by strong temporary exertion but
also by a change in position ) are special
stretch receptors on the aortic arch and at
the bifurcation of the carotid artery. They
deliver the necessary information that is
processed by the central nervous system to
quickly adapt the blood pressure to the new
situation. However, it is also crucial whether
it is static work done over a longer period
of time or dynamic work that allows for a
continuous blood supply to the muscles.
This type of muscle activity occurs with all
types of locomotion, so with finswimming
in particular as well. Here, the performance
level is the decisive factor for the heart rate
setting: if a person swims faster or has to
fight strong currents he or she needs more
oxygen in the muscles used than somebody
who calmly glides over a coral reef with an
occasional fin stroke.
This greater need for oxygen does not
mean that the breathing rate needs to be
increased immediately to raise the oxygen
uptake, but rather that more oxygen needs
to be transported to the muscles used.
WHILE DIVING
On the previous two pages we’ve
explained what means the body uses to
adapt to certain situations. Of course, these
mechanisms are also effective in diving,
both before the dive and later underwater.
Carrying and putting on heavy equipment
is usually already the first physical strain,
which does not only exercise the muscles
but also the cardiovascular system.
The body position also influences the
heartbeat. In particular it determines the
venous return to the heart: in a horizontal
position for example, when the body lies
more or less on an even level, more blood
can flow to the heart. Why? The answer is
very simple: when standing up the blood
moves to the lower extremities. The blood
has to flow against the hydrostatic pressure
gradient – meaning virtually against the
force of gravity – back up to the heart. But if
you are lying down and thus move your legs,
torso and head at the same level, the blood
volume shifts: blood from the legs moves to
the heart whereby initially the stroke volume
increases and the heart rate decreases.
The reason for this is the increased blood
supply to the right heart chamber (ventricle,
atrium), which the body interprets as a
signal for a higher fluid balance –, since
this is exactly what also happens when you
drink a lot and the blood volume rises as a
result. In both cases, another compensation
mechanism takes effect: more urine is
produced. This increased urine production
and the resulting blood volume reduction
will over time compensate for at least part
of this effect. When you stand up again the
exact opposite happens: the stroke volume
decreases and the heart rate increases.
The blood volume increased once again
through fluid supply.
WHILE DIVING
As just described, this effect arises from
the influence gravity has on the body. If
the body moves to a horizontal position it
neutralizes gravitation to a certain extent.
And exactly the same thing happens
when the body is submerged in water up
to the neck, because the water pressure
INFLUENCE OF BODY POSITION
ON THE HEART RATE
Even more strenuous is when you are in the
water with the equipment, which gives a
strong water drag (much stronger than the
air resistance during jogging or bicycling)
and you are moving along by finning, your
muscles and heart are being exercised.
Obviously, the faster you swim the
more physical effort is required. But this
relationship is also heavily dependent
on the diving equipment worn and the
movement technique employed. A diver
who has a refined, economic finning
technique needs to exert himself a lot
less to achieve the same velocity than a
swimmer with less training. However, in this
context the heart rate can’t be used as an
indicator for the absolute metabolic value.
Heart rate is a useful tool to measure and
prove changes in one’s physical fitness, but
it is not the best and only one.
The heart rate behaves
independently from the depth
Maximum
depth
When submerging into the water
the venous blood volume shifts
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HEART RATE
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HEART RATE
10
So, breathing influences the heart rate. But
what happens when you are not breathing?
Particularly while diving? Of course, you
can also hold your breath above water, but
during a dive it can be absolutely necessary
– for example while buddy breathing. And
there are different «levels» of holding your
breath , the diving reflex and apnea diving,
that is to say intentionally diving without a
compressed air tank, just using the air in your
lungs.
THE DIVING REFLEX
The diving reflex is a natural reflex that allows
mammals to stay under water for extended
periods of time. It is especially pronounced
in aquatic animals, but also detectable in
humans. The trigger signal is a facial cold
stimulus, so water as well, which is designed
to extend survival. This cold stimulus, which
can be triggered by an ice pack pressed to
the face for example, also triggers an easily
measurable reaction while resting: the heart
rate slows down (bradycardia).
This is due to receptors around the nose,
eyes and mouth. The slowdown of the heart
rate can reach more than 10 heartbeats per
minute in humans, in animals a slowdown of
over 50% has been shown.
This bradycardia is accompanied by other
reactions used by the body to adapt to
the new situation. The blood vessels in
the tissue, which can function without
oxygen for a short period of time, constrict
(vasoconstriction).
This way, oxygen is conserved for vital
organs (for example the central nervous
system or the heart) and simultaneously
an increase in blood pressure is prevented.
HEART RATE WHEN IN APNEA
The cardiopulmonary system shifts
according to the body position
Previously, we’ve explained how physical
exertion and body position affect the
heart rate. But there are other factors that
influence the heartbeat as well. One of
which is breathing. Of course, a person’s
breathing and in particular the breathing
volume is often times impacted by physical
exertion. When muscles and tissue need a
lot of oxygen, the vessels are dilated and
the heart pumps quickly, the necessary
amount of oxygen needs to get into the
system via the lungs, i.e. through breathing.
The breathing rate and breathing volume
increase. You inhale more air into the
lungs more often. But even when you are
not puffing like a grampus, heart and
lung function are closely interconnected.
This is due to the way the human body
is constructed: namely that the heart is
embedded between the two lungs (see
figure on page 6). Therefore, any negative
or positive pressure in the lungs also affects
the activity of the heart.
During inhalation the lung develops a
negative pressure, which causes air to be
sucked in through the pharynx.
This negative pressure provides for a better
CHANGE OF HEART RATE THROUGH
BREATHING
During exhalation it’s exactly the opposite.
Especially during exhaling on exertion,
for example during pressure equalization
using the Valsalva maneuver, the venous
return flow is impeded, but the blood
pressure, at least temporarily, increased. For
these two blood pressure fluctuations, the
body has a compensation mechanism at
hand as well: the so-called autonomous
regulation. It limits the increase or decline
in blood pressure through corresponding
heart rate reactions. As a result, more or
less distinct heart rate fluctuations occur,
particularly while resting.
WHILE DIVING
The water pressure that impacts the
submerged body leads to a greater
pressure difference between the gas-filled
and the fluid-filled part of the lung, because
unlike the fluid-filled part the gas-filled part
can be compressed, i.e. squeezed. The
rule is: in an upright position the difference
is greater than in a horizontal position.
So, if you are floating under water in an
upright position, for example during a short
break in order to look at something more
closely on a steep face, the blood pressure
fluctuations of the body are more extreme
as well. But this effect can also occur while
swimming in a horizontal position, namely
while snorkeling. A snorkel can increase the
pressure difference as well. It too directly
impacts the return flow to the heart and
therefore influences the heart activity and
the heart rate.
neutralizes the pressure gradient effective
outside the water.
When submerging into the water, the venous
blood volume shifts: outside the water (left
red) a large portion of the volume is found in
the leg veins. After submerging (right blue)
the volume shifts towards the chest/heart.
This affects the cardiac output and leads
to an increased urine production. Thus, the
blood volume is significantly reduced after
diving.
However, as already explained in the
previous chapter, the position within the
water also affects the heart rate, though
no longer because the blood shifts, but
rather because the position within the water
affects the breathing (see figure on page 9).
venous return flow, but simultaneously also
for a light decline in arterial blood pressure.
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HEART RATE
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HEART RATE
12
When the ambient temperature changes,
the body exhibits a similar reaction as when
fluid is supplied or withdrawn. If you go
outside on the balcony in the middle of the
winter just wearing a t-shirt you will sooner or
later feel cold. The body counteracts the loss
in temperature by constricting the vessels on
the body’s surface, i.e. in those places where
the heat escapes. The constriction causes
the pressure on the vascular walls to rise and
the cardiovascular system reacts like it does
to a fluid surplus: the heart rate is slowed
down. Subsequently, when the body tries to
stabilize its temperature by producing its own
heat through an increased metabolism, the
heart rate rises again. Later on, continued
cold exposure leads to further adjustments,
which we won’t discuss here.
Heat has exactly the opposite effect. The
heart rate rises because the vessels on
the body’s surface are dilated. As a result,
blood volume is shifted to this tissue and
thus missing in the venous return flow.
Furthermore, the cardiac output and blood
pressure need to be increased. Later on,
HEARTBEAT - HEAT AND COLD
influencing factors might follow that are
caused by perspiration, i.e. fluid loss.
WHILE DIVING
Of course, the same effects occurring on
the surface also occur under water. The
only difference is that under water you start
feeling cold much faster. The reason for this is
water’s higher thermal conductivity. While air
is a poor heat conductor and has an almost
insulating effect, water «sucks» the heat
from our body, figuratively speaking. While
we perceive a day with an air temperature
of 25 °C (77 °F) as pleasantly warm, without
cold protection and at rest the body already
starts to increasingly release heat at water
temperatures of below 32 °C (90 °F). The
body starts to become hypothermic and
tries to counteract this by constricting the
vessels that are close to the body’s surface.
The question of how the fluid balance
impacts the heart rate can be easily
answered by applying what we’ve learned
in chapter five. That’s because severe fluid
loss or excessive fluid intake has the same
effect as a change in body position or
getting out of or into the water, however for
different reasons (see figure on page 9). If
the body is supplied with fluid by drinking,
the amount of blood available to the heart
also changes: the stroke volume increases
and the heart rate slows down. The opposite
case, too little fluid, has the same effect as
getting into an upright position or leaving
the water: the stroke volume decreases, and
the heart rate speeds up.
WHILE DIVING
Regarding the fluid balance a peculiarity
needs to be pointed out as well. On a
diving vacation in particular, several factors
combine that can have a strong impact on
the heart rate. As described earlier, during
FLUID BALANCE
AND HEART RATE
The more pronounced the vasoconstriction,
the greater the slowdown in heart rate. This
virtually means that the diving reflex leads
to the exact opposite reaction physical
exertion brings about. While the body
increases the heart rate during exertion
in order to be able to supply the entire
tissue and therefore dilates the vessels so
the blood pressure doesn’t go through the
roof, under apnea all systems are geared
towards conservation.
APNEA DIVING
During apnea diving, exactly the same
effects occur since the face comes into
contact with water in this case as well.
However, apart from the aforementioned
reactions additional compensation
mechanisms of the body come into
effect, some of which have already
been described. For example, the blood
volume also shifts towards the heart when
diving without a compressed air tank (see
«Influence of body position on the heart
rate»). During apnea diving this effect is
even more pronounced, because the air-
filled lungs are being compressed more
and more the deeper the diver goes, which
leaves more space for the blood flowing
into the chest area.
This doesn’t have any additional impact
on the heart rate however, since this shift
in blood volume prevents the build-up of
negative pressure in the chest area and
thus a barotrauma of the lungs. But another
factor (which hasn’t been mentioned
before and which only exists during apnea
diving) further slows down the heart rate: the
rise of the carbon dioxide ratio. The longer
an apnea diver is under water, the higher
the CO2 ratio in his blood gets. This leads to
an additional slowdown of the heart rate.
Physical exertion during the apnea time,
like dynamic apnea, further intensifies this
effect.
the dive the blood volume shifts towards the
heart. This signals the body that there is a
perceived fluid surplus and the body begins
to produce urine in order to release fluid
(diver’s diuresis). After the dive, the blood
volume doesn’t only shift back towards the
lower extremities and away from the heart
(see chart on page 9), but two additional
factors come into play: a low fluid balance
and high heat. At many popular diving
destinations, like the Mediterranean, the Red
Sea and the Indian Ocean, temperatures
are very high. Here, an adequate fluid
intake after the dive is essential as the blood
volume will otherwise drop so severely that
even an increased heart rate can’t prevent
an undersupply of the tissue. A circulatory
collapse might result. And another, diverspecific risk increases as well: namely, to fall
victim to a decompression accident during
the dive. Because the lower blood volume
makes the blood thicker, the viscosity rises
and thus the risk that nitrogen bubbles won’t
dissolve in the blood and therefore cause
an embolism.
Page 8
FITNESS
15
FITNESS
14
additional advantage. It makes it relatively
easy to evaluate your own fitness level. One
reference point is the resting heart rate,
which is about 50 beats per minute for an
endurance-trained person and about 75
beats per minute for an untrained person.
Another reference point is the maximum
heart rate, which is assumed to be about
five times the resting heart rate for a trained
athlete, while an untrained person can only
increase it to three times the resting heart
rate. The reason for this difference is the
efficiency of the «athlete’s heart» that offers
a better transport performance. But it’s not
just the training status that’s important ,this
leads us back to the before mentioned
background knowledge: the maximum
heart rate is significantly restricted by a
person’s age. This means that older divers
– even if they are well trained – can’t reach
the same maximum heart rate as 20 year-old
divers.
A simple rule of thumb has been
established for mass sports:
Average maximum heart rate: 220 – years
of age=beats per minute
Example: a 75 year-old man has an
average maximum heart rate of 145 beats
per minute. 220 – 75 years=145 beats per
minute
According to this rule of thumb, the heart
of a 20 year-old however could beat 200
times per minute under maximum stress.
220 – 20 years = 200 beats per minute.
But it’s actually much more interesting to
look at the resting heart rate described
earlier. The heart rate differs greatly from
person to person for a number of reasons:
the point of time at which the resting heart
rate is reached again after an exertion has to
be compared subjectively and objectively.
After an exertion, an endurance-trained
person will be back at his or her resting heart
rate much faster than an untrained person.
Based on this knowledge, it’s actually
quite easy to design a targeted fitness and
endurance training , because you now know
how to use the heart rate to assess your own
stress level and thus keep your training within
the right range of intensity.
There is another rule of thumb with which to
calculate the average heart rate you should
maintain while training.
Training heart rate: 180 – years
of age = beats per minute
If we take our 75 year-old athlete and
his 20 year-old training partner as an
example once again, we can give
them the following training advise:
180 – 75 years = 105 beats per minute
This means that our older diver should train
FITNESS TRAINING
AND TRAINING TIPS
As already mentioned in the introduction,
the heart rate is a good indicator for arising
stress. And just one glance at a SCUABPRO
dive computer will immediately tell you how
high the exertion under water is, based on
completely objective criteria. Of course,
other parameters could also be used to
assess the intensity of stress such as swimming
or running speed, but these can’t illustrate
the individual exertion in a meaningful way.
To give you an example: the heart rate of a
recreational athlete would likely go through
the roof if he completed his usual Sunday
jogging route of 8 kilometers (5 miles) in
less than 30 minutes. For a professional
marathon runner however, such training
sessions are part of his regular training
program and his heart rate wouldn’t even
come close to the maximum value possible.
This example shows how important it is to
know your own individual performance limits
and to use them to orient yourself in order
to experience a meaningful endurance
training. Personal limits can be easily but
effectively established by using the resting
and maximum heart rates.
However, in reality these parameters are
just auxiliary values, because what’s key for
the right training is the muscle metabolism
or, more specifically, the ratio of aerobic
metabolism to anaerobic metabolism. That
is to say the metabolism that takes place
with sufficient oxygen and the metabolism
for which insufficient oxygen is available.
But since this is only measurable using
elaborate technical equipment the heart
rate is the easiest parameter to assess
the intensity of stress. And the readily
determinable resting heart rate offers an
HEART RATE TRAINING INDICATOR
Finally, we want to discuss a change in heart
rate that though it is also brought about
by external influences can’t be explained
by temperature, water pressure or fluid
amounts: emotional excitement.
During human evolution the body has
learned a lot, including the concept that
emotional excitement is usually related
to a certain danger, which requires high
performance or at least the willingness
to physically react. Accordingly, stress
hormones cause a change in blood
pressure and heart rate. The organism is put
on alert. In this sense, the heart rate is no
longer an expression of physical exertion,
but it prepares the body for increased
requirements.
Emotional excitement also differs from
person to person. A dive instructor who has
been working in the Indian Ocean for many
years will be less excited when sighting a
whale shark than a diver who has never
before come across one of these giants.
Though no matter why you are excited,
whether its because you got caught up in
a net or because you just spotted a tiger
shark for the first time ,it is important to take
emotions into account when assessing a
change in heart rate!
WHY DOES EXCITEMENT MAKE
THE HEART RACE
Page 9
FITNESS
17
FITNESS
16
at an average heart rate of 105 beats per
minute if he wants to improve his endurance.
180 – 20 = 160 beats per minute
His 20 year-old counterpart probably
needs to step on the gas a bit more to
reach an average heart rate of 160 beats
per minute.
But there are a few basic tips that apply to
both of them and that they should keep in
mind when using the heart rate to control
their training:
The ambient conditions, in particular the
temperature, should stay the same.
The body position should not be changed
during the exertion.
Ensure fluid intake at regular intervals.
Pay attention to regular breathing.
Avoid exhaling on exertion!
Despite all the rules described herein, the
maximum heart rate, which declines the
older you get, always differs from person
to person. Therefore, it should ideally be
determined through a physical workout.
Anybody can do this with the aid of a heart
rate watch by exerting himself or herself
exhaustively for a short period of time. In
particular for beginners, it is recommended
to have a physician do an ergometry test.
WHILE DIVING
Comparing the resting heart rate before the
dive to the heart rate during the dive helps
to assess the physical and mental strain. A
beginning diver will certainly experience a
much greater difference than an advanced
diver. This difference can also be used as an
indicator for the physical state of the day.
If an experienced diver detects a greater
difference than usual he should analyze
the underlying cause and adjust his dive
accordingly (shallower dive, less exertion
before ending the dive). A beginner can
track his progress with regard to physical
and mental strain as the difference gets
smaller and smaller. Performing an analysis
shortly after the dive on the basis of the
recorded heart rate will help to determine
the cause for the increase, as it could be
brought about by physical strain (unusual
exertion due to currents, buddy breathing,
excessive weights, unusually long dive...)
or mental strain (depth, excessive weights,
problems with the equipment or with the
buddy, joy or fear when sighting a large
fish...). By recognizing the root causes, the
diver can target his training to improve.
For apnea diving as well, performing an
analysis after the session helps to design
a training program and to evaluate the
diver’s progress. The alarm function for an
insufficient heart rate is a security aspect
that is not to be underestimated.
SCUBAPRO is always striving to improve
your diving experiences through
innovative technologies. Measuring
your heart rate while diving is one of the
milestones we are especially proud of.
Now and in the future, we stand behind
our motto:
DEEP DOWN YOU
WANT THE BEST
SCUBAPRO CURRENTLY
HAS THE WORLD’S ONLY
DIVE COMPUTERS WITH
HEART RATE MEASUREMENT.
Page 10
GLOSSARY
19
GLOSSARY
18
Adiposity - Obesity, fatness: excessive
proliferation or build-up of fatty tissue.
Aerobic energy metabolism - Energy-
supplying processes, which only
take place when sufficient oxygen
is present. (Complete burning of fat
and carbohydrates to CO2 and water.
Very efficient, allows for several hours
of exertion at low to medium levels of
intensity.)
Anaerobic energy metabolism - Energy-
supplying processes, which take place
without the use of oxygen. (Incomplete
burning, therefore very inefficient,
but allow for very high performance
over a short period of time. Burning of
carbohydrates, produces lactate.)
Active musculoskeletal system
- Comprises the entire skeleton,
musculature and the associated
tendons and ligaments.
Anaerobic threshold - Stress intensity at
the transition between purely aerobic
and partially anaerobic energy
generation. Marks the highest possible
intensity at which lactate production
and lactate removal are in balance
(max. lactate steady state). It differs from
person to person and isn’t subject to any
rigid law, so it should be re-determined
on a regular basis.
Arteriosclerosis - Most common morbid
arterial change, characterized by
hardening, thickening and loss of
elasticity. At an advanced state acutely
life-threatening. Counter measures
include moderate endurance training
and dietary change.
Arthrosis - Degenerative joint disease
that mainly develops due to an
imbalance between the strain and
the condition or performance of the
individual joint parts or tissue. Regular
customized exercise can prevent or
ease arthrotic problems.
Blood pressure - The pressure in the
blood vessels and heart chambers
that causes the blood circulation and
depends on the cardiac output and the
vascular resistance (e.g. elasticity of the
vascular wall).
Body mass index - Abbreviated BMI,
calculated by dividing the body weight
(measured in kg or lb) by the square of
the body height (measured in m or ft).
Index for evaluating the body weight.
Cardio training - Refers to the training
of the cardiovascular system, mainly
through endurance sports, also in a
sports club or fitness studio.
Cholesterol - Is both generated by
the body itself and ingested through
food (primarily animal fat) and is an
important and essential component
for the production of many hormones.
In high concentrations (permanently >
220 mg/dl), cholesterol is considered
to be a risk factor for cardiovascular
diseases, taking into account the ratio
of «good cholesterol» or HDL (high
density lipoprotein) to LDL (low density
lipoprotein), the main cause for vascular
diseases.
Dehydration - Decrease of body water
caused by increase of water discharge
(e.g. excessive sweating) without
sufficient replenishment. This worsens
the blood’s flow characteristics in a
performance-reducing manner. Severe
dehydration (also dehydrogenation)
can lead to circulatory failure.
Ergometry - Measuring physical
performance under controlled levels
of stress using an ergometer and
establishing various parameters of
cardiovascular function.
Fluid balance - Refers to the water
intake, water distribution and water
discharge processes of the human body.
Glycogen - A form of sugar
(polysaccharide) that represents the
stored form of carbohydrates. It is
mainly found in the liver and muscles.
Under intensive endurance stress with
a carbohydrate utilization of close to
100% the stored reserves of an averagely
trained athlete last for a maximum of
60-90 minutes of stress.
Heart rate variability - Measurement
of time lag between two consecutive
heartbeats in milliseconds. Based on
the extent of time changes, conclusions
regarding the individual training status
can be drawn.
Hypertension - Elevated blood pressure
Coronary heart disease - The result of
circulatory disorders in the coronary
vessels. Main cause of heart attack. Can
be influenced through exercise and
moderate endurance training.
Lactate - Salt of lactic acid; lactate
is the end product of the glycolysis
and is generated when glucose isn’t
completely burned. This is the case
when insufficient oxygen is available
to the musculature during physical
exertion. For example, the lactate
concentration rises significantly
during intensive muscle activity (see
«Anaerobic energy metabolism»).
Maximum oxygen uptake - Maximum
amount of oxygen the body can take
up and transform during an exertion.
Metabolites - Substances that are
generated as intermediate stages
or decomposition products during
metabolic processes within the body.
Metabolism - Entirety of metabolic
processes, composition, decomposition
and transformation of nutrients.
Mitochondria - The «power plants» of
the cell. This is where the body’s aerobic
energy generation takes place.
Muscle ache - Microscopic tears in the
muscle tissue caused by excessive stress,
which lead to inflammation and pain.
Muscle ache is a precursor to strains
or torn muscle fibers and therefore
should be regarded as a sports injury.
Subsequent regeneration by resting the
affected muscle, measures stimulating
the blood flow, rehab training and
the intake of fluids should lead to a
complete «recovery».
Respiratory quotient - Abbreviated
RQ. Describes the ratio between the
CO2 exhaled and the O2 inhaled. The
RQ plays a role when determining
the amount and ratio of fat and
carbohydrates burned.
Spiroergometry - Measuring physical
performance under controlled levels
of stress using an ergometer and
establishing various parameters of
cardiovascular function and respiration.
Side stitch (side ache) - Possible causes
include reduced circulation of the
diaphragm, training with a full stomach,
excessive strain and irregular breathing.
Increased blood flow in the body can
cause pain in the spleen and liver as
well.
Page 11
Our Authorized Dealers will be happy to
give you additional information.
You can find our retailers at scubapro.com
or use our SCUBAPRO app.
Dr. Tobias Dräger
Studied biology, sports science, and sports economics,
with a PhD. from the Deutsche Sporthochschule Köln
(DSHS) in Performance Physiology. Head of Business
Development at the diver emergency call center qua ed.
CMAS dive instructor.
Dr. Uwe Hoffmann
Studied mathematics and sports science, with a PhD.
from the Deutsche Sporthochschule Köln (DSHS) in
Performance Physiology. Research associate at the
Institute for Physiology and Anatomy and Head of the
Sports Department of «Recreational Diving» at the DSHS.
CMAS dive instructor.
Version I - March 2012
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