THE EFFECT OF

LIFESTYLE AND GENDER

ON CO2 OUTPUT

BEFORE AND AFTER

PHYSICAL ACTIVITY BY

JULY 22, 2016

1

INTRODUCTION

External respiration is the ventilation of air (breathing) and the gaseous exchange that occurs as a result,

with oxygen coming into the body and carbon dioxide leaving (Daniel, 2016, p. 1). Respiration has four major

steps: ventilation, gas exchange in the lungs, circulation of blood between the lungs and tissues and gas exchange

between the blood and tissues (Daniel, 2016, p. 1). Oxygen is inhaled and travels through the blood to the organs

and tissues to give the body the substance it needs to perform processes that make the body function.

Humans need energy to maintain daily activities. Glucose from the food we eat is needed for aerobic and

anaerobic cellular respiration that provides us with energy, and oxygen plays a key role in this cellular respiration.

In the absence of oxygen, anaerobic respiration occurs and little energy is created (Burton, Stokes, Hall, 2004, p.

185). However, in the presence of oxygen, aerobic respiration occurs and yields copious energy and carbon

dioxide (Arthurs, Sudhakar, 2005, p. 207). Carbon dioxide is a waste product of aerobic respiration and after

being produced in the muscles it must travel back to the lungs to be exhaled (Arthurs, Sudhakar, 2005, p. 210).

Carbon dioxide is considered a waste product because of its potential to be harmful to the body, by

making blood more acidic and decreasing the pH (Callahan, 2013). The body responds to the increased carbon

dioxide and finds ways to regulate the pH of the blood. The pons and medulla respiratory centers in the brain

detect a decrease in the pH of blood (Daniel, 2016, p. 1-2). As a result, the respiratory centers increase the

respiratory rate to increase the exchange of carbon dioxide and oxygen so more carbon dioxide can be exhaled

from the body (p. 2). When there is too much carbon dioxide in the body, vasodilation also occurs. Vasodilation is

the widening of the blood vessels to increase blood flow so more oxygen and glucose can get to the muscles

(Burton, Stokes, Hall, 2004, p. 187), allowing aerobic respiration to continue. The combination of vasodilation

and increase in heart rate and blood pressure brings large amounts of oxygen and glucose to muscle tissues

(p.187).

Performing any kind of physical activity has certain physiological effects on the body, including

increased oxygen consumption (Daniel, 2016, p. 2). The increase in oxygen intake increases the rate of aerobic

respiration, which provides the body with more energy and produces more carbon dioxide. As previously stated,

an increased amount of carbon dioxide must be regulated. The body responds by exhaling the excess carbon

dioxide (p. 2). Heart rate and blood pressure also increase when performing physical activity.

Physical activity encompasses physical work, muscular activity, and purposeful exercise (Poehlman,

1989). There are two main branches of physical activity: aerobic and anaerobic activity. Aerobic and anaerobic

respiration are cellular processes that occur within muscle tissue. The Type I or “slow twitch” muscle fibers of the

body are used for aerobic respiration (Burton, Stokes, Hall, 2004, p. 186). Aerobic activity uses aerobic

respiration, which requires oxygen and produces carbon dioxide. Aerobic activity is categorized as prolonged

activity, (p. 186) like running, swimming and jogging (NHLBI, 2015). Anaerobic respiration uses the Type IIB or

“fast twitch” muscle fibers (Burton, Stokes, Hall, 2004, p. 186). Anaerobic activity uses anaerobic respiration

that, inversely, does not require oxygen and does not produce carbon dioxide. Anaerobic activity is classified as

2

quick and explosive movements (p. 186) performed in activities, like sprinting, squatting, and weightlifting

(NHLBI, 2015). Although they are strictly separate types of physical activity both muscle fiber types are used at

all times during physical activity. For example, during an anaerobic physical activity, Type IIB muscle fibers are

primarily used but some Type I are still in use. Since the body constantly requires oxygen and is continuously

going through aerobic respiration, it will always be producing carbon dioxide; however, as physical activities

(aerobic and anaerobic) are performed, aerobic respiration increases.

Considering many functions are involved in the exhalation of carbon dioxide, the purpose of both of our

studies was to see if factors, like lifestyle and gender, can influence carbon dioxide output. We chose to study

carbon dioxide output in the cases of aerobic and anaerobic physical activity between genders and lifestyles. Since

aerobic activity utilizes mainly Type I muscle fibers (aerobic respiration), carbon dioxide output should increase.

Considering Type IIB muscle fibers are primarily used during anaerobic physical activity (anaerobic respiration),

carbon dioxide output should not increase or change as much during anaerobic activity as it would during aerobic

physical activity.

The first study tested if lifestyle factors influence carbon dioxide output. In a study by Shahraki et.al.

(2012), athletic individuals were found to have lower resting heart rates than non-athletes (p. 14). Additionally,

the heart rates and systolic blood pressure of the non-athletes increased more than that of the athletes after aerobic

activity. This allowed us to pose the question about differences in carbon dioxide output between active and

sedentary participants. We chose to create our own criteria for participants since the categories of athlete or non-

athlete were not specific enough. From an article on exercise and cardiovascular health (Myers, 2003, p. 2), we

decided active participants must have participated in at least three hours of purposeful exercise per week for at

least six months prior to the data collection. Participants were considered sedentary if they had not met the

minimum criteria of three hours of purposeful exercise a week, similar to the non-athletic individuals in the

Shahraki study (2012, p. 13). Since the heart rate and systolic blood pressure of non-athletes increased more than

athletes after aerobic activity, we expected that the sedentary participants will also have a bigger increase in their

carbon dioxide output.

Our null hypothesis was that there would not be a statistically significant difference between the change

in CO2 output of active participants compared to sedentary participants after aerobic and anaerobic physical

activity. We alternatively hypothesized that there will be a statistically significant difference between the change

in CO2 output of active participants compared to sedentary participants after aerobic and anaerobic physical

activity. We predict that the sedentary participants will have a greater change of carbon dioxide output after both

aerobic and anaerobic physical activity compared to active participants because of the increase in heart rate and

systolic blood pressure found in the Sharaki study (2012, p.14).

In addition to exploring the effects of lifestyle on carbon dioxide, the second study tested if gender

influences CO2 output. There are differences in muscle fiber composition between males and females. According

to a study by Staron, Hagerman, Hikida, et al. (2000), males and females have a similar percent distribution of

3

muscle fiber types, but males have a larger muscle mass and larger muscle fibers (p. 626-627). This gave us

reason to compare the differences in carbon dioxide output of males and females. While males should have a

higher carbon dioxide output than females, we expect females will have a greater change in CO2 output after

physical activity, because females have larger Type I muscle fibers compared to their Type IIB fibers and would

have to undergo more aerobic respiration to complete the same physical activity as a male.

Our null hypothesis was that there will be no statistically significant difference in the change in CO2

output between males and females after aerobic and anaerobic activity. We alternatively hypothesize that there

will be a statistically significant difference in the change in CO2 output between males and females after aerobic

and anaerobic activity. We predict that female participants will have a greater change in CO2 output than male

participants after both aerobic and anaerobic physical activity.

METHODS

The Frostburg State University Institutional Review Board approved our study to ensure the ethical

treatment and use of our human participants. We gained approval on June 7, 2016 upon full review of our

submitted procedure. To make certain our participants were aware of the conditions of the study, they reviewed

and signed a waiver (minors participating in the study had to obtain a parent/guardian signature). In accordance

with the requirements of the Institutional Review Board, the data was to be kept anonymous and the waivers

cannot be destroyed until three years after the completion of the study.

Data collection occurred on Tuesday, July 5, 2016 between the hours of 1:00 and 4:00 pm in room 231

and outside of the Compton Science Center at Frostburg State University. The temperature outside was around

24°C and the temperature inside ranged from 18 to 21°C.

We began by giving participants a numbered tag from 1 to 26 in order to keep data anonymous. We then

surveyed the participants on their age, gender, and lifestyle (active or sedentary). We measured the height and

weight of the participants with their shoes off. Following that, we entered those measurements into an Omron Fat

Loss Monitor to calculate the percent body fat of the participants. We took the resting blood pressure and heart rate

of the participants with an Omron Upper Arm Blood Pressure Monitor. Participants then proceeded to get their

resting carbon dioxide (CO2) output measured with a respirometer. Based on a study by Janet Daniel (2016), we

built our respirometer using a 250 mL Erlenmeyer flask, a straw and 100 mL of a pH indicator solution (p. 8). Our

pH indicator solution consisted of deionized water, phenolphthalein, and sodium hydroxide (NaOH). Sodium

hydroxide has a basic pH and phenolphthalein is a pH color indicator. Our basic solution was pink and once carbon

dioxide was added to the solution (by participants blowing into the straw), the CO2 dissolved in the water to produce

carbonic acid that neutralized the sodium hydroxide and turned the solution colorless (color change occurred). We

instructed the participants to take a full breath and to blow at a normal rate into the straw. Timers paused the

stopwatch by the cue of the participants as they paused to take breaths. While participants exhaled through the straw

into the solution, we observed and timed the color change. We used the time of the color change as a gauge of the

CO2 output time. CO2 output time was the time needed to exhale a fixed volume of CO2 needed for the color change

4

to occur. A shorter time recorded would indicate a greater rate of CO2 exhaled and a longer time recorded would

indicate a slower rate of CO2 exhaled.

After recording their resting blood pressure, heart rate and CO2 output time, participants performed a

physical activity according to their numbered tag. Odd numbered participants started with an aerobic physical

activity and completed the 20 meter FitnessGram Pacer test to lap 20. Right after their aerobic activity was

completed, we measured the blood pressure, heart rate and CO2 output time of the participants. Participants then

took a 15-minute break to restore their blood pressure, heart rate and CO2 output to resting levels before completing

the other physical activity. Even numbered participants started with an anaerobic physical activity, and they

completed 15 seconds of instructed jump squats. Once they completed their anaerobic activity, we measured the

blood pressure, heart rate and CO2 output time of the participants again.

We found the average change of time until color change between the active and sedentary participants and

the male and female participants before and after both aerobic and anaerobic physical activity. We calculated the

change by subtracting each time until color change after physical activity from the resting time until color change

and then took the average. We decided to subtract in this order to keep our data in terms of positive numbers. To

analyze the data, we performed an unpaired statistical t-test. We used a t-test to compare the averages between the

active and sedentary participants and the male and female participants before and after both aerobic and anaerobic

physical activity. We performed an unpaired t-test, because they are utilized to compare the data of two

independent groups (active and sedentary or males and females) and sample sizes that are not equal (14 active

participants and 12 sedentary participants; 10 males and 16 females). The purpose of analysis was to determine if

there was statistical significant difference in CO2 output times between the active and sedentary participants and

the male and female participants before and after aerobic and anaerobic physical activity.

RESULTS

Average heart rates of all participants were significantly greater after aerobic physical activity than before

(Fig. 1). All participants had higher average systolic blood pressure values after aerobic physical activity. The

participants had elevated average systolic blood pressure values after anaerobic physical activity, but there was

not a significant difference (Fig. 2). Average diastolic blood pressure values of all participants before and after

aerobic and anaerobic physical activity remained relatively the same (Fig. 3). The average change in time until

color change after aerobic physical activity was larger than the average change in time until color change after

anaerobic physical activity (Fig. 4), which means CO2 output increased more after aerobic activity.

LIFESTYLE

Active participants had an average resting heart rate lower than sedentary participants. Sedentary

participants had a higher average heart rate after aerobic activity compared to active participants. Systolic and

diastolic blood pressures both increased after aerobic physical activity in all participants. There was a larger

increase in systolic and diastolic blood pressure as well as heart rate of sedentary participants after aerobic

physical activity compared to active participants.

5

The average change in time until color change of active participants after aerobic physical activity was

14.03 seconds. Before and after aerobic physical activity the average change in time until color change of

sedentary participants was 11.95 seconds. Our p-value was 0.5727, which is less than 0.05, so there was no

significant difference in the average change in time until color change, or CO2 output, between sedentary

participants and active participants after aerobic physical activity. Although there was no significant difference

between the two, active participants had a larger average change in time until color change after aerobic physical

activity than the average resting time until color change of sedentary participants (Fig. 5). Before and after

anaerobic physical activity the average change in time until color change of active participants was 8.559 seconds.

The average change in time until color change of sedentary participants after anaerobic physical activity was 9.49

seconds. Our p-value was 0.7463, which is less than 0.05, so there was also no significant difference in the

average change in time until color change, or CO2 output, between sedentary and active participants after

anaerobic physical activity. Sedentary participants had a larger average change in time until color change after

anaerobic physical activity than the average resting time until color change of active participants, even though

there was no significant difference (Fig. 6).

GENDER

The average change in time until color change after aerobic activity for females was 15.082 seconds. The

average change in time until color change after aerobic activity for males was 9.855 seconds. The p-value for

these data sets was 0.1544, which is less than 0.05, so there was not a significant difference in change in time until

color change before and after aerobic activity between males and females. The average change in time until color

change after aerobic activity was greater in females than in males (Fig. 7).

The average change in time until color change after anaerobic activity for females was 10.177. The

average change in time until color change after anaerobic activity for males was 7.088. The p-value for these data

sets was 0.2999, which is less than 0.05, so there was not a significant difference in change in time until color

change before and after anaerobic activity between males and females. The average change in time until color

change after anaerobic activity was greater in females than in males (Fig. 8).

DISCUSSION AND CONCLUSIONS

All of the general trends of the data referenced in the results were supported by background research and

were expected to occur in this study. Aerobic activity increased heart rate and systolic blood pressure, but had little

effect on diastolic blood pressure, and impacted the change in time until color change by an average of 13 seconds.

Anaerobic activity had little effect on heart rate, systolic and diastolic blood pressure, and impacted the change in

time until color change by an average of 9 seconds. Aerobic activity had an average larger impact on the change in

time until color change than anaerobic activity. Since there was a decrease in time until color change, we can

conclude that more CO2 is being exhaled after physical activity than at rest. We used the time of the color change

as a gauge of the CO2 output time. A shorter time recorded would indicate a greater rate of CO2 exhaled and a longer

time recorded would indicate a slower rate of CO2 exhaled.

6

LIFESTYLE

The purpose of this study was to see if factors, like lifestyle, could influence carbon dioxide output. We

found there was no significant difference in the data in terms of CO2 output between the active and sedentary

participants after aerobic and anaerobic activity. During rest, active participants had a lower CO2 output than

sedentary participants. Active participants also had a lower CO2 output compared to sedentary participants after

aerobic and anaerobic physical activity; however, statistically this difference was not signficant. The change in

CO2 output after aerobic and anaerobic physical activity was greater in sedentary participants.

We tested two hypotheses. Our null hypothesis was that there would not be a difference between the

change in CO2 output of active participants compared to sedentary participants before and after aerobic and

anaerobic physical activity. Our alternative hypothesis was that there will be a difference between the change in

CO2 output of active participants compared to sedentary participants before and after anaerobic physical activity.

We failed to reject our null hypothesis because we found no significant difference between the active and

sedentary participants before and after aerobic and anaerobic physical activity. The p-values for the two main tests

we did were 0.5727 and 0.7463, respectively, for aerobic and anaerobic activity and are all above our significance

level of 0.05.

The Shahraki study (2012) supported the findings that active participants had a lower average resting

heart rate compared to sedentary participants, and sedentary participants had a higher average heart rate after

aerobic activity compared to active participants. Blood pressure increases when there are greater amounts of

carbon dioxide in the blood. This is why the systolic and diastolic blood pressure values both increased after

aerobic physical activity in all participants, which was partially supported by the Shahraki study (2012). In the

study by Shahraki et.al. (2012), systolic blood pressure values increased in all participants, but diastolic blood

pressure values decreased in active participants. We also expected the larger increase in systolic and diastolic

blood pressure, as well as heart rate, of sedentary participants after aerobic physical activity compared to active

participants. An error in comparing these two studies was that the Shahraki study (2012) compared only athletic

females to non-athletic females before, during and after aerobic activity, while our study compared active and

sedentary males and females before and after aerobic physical activity (p. 13). We expected our results to

correlate to the Shahraki study (2012), but the differing results could be explained by the difference in test

participants. Observing no difference in CO2 output times within our own data does not reflect the increase in

heart rate and systolic blood pressure after aerobic physical activity. We concluded that there may be another

factor besides CO2 that effects heart rate and systolic blood pressure in the human body.

Several components of our study could have affected the data we collected. We did not expect there to be

no difference between active and sedentary participants before and after aerobic and anaerobic physical activity.

We had high standard deviation values that impacted our results because our data had a large variation of times

until color change. A large standard deviation means the data is widespread, making our results less reliable.

7

GENDER

The purpose of the second study was to see how gender affected carbon dioxide output before and after

aerobic and anaerobic activity. Our results showed that the average change in time until color change was higher

for females after both aerobic and anaerobic activity. Even though these averages supported our expectations, our

t-test did not. The p-values for our aerobic and anaerobic data sets between males and females were 0.1544 and

0.2999, respectively. Both these p-values are greater than 0.05, so there was no significant difference in change in

time until color change after aerobic and anaerobic activity between males and females. So, our study showed that

there was no difference in change in CO2 output after physical activity between males and females. This was,

again, most likely due to large standard deviations. The results of the t-test of our data indicated that the different

muscle fiber compositions in males and females do not affect carbon dioxide output. Therefore, we failed to reject

our null hypothesis.

We expected the change in CO2 output after physical activity to be significantly different in males and

female because the study by Staron, Hagerman, Hikida, et al. (2000) found that males and females have different

muscle fiber compositions. The fact that we found no significant difference between the change in CO2 output

after physical activity could be due to error in our respirometer procedure. Another possibility is that differences

in muscle fiber composition between males and females may not have as great of an effect on CO2 output as we

had originally thought.

Our study could have been limited by a number of factors. Our participants were all relatively similar in

age, weight and height, but how a subject categorized themselves in terms of active or sedentary lifestyle may not

have been completely accurate. The simplicity of our respirometer may have been a factor in the accuracy of

measuring CO2 output and could have contributed to the large standard deviations in our data. The principle

investigator had to remake the respirometer solution 3 times due to not having a large enough container to hold all

of the solution. The exact proportion of the components may not have been the same every time, which may have

slightly skewed results. There could have also been errors in the timing and following a constant testing procedure.

The color change of the respirometer was judged by two different timers that may have had different reaction to

pausing the stopwatch when participants took breaths and different interpretations of when the solution was

completely colorless. Participants failing to correctly and completely following protocol may have also posed a

limitation. The intensity the participants blew into the respirometer may have impacted results. The manner the

participants cued taking a breath may have also swayed results by affecting when the timers paused the stopwatch.

Since there were only two respirometer stations and, at times, multiple participants waiting to get measurements

taken, post-physical activity data could be slightly inaccurate due to participants having to wait in line because the

measurements were closer to a resting state than they should have been. The temperature difference between our

inside location and our outside location could have affected our data.

Improvements to this study could include retesting CO2 output using a lab grade respirometer to provide

more accurate results. Also, redoing the study with a better regulated test procedure and more training with the

8

equipment beforehand may yield more accurate results. Running the study with one timer and having set time

increments between participants would ensure no lines at the measuring stations after the physical activity.

Another way to increase the accuracy of results could be using a larger sample of people with a greater variety in

lifestyle and an equal gender ratio. A larger sample size may affect the significance and variability of our data

since our standard deviation was large.

Future studies related to CO2 output may include studying the ratio of oxygen consumed to carbon

dioxide exhaled. Oxygen to CO2 output ratios could be measured using a blood oxygen reader and a respirometer.

We could look into muscle fibers influence on carbon dioxide output by isolating certain muscle fibers and taking

the blood pH surrounding the fibers. It would be interesting to study the effect of training in a higher altitude on

oxygen consumption and carbon dioxide output because as altitude increases atmospheric oxygen increases. We

could also study if other organisms follow the same trends, in regards to carbon dioxide output, as humans do

before and after physical activity. A study investigating animals would also be easier to control and possibly more

beneficial because we could directly control the lifestyle of animals, like dogs, by walking one group for a certain

number of hours per week while the other group of animals remained sedentary. In our limitations, we stated that

temperature could affect our data, this led us to ponder if temperature influences CO2 output. We would test this

by having participants do the same physical activity in different temperatures. While collecting data, we found the

body fat percentage of the participants. In the future we could see if there is a correlation between CO2 output

after physical activity and body fat percentage. While this particular study did not yield new information, oxygen

consumption and carbon dioxide output are still valuable areas of study that could contribute a great deal of

knowledge to the scientific community, especially the field of exercise physiology.

9

TABLES AND GRAPHS

0

20

40

60

80

100

120

Resting Aerobic Anaerobic

Dia

stol

ic B

lood

Pre

ssur

e (m

mH

g)

Activity

Fig. 3. - The average diastolic blood pressure of all participants before and after aerobic and anaerobic physical activity. Error bars represent one standard deviation.

0

5

10

15

20

25

Aerobic Anaerobic

Chan

ge in

TIm

e U

ntil

Colo

r Ch

ange

(s

cond

s)

Activity

Fig. 4. - The average change of time until color change of all participants before and after aerobic and anaerobic physical activity. Error bars represent one standard deviation.

Fig. 1. - The average heart rate of all participants before and after aerobic and anaerobic physical activity. Error bars represent one standard deviation.

0

20

40

60

80

100

120

140

Resting Aerobic Anaerobic

Hea

rt r

ate

(bea

ts p

er m

inut

e)

Activity

0

20

40

60

80

100

120

140

160

180

Resting Aerobic Anaerobic

Syst

olic

Blo

od P

ress

ure

(mm

Hg)

Activity

Fig. 2. - The average systolic blood pressure of all participants before and after aerobic and anaerobic physical activity. Error bars represent one standard deviation.

10

0

2

4

6

8

10

12

14

16

18

Active Sedentary

Chan

ge in

Tim

e U

ntil

Colo

r Cha

nge

(sec

onds

)

Lifestyle

Fig. 6. - The average change of time until color change of active and sedentary participants before and after anaerobic physical activity. Error bars represent one standard deviation and the p-value is 0.7463

0

5

10

15

20

25

30

Active Sedentary

Chan

ge in

Tim

e U

ntil

Colo

r Cha

nge

(sec

onds

)

Lifestyle

Fig. 5. - The average change of time until color change of active and sedentary participants before and after aerobic physical activity. Error bars represent one standard deviation and the p-value is 0.5727

Fig. 8. - The average change of time until color change of male and female participants before and after anaerobic physical activity. Error bars represent one standard deviation and the p-value is 0.2999

Fig. 7. - The average change of time until color change of male and female participants before and after aerobic physical activity. Error bars represent one standard deviation and the p-value is 0.1544

11

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