If you think the water just makes people feel
good, you don’t know the half of it. Here’s a
physiological explanation of the surprising and
amazing ways the simple act of being in the
water promotes well-being.
It doesn’t take long to notice that people in pools
are having fun. Nor does it take long to see
happy faces in a group of aquatic exercisers, or a
smile replace the facial stress lines of someone
sinking into a hot tub. The feeling of relaxation
after a vigorous pool workout is wonderful, and
unlike most other exercise experiences.
As a scientist, I’ve been impressed with the
consistency and universality of these observa-
tions. When I began to work with Olympic
athletes who were used to vigorous exercise
routines, they often commented on the difference
in their post-exercise comfort from an aquatic
exercise session vs. their normal exercise routine
. But there’s too much scientist in me not to
wonder why these findings occur with such
frequency and regularity. As I researched the
medical literature,I couldn’t find much to
explain such common events. But when I began
to dig into the basic science literature, I did find
information that provided some potential
explanation.
The physiology of immersion has been studied
extensively since we prepared to put man into
space in the late 1960s because the closest proxy
to weightlessness on the planet is to be found
when immersed in water. To study the physio-
logical changes that would occur in space, it
became important to study those changes
occurring during immersion. The physiological
alterations were profound and led to further
research of specific body systems. Still, most of
this research was not translated into medical
applications, but rather, was located in highly
scientific physiology journals.
Even today, there’s relatively little research on
the clinical applications of aquatic activity or
exercise to be found in medical journals. This
crossover from basic science into clinical
application is called translational research
and it is only beginning to emerge for aquatics.
But as more people turn to the water for therapy
and healing, that body of evidence is growing
daily. If the industry can capitalize on these
findings, understand and promote them
effectively, aquatics could become the next big
health craze, with the promise of helping
everything from high blood pressure
to heart failure.
Given that the American Heart Association says
72 million Americans suffer from high blood
pressure and more than 79 million have cardio-
vascular disease, that could be a powerful
incentive. The nation, in turn, could save huge
amounts in health expenses if the public were
educated about the value of aquatic activity, if
the political powers directed public expenditures
toward pool construction to improve public
access and the medical establishment understood
the potential value of aquatic activity across a
wide range of clinical problems. But it must start
with us. It must start with understanding why
water is so healing.
Finding balance
To understand why aquatics is so good for your
health, you must first understand some basic
physiology. Our bodies are constantly trying to
seek a physiological balance point called
homeostasis. This state preserves optimum
function despite changes in position, activity,
stress, aging or disease. The effort to find
homeostasis is what propels most of the
functional adaptations that occur during
immersion in water, with some changes being
immediate and others only after a period of time.
Like many adaptations, a cascade of other
physiological changes occur, some sequentially
and some concurrently.
Here’s how it works: Because water compresses
the body, it pushes blood into the deep vessels
during immersion. As the bather steps into
deeper water, blood is pushed upward, first into
the large capacity vessels of the pelvis and
abdomen. Then as depth increases yet further,
blood is pushed above the diaphragm into the
chest. With neck depth immersion, nearly three-
quarters of a quart (1 US quart=946.353 ml) of
blood is displaced, with two-thirds of it going
into large pulmonary vessels and one-third into
the heart.
The heart responds to this extra volume of blood
by increasing the amount propelled with each
beat, which is called stroke volume. At rest
during neck-depth immersion, stroke volume
normally increases approximately 30 percent.
The total volume of blood propelled by the heart
during a minute is called cardiac output, and this
also increases nearly 30 percent. That’s approxi-
mately the same increase that occurs during light
exercise, so even at rest during neck-depth
immersion, the heart is performing just as it
would during exercise on land. At the same time
, the body senses that more blood is being
pushed into circulation,so to adjust, the arterial
blood vessels relax without causing an increase
in blood pressure. Thus, healthy individuals will
lower their blood pressure during immersion,
and usually so will individuals with elevated
blood pressure (hypertension.) The magnitude
of this drop is related to the temperature of the
water.
Usually, there’s an initial brief increase in blood
pressure upon entering cold water and also
extremely warm water. Maybe that’s why in the
past, it was often stated that individuals with
hypertension should avoid hot tubs. Many
physical therapy texts also say that patients with
elevated blood pressure should not undergo
aquatic therapy. In actual fact, immersion may
benefit such patients.
Heart and health
Patients with congestive heart failure are another
clinical population that has been counseled to
avoid aquatic exercise or even immersion. But
several recent Japanese and Israeli studies have
found that for people with mild to moderate
heart failure, aquatics may be a very useful and
therapeutic environment. That’s because
immersion offers a unique combination of
benefits: It decreases circulatory resistance and
improves heart contraction efficiency. One of
these studies compared the effects of aquatic
exercise with rest in a group of patients with
moderate congestive heart failure. It was found
that the aquatic exercise group of patients
significantly improved in muscle function,
walking distance, aerobic fitness and exercise
capacity.
They also experienced nearly 40 percent
improvement in their quality of life. One reason
may be that during immersion, the increased
blood volume is pushed into deeper tissues.
Muscle circulation then improves and there’s a
consequent increase in oxygen delivery, which
is useful for muscle healing or recovering from
exercise. A study done on astronauts in training
showed that the blood flow into their calves was
increased by nearly 250 percent at rest during
neck-depth immersion. At the same time, the
kidneys see an increase in blood volume.
Sensors within the heart and elsewhere interpret
the increase in blood volume as a potential
overload, so the body sends signals to the
endocrine system to reduce this blood volume.
As a result, the kidneys begin their role in
regulating blood volume through excreting
sodium and potassium, and along with those
ions, water. As all aquatics professionals have
experienced firsthand, this process produces an
increase in urine volume and the kidneys also
become slightly more efficient. In ancient Greek
and Roman times, when medications were very
limited, immersion was actually used as a way
to treat individuals with kidney disease.
Stress is another ailment that immersion can
help alleviate. Some of the same hormones that
the body uses to regulate arterial function and
tone are a component part of our body’s
response to stress. These hormones are called
catacholamines. During immersion, the body
sends out a signal to alter the balance of these
catacholamines in a manner that is similar to the
balance found during relaxation or meditation.
Not all of the effects of this alteration are known
, but probably these changes are important in
modifying the heart rhythm in a manner to
mimic a relaxed state, and also in creating some
of the feeling of relaxation that occurs following
aquatic activity.
Exercise and endurance
The connection between exercise and stress
reduction has been well-established, and the
work the body must do in water may be one
reason. During immersion, compression of the
chest wall combined with the increased blood
volume makes it more work to breathe —
approximately 60 percent more with water up
to the neck. This, in turn, can lead not only to
lower stress,but also better performance during
land workouts.
In my experience working with Olympic level
athletes, a frequent comment was how much the
aquatic workouts had added to their overall
feeling of fitness. I believe what they were
noticing is that strengthening the muscles of
respiration had significantly improved their
respiratory efficiency, so during a land based
workout they didn’t feel so “winded.”
If the workload increase is 60 percent during
inactive immersion, there is almost certainly a
much greater workload increase during
immersed exercise. Blood and water are viscous
substances, and the force required to move
against viscosity is related to velocity in a
complex equation. Essentially, as the frequency
of respiration increases, so does the work of
displacing blood from the chest cavity to allow
air in. The chest wall must then expand against
the compression of surrounding water. As a
consequence, deep-water exercise potentially
could be a very useful method of strengthening
the muscles of respiration,which could be
helpful in athletes, as well as in the rehabilita-
tion of people with respiratory weakness or
other lung diseases.
We decided to test that possibility in astudy
completed last year at Washington State
University. We worked with two groups of WSU
students, 50 in each group. One group did land-
based aerobics for a 50-minute period, three
times per week for a semester.
The other group did aquatic aerobics 50 minutes
per session three times per week. We measured
aerobic conditioning, percent age of body fat,
and a number of measures of respiratory
efficiency and strength. All of the students
increased in their aerobic fitness, all decreased
their body fat percentages, and all improved in
some of the respiratory measures. But only the
aquatic students showed improvement in their
respiratory endurance measures. We plan to
repeat this study with more focus on higher-fit
student athletes to see if the same effect is noted.
There is a potentially major benefit of improving
respiratory endurance because as the muscles of
respiration fatigue, the body begins to shunt
blood from the lower extremities up to the chest
muscles to support respiratory effort. Obviously,
in an athlete who is reliant upon the legs,
robbing these muscles of blood flow to supply
the muscles of respiration causes a decrease in
athletic performance. A basketball player who is
getting respiratory fatigue will “hang on his
shorts,” which can be seen often at the end of a
basketball game. This action aids the accessory
muscles of respiration. But if at the same time,
the leg muscles are being starved of blood, the
player is going to feel like his or her legs are
“dead.” Studies have shown that exercise
activities to improve endurance of the muscles
of respiration actually do improve athletic
performance, but deep-water exercise would be
an easier and potentially more efficient means of
producing such an effect, while allowing the
athlete to decrease stress forces upon the spine
and lower extremities simultaneously.
Rehab and weight loss
This latter effect occurs because of the off-
loading effects of buoyancy. At waist-level
immersion depth, the hips, knees, ankles and
feet have a 50 percent reduction in loading due
to buoyancy; at mid-chest depth, there’s a 75
percent offloading. As a consequence, this effect
may be used to excellent clinical benefit in
facilitating recovery from training, or
rehabilitating from a lower extremity or spine
injury. The combination of joint offloading, with
the improvement in deep-tissue circulation
makes the aquatic environment very useful in
rehabilitation. In fact, even before these effects
were known, deep-water exercise was used to
improve racehorse performance without
exposing the animals to the trauma of the
racetrack. Owners found they could nearly triple
the expected race career of a horse if they used
aquatic training for a significant part of the
workout regimen. In working with Olympic
distance runners through the Nike development
program, we tried to have about one-third of the
training done in water, which seemed to reduce
injuries as well as improve performance. The
value of aquatic exercise in patients with osteo-
porosis has been controversial. The aquatic
environment would be ideal for this group
because of the frequent coexistence of joint
disease and the decreased risk of fractures from
falling during land based exercise. Many such
patients have a fear of falling that limits their
tolerance of a land-based walking program, an
activity that has been shown to build bone
mineralization and reduce osteoporosis. Most
studies of aquatic exercise have not shown a
useful benefit upon bone mineralization,
however. Studies comparing regular aquatic
exercisers with regular land-based exercisers
have shown better bone mineralization in the
land-based groups at nearly all ages from
adolescence through senior groups. This does
not mean that aquatic exercise lacks a place in
this group of individuals. In my practice, I will
typically start such a patient in an aquatic
exercise regimen, which has been well shown to
boost lower extremity strength and endurance,
as well as improve balance. The combination of
increased strength and balance skills is usually
sufficient to enable that individual to embark
upon a walking program safely and begin the
bone-building process. Another controversial
point is how aquatic exercise works for obese
individuals. Because of the offloading produced by buoyancy, the aquatic environment seems ideal, especially in persons with decreased lower extremity strength. It has been shown that aquatic exercise is less efficient in decreasing body fat percentages than land-based programs. Even at Olympic levels of training, these athletes have a higher percentage of body fat than their track athlete peers, as can be seen readily. The swimmers have sculpted
beautiful bodies with higher percentages of body fat,
whereas the track athletes have greyhoundslim
bodies with very, very low percentages.
Despite this concern, the value of
exercise in obese individuals is absolutely
essential, and aquatics may be a tremendously
useful method of initiating a program
and losing weight over time. While
it may not be as efficient from an absolute
standpoint, it is still effective and likely to
be better sustained because of the lower
risk of joint injury in aquatics for this group.
STRESS RELIEF During immersion, the body sends out a signal to alter the balance of a certain
type of hormone, which creates a balance similar to relaxation or meditation.
Many of these individuals can participate
successfully for years in a group format, and
I’ve seen people whose lives were totally
changed because of such a program.
On the whole, the response of the human
body to the aquatic environment is profound.
Perhaps it is because all of us spent the initial
formative months of our lives immersed
in a warm-water pool of amniotic fluid that
we can so readily sink into a pool with
relief. Such an environment would provide
protection and the optimum conditions for
growth during this critical period.
But the combined effects of all the properties
of water, from buoyancy through
hydrostatic pressure to its thermal conductive
properties make the aquatic environment
tremendously useful and effective for health
recovery and maintenance, and recreation.
At Washington State University, we are striving
to create a body of clinically directed
translational research so that such an
understanding might emerge within the
public, as well as the medical profession.
We’re also trying to create a broader
understanding of the immense value of aquatics
for high-level athletic training because the
public seems to relate to the effectiveness of
this kind of effort as well.
It is my hope and belief that in the
future, we will see a wetter, happier and
healthier world. ■
WAYS TO BROADEN SUPPORT
FOR AQUATIC HEALTH
■ Broad public awareness campaigns
■ Education within the medical community
■ More active community involvement
■ Legislative advocacy
■ Promotion and dissemination of clinical
research in consumer and medical media.
This diagram shows what’s happening in the body before a person enters the water, and what happens afterward. The changes are significant, especially those involving blood flow and the heart. The deeper a person is immersed, the more the health benefits increase. At neck level, even the brain
is affected because more blood is forced upward from the lower extremities.
PHYSIOLOGY AND IMMERSION
Negative atrial pressure
Negative pleural pressure
Flattened diaphragm
Blood pooled in abdomen,pelvis,and lower
extremities
BEFORE IMMERSION DURING IMMERSION
More venous compression. Heart size
increases 30% and rate slows 20%.
Heart pumps more blood; chest wall is
compressed. Plural pressure increases.
Lungs contain more blood and body
works harder to move air.
More blood is distributed to kidneys and brain.
The diaphragm is elevated higher during
inspiration and expiration.
As the water level rises, the abdomen is
compressed and more blood is forced
upward into the chest cavity.
Pelvis vessel compression occurs.
Venous and lymphatic compression begin
progressively pushing blood upward.
Neck Level
Diaphragm level
This diagram shows what’s happening in the body before a person enters the water, and what happens afterward. The changes are significant, especially those involving blood flow and the heart. The deeper a person is immersed, the more the health benefits increase. At neck level, even the brain is affected because more blood is forced upward from the lower extremities. PHYSIOLOGY AND IMMERSION Negative atrial pressure Negative pleural pressure Flattened diaphragm Blood pooled in abdomen, pelvis, and lower extremities BEFORE IMMERSION DURING IMMERSION More venous compression. Heart size increases 30% and rate slows 20%. Heart pumps more blood; chest wall is compressed. Plural pressure increases. Lungs contain more blood and body works harder to move air. More blood is distributed to kidneys and brain. The diaphragm is elevated higher during inspiration and expiration. As the water level rises, the abdomen is compressed and more blood is forced upward into the chest cavity. Pelvis vessel compression occurs. Venous and lymphatic compression begin progressively pushing blood upward. Neck Level Diaphragm level
(CLICK FOR DIAGRAM )
good, you don’t know the half of it. Here’s a
physiological explanation of the surprising and
amazing ways the simple act of being in the
water promotes well-being.
It doesn’t take long to notice that people in pools
are having fun. Nor does it take long to see
happy faces in a group of aquatic exercisers, or a
smile replace the facial stress lines of someone
sinking into a hot tub. The feeling of relaxation
after a vigorous pool workout is wonderful, and
unlike most other exercise experiences.
As a scientist, I’ve been impressed with the
consistency and universality of these observa-
tions. When I began to work with Olympic
athletes who were used to vigorous exercise
routines, they often commented on the difference
in their post-exercise comfort from an aquatic
exercise session vs. their normal exercise routine
. But there’s too much scientist in me not to
wonder why these findings occur with such
frequency and regularity. As I researched the
medical literature,I couldn’t find much to
explain such common events. But when I began
to dig into the basic science literature, I did find
information that provided some potential
explanation.
The physiology of immersion has been studied
extensively since we prepared to put man into
space in the late 1960s because the closest proxy
to weightlessness on the planet is to be found
when immersed in water. To study the physio-
logical changes that would occur in space, it
became important to study those changes
occurring during immersion. The physiological
alterations were profound and led to further
research of specific body systems. Still, most of
this research was not translated into medical
applications, but rather, was located in highly
scientific physiology journals.
Even today, there’s relatively little research on
the clinical applications of aquatic activity or
exercise to be found in medical journals. This
crossover from basic science into clinical
application is called translational research
and it is only beginning to emerge for aquatics.
But as more people turn to the water for therapy
and healing, that body of evidence is growing
daily. If the industry can capitalize on these
findings, understand and promote them
effectively, aquatics could become the next big
health craze, with the promise of helping
everything from high blood pressure
to heart failure.
Given that the American Heart Association says
72 million Americans suffer from high blood
pressure and more than 79 million have cardio-
vascular disease, that could be a powerful
incentive. The nation, in turn, could save huge
amounts in health expenses if the public were
educated about the value of aquatic activity, if
the political powers directed public expenditures
toward pool construction to improve public
access and the medical establishment understood
the potential value of aquatic activity across a
wide range of clinical problems. But it must start
with us. It must start with understanding why
water is so healing.
Finding balance
To understand why aquatics is so good for your
health, you must first understand some basic
physiology. Our bodies are constantly trying to
seek a physiological balance point called
homeostasis. This state preserves optimum
function despite changes in position, activity,
stress, aging or disease. The effort to find
homeostasis is what propels most of the
functional adaptations that occur during
immersion in water, with some changes being
immediate and others only after a period of time.
Like many adaptations, a cascade of other
physiological changes occur, some sequentially
and some concurrently.
Here’s how it works: Because water compresses
the body, it pushes blood into the deep vessels
during immersion. As the bather steps into
deeper water, blood is pushed upward, first into
the large capacity vessels of the pelvis and
abdomen. Then as depth increases yet further,
blood is pushed above the diaphragm into the
chest. With neck depth immersion, nearly three-
quarters of a quart (1 US quart=946.353 ml) of
blood is displaced, with two-thirds of it going
into large pulmonary vessels and one-third into
the heart.
The heart responds to this extra volume of blood
by increasing the amount propelled with each
beat, which is called stroke volume. At rest
during neck-depth immersion, stroke volume
normally increases approximately 30 percent.
The total volume of blood propelled by the heart
during a minute is called cardiac output, and this
also increases nearly 30 percent. That’s approxi-
mately the same increase that occurs during light
exercise, so even at rest during neck-depth
immersion, the heart is performing just as it
would during exercise on land. At the same time
, the body senses that more blood is being
pushed into circulation,so to adjust, the arterial
blood vessels relax without causing an increase
in blood pressure. Thus, healthy individuals will
lower their blood pressure during immersion,
and usually so will individuals with elevated
blood pressure (hypertension.) The magnitude
of this drop is related to the temperature of the
water.
Usually, there’s an initial brief increase in blood
pressure upon entering cold water and also
extremely warm water. Maybe that’s why in the
past, it was often stated that individuals with
hypertension should avoid hot tubs. Many
physical therapy texts also say that patients with
elevated blood pressure should not undergo
aquatic therapy. In actual fact, immersion may
benefit such patients.
Heart and health
Patients with congestive heart failure are another
clinical population that has been counseled to
avoid aquatic exercise or even immersion. But
several recent Japanese and Israeli studies have
found that for people with mild to moderate
heart failure, aquatics may be a very useful and
therapeutic environment. That’s because
immersion offers a unique combination of
benefits: It decreases circulatory resistance and
improves heart contraction efficiency. One of
these studies compared the effects of aquatic
exercise with rest in a group of patients with
moderate congestive heart failure. It was found
that the aquatic exercise group of patients
significantly improved in muscle function,
walking distance, aerobic fitness and exercise
capacity.
They also experienced nearly 40 percent
improvement in their quality of life. One reason
may be that during immersion, the increased
blood volume is pushed into deeper tissues.
Muscle circulation then improves and there’s a
consequent increase in oxygen delivery, which
is useful for muscle healing or recovering from
exercise. A study done on astronauts in training
showed that the blood flow into their calves was
increased by nearly 250 percent at rest during
neck-depth immersion. At the same time, the
kidneys see an increase in blood volume.
Sensors within the heart and elsewhere interpret
the increase in blood volume as a potential
overload, so the body sends signals to the
endocrine system to reduce this blood volume.
As a result, the kidneys begin their role in
regulating blood volume through excreting
sodium and potassium, and along with those
ions, water. As all aquatics professionals have
experienced firsthand, this process produces an
increase in urine volume and the kidneys also
become slightly more efficient. In ancient Greek
and Roman times, when medications were very
limited, immersion was actually used as a way
to treat individuals with kidney disease.
Stress is another ailment that immersion can
help alleviate. Some of the same hormones that
the body uses to regulate arterial function and
tone are a component part of our body’s
response to stress. These hormones are called
catacholamines. During immersion, the body
sends out a signal to alter the balance of these
catacholamines in a manner that is similar to the
balance found during relaxation or meditation.
Not all of the effects of this alteration are known
, but probably these changes are important in
modifying the heart rhythm in a manner to
mimic a relaxed state, and also in creating some
of the feeling of relaxation that occurs following
aquatic activity.
Exercise and endurance
The connection between exercise and stress
reduction has been well-established, and the
work the body must do in water may be one
reason. During immersion, compression of the
chest wall combined with the increased blood
volume makes it more work to breathe —
approximately 60 percent more with water up
to the neck. This, in turn, can lead not only to
lower stress,but also better performance during
land workouts.
In my experience working with Olympic level
athletes, a frequent comment was how much the
aquatic workouts had added to their overall
feeling of fitness. I believe what they were
noticing is that strengthening the muscles of
respiration had significantly improved their
respiratory efficiency, so during a land based
workout they didn’t feel so “winded.”
If the workload increase is 60 percent during
inactive immersion, there is almost certainly a
much greater workload increase during
immersed exercise. Blood and water are viscous
substances, and the force required to move
against viscosity is related to velocity in a
complex equation. Essentially, as the frequency
of respiration increases, so does the work of
displacing blood from the chest cavity to allow
air in. The chest wall must then expand against
the compression of surrounding water. As a
consequence, deep-water exercise potentially
could be a very useful method of strengthening
the muscles of respiration,which could be
helpful in athletes, as well as in the rehabilita-
tion of people with respiratory weakness or
other lung diseases.
We decided to test that possibility in astudy
completed last year at Washington State
University. We worked with two groups of WSU
students, 50 in each group. One group did land-
based aerobics for a 50-minute period, three
times per week for a semester.
The other group did aquatic aerobics 50 minutes
per session three times per week. We measured
aerobic conditioning, percent age of body fat,
and a number of measures of respiratory
efficiency and strength. All of the students
increased in their aerobic fitness, all decreased
their body fat percentages, and all improved in
some of the respiratory measures. But only the
aquatic students showed improvement in their
respiratory endurance measures. We plan to
repeat this study with more focus on higher-fit
student athletes to see if the same effect is noted.
There is a potentially major benefit of improving
respiratory endurance because as the muscles of
respiration fatigue, the body begins to shunt
blood from the lower extremities up to the chest
muscles to support respiratory effort. Obviously,
in an athlete who is reliant upon the legs,
robbing these muscles of blood flow to supply
the muscles of respiration causes a decrease in
athletic performance. A basketball player who is
getting respiratory fatigue will “hang on his
shorts,” which can be seen often at the end of a
basketball game. This action aids the accessory
muscles of respiration. But if at the same time,
the leg muscles are being starved of blood, the
player is going to feel like his or her legs are
“dead.” Studies have shown that exercise
activities to improve endurance of the muscles
of respiration actually do improve athletic
performance, but deep-water exercise would be
an easier and potentially more efficient means of
producing such an effect, while allowing the
athlete to decrease stress forces upon the spine
and lower extremities simultaneously.
Rehab and weight loss
This latter effect occurs because of the off-
loading effects of buoyancy. At waist-level
immersion depth, the hips, knees, ankles and
feet have a 50 percent reduction in loading due
to buoyancy; at mid-chest depth, there’s a 75
percent offloading. As a consequence, this effect
may be used to excellent clinical benefit in
facilitating recovery from training, or
rehabilitating from a lower extremity or spine
injury. The combination of joint offloading, with
the improvement in deep-tissue circulation
makes the aquatic environment very useful in
rehabilitation. In fact, even before these effects
were known, deep-water exercise was used to
improve racehorse performance without
exposing the animals to the trauma of the
racetrack. Owners found they could nearly triple
the expected race career of a horse if they used
aquatic training for a significant part of the
workout regimen. In working with Olympic
distance runners through the Nike development
program, we tried to have about one-third of the
training done in water, which seemed to reduce
injuries as well as improve performance. The
value of aquatic exercise in patients with osteo-
porosis has been controversial. The aquatic
environment would be ideal for this group
because of the frequent coexistence of joint
disease and the decreased risk of fractures from
falling during land based exercise. Many such
patients have a fear of falling that limits their
tolerance of a land-based walking program, an
activity that has been shown to build bone
mineralization and reduce osteoporosis. Most
studies of aquatic exercise have not shown a
useful benefit upon bone mineralization,
however. Studies comparing regular aquatic
exercisers with regular land-based exercisers
have shown better bone mineralization in the
land-based groups at nearly all ages from
adolescence through senior groups. This does
not mean that aquatic exercise lacks a place in
this group of individuals. In my practice, I will
typically start such a patient in an aquatic
exercise regimen, which has been well shown to
boost lower extremity strength and endurance,
as well as improve balance. The combination of
increased strength and balance skills is usually
sufficient to enable that individual to embark
upon a walking program safely and begin the
bone-building process. Another controversial
point is how aquatic exercise works for obese
individuals. Because of the offloading produced by buoyancy, the aquatic environment seems ideal, especially in persons with decreased lower extremity strength. It has been shown that aquatic exercise is less efficient in decreasing body fat percentages than land-based programs. Even at Olympic levels of training, these athletes have a higher percentage of body fat than their track athlete peers, as can be seen readily. The swimmers have sculpted
beautiful bodies with higher percentages of body fat,
whereas the track athletes have greyhoundslim
bodies with very, very low percentages.
Despite this concern, the value of
exercise in obese individuals is absolutely
essential, and aquatics may be a tremendously
useful method of initiating a program
and losing weight over time. While
it may not be as efficient from an absolute
standpoint, it is still effective and likely to
be better sustained because of the lower
risk of joint injury in aquatics for this group.
STRESS RELIEF During immersion, the body sends out a signal to alter the balance of a certain
type of hormone, which creates a balance similar to relaxation or meditation.
Many of these individuals can participate
successfully for years in a group format, and
I’ve seen people whose lives were totally
changed because of such a program.
On the whole, the response of the human
body to the aquatic environment is profound.
Perhaps it is because all of us spent the initial
formative months of our lives immersed
in a warm-water pool of amniotic fluid that
we can so readily sink into a pool with
relief. Such an environment would provide
protection and the optimum conditions for
growth during this critical period.
But the combined effects of all the properties
of water, from buoyancy through
hydrostatic pressure to its thermal conductive
properties make the aquatic environment
tremendously useful and effective for health
recovery and maintenance, and recreation.
At Washington State University, we are striving
to create a body of clinically directed
translational research so that such an
understanding might emerge within the
public, as well as the medical profession.
We’re also trying to create a broader
understanding of the immense value of aquatics
for high-level athletic training because the
public seems to relate to the effectiveness of
this kind of effort as well.
It is my hope and belief that in the
future, we will see a wetter, happier and
healthier world. ■
WAYS TO BROADEN SUPPORT
FOR AQUATIC HEALTH
■ Broad public awareness campaigns
■ Education within the medical community
■ More active community involvement
■ Legislative advocacy
■ Promotion and dissemination of clinical
research in consumer and medical media.
This diagram shows what’s happening in the body before a person enters the water, and what happens afterward. The changes are significant, especially those involving blood flow and the heart. The deeper a person is immersed, the more the health benefits increase. At neck level, even the brain
is affected because more blood is forced upward from the lower extremities.
PHYSIOLOGY AND IMMERSION
Negative atrial pressure
Negative pleural pressure
Flattened diaphragm
Blood pooled in abdomen,pelvis,and lower
extremities
BEFORE IMMERSION DURING IMMERSION
More venous compression. Heart size
increases 30% and rate slows 20%.
Heart pumps more blood; chest wall is
compressed. Plural pressure increases.
Lungs contain more blood and body
works harder to move air.
More blood is distributed to kidneys and brain.
The diaphragm is elevated higher during
inspiration and expiration.
As the water level rises, the abdomen is
compressed and more blood is forced
upward into the chest cavity.
Pelvis vessel compression occurs.
Venous and lymphatic compression begin
progressively pushing blood upward.
Neck Level
Diaphragm level
This diagram shows what’s happening in the body before a person enters the water, and what happens afterward. The changes are significant, especially those involving blood flow and the heart. The deeper a person is immersed, the more the health benefits increase. At neck level, even the brain is affected because more blood is forced upward from the lower extremities. PHYSIOLOGY AND IMMERSION Negative atrial pressure Negative pleural pressure Flattened diaphragm Blood pooled in abdomen, pelvis, and lower extremities BEFORE IMMERSION DURING IMMERSION More venous compression. Heart size increases 30% and rate slows 20%. Heart pumps more blood; chest wall is compressed. Plural pressure increases. Lungs contain more blood and body works harder to move air. More blood is distributed to kidneys and brain. The diaphragm is elevated higher during inspiration and expiration. As the water level rises, the abdomen is compressed and more blood is forced upward into the chest cavity. Pelvis vessel compression occurs. Venous and lymphatic compression begin progressively pushing blood upward. Neck Level Diaphragm level
(CLICK FOR DIAGRAM )
The crisis in Japan has also brought into the open the unspoken relationship between nuclear energy and nuclear war.
. See the 
and 
. 