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Biology 1108L
Laboratory Exercises: Variation in Natural Systems

Kennesaw State University
Department of Ecology, Evolution, & Organismal Biology

and
Department of Molecular and Cellular Biology

LABORATORY
Correlation between Common Measures of

Cardiovascular Health

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HUMAN CARDIOVASCULAR PHYSIOLOGY
In order to maintain a stable internal environment, known as homeostasis, cells must exchange nutrients and
wastes with the external environment. In single celled organisms, acquisition of nutrients and removal of
wastes occurs directly across the cell membrane. However, the cells of complex organisms are isolated from
the external environment, and normal cell homeostasis must be maintained by coordinated function of
specialized organ systems. In mammals, the cardiovascular system functions to allow exchange between
cells and the external environment by transporting blood throughout the different tissues of the body. For
example, blood is delivered to the lungs where oxygen is provided from the external environment and
delivered to cells. Conversely, CO2 generated by cells is released into the blood and transported to the lungs
for elimination into the external environment. Other wastes are transported by the cardiovascular system to
the kidneys and liver to enable excretion from the body. Nutrients from the diet are picked up from the
digestive system by the cardiovascular system and distributed to cells for storage and use. The

cardiovascular system also functions in the delivery of chemical signals within the body, enabling
coordination of function between different organ systems. A healthy and efficient cardiovascular system will
more easily maintain homeostasis, and measures such as breathing rate, pulse rate, and blood pressure are
expected to return to baseline levels faster in individuals with better cardiovascular health.

Blood flows throughout the body as a result of a pressure difference generated by the pumping of the
muscular heart. At rest, the average heart beats 70-75 times per minute. Diastole is the period of the cardiac
cycle during which the ventricles are relaxing, and systole is the period during which the ventricles are
contracting. Blood pressure is usually given as an approximation of systolic blood pressure over diastolic
blood pressure. The average blood pressure in healthy individuals at rest is 120/80. Both resting pulse rate
and resting blood pressure are commonly used by doctors as measures of cardiovascular health.

In this week’s lab, you’ll be measuring resting pulse and calculating two other independent measures of
cardiovascular health- fitness index (FI) and Body Mass Index (BMI)- and analyzing them to see whether they
are correlated. Correlation means one variable is predictive of another (i.e. is a high BMI predictive of a low
fitness index?). Sometimes the correlation of two variables may indicate a causal relationship. Correlation of
attendance with grades could be indicative that attending class improves learning and leads to better grades.
However, there is a famous saying in statistics that “correlation does not imply causation.” Just because one
variable is predictive of another, it may not be the direct cause of corresponding variation in the other. Higher
grades correlating with better attendance may have nothing to do with attendance improving learning;
perhaps students who work long hours are more likely to miss class and also have less time to study outside
of class. If two variables are both independently good measures cardiovascular health, you would expect
them to be correlated.

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Activity 1: MEASUREMENT OF RESTING PULSE

Try to take these measurements during a time period away from when you have exposed your body to
substances that might artificially affect your pulse rate, such as caffeine, nicotine, or alcohol. Take your pulse
through manual palpatation of a superficial artery. You should be able to feel your pulse by placing two
fingers on the inner wrist below the thumb or on the soft part of the neck to either side of the voice box. Sit
still in a calm environment for at least two minutes before taking your resting pulse measurement. Time for
20 seconds while counting the number of beats, then multiply by 3 to calculate beats per minute.

Resting Pulse

Activity 2: MEASUREMENT OF CARDIOVASCULAR RECOVERY FROM EXERCISE

During exercise, the demand for blood flow to the heart and exercising muscles increases to several times
the resting demand. People who are more physically fit may recover homeostatic balance more rapidly after
exercise than those who do not exercise regularly.

Experimental Exercise:
Note: any student with a heart problem or other issues that make vigorous exercise unwise, such as
a respiratory infection or pregnancy, should not participate in data gathering. The exercise for
ascertaining physical fitness is a protocol based on the Harvard Step Test.

a. Perform the step-test: You should stand in upright posture at the base of stairs or another

appropriate step roughly 16 inches (40 cm) high. In the case of most stairs, stepping up and
down a distance of two steps at a time will work. Set a timer for 5 minutes. Step up and
down on the bench at a rate of 30 steps per minute. All the way up and down equals one
step cycle, which should be completed every 2 seconds. The pace can be set by thinking
“up-2-3-4, up-2-3-4” so that each “up-2-3-4” requires 2 seconds. Ensure that you step fully
on the bench, maintaining an upright posture and keeping the pace while not using your
hands/arms on railing to assist.

b. Once you complete the full 5 minutes of exercise, sit down and rest while starting another
timer. Your pulse rate should be measured after 1 minute of rest using the same technique
you used for your resting pulse rate (palpitation with two fingers, counting beats for a timed
20 second period, and multiplying by 3 to extrapolate beats per minute). Wait a full minute
after the first reading has been taken and then take another reading. Repeat for a total of 3

readings, each separated by at least a full minute’s wait.

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Post-
Exercise 1 min. 2 min. 3 min.

Pulse Rate

Calculation of Fitness Index (FI):

FI = 15,000 / (Sum of the 3 pulse counts during recovery)
FI should fall between 20 and 80: if your value falls outside that range, you likely miscalculated.

Faster recovery will lead to more rapid lowering of pulse rates over time after exercise. Because the sum
of these pulse rates is the denominator of the calculation, better cardiovascular fitness- based on lower
pulse rates- is predicted to be reflected by a higher FI.

Activity 3: CALCULATION OF BMI

Another commonly used measure of overall health is Body Mass Index (BMI). BMI does not directly measure
anything related to the cardiovascular system but, instead, relies upon a ratio of the subject’s height and
weight. If you don’t have a scale or measuring tape handy, please approximate your height and weight
based on your most recent doctor’s visit.

Calculate your Body Mass Index using the following formula:

BMI = [Weight in lbs x 703] / [(Height in inches)2]

For example, a person who weighs 200 pounds and is 6 feet 0 inches tall has a BMI of 27.1.

[200 lbs x 703] / [72 inches x 72 inches] = 27.1

BMI should fall between 15 and 75: A value beyond that range means you likely miscalculated.

After you have completed your calculations, enter your Resting Pulse, FI, and BMI values
anonymously to your instructor per their instructions.

FI

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ADDITIONAL CALCULATIONS FOR RESEARCH MANUSCRIPT

1. Using the website http://www.alcula.com/calculators/statistics/linear-regression/ , calculate the linear
regression equation for the best fit trend line through the data and a graph of this line for the
following pairs of variables from the overall class data:
A. BMI vs FI
B. BMI vs. resting pulse
C. FI vs. resting pulse

Include these equations and graphs in the results section of your research manuscript (should be 3 equations
and 3 graphs).

2. Use the following website to calculate the correlation coefficient from the data:

http://www.alcula.com/calculators/statistics/correlation-coefficient/
Correlation coefficient is a statistic that measures how well 2 variables fit a regression line. If Fitness
Index increases linearly as BMI increases, the correlation coefficient will be close to 1. If Fitness
Index decreases perfectly linearly as BMI increases, the correlation coefficient will be -1. If there is
no trend to the data at all, and the points are randomly distributed, the correlation coefficient will be 0.
Record the Correlation Coefficients for all of the comparisons above and include them in the results
section of your research manuscript. You should make a table to show all 3 correlation coefficients.

3. Much like a t-test, whether two variables are significantly correlated depends on the sample size as
well as how close the data fit the regression line. A dataset of 7 points with a correlation coefficient
of 0.9 has a highly significant p-value of 0.006, whereas a dataset of 3 points with a correlation
coefficient of 0.9 is not statistically significant (p-value= 0.29). Use the following website to determine
whether the correlation coefficients from the above comparisons are statistically significant (use two
tailed probability):
https://www.danielsoper.com/statcalc/calculator.aspx?id=44

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ASSIGNMENT
Your assignment on this lab will be to write a full research manuscript based on the class data.

-The Title should be less than 20 words and give the reader a good idea of the subject of the manuscript

-The Abstract should summarize your introduction, Results, and Conclusions in 150 words or less. It is
something quick for the reader to peruse in order to ascertain if it is worth their time to read the entire
manuscript.

-The Introduction should give a brief background on the subject matter and present the hypotheses to be
tested. You should have a hypothesis for each of the 3 comparisons you are performing to calculate
Correlation Coefficient. You should cite the lab protocol if you use it for background information. An example
hypothesis: “There will be a negative relationship between body mass indexes (BMI) and fitness indexes (FI)

among individuals.”

-The Materials and Methods section should allow someone to replicate the experiment exactly, but you
shouldn’t re-write everything in the lab manual. After summarizing how the experiment was performed, cite
this lab manual for further details. Also be sure to state how the analyses were performed and cite the web
sites used.

-In the Results section, you should present all of your data (class data, regression line equations and graphs,
correlation coefficients and their p-values for the 3 comparisons).

-The Discussion section is where you should interpret the meaning of the results. This includes discussing
the significance (or lack thereof) of the p-value for the correlation coefficent. Clearly state how the results
compared to your predictions (hypotheses).
• Describe whether or not the data and statistical tests support your predictions.
• For any results that don’t support your predictions, give possible explanations as to why the results
didn’t support your hypothesis; note any flaws in the lab procedure that may have influenced the results,
but also mention biological reasons as to why the results might differ from what you predict.
• Discuss future experiments and experimental design that could more accurately test the relationship
between physical fitness and obesity.

-Literature Cited
To cite the lab manual, use the template provided in the assignment for the Fish Lab.

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For the websites, cite according to the following example:
Arcidiacono, G. Statistics Calculator: Linear Regression. 2020. Aluca. 10/6/2020.

10/6/2020 refers to the date you accessed the website. In general, it’s best to cite research published in
peer-reviewed journals and not to cite web pages, but we’re making an exception for this course since
there isn’t a lot of current research on this particular type of experiment.

This assignment is to be done individually; the assignment will be checked for plagiarism in turnitin.com. Do
not read anyone else’s manuscript or let them read yours. If you are re-taking this course, do NOT re-
use your old manuscript. The work must be both original and your own.

Literature Cited
Smith JJ, Kampine JP, Circulatory Physiology, The Essentials (2nd edition). Baltimore: Williams and Wilkins,
1984.
Tharp GD, Experiments in Physiology (4th edition) Burgess Publishing Company, 1980.