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Factors affecting the rate of breathing

Factors affecting the rate of breathing

Introduction: (Initial Observation)

After running for a while, you may say that “I am out of breath!”. That simply means that you can not breathe as fast as your body needs. So running makes you breathe faster.

What other factors can make you breathe faster? How do different factors affect the rate of breathing?

Breathing is our way of supplying oxygen to our body and is important to our health and well being.

Knowing the factors that may change the rate of breathing can help us maintain a balance in our activities and detect harmful conditions that may have symptoms such as unusual reduction or increase in our rate of breathing.

In this project you must study one factor (of your choice) to determine how it affects the rate of breathing.

Some of the factors that may be studied for their effects on the rate of breathing are:

Exercise, elevation, air pressure, rate of oxygen in air, food, sleep, and age.


This project guide contains information that you need in order to start your project. If you have any questions or need more support about this project, click on the “Ask Question” button on the top of this page to send me a message.

If you are new in doing science project, click on “How to Start” in the main page. There you will find helpful links that describe different types of science projects, scientific method, variables, hypothesis, graph, abstract and all other general basics that you need to know.

Project advisor

For the purpose of this project guide, I assume that you want to study the effect of exercise on the rate of breathing. Later I will explain how you may change your experiment if you want to study any other factor.

Information Gathering:

Gather information about the function of lungs in human circulatory system. Read books, magazines, or ask professionals who might know in order to learn about the factors that may effect our circulatory system. Keep track of where you got your information from.

Following are samples of information that you may find.

On average, your body has about 5 liters of blood continually traveling through it, delivering oxygen and nutrients to different parts of it. The pumping of the heart forces the blood on its journey.
The body’s circulatory system really has three distinct parts: the lungs (pulmonary), the heart (coronary), and the rest of the system (systemic). Each part must be working independently in order for them to all work together.

Pulmonary circulation is the movement of blood from the heart, to the lungs, and back to the heart again. It starts from the right ventricle where it fills and then contracts, pushing the blood into the pulmonary artery which leads to the lungs. In the lung capillaries, the exchange of carbon dioxide and oxygen takes place. The fresh, oxygen-rich blood enters the pulmonary veins and then returns to the heart, re-entering through the left atrium.

Red blood cells carry oxygen from the lungs to all the cells of the body.

White blood cells are like soldiers protecting the body.

ARTERIES are vessels that carry blood away from the heart.

VEINS are vessels that carry blood back to the heart.

Blood CIRCULATES (circles) all around your body in about one or two minutes.

Inside the heart are four hollow chambers. Each chamber is a little pump. The pumping pushes blood all around your body.

Question/ Purpose:

What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.

The purpose of this project is to determine if exercise affects the rate of berating. We measure the amount of exercise by the amount of energy that a person consumes to do exercise.

Note: When you lift a weight, the amount of energy that you consume is measured by multiplying weight by acceleration of gravity by height.


where E is the amount of energy in Joule, m is the mass of object in Kilogram, h is the height you lift in meter and g is acceleration of gravity (9.8 m/s/s). So if you lift a 2 kilogram dumbbell one meter, the amount of energy that you use is

E = 2 x 1 x 9.8 = 19.6 Joules.

Identify Variables:

When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.

Independent variable is the the amount of exercise measured by the amount of energy consumed during the exercise.

Dependent variable is the rate of breathing.

Controlled variables are: Air flow, temperature, age, elevation, and air pressure.


Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis.

Following is a sample hypothesis:

Exercise increases the rate of breathing. Changes in the rate of breathing have a direct linear relation with the amount of energy that we consume during the exercise. My hypothesis is based on my personal experience while doing daily exercise.

Experiment Design:

Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”

Experiment: Test the effect of exercise on the rate of breathing.

Introduction: The rate of breathing will be measured during and after certain amounts of weight lifting. Experiment will be performed on four to six same age, same sex, randomly selected healthy individuals.


  1. Get a pair of dumbbells about 2 kg in weight (depending on the size and age of person whom you are testing).
  2. Attach a feather to the upper lips of the person so his/her cycles of breathing can be visualized and counted.
  3. Measure and record the distance that the person can lift the weight. This depends on the length of arms.
  4. Ask the person to stand and wait for 60 seconds while you count his normal rate of breathing. Record the results.
  5. Ask the person to hold one dumbbell in each hand, while one is all the way down and the other is up next to his shoulder. Then every 3 seconds he should raise the one that is down up to his shoulder while bringing the other one down. While he repeats this cycle for one full minute, you should count and observe and count his breathing rate. (At the end of one minute, he should have lifted 20 times)
  6. Then he should put the dumbbells down and stand waiting another full minute while you count his breathing cycles.
  7. Let the person rest for about 5 minutes so his breathing rate will get normal again.
  8. Repeat steps 4 to 7 with 2 second lifting cycles, so he will lift 30 times in one minute.
  9. Repeat steps 4 to 7 with 1 second lifting cycles, so he will lift 60 times in one minute.
  10. Repeat steps 4 to 7 with 1/2 seconds lifting cycles, so he will lift 120 times in one minute (ask him to count). It is OK if it is less than 120 lifts, but do not exceed one minute.
  11. Record your results in a table like this:
Number of lifts per minute
Lifting Height
Weight of each dumbbell
Energy (Joules)
Breathing cycles during exercise Breathing Cycles during a minute after exercise.

For zero number of lifts, write the normal rate of breathing.

Repeat this entire experiment with all your test subjects and create one table for each of them.

Combine all tables and create a new table that shows the average of your results. Every cell of this table will contain the average of all identical cells in your original results table. This will be your final result table that you use to create a line graph and draw a conclusion.

Use the Energy column and breathing cycles during and after exercise to draw a line graph. Use two different colors for breathing rate during and after exercise.

Other questions and Experiments:

To check the effect of elevation on the rate of breathing of your test subjects, first examine their normal rate of breathing and then get into an elevator and go up to the highest level of a tall building. Measure the rate of breathing again.

To test the effect of air pressure in the rate of breathing, you will not usually have access to the equipment that is needed for conducting such tests on humans. You may use a mouse in a glass bottle for such tests. Breathing rate of mouse can be counted visually by movements of his chest and ribs. Pressure change in a bottle can be performed using a simple hand pump. You may usually want to test normal pressure, less than normal pressure, and higher than normal pressure.

Effect of temperature in the rate of breathing can be tested on humans and mice. It is much easier to create warm and cold temperature for mice than humans. A desk lamp can create extra heat and a block of ice can create low temperatures.

Expansion and contraction of the lungs

Have you ever wondered what makes the lungs expand and contract? Lungs have no muscles by themselves. Can the expansion and contraction of the chest be the factor that makes the lungs expand and contact? This experiment/demonstration will show how it works. With this demonstration you can show how does the expansion and contraction of chest cage help the lungs to work.


  • An empty 2 liter or 3 liter bottle (no cap needed)
  • A balloon.
  • A small nail
  • A good set of lungs!


  1. Using the nail, make a small hole three-quarter’s way down the bottle.
  2. Blow up the balloon and let it stay inflated for a few hours. This will make the balloon softer and reduce its elasticity.
  3. Deflate the balloon; Place it into the bottle, fixing the elastic end around the lip of the bottle.
  4. With the hole uncovered, blow up the balloon into the bottle (just a little).
  5. Before you release your mouth from balloon, cover the small hole near the base of the bottle with a piece of tape.
  6. Remove your mouth and watch how the balloon remains inflated for as long as you keep the small hole covered.
  7. The bottle works like a chest cage. The balloon works like the lungs. With your hands push the sides of the bottle inward and watch what happens to the balloon. Now release your hands and let the bottle expand. What happens to the balloon?

Materials and Equipment:

  • Dumbbells
  • Timer or watch with seconds hand
  • feather

Results of Experiment (Observation):

Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.


You need to use your experiment results to calculate the amount of energy used to lift weights.

When you lift a weight, the amount of energy that you consume is measured by multiplying weight by acceleration of gravity by height.


where E is the amount of energy in Joules, m is the mass of object in kilograms, h is the height you lift in meters and g is acceleration of gravity (9.8 m/s/s). So if you lift a 2 kilogram dumbbell one meter, the amount of energy that you use is:

E = 2 x 1 x 9.8 = 19.6 Joules.

You will also need to calculate the averages of all values in your results tables and make a final results table.

Summary of Results:

Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.

It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.


Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.

Related Questions & Answers:

What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.

Could you use a treadmill to do a similar experiment?

Possible Errors:

If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.

If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.

Bringing down the weights may also require some energy that is ignored in our calculations.


Books and websites related to circulatory system and physics of work and energy can be used as references.





Gravitational Potential Energy