How Exercise Affects Cardiac Activity
Between Males And Females, And People
Of Differing Weights
Ta: Hansi Liu
Bio 240W Section 901
In order to supply organs with proper nutrients, and remove wastes the human
body needs to preform gas exchange with the environment. The circulatory system and
the respiratory system are involved in this gas exchange process. The main component of the circulatory system is the heart, accompanied by arteries veins
and capillaries, which interact with the lungs of the respiratory system. The respiratory
system consists of the lungs trachea bronchial tubes, mouth and nose.
The human heart consists of four chambers and valves the left and right atrium and the
left and right ventricle. The heart is responsible for regulating the cardiac cycle, “which
refers to the alternating contraction and relaxation of the myocardium in the walls of the
heart chambers, coordinated by the conduction system, during one heartbeat.” This
harmonized contraction and relaxation forces unoxygenated blood to the lungs (through
the pulmonary system) and oxygenated blood to the extremities (through the systemic
system). The SA and AV nodes, bundle of His, bundle branches and Purkinje fibers
makeup the conduction system. “The SA node (anatomical pacemaker) starts the
sequence by causing the atrial muscles to contract” after the signal has been fired it
travels to the AV node, “through the bundle of His, down the bundle branches, and
through the Purkinje fibers” , which creates a delay before “causing the ventricles to
contract”. The most prominent factors responsible for blood pressure are Cardiac output
(unit of blood pumped by left ventricle over a period of time), and peripheral resistance
(resistance to flow due to the decreasing diameter of capillaries and arterioles).
The phases of focus when measuring blood pressure are the systolic phase “the
contraction phase” and the diastolic phase which “is the relaxation phase”. The sound
associated with these phases, which “are due to vibrations in the tissues and blood caused
by closure of the valves” and are what we base our pressure measurements off of.
For Clarification “Several studies have been done to determine what is a ‘normal’
variation between right and left arm. In general, any difference of 10 mm Hg or less is 3
considered normal and not a cause for concern. This means that while whichever are we
took the blood pressure reading from may vary from the other arm or the actual pressure,
the difference is not significant enough to cause any change in our experimental results.
In order to measure heart rate we use a pressure cuff wrapped around a person’s
arm and placed a stethoscope in the crook of the elbow beneath the pressure cuff on the
patient’s brachial artery. Then the pressure in the cuff was increased to approximately
160 and slowly released. The pressure in which the first beat is heard is the systolic blood
pressure and the last beat heard is the diastolic pressure.This concept is illustrated below
Figure 1: The relationsh5p of blood pressure changes to the inflatable cuff pressure of the
Heart rate is the measure of beats per minute and is measured by placing a
forefinger on your neck and counting the beats over the period of 30 seconds and
doubling it. “The pulse counter will find the exerciser’s carotid pulse on their neck, next
to their trachea” 5
There are many factors that could affect an individual’s blood pressure and heart
rate. Fitness level of an individual (which often corresponds to weight) will affect heart
rate because the human heart is just like any other muscle in the way that “you have to exercise it and keep fit so that your heart rate can remain steady” . The heart of a less fit
person is likely to show greater variation before and after exercise since it is not
accustomed to that level of exertion. Vices like smoking, excessive drinking, and
excessive consumption of caffeine are also likely to promote higher blood pressure and
pulse counts. General differences in height and weight (such as those between males –
who are generally taller and heavier, and females) may also play a role in heart rate and
blood pressure too.
•What role might weight and gender play? As discussed above, gender and weight may
affect blood pressure because the heart may have to pump harder in order to circulate a
greater volume of blood (males are often taller and heavier than females) or the heart may
have to pump harder after faced with exercise because it is not accustomed to such physical
•Although we have not discussed genetic variation, might this also be a factor? Genetic 5
variation could play a role in blood pressure and heart rate because there are certain genetic
factors that could predispose people to higher or lower heart rates than others.
• How might you control for genetic variability? In order to control for genetic factors we
could group by ethnicity.
•Do you think smokers might show a different response compared to nonsmokers?
“Cigarette smoke contains many chemicals that interfere with the body's method of
filtering air” inefficient air filtering would lead to inefficient gas exchange and thus
require greater exertion by the heart . •What other variables might influence your results? Other variables such as inaccuracies in
measurement and ingestion of stimulants or depressants (caffeine or alcohol, prior to class)
could affect our results.
In this lab we plan to obtain the heart rate, systolic and diastolic blood pressures
of student prior to and after two types of exercise (15 seconds of step exercise and 30
seconds of step exercise).
I believe that heart rate, and blood pressure will show significant differences in
both people of differing gender and weights (ie: males will show increased values as will
people with higher weights).
Materials And Methods:
In this experiment we used a beat counter, a stethoscope, a pressure cuff and
different sized boxes (in order to standardize the exercise by height).
In our groups we each measured our pulse rates and blood pressures prior to exercise and
then took turns exercising by stepping up and down off a box (corresponding to our
individual heights) to a predetermined beat count for a predetermined amount of time,
recording our pulses and blood pressures after each interval.
We then placed all values collected into a class wide table in an excel file, and
preformed calculations to aid us in further analysis of the results.
We preformed calculations to find the average, Standard Error and Pvalue in order to
better assess the accuracy of our experiment and compare data.
Many people took their pulse rate form their wrist rater than their neck, as the lab manual
instructed. This could affect pulse counts because in the wrist the pulse is weaker than that of the carotid pulse (pulse of the neck), which makes this method less accurate, and if
the students used their thumb in the measurement of pulse their counts could be off
because the thumb has its own pulse.
Two rows of data were deleted from the male section because they were missing all
values for heart rate and blood pressure.
Comparison between Males and Females
** Denotes value’s significance via TTest results
Standard error was calculated by taking the standard deviation of all values in question
divided by the square root of the number of values.
Averages were calculated by taking the sum of values over the number of values.
PValues were calculated by preforming a ttest using both sets of vales (ie: male and
female, or above 145lbs or ≤145lbs).
Table 1: Resting Level Values
Between Males and Females
Pulse count 39.778 Females Males Females
Sys.BP 120.85 39.25 1.114 0.69
Dias.BP 76.815 116.57 1.433 1.337
Graph 1: Resting Level Values Between Males and Females These resting values give us a baseline from which to draw conclusions from and make
comparisons to our post exercise data. (None of the differences between males and
females were found to be statistically significant through TTests.)
Table 2: Normalized Average Change in Pulse Count After
Exercise Between Males and Females
av. % diff SE
Pulse count Males Females Males Females
15steps 17.5 21 1.458 0.967
30steps 46.46 44.37 2.12 1.4105
Graph 2: Normalized Average Change in Pulse Count After Exercise Between Males and
These values were calculated by taking the difference between pulse count after both
types of exercise and resting pulse count over resting pulse count in order to find the
average percent difference. (These values were not found to be significant after TTest
Table 3: Normalized Average Change in Systolic BP After
Exercise Between Males and Females
av. % diff