Measuring Grip Strength

MEASURING GRIP STRENGTH

Biomechanical engineers are interested in knowing exactly how much force our muscles are capable of producing. With this information, they can design many everyday products. For example, a jar seal can be designed so that it is easily opened with our hands. What if the packaging of your favorite snack or the door to the restrooms required the strength of an Olympic body builder to open?! There are many reasons engineers must be able to accurately measure the capabilities of human muscles.

Have you ever injured your elbow or knee and felt like your arm or leg was weak as a result of the injury? Sometimes we put large stresses on our muscles during the course of regular daily activities, with heavy lifting or during sports activities. Too much stress can lead to injuries, such as extremely painful muscle strains (often called "pulled muscles"), in which muscles are actually torn. Often stretching and strengthening rehabilitation exercises help these muscles, tendons or ligaments recover from the injury and prevent it from happening again.

Today, you are going to be biomechanical engineers employed by a medical practice specializing in physical therapy. The doctors need an instrument to help monitor the hand strength of a 6-year-old patient recovering from "tennis elbow," a condition in which the person applied unaccustomed force to one or more tendons in his/her elbow, leading to a weakened grip. The doctors tried to use their existing hand dynamometer, an instrument for measuring grip strength, but it was not effective for the size and strength of the young patient. You will begin by using an existing hand dynamometer to measure the strength of students in our class. You will analyze these measurements to make a recommendation to the medical office for a similar device for their patient. Then, we will think about other devices that could be designed to measure the grip strength of different muscles.

Vocabulary/Definitions

Objective: Design an instrument to help monitor the hand strength of a 6-year-old patient recovering from "tennis elbow," a condition in which the person applied unaccustomed force to one or more tendons in his/her elbow, leading to a weakened grip.

Predictions:

• How much force do you think your hand muscles are capable of producing? More specifically, what is your grip strength? What do you predict? 2 lbs? 200 lbs?
  
• Why might a person want to know his/her grip strength?
  

Grip Strength Data Worksheet

1. Using the hand dynamometer, record your grip strength in the table below.

1. Re-organize your data to determine what factors affect an individual’s grip strength.

3. Choose one of the 3 variables to graph. What type of graph should you make and why?

4. Create a graph. Include your title and variables with units.

5. Identify the independent and dependent variables in this activity?

6. Which group had stronger grip strength? Give a reason you think this could be. Explain your reason. Was the difference significant?

7. Suggest another variable that might affect grip strength. How do you think grip strength would be affected and why?

8. Considering the 6 year old boy with an injury to the tendons in his elbow, make a recommendation to the doctors and engineers about how to modify the hand dynamometer for their patient.

9. Think of how you could design a device to measure the strength of other muscles in the body. For example, muscles of the upper arm, the lower leg, the shoulder, the foot, etc. Make a detailed sketch of your device. Make sure to explain what it’s made from and how it works.

Use separate paper for this part.

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