Areas of Science Sports Science
Science With Your Smartphone
Time Required Very Short (≤ 1 day)
Prerequisites None
Material Availability Readily available
Cost Very Low (under $20)
Safety Requires adult supervision when seeking volunteers
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Do you ever feel like you need to move your legs faster than your parents do just to keep up with them? This could be because of the difference in leg length between you and your parents. How many more steps do you need to take compared to your parents to walk down the block? Can you use a walking test to determine how tall a person is? This science project will help you find out! You can even use your phone and Google's Science Journal app to record the steps and determine the pace.


Test if the height of a person is related to the length of their steps, and if this information can be used to estimate a person's height.

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Sabine De Brabandere, PhD, Science Buddies
Sara Agee, PhD, Science Buddies

Cite This Page

General citation information is provided here. Be sure to check the formatting, including capitalization, for the method you are using and update your citation, as needed.

MLA Style

De Brabandere, Sabine. "Keeping Up." Science Buddies, 20 Nov. 2020, Accessed 28 Feb. 2021.

APA Style

De Brabandere, S. (2020, November 20). Keeping Up. Retrieved from

Last edit date: 2020-11-20


An activity tracker or fitness tracker is an electronic device that is often used by joggers or walkers to tell them how far a distance they have traveled, how much energy was used during the activity, etc. Its predecessor is the pedometer (Figure 1). The name pedometer comes from the Latin words "ped," which means to walk, and "meter," which means to measure. Pedometers measure the number of steps taken and use that to calculate the distance walked.

A watch style fitness tracker and a pedometer side-by-side
Figure 1. A picture of a fitness tracker (left) and a pedometer (right).

Wondering how a pedometer works? Pedometers detect the swinging or bouncing motion that occurs with every step you take. They count the number of swings or bounces to obtain a number of steps. Older pedometers used mechanical switches or swinging levers to pick up motion. Newer electronic devices contain special measuring parts called accelerometers. These measure changes in motion in three different directions (up/down, front/back and side-to-side). Figure 2 shows how an accelerometer in a cellphone measures changes in motion in three directions. Newer electronic pedometers use data from the accelerometer to measure the number of steps taken.

Diagram of a smartphone measuring movements in the x, y and z directions
Figure 2. Accelerometers in cell phones and other electronic devices measure the change in motion in three directions. In mathematics and physics, these directions are usually labeled X, Y, and Z.

How can a pedometer or fitness tracker determine how far you have walked based on how many steps you have taken? It does this by assuming each step is the same length. Some pedometers ask you to enter your height, or how tall you are, before you start walking, and use that to estimate the length of your step. By multiplying the length of each step by the counted number of steps, the pedometer can calculate the total distance traveled. This relies on an important assumption, though—that a person's height can be used to predict the length of their step! Do you think this is true? In this project, you will find out by asking people of different heights to walk a certain distance, and counting how many steps each of them takes.

Terms and Concepts

  • Activity tracker or fitness tracker
  • Distance
  • Pedometer
  • Accelerometer
  • Height
  • Hypothesis
  • Pattern
  • Best fit
  • Estimate


  • What does a pedometer measure, and what does it calculate?
  • Do you think that taller people have longer steps and smaller people have smaller steps? If so, why would this be?
  • If you measure a person's height, do you think you can estimate how long their step will be? Do you think you will be able to do it after you have completed this project?
  • What about the other way around—if you measure the length of a person's step, do you think you can estimate how tall they are?


  • Peaceful Playgrounds. (n.d.). Pedometers for Kids Track Physical Activity. Retrieved October 23, 2013.
  • Klein, Aaron. 1977. You and Your Body: A Book of Experiments to Perform on Yourself. Garden City, New York: Doubleday and Company, Inc.
  • Rubber Bug Animation (n.d.) Anatomy of a Walk.. Retrieved March 2, 2017.

For help creating graphs, try this website:

  • National Center for Education Statistics, (n.d.). Create a Graph. Retrieved June 25, 2020.

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Materials and Equipment

  • Pen or pencil
  • At least 10 volunteers; try to get people with different heights
  • Sidewalk chalk
  • Tape measure, metric
  • Optional: Graph paper
  • Straight edge ruler
  • Lab notebook
  • Optional: armband cell phone bag, like this one from Amazon
  • Optional: A smartphone to record your data
    This project uses Google's Science Journal app, a free app that allows you to gather and record data with a cell phone. You can download the app from Google Play for Android devices (version 4.4 or newer) or from the App Store for iOS devices (iOS 9.3 or newer).

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Experimental Procedure

Note: There are two different ways to do the experiment. In one method, the volunteer will count his or her own steps. In the other method, you will use a smartphone and Google's Science Journal app to record the motion of your volunteer's ankle as the volunteer walks, then count the number of steps based on the recorded motion. The procedure describes both ways.

Preparing the Experiment

  1. In your lab notebook, make a table like Table 1 to record your data while you do your experiment. Make sure your table has enough rows for at least 10 volunteers.
Data taken for walking 20 meters
 Height (cm) Number of Steps Taken
Volunteer 1   
Volunteer 2   
Volunteer 3   
Volunteer 10   
Table 1. Table to record volunteer's height in centimeters (cm) and the number of steps they needed to walk 20 meters (m.)
  1. Decide on a place for your experiment. The ideal place would be a park with a jogging path.
  2. Gather volunteers and explain the experiment to them. You may also want to check your science fair rules on involving human subjects in your project.
    1. Use friends and family as volunteers. Make sure you have volunteers of different heights.
    2. As an alternative, you can ask people walking by to help you with your science project. If you choose this option, be sure to ask your parents' permission to speak with strangers and have a parent or adult come with you and supervise while you seek and talk to volunteers.
  3. Decide on how to count the number of steps. The options are:
    1. Let each volunteer count his/her steps taken as they walk.
    2. Use a smartphone and Google's Science Journal app to obtain the number of steps taken by the volunteer. See section Counting the Number of Steps with Google's Science Journal for details on how to do this.

Counting the Number of Steps with Google's Science Journal

This section explains how to use Google's Science Journal app to collect data. You can skip this section if you decided to let your volunteers count the number of steps taken. Science Journal is an app that lets you record data using sensors that are built into many smartphones, including an accelerometer, which measures motion. Specifically, it measures acceleration, or the changes in an object's speed. You can learn how to use the Science Journal app and how to use the accelerometer by reviewing the releveant tutorials on this Science Journal tutorial page. The following section explains how to use the accelerometer to record the motion of the ankle of a person walking, and then how to count the number of steps taken from the recorded data. Be sure to practice using the app to count the number of steps before you go out and do the experiment.

A smartphone is strapped to a persons ankle
Figure 3. Phone attached to the ankle using an armband cell phone holder. The phone is positioned so its X-direction aligns with front-to-back motion when you walk.
Show step-by-step instructions

Doing the Experiment

  1. Go to the set location. Do not forget to bring your lab notebook, pen, chalk, tape measure, your supervisor, and, optionally, a phone with the Science Journal App installed and the armband cell phone bag.
  2. At the location, mark off a distance of 20 meters (m) with a piece of sidewalk chalk.
  3. Briefly explain your science project to the volunteers. Make sure to explain that they should walk at their natural pace and not try to speed up or walk extra slow!
  4. Run the test for each volunteer, one at a time (people may adjust their natural pace when walking next to each other):
    1. Measure the height of the volunteer with your measuring tape in centimeters (cm). Write down the measured height in your data table.
    2. Option 1: The volunteer counts steps.
      1. Ask the volunteer to walk from the beginning to the end of the 20 m course you marked, while counting the number of steps they take. Write down the number of steps in your data table.
    3. Option 2: Use Google's Science Journal app to count the number of steps.
      1. Have the Google Science Journal app open. Make a new recording for each volunteer.
      2. Remember to take your measurements with the X accelerometer.
      3. Attach the phone to the ankle of the volunteer as shown in Figure 3.
      4. Position the volunteer at the beginning of your 20 m course.
      5. Press the record button to start recording and ask the volunteer to walk to the end of the course.
      6. Press the record button to stop recording.
      7. Detach the phone.
      8. Important: Make sure you keep track of which recording is for which volunteer. You can for example change the default name of the trial in the app.
  5. Politely thank the volunteer for helping you with your experiment.
  6. Repeat for a total of at least 10 volunteers.
  7. Walk the 20 m course yourself, and write down the number of steps you took in your lab notebook.

Analyzing the Data

  1. If you used Science Journal to collect data: go over the graphs for each volunteer, count the steps, and write the number of steps down in your table like Table 1. Remember, each repetition of the pattern represents two steps. Look back at section Counting the Number of Steps with Google's Science Journal if you need help with counting the number of steps.
  2. Create a graph. You can make the graph by hand or use a website like Create a Graph to make an XY scatter graph and print it out.
    1. Plot the height (in cm) on the horizontal axis (X-axis) and the number of steps on the vertical axis (Y-axis).
    2. When you are done plotting your points, you should have one dot for each volunteer.
  3. Look at your dots and see if they almost make a straight line. Use a ruler to draw a "line of best fit" through the dots. To make a line of best fit, do the best you can to line up a ruler through the middle of the dots and draw your line. Some points will be above the line, some under. That is fine.
  4. Can you find how you can use your line of best fit to estimate, or roughly calculate, the height of a person when you know the number of steps they take to walk 20 m? To test this, find the number of steps you took to walk 20 m in your lab notebook and use your line of best fit to estimate your own height (in cm). Compare the estimated height with your real height (in cm). How accurate is your estimate?
  5. Looking back at your data and graph, do you think there is a reliable relationship between the height of an individual and the number of steps they take to walk 20 m? How can this information be used by a pedometer or fitness tracker?

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  • Make another data table for estimating the height of a person based on how many steps they take to walk a certain distance, using the best fit line from your graph. It should have columns for the number of steps, the estimated height, and the actual height. Now find more volunteers and try to estimate their height based upon your line of best fit and the number of steps they take to walk 20 m. How often are you close to their real height? How accurate are your estimates?
  • Do you think the distance you have people walk affects the precision of your experiment and the quality of your best-fit line? What happens if you only count steps over a short distance (5 meters) or a longer distance (40 meters)?
  • How does the speed of walking affect the number of steps required to go a certain distance? You can do an experiment where you walk the 20 meter distance slowly, moderately fast, or very fast to see if the number of steps changes with speed. Will there be more steps for slower or faster walking? What about running?
  • Would taller people take less time to walk the 20 m course? If you recorded your data with the Science Journal App, you can look back at your recorded graphs and read the duration of the walk from the graphs. Make a new scatter plot with the height of the person on the X-axis and the duration on the Y-axis. Do you see a clear relation? If you did not use the Science Journal app, you can use a stopwatch to time how long it takes each volunteer to walk 20 meters.
  • Do people of the same height all take steps of the same length? What if two people are the same height but one of them has longer or shorter legs relative to their body? Try to find a bunch of volunteers who are about the same height, and measure their total height and the length of their legs. Does the ratio of leg length to body length affect how many steps they take to walk a certain distance?
  • If you have a video camera, you can use it to find out how exactly the graph from the Science Journal app corresponds to walking motion. Use the camera to film a person walking from the side, and hit record on the camera at the same time someone hits record in the app. Then, the video's timeline will be synced up with the x-axis time of the recorded data. What point in your step (for example, when you first lift your foot up, when your foot is off the ground, when you put your foot down, etcetera) do the peaks and valleys in the graph correspond to?

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