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The Biomechanics of Pitching

Time Required Short (2-5 days)
Prerequisites You should do this sports science fair project in a location where you can tie a clothesline either between two trees or two poles. Since you will be throwing a baseball, make sure that the location is away from windows and other breakable structures.
Material Availability You must have access to a camcorder and baseball equipment. Make sure that the camcorder has a timer and the ability to display the recording in slow motion.
Cost Low ($20 - $50)
Safety Minor injury is possible. Adult supervision is recommended.


What do Nolan Ryan, Mark Wohlers, Armando Benitez, and Roger Clemens have in common? These men are all major league baseball pitchers who have pitched baseballs at 100 miles per hour or greater! What does it take to throw a baseball this fast? Does it come down to having the biggest muscles? Can a ball thrown this fast also be accurate? In this sports science fair project, you will learn about the biomechanics of pitching. Investigate how body position and physics interact to produce fast pitching, and find out if you have the skill and speed to become a major league baseball pitcher.


To determine how body position affects baseball speed.


Michelle Maranowski, PhD, Science Buddies

The author would like to thank Mr. Jack Duffy for testing this project.

Cite This Page

MLA Style

Science Buddies Staff. "The Biomechanics of Pitching" Science Buddies. Science Buddies, 22 Oct. 2014. Web. 30 July 2015 <>

APA Style

Science Buddies Staff. (2014, October 22). The Biomechanics of Pitching. Retrieved July 30, 2015 from

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Last edit date: 2014-10-22


Baseball is widely known as America's favorite game and pastime. It's fun to watch two teams pit their skill and strategy against each other. There are many factors that affect the score and which team wins the game. The teams need to hit the ball, field the ball, and run fast. One of the most important factors is good pitching. If the pitcher is not in top form, then the opposing team has more chances to hit the ball, get on base, and score.

Baseball game at Wrigley Field in Chicago

Figure 1. This image shows a baseball game in progress at Wrigley Field in Chicago, Illinois. (Wikipedia, 2004.)

Pitching a ball quickly and accurately is complicated. It is dependent on how the pitcher controls and uses his or her body to eject the ball from his or her hand. Biomechanics is the study of the human body in motion. Biomechanists apply principles from mechanics and engineering to study the forces that act on the body and the effects they produce. A pitcher needs to understand how to use his or her body and become familiar with all of its possible positions in order to pitch a ball as fast as he or she can. In fact, pitchers can get injured if they don't know how to use their bodies properly.

The American Sports Medicine Institute has separated the act of pitching into six phases. It is important for the pitcher to properly perform each step in order to prevent injury. These six phases are as follows:

  1. Windup: The windup phase begins when the pitcher steps back with the front foot, balances on the back foot, and picks the front leg up. The windup phase ends when the front leg is at its maximum height and the two hands begin to separate.
  2. Stride: During the stride phase, a pitcher moves the front foot toward home plate as the two arms swing down and apart from each other. The stride phase ends when the front foot touches the mound.
  3. Arm cocking: During the arm-cocking phase, the pelvis and then upper body rotate to face home plate as the throwing arm externally rotates at the shoulder. The arm-cocking phase ends when the shoulder reaches its maximum external rotation.
  4. Arm acceleration: The phase from the instant of maximum shoulder external rotation until ball release is arm acceleration.
  5. Arm deceleration: The phase from ball release until the arm stops internally rotating is defined as the arm deceleration.
  6. Follow-through: Follow-through begins with maximum shoulder internal rotation and ends when the pitcher regains a balanced position.
Four phases of pitching

Figure 2. Four of the different phases of pitching: a) Windup, b) Stride, c) Arm cocking and d) Follow-through. (wikiHow, 2004.)

Pitching puts a great amount of stress on the throwing arm, especially at the elbow and arm. During pitching, there are both external and internal forces acting on the body. External forces include gravitational force and the ball's resistive force. Internal forces include how each part of the arm (the hand, the wrist, the elbow) act against each other. There is a lot of physics that describes the motion of the throwing arm.

In this sports science fair project, you will experiment with the biomechanics of pitching. You will determine if the stride step and the length of the stride affect the speed of a pitch. Remember to warm up your arm prior to starting this science fair project, and stop pitching if your arm starts to hurt. You don't want to get injured as you perform your project. Have your coach or an adult standing by to help, if necessary. Batter up!

Terms and Concepts

  • Biomechanics
  • Stride
  • Pelvis
  • Rotate
  • Acceleration
  • Deceleration
  • Force
  • Gravity
  • Resistance
  • Speed


  • What are the different parts of the arm? Is it just the arm that throws, or are different parts of the body involved in throwing?
  • What are two joints in the arm that can be injured due to poor pitching? What can happen to these joints?
  • What are the biomechanics of other sports, such as golf, soccer, or football?


The following website shows the different phases of pitching and provides more information about pitching:

For help creating graphs, try this website:

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Materials and Equipment

  • Clothesline
  • Bed sheet, choose a color that contrasts with the color of the baseball.
  • Permanent marker
  • Clothespins (6)
  • Tape measure
  • Adult volunteer to use the camcorder
  • Camcorder
  • Baseball
  • Pitching volunteers (3). Your volunteers should have experience throwing a ball.
  • Lab notebook
  • Graph paper

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Experimental Procedure

Preparing the Setup

Note: You should not perform this science fair project on a breezy or windy day.
  1. Read the operating instructions of the camcorder you are using. Make sure that the adult who will operate it understands how to work the camcorder, how the timer works, and how to replay a recording in slow motion.
  2. At your test location, find two poles or two trees to which you can tie a clothesline. Make sure that the clothesline is securely tied and nowhere near any windows or other breakable objects.
  3. Using the permanent marker, draw a large "X" in the middle of the bed sheet. The "X" should be about 2 feet tall.
  4. Attach the bed sheet to the clothesline, lengthwise, with the six clothespins. The ends of the bed sheet should touch the ground.
  5. Measure a spot 40 feet away from the sheet with your tape measure. This is the position from where you will be throwing the ball. If this distance is too far and you don't think that you will be able to hit the sheet, then move forward to a distance from where you will be able to hit the sheet. Record the distance in your lab notebook.
  6. Have your adult volunteer find a safe location from where to record your pitching with the camcorder. The camcorder should be positioned so that the pitcher and the sheet are both in the shot; in other words, the adult volunteer should not pan the camera from the pitcher to the sheet. Be sure the volunteer records each pitcher's entire throw, until the ball is released from the hand. Make sure that the camcorder timer is on.

Performing the Trials

  1. Exercise your arm in preparation for pitching. You should never start any kind of exercise without warming up properly. Pitch the ball with a comfortable and normal stride forward. Try to get an idea of how long your normal stride is.
  2. Have your adult volunteer start the camcorder. Do this first pitch just with your arm and no stride forward. Now aim for the "X" and throw the ball at the sheet.
Pitching with no stride

Figure 3. This pitcher is getting ready to pitch the ball with no stride.

  1. Now pitch the ball with a stride that is the length of your normal and comfortable stride length. Make sure that the volunteer is recording (with the timer on) your pitching and the ball hitting the sheet each time.
  2. Repeat steps 2–3 of this section two additional times each. If the ball fails to hit the sheet during any of the trials you will have to redo that trial.
  3. Repeat step 5 in the previous section and steps 1–4 of this section with each of your pitching volunteers.
  4. Now review the recordings in slow motion for each volunteer. Note the start time and end time for each pitch. The start time is when you can see that the ball has left the volunteer's hand. The end time is when the ball hits the sheet. You can see the sheet start to billow and move when the ball hits the sheet. Record the data in your lab notebook in a data table like the one shown below.

Distance to Sheet =

  Trial Start Time End Time Pitch Time = End Time - Start Time
Speed =   Pitch Distance
Pitch Time
No Stride           Average speed =
Stride           Average speed =

Analyzing Your Data

  1. Once you have collected the data for all of the volunteers, it is time to analyze it. First, calculate the pitch time, which is the difference between the start time and the end time, for each trial, of each stride position for each volunteer. This is the time it takes to leave the hand and hit the target. The less time it takes to pitch the ball, the faster the speed of the ball. Record the calculations in your data table.
  2. The speed of the ball is calculated by dividing the distance between the pitcher and the target by the pitch time. If you would like to learn more about calculating speed, check out the following Science Buddies project: Speed Quest. Calculate the average speed for no stride and then again for stride.
  3. Graph the average speed data. If you would like to learn more about graphing or would like to do your graphs online, try the following website: Create a Graph. Label the x-axis with the following labels: No Stride and Stride. Label the y-axis Average Pitching Speed. Plot the data for all of your volunteers. Can you see a pattern? Is there a difference between striding and not striding?

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  • Does striding affect accuracy? Is it easier to hit a target when you stride forward? Do the experiment and find out!
  • How does the pitcher's height and weight affect speed? Does it make a difference? Collect 10 volunteers of varying heights and weights and do the experiment.
  • What happens if your stride length is longer than your normal and comfortable stride length? Does this affect the speed of the pitch or how you control the ball?
  • Kinematics is the branch of mechanics that describes the motion of objects without consideration of the circumstances leading to the motion. Can you see the difference in the motion of the arm between striding and not striding? You can investigate this by taping reflective tape to the joints of the pitching arm and videotaping the pitching.

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