Exercise Physiology Lab: the demands of exercise on the body
Amy Ketcham
Biology 142
November 30, 2012
Introduction
The demands of exercise put strains on the body in various ways. These strains threaten
homeostasis, the internal stability that is maintained within a certain perimeter (Waters). Three
major parts of our metabolism are seriously affected during exercise, and the human body
reciprocates with physiological adaptations to this environment. The demands of exercise
directly cause increased heat production, increased oxygen cost, and increased carbon dioxide
waste product in the body (Waters). These metabolic consequences result from the cells of the
body requiring more energy, which can be produced via cellular respiration, in order to power
the movement of exercise, and those threats are by-products of the process of cellular respiration.
In this lab, 3 subjects spent time on a treadmill at varying speeds and inclines, while having
various measurements taken, including heart rate, carbon dioxide clearance, oxygen
consumption, temperature, hemoglobin saturation, and mean arterial pressure. These
measurements provide a comprehensive view of the physiological changes that occur due to
stresses put on the body during exercise. This information can be used to provide a template
which can be used by doctors and physical therapists when determining abnormal conditions
caused or aided by exercise in their patients. Furthermore, anyone can use this information to
decide if there is an issue with their exercising or if this is simply a natural reaction to the
stresses of exercise.
Threats to homeostasis during exercise include denaturing of proteins due to increased core
body temperature, acidosis from increased carbon dioxide in the blood, lowered blood pressure,
and decreased hemoglobin saturation from increased needs of oxygen. These threats are
addressed by physiological processes in the body.
The data values collected during rest acted as the control for the data collected during
exercise and after exercise. It is predicted that during exercise heart rate will increase, carbon
dioxide and oxygen consumption will increase significantly, hemoglobin saturation will
decrease, and mean arterial pressure will increase slightly due to the sudden homeostatic needs
of the body, while all of these factors will return to around their resting values during the
recovery period.
Method
Subject 1 was an 18-year-old female, measuring 68 inches and weighing in at 59.77 kg.
Subject 2 was an 18-year-old female, measuring 62 inches and weighing in at 59.09 kg. Subject
3 was an 18-year-old female, measuring 60 inches and weighing in at 63.64 kg. The subject’s
initial heart rate and blood pressure was determined during rest before the experiment began. The
subject spent a maximum of 21 minutes running on the treadmill at a maximum of 5 mph with
increasing inclines at every 3 minutes. Each subject ended their trial before reaching 15 minutes
of running. Data was taken the last 45 seconds of every 3 minute interval. A heart rate monitor
was put on the subject around her chest area, but this heart rate monitor was not successfully
utilized during the actual procedure due to complications with the equipment, but heart rate was
able to be monitored using another type of heart rate monitor. Heart rate was monitored every
three minutes during the trial for each subject. A spirometer was used to determine volume of air
breathed out during exercise (Waters). This measurement provided the total amount of air being
exhaled per breath by dividing total volume of air by number of breaths (Waters).
A capnometer measured the amount of carbon dioxide exhaled, which showed how much
oxygen was being used by the cells of the subject’s body and how much carbon dioxide was
being produced (Waters). This capnometer measured exhaled tidal carbon dioxide concentration
in millimeters of mercury or mmHg (Waters). Furthermore, respiratory rate in breaths per minute
as well as exhaled oxygen concentration was measured by the capnometer (Waters). Carbon
dioxide clearance, the amount of carbon dioxide being dumped from the body each minute, was
calculated by multiplying percentage of carbon dioxide in the exhaled air by tidal volume, which
was then multiplied by respiratory rate (Waters).
% CO2 exhaled x Tidal volume (liters per breath) x Respiratory rate (breaths/minute) =
CO2 clearance
Because the oxygen concentration of the surrounding air is 20.9%, the difference between
this and the O2 concentration of the exhaled air will yield the percent absorbed by the body
during respiration (Waters). The equation for this is (Waters):
(20.9% - % of oxygen exhaled) x tidal volume x respiratory rate = O2 consumption (l O2/min)
A pulse oximeter was used to determine the amount of oxygen in the subject’s blood, and
a sphygmomanometer was used to determine blood pressure. The pulse oximeter and
sphygmomanometer was only used after the subject had stopped running on the treadmill.
Results
As predicted, heart rate was shown to increase significantly after exercise began and to
begin to return to its resting rate after 6 minutes of rest. Carbon dioxide clearance, oxygen
consumption, temperature, and mean arterial pressure also increased during exercise. However,
hemoglobin saturation decreased during exercise. These values began to return to their resting
state minutes after exercise. The tables below can be referenced to show these trends for each
individual measurement.
Table 1: Changing heart rate based on time spent exercising and resting
Heart Rate vs. Time
Heart Rate (bpm)
250
200
150
100
Subject 1
50
Subject 2
Subject 3
0
Time period
Table 2: Changing Co2 clearance based on time spent exercising
Co2 Clearance vs. Time
Co2 Clearance (l Co2/min)
3.5
3
2.5
2
1.5
Subject 1
1
Subject 2
0.5
Subject 3
0
Time Period
Table 3: Changing O2 consumption based on time spent exercising
O2 Consumption (l O2/min)
O2 Consumption vs. Time
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
Subject 1
Subject 2
Subject 3
Time Period (minutes)
Table 4: Changing Hemoglobin Saturation based on time spent exercising
Hemoglobin Saturation (%)
Hemoglobin Saturation vs. time
105
100
95
90
Subject 1
85
Subject 2
80
Subject 3
75
Rest 0
Rest 3
Exercise
Recovery 3 Recovery 6
Time Period (Minutes)
Table 5: Changing Mean Arterial Pressure based on time spent exercising
Mean Arterial Pressure (mmHg)
Mean Arterial Pressure vs. Time
120
100
80
60
Subject 1
40
Subject 2
Subject 3
20
0
Rest 0
Rest 3
Exercise
Recovery 3 Recovery 6
Time Period (minutes)
Table 6: Changing temperature based on time spent exercising
Temperature vs. Time
Temperature (degrees celsius)
39
38
37
36
Subject 1
35
Subject 2
34
Subject 3
33
32
Rest 0
Rest 3
Exercise
Recovery 3 Recovery 6
Time Period (minutes)
Discussion
These results correlate with the hypothesis that all factors would increase but hemoglobin
saturation, which would decrease during exercise. Heart rate was expected to increase because
the body is in need of more oxygen to perform cellular respiration during exercise. Oxygen is a
necessary ingredient to produce ATP, the form of energy used by the cells, during cellular
respiration. Delivered by the blood to the cells, increased oxygen needs would directly correlate
with increased blood pressure (Waters). Chemoreceptors throughout the body would sense
increased carbon dioxide in the blood with a low pH (Waters). Low pH is an indicator of
increased carbon dioxide levels due to the carbonic acid equation:
CO2 + H20 = H3CO3 = HCO3- + H+
This carbon dioxide is a by-product of cellular respiration. Increased levels would indicate an
increased need for oxygen. Respiratory rate increased due to this, and the cardiac acceleratory
center in the medulla of the brain would have signaled for increased heart rate so that more blood
could travel throughout the body more quickly (Waters). Increased heart rate would allow for
carbon dioxide to be dispelled from the body faster and would allow for the body to return from
hypernea, a state of increased carbon dioxide in the blood (Waters). Furthermore, increased tidal
volume is a marker for homeostatic maintaining of blood pH, as more carbon dioxide from the
body is being dispelled with higher tidal volume. Blood pressure can be maintained by
constriction in inactive tissue. This occurs during exercise to prevent a significant drop in total
peripheral resistance in the equation: Mean Arterial Pressure = Cardiac Output X Total
Peripheral Resistance. Furthermore, proprioreceptors, which recognize movement, in the arms
and legs would signal that there was increased physical activity, which would cause the body to
compensate for even before there were significant increased oxygen needs with increased heart
rate and increased blood pressure (Waters). Baroreceptors in the heart would also notify the
Cardiac Acceleratory and Vasomotor Center of a decrease in blood pressure, causing constriction
of blood vessels and increased heart rate (Waters).
An increase in core body temperature is expected because heat is a by-product of cellular
respiration as well. Increased temperature is maintained by the release of sweat from sweat
glands in the skin and also from skin dilation. Sweat would cool the skin.
The hemoglobin saturation was hypothesized to have dropped, which occurred in the lab.
Hemoglobin saturation is influenced by temperature, blood pH, and partial pressure of carbon
dioxide. Increases in any of these factors will lower hemoglobin’s affinity for oxygen
(“WiseGEEK: What is Hemoglobin Saturation?”). Therefore, strenuous exercise may decrease
hemoglobin saturation slightly in long distance athletes. However, hemoglobin saturation should
have remained relatively stable throughout exercise and rest. The changes in hemoglobin
saturation during this lab were slight.
Possible sources of error in this lab would have come from certain issues with recording
data. For example, subject 1 did not have the proper heart monitor on during exercise.
Furthermore, data sets are missing at times due to unexpected problems taking this data during
the lab. Also, data for hemoglobin saturation and mean arterial pressure were unable to be
measured during running, and data for those factors may be more accurate or revealing if there
had been a way in which to measure those during running.
The data from this lab can be used by doctors, trainers, and physical therapists to set
limits for patients in need of treatment in which exercise is essential. Physiological trends may
also be deduced from this lab.
Works Cited
Waters, John R. Reading. Heart Sounds and Blood Pressure. Penn State University, State
College. 29 Nov. 2012. Penn State Angel Course Management System. Penn State University.
Web. 29 Nov. 2012.
Waters, John R. Physiology Laboratory Manual. 2nd Ed. McGraw Hill. 2003. Pg 65-78.
“WiseGEEK: What is Hemoglobin Saturation?” What is Hemoglobin Saturation? N.p., n.d.
Web. 30 Nov. 2012.