for exercise physiologists
5 No 11 November 2002
Tool for Integrating Critical Thinking and Cardiovascular Physiology
PhD, MPH, MA, FASEP, EPC
of Exercise Physiology
of St. Scholastica
pay only for what is of use to them and gives them value.” -- Peter
Not only is
“gravity inversion” used to decompress the spine and reduce low back pain
, it is used to strengthen the abdominal muscles during
vertical head-down sit-up exercises . It can
also be used to integrate critical thinking and cardiovascular physiology.
For example, what is the answer to the question: “Aside from aerobic
training, can heart rate decrease with an increase in stroke volume?”
Students are likely to think that an increase in stroke volume is always
associated with an increase in heart rate. If stroke volume can increase
with a decrease in heart rate, what are the reasons for the physiologic
response? Similarly, “What happens to systolic blood pressure with
the transition from standing position to the head-down position?”
Or, the reverse direction, that is, “Does blood pressure increase, decrease,
or stay the same with the transition from lying down to sitting up or standing?”
Finding answers to these questions helps to encourage critical thinking?
Nearly every professor works at teaching students and, of course, asking
questions is a big part of the process. But, still, far too many
students are allowed to sit and passively receive information .
We continue to cling to our traditional system of educating students.
The inertia of the traditional system will change, however. Students
and their parents have come to believe that they are paying for a product,
not just an education. If colleges and universities are to move ahead
in the 21st century, the faculty will need to place emphasis on new ideas
and new technology that allow for new opportunities.
check shows that, in an effort to produce knowledge (research), exercise
physiologists are dancing a tango with students who need to learn how to
think. If left unchecked, the academic world demonstrates to everyone
its inadequate response to current educational concerns. In this
country, if not worldwide, teaching students to think critically is important.
Unfortunately, a look at how exercise physiologists teach exercise physiology
courses is a good illustration of little to no change in the rigidity and
inflexibility of our thinking about the curriculum. But change we
must, for if we are too busy or too little interested to reform our own
profession, then it will be done by others who may further undermine our
credibility. To address this weakness, one recommendation is a paradigm
shift from a model of few, if any, hands-on laboratory experiences to one
that is transformational. More undergraduate courses need a laboratory
component, and more labs need equipment that is effective in producing
physiological data. As a consequence, why not purchase a gravity
inversion apparatus? It will help students learn. Students
will be able to identify specific physiological responses important to
understanding cardiovascular physiology. In addition to other mandatory
pieces of equipment (e.g., metabolic analyzers, heart rate and blood pressure
monitors), it is incomprehensible that students will not learn to think
differently. The gravity-facilitated effects on the cardiovascular
system are immediate. Students can determine what happens to the
physiology of the body from one body position to the next. They stand
to gain immeasurably from its use. There is an immediate reinforcement
of physiological principles when students are involved simultaneously in
the collection of data.
the Idea to Use
what it means to sit in class and take notes. Much, if not, most
of their education has been essentially a passive experience .
When done correctly, the value of a hands-on laboratory experience is that
it is an active experience. However, current thinking suggests that
undergraduate students receive less than the desired time in the laboratory
setting. This deficiency is a problem. Lecture courses need
a laboratory component and every exercise physiology laboratory can benefit
from having a gravity inversion apparatus to teach critical thinking and
cardiovascular physiology. In order to begin the instructional discourse,
the “cognitive process model” of incorporating non-traditional pieces of
equipment helps to explain why and how new thinking is valued. This
model is loosely defined by the ten statements that enable faculty to put
ideas to use and, therefore, to catapult students into a leadership role
in the profession.
for the teaching tool. For several decades, gravity inversion
has been used as a research method to study physiologic responses to simulated
weightlessness [4-6]. The findings from these studies
have been used to help explain the cardiovascular effects of space flight
. For this reason, gravity inversion affords
exercise physiologists an important step for elevating the status of the
scholarship of teaching. Its simplicity is a resource that is within
the budget of most departments ($500). Since it is important that
faculty improve their teaching skills, the purchase and use of the apparatus
should be embraced and even demanded to improve the delivery of academic
of discordant findings. Heng and colleagues 
reported a statistically significant increase in heart rate during gravity
inversion (relative to standing) while other researchers have reported
a decrease [9,10] or no change in heart rate [11-13].
The cardiac output response to gravity inversion has been reported as increased
[11, 14] or decreased . Systolic
blood pressure has been reported to decrease , increase
[16-18] or not change at all during inversion .
The point is that the subjects in the different studies responded differently
under a variety of circumstances. The inversion apparatus allows
for distinguished effects without long, tedious hours (or months) to realize
the physiology of change.
3. We perceive
what we expect to perceive. This statement may seem somewhat
trite. There is a certain truth to the statement though. It
means that we tend to see (or think) what we expect to see (or think).
The unexpected often comes as a surprise, which is often a finding after
the data have been treated with statistics. Of course, what is truly
important is that the unexpected is often times the opposite of what students
think. To their surprise, when they see the actual data, they begin
to understand and become more responsible for their own thinking.
This is particularly true with respect to the cardiovascular data such
as heart rate, stroke volume, cardiac output, systolic blood pressure,
systemic vascular resistance, and arteriovenous oxygen difference.
Together they represent the opportunity to build confidence in their abilities
to evaluate the effects of stressors and continue to grow in critical reflection.
is believing. Here, students can be heard saying, “I was wrong.
Blood pressure didn’t change with the different body positions.”
Or, “I can’t believe what we found disagrees with the textbook?”
It is meaningful to not only say to the class that oxygen consumption does
not increase or decrease with a change in body position (i.e., as in standing
vs. lying down or standing vs. head-down inversion), but to demonstrate
it. Skeptical students may exhibit a pattern of thinking that is
less distrustful or defensive, especially when their laboratory work progresses
to the point of hands-on communication. When students learn to find
answers for themselves in their own laboratories, it is the beginning of
important learning (i.e., seeing is believing).
is learning. What is important is not just sitting in class,
but getting involved in the learning process. To supply data to the
students is not enough. Students must create the data, too.
Then, they must integrate the data with critical reflection and strategy.
One way to do that is with a “research tool” such as the gravity inversion
apparatus. The use of a non-traditional research apparatus helps
to define the laboratory experience as a unique opportunity to create a
learning environment. Good teaching requires lectures, discussions,
and the performance of all activities that go into teaching. It also
requires an excellence that comes from learning through experience; a journey
to knowledge through doing.
requires the right attitude and a radically different view. In
the end, it is not the size of the university that makes the teachers or
how well students learn and develop professionally. It is the size
of the teachers! This should not be misunderstood. Big is good
if big is doing the right thing. But big is not necessary to do the
right thing or to see that the right think is done. This is true
of those that aim at teaching critical thinking by manipulating human physiology.
So far, it seems that most academic exercise physiologists don’t get this
point. This may explain the popularity of research equipment that
is used only by the faculty. Never mind the students or, better yet,
leave the “real learning” to the doctorate students. This raises
questions rather than answering questions about the undergraduate degree.
Just think how much better the students would be today had such thinking
not become standard practice for the past fifty years. Attitude is
everything. Each member of the faculty must contribute toward a visionary
view, if not, a radical view of the education of exercise physiology students.
do it. It is not enough to have a great idea. There has
to be action. The design of a laboratory-research project is worthless
unless students commit to data collection. To ask, “What can I learn?”
or “What can I do to think better?” is to focus on managing subjects and
turning attention to a meaningful interaction with the research design
and data collection procedures.
ideas into action. It
may not appear to be all that difficult or an important contribution to
the hands-on activities, but converting new thinking into action isn’t
easy. New data cannot become new ideas without a ruthless effort
in thinking and decision making that makes a radical difference.
can I contribute? Those who have to ask haven’t been encouraged
to think outside of the box. And yet they have the opportunity to
take responsibility in terms of the overall organizational structure of
the critical thinking that is woven into the subjects’ responses.
Within a fairly short period of time, one or more students may commit to
statistical analysis, another will take blood pressure measurements, and
still another will oversee the cardiac output procedures. Of particular
importance is the contribution of individual thinking that is complementary
to the overall performance of the team of students.
new exercise physiology is entrepreneurial. Every research decision
in exercise physiology sets the stage for critical reflection with implications
for understanding human physiology and communication of lifestyle factors
that may impact health and fitness. But also, contrary to popular
belief in the Gold’s Gym jobs, there are “flashes of entrepreneurial thinking”
that are real and innovated; thinking that is driven by the need to help
others or to simply understand the physiology of a stressor. Unfortunately,
there is little serious talk today about the application of the exercise
physiology body of knowledge beyond traditional thinking. The shift
to the new thinking puts exercise physiology in the center of increased
the 10 statements for putting the idea to use, students are encouraged
to write a research report that demonstrates their critical thinking skills.
The report is based on the research purpose(s). For example, the
undergraduate students were asked to answer the following “multifaceted”
question: “Does oxygen consumption, cardiac output, heart rate, stroke
volume, tissue extraction, systemic vascular resistance, systolic blood
pressure, and mean arterial pressure increase, decrease, or stay the same
with the transition from standing to horizontal to head-down (45 degrees)?”
Of all the decisions that go into the research effort, none is as important
as the decisions regarding: (a) purpose(s), (b) subjects, (c) research
design, (d) statistics, (e) findings, and (f) discussion/conclusions.
To take command of the research project is both bold and demanding.
Each decision requires a careful and thoughtful analysis and preparation.
Note that the following brief description of each component of the research
effort is consistent with an undergraduate hands-on laboratory “report”
only. The intent is not to reproduce the report but to show some
of the content effort on their behalf.
As an example,
the “purpose” of the assignment that was given to my undergraduate students
was primarily to integrate critical thinking with several cardiovascular
responses to three different body positions (standing, horizontal, and
head-down). The critical thinking that went into the data gathering
procedures and the analysis of the relationship of the dependent variables
to each other was made possible using the gravity-inversion apparatus.
The secondary purpose of the hands-on laboratory session was to place the
students in a situation where they would be responsible for calibration
of the Medical Graphics metabolic analyzer and the steps necessary to use
the CO2 rebreathing procedure to determine the subjects’
cardiac output. Following data collection, the data were analyzed
for statistical significance. Students were encouraged to figure
out the reasons for the different cardiovascular responses by comparing
their findings with a sound contemporary explanation. This analysis
involved content from textbooks and findings from published articles.
subjects attended the hands-on laboratory session. None of the subjects
had a prior history of back trauma or lumbar spine complaints. Most
of the subjects were familiar with the gravity-inversion apparatus, having
participated as subjects in other labs. Due to their familiarity
with the laboratory equipment and the head-down position, they concentrated
on the specifics of the project. Most of the students worked in “threes”
– one student was responsible for the metabolic analyzer, one did heart
rate and blood pressure, and one was the subject. Following data
collection, the students shifted responsibility until data were collected
for all three students in that group. The rest of the groups did
the same thing as their turn became available. There were two metabolic/gravity-inversion
stations set up for the students.
in the group positioned him- or herself in front of the gravity-inversion
apparatus facing away from it while remaining in the standing position.
Baseline recordings were done with the subject standing upright for five
minutes. Resting blood pressure and heart rate were measured at the
fourth minute while cardiac output was determined at the end of minute
5. Oxygen consumption was averaged across the five-minute period.
Students had previously worked with the metabolic analyzer and all other
equipment for several months in related labs. At the beginning of
the sixth minute, the subject was positioned on the inversion apparatus
and rotated to the horizontal position (as in lying down). The subjects’
arms remained alongside the body on the apparatus for a second, 5-minute
period. The same data were collected in exactly the same manner.
Then, the subject was rotated to the 45-degree head-down position for the
final 5 minutes of data collection. Again, all data were collected
as described using the Medical Graphics analyzer, a heart rate monitor,
and auscultation of the left brachial artery using a standard sphygmomanometer.
Students used the plateau method to determine cardiac output, using 10%
CO2 in a 35% O2 mix. The
students followed the standard steps in performing the CO2
rebreathing procedure. The analyzer’s software for calculating arterial
CO2 (PaCO2) derived from the end-tidal PCO2 (PETCO2),
mixed venous PCO2 (PvCO2) derived
from the rebreathing procedure, and VCO2. Otherwise,
the students calculated the related cardiovascular responses according
to the following formulae: (1) stroke volume was calculated by dividing
cardiac output by heart rate; (2) arteriovenous oxygen difference was calculated
by dividing oxygen uptake by cardiac output; (3) systemic vascular resistance
was calculated by dividing mean arterial pressure by cardiac output; and
(4) mean arterial pressure was calculated using the formula: [MAP = DBP
variance with repeated measures was used to determine significance of change
in the cardiovascular responses. The alpha level was set at 0.05
for statistical significance.
standard deviations were computed for all measurements (refer to Table
1). During the transition from standing to horizontal to head-down,
oxygen uptake was unchanged. Cardiac output and stroke volume were
increased during the horizontal position (relative to standing) and increased
further during the head-down position (relative to horizontal and standing).
Heart rate decreased during the horizontal and the head-down positions
(relative to standing). Arteriovenous oxygen difference and systemic
vascular resistance were decreased during the horizontal position (relative
to standing) and decreased further during the head-down position (relative
to horizontal and standing). Systolic blood pressure was increased
from during the head-down position (relative to standing and horizontal).
Mean arterial pressure was unchanged.
Cardiovascular responses during three different body positions, using an
ANOVA with repeated measures (M = ± SD).
= oxygen uptake
diff = arteriovenous oxygen difference
= systemic vascular resistance
= systolic blood pressure
= mean arterial pressure
in “threes” at first, then, they came together as a class with a written
discussion based on the statistical findings of published work on the physiology
of standing and different body positions. It is not the purpose of
this article to extend this point too much further (i.e., taking on a research
manuscript form). The earlier information that characterizes the
students’ report is representative of their laboratory effort. Instead
of extending this view, several conclusions will be put forward in a form
of a “discovery of information” that encouraged critical reflection and
acquisition of new knowledge.
For example, a turning point in their lab was the sense that oxygen consumption
was not changing with the transition from one body position to the next.
A few students felt, “So what’s the problem?” In actuality, though,
they came to realize that oxygen uptake is unchanged. The subjects’
need for energy was not altered as a function of whether they were standing,
lying down, or in a head-down position. This surprised the students
since an earlier discussion revealed that they believed it would be higher
during the standing and head-down positions versus lying down. With
no change in oxygen uptake, the students felt that one side of the VO2
equation (i.e., VO2 = Q x a-vO2
diff) must have increased and one side must have decreased. As it
turns out, that is exactly what happened. The increase in the central
component of the VO2 response was balanced by the
decrease in the peripheral component of VO2.
The students found that the extraction of oxygen by all the tissues of
the body was decreased. In other words, the tissues’ need for oxygen
was met by the increase in cardiac output.
output increased when lying down versus standing and during the head-down
position versus lying down and standing. The increased cardiac output
is directly related to the reduction in the effects of gravity when in
the upright standing position that encourages the pooling of blood in the
dependent regions of the lower extremities. Since the lying down
position essentially neutralizes the effect of gravity on the cardiovascular
system with regards to a pooling of blood in one primary area, the transition
from standing to lying down increased venous return, end-diastolic volume,
and therefore stroke volume. When the subjects were moved from the
lying down position to the head-down position, the effect of gravity demonstrated
a further increase in venous return with a significant increase in cardiac
output. In other words, students learned that the physiology of standing
is exactly the opposite effect of the physiology of being in a head-down
position. They also learned that the cardiac output response (and hence,
the stroke volume response) was directly a function of the decrease in
systemic vascular resistance.
Since the subjects’ heart rate decreased from standing to lying down and
head-down positions (and yet cardiac output increased), then stroke volume
must have increased. Students found that the stroke volume response
was responsible for the cardiac output response. Stroke volume increased
when the subjects assumed the lying down position and increased even further
during the head-down position.
First of all,
this is not a research paper. The layout is designed to help the
academic exercise physiologists manage the idea of using a gravity-inversion
apparatus in the laboratory component of the typical “physiology of exercise”
course. The best one can then hope is that the idea will be put into
action. Of course, the problem of too few labs will not be corrected
anytime soon. The lack of adequate budget focus and of the right
departmental policies is, by contrast, the greatest threat to the integrity
of our academic programs. The next questions we must ask are: “Why
aren’t we doing whatever is necessary to meet the customers’ needs?
And, while it is never easy, “When are the academic exercise physiologists
going to update their body of knowledge with accreditation?” Perhaps
because “being trapped in the manufactured notion of what is exercise physiology”
there is the necessity to engage in new thinking. The risk of doing
so is likely to correlate with better jobs for our students who have increased
abilities to think critically, who are in position to be leaders in the
field, and who are willing to compete for the rights of the profession.
4. The final
consideration was the significant increase in systolic blood pressure of
1 mmHg that set the stage for a meaningful discussion regarding statistical
significance versus practical significance. Further discussion allowed
for an understanding of the pressure receptors in the neck and other structures
that are involved in the regulation of blood pressure and heart rate.
thanks the members of the exercise physiology Fall Semester senior class
at The College of St. Scholastica for their hands-on laboratory work in
collecting the cardiovascular physiology data presented in Table 1 in this
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