Lesson Muscles, Oh My!

Learning Objectives

After this lesson, students should be able to:

• Explain why biomedical engineers are interested in the muscular system.
• Name some devices biomedical engineers have created to aid the muscular system.
• Explain some specific injuries related to the muscular system.

Educational Standards

Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.

All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org).

In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.

NGSS: Next Generation Science Standards - Science

International Technology and Engineering Educators Association - Technology

State Standards

Worksheets and Attachments

Pre-Req Knowledge

A basic understanding of the human muscular system.

Introduction/Motivation

Imagine if the muscles that control your thumbs were not working properly. Try to pick up your pencil and write your name on a sheet of paper without using your thumb. What if you had to pick up a baseball and throw it? It would not be very easy, or as effective, as if you could use your thumb. These muscles are just a few of the approximately 600 muscles in our bodies. The muscular system, which is comprised of cardiac, smooth and skeletal muscles, controls our body's motion from each beat of our heart to the movements of our arms and legs. How important is a healthy muscular system in our daily lives?

Engineers play an important role in the medical health world. By understanding the human body, engineers are able to design machines to help doctors and patients heal and repair damaged muscles. These engineers are called biomedical engineers and they work on the entire human body, including the muscular system. They can design machines to help heal torn muscles, and even change non-working muscles into fully-functioning ones. Biomedical engineers have been able to help people — ranging from infants to elderly to professional athletes — with injuries as common as a muscle strain to more serious conditions, such as paralysis. Refer to the associated activity The Artificial Bicep to give students a better understanding of the muscular system and engineering by designing a biomedical device to aid in the recovery of a strained bicep.

Muscle strains occur when you overwork a particular muscle. For example, if you picked up a baseball and threw it as hard as you could many, many times, there is a good chance that you would hurt your arm, specifically its muscles and tendons. For injured muscles, such as a muscle strain, engineers have developed several machines to help the muscle recover quickly. One of these pieces of equipment is an ultrasound device. Basically, an ultrasound device focuses sound waves (which we cannot hear) on the injured muscle providing deep muscle stimulation, which increases blood flow and promotes healing. The end result is a muscle that recovers more quickly than if it was left alone. The faster a muscle recovers, the sooner you can resume playing your sport or performing your regular daily activities.

Biomedical engineers also help develop machines for people who are paralyzed. Paralysis is the loss of the ability to use part or all of the body. Biomedical engineers work on designing devices that can help undo the effects of paralysis. For example, engineers created a robotic brace to help stroke victims with resulting arm paralysis (see Figure 1). This device helps a person use their arm by providing machine-powered assistance. In addition, it doubles as physical therapy because as the machine moves the arm, the injured arm learns to function again. Over time, most stroke victims, in this example, eventually regain full functionality of their arm, which was directly affected by their stroke. Devices such as this one make biomedical engineering an important part of people's health and wellbeing. Refer to the associated activity Measuring Our Muscles for students to investigate other ways in which biomedical engineers provide more insights into muscle performance by  designing and developing a model hand dynamometer to collect and analyze data on grip strength and determining how much force muscles can produce. 

(optional) Read aloud to students or give as a handout the attached Robotic Brace Reading, a description of the engineering design and prototype testing of a medical device technology (shown in Figure 1) that helps people relearn how to move severely weak or partially paralyzed limbs.

Lesson Background and Concepts for Teachers

Biomedical engineers understand the muscular system and the three different types of muscle groups: skeletal, smooth and cardiac. Skeletal muscles (which we are focusing on in this lesson) connect to tendons and then to bones to provide for movement. Smooth muscles work with the body's organs. Cardiac muscles provide the force to pump the heart.

Biomechanics is a discipline involving the analysis of forces acting on and produced by a living system. Engineers who work in biomechanics are interested in finding out exactly how much force muscles are capable of producing and how the muscles react when outside loads are applied. By examining the effect of forces placed on muscles, bones and joints, engineers can determine the physical capabilities and limitations of the human body. As a result, doctors, physicians, athletes and others have found biomechanical engineers helpful in solving real-life problems related to health, the human body and especially, the muscular system.

Although muscles are necessary for movement, many components work together to provide human motion; these basic parts are collectively known as the musculoskelatal system. The system consists of muscles, tendons, ligaments, bones and cartilage, which are typically found where two or more bones are joined together, at a joint. Each bone usually has at least two pairs of muscles to exert forces on neighboring bones connected at the joint.

Our musculoskeletal system is essentially the combination of many simple levers (bones) operated by ropes (muscles) to move the structure about. Muscles produce motion in a similar way to ropes in an engineering system; they can pull, but they cannot push. In studying mechanics, engineers call a pulling force tension and a pushing force compression. Since bones are secured at the joint, when a tension force from a muscle pulls on a bone, a tendency for the bone to rotate about the joint is created. This turning, or rotating effect, produced by such a force is what engineers call a moment, or torque. Because each group of muscles produces tension forces in only a single direction, every bone usually has at least two muscles to achieve motion in multiple directions; one is called a flexor and another called an extensor. For motion in one direction, the flexor contracts to pull and rotate the bone one way, while the extensor is relaxed. For motion in the opposite direction, the extensor contracts to pull and rotate the same bone the other way, while the flexor is relaxed. Nearly every motion of the body is produced by a combination of these two pairs of muscles contracting and relaxing in unison.

Biomedical engineering blends traditional engineering techniques with the biological sciences and medicine to improve the quality of human health and life. Biomedical engineers are increasingly demonstrating that traditional engineering expertise applied to the life sciences is helpful in solving problems in human health. This relatively new area of engineering applies to several diverse disciplines including biology, ergonomics, kinesiology, physiology, medicine, orthopedics and mechanical physics. Professionals in these fields depend upon the assistance of engineers with a strong understanding of biomechanics and the musculoskeletal system. Their passion for improving human health and our quality of life ultimately improves the lives of hundreds of thousands of people who are injured every year.

The attached Robotic Brace Reading provides more information on the engineering design and prototype testing of medical device technology that helps people relearn how to move severely weak or partially paralyzed limbs.

Associated Activities

• The Artificial Bicep - Students further their understanding of the muscular system and engineering by designing a biomedical device to aid in the recovery of a strained bicep.

  Watch this activity on YouTube

• Measuring Our Muscles - Student teams act as engineers, designing and developing a model hand dynamometer to collect and analyze data on grip strength and determining how much force muscles can produce.

Lesson Closure

Why is it important to care for our muscles and not overstress them? (Answer: Our muscles are important to being able to move in order to perform our everyday activities. Our muscles may become injured if they are exerted beyond their capabilities. One example is a muscle strain.) How do biomedical engineers help us heal and repair injured muscles? (Answer: Engineers design machines that repair torn muscles, and even change non-working muscles into fully-functioning ones.) Who might biomedical engineers help? (Answer: Anyone, ranging from children to elderly to professional athletes with injuries.) What types of injuries might they help to restore? (Answer: Common injuries such as muscle strains, along more serious injuries such as paralysis.) So, we have learned today that the human body, and in particular the muscular system, can be analyzed by engineers to help solve medical and engineering problems and improve the quality of life for persons with disabilities, either on short-term or long-term basis.

Vocabulary/Definitions

biomechanics: The study of the mechanics of a living body, especially of the forces exerted by muscles and gravity on the skeletal structure. May also include the study of the mechanics of a part or function of a living body, such as of the heart or of locomotion.

biomedical engineer: A person who blends traditional engineering techniques with the biological sciences and medicine to improve the quality of human health and life.

cardiac muscle: An involuntary muscle found in the walls of the heart that pumps the blood through our bodies.

engineer: A person who applies his/her understanding of science and math to creating things for the benefit of humanity and our world.

muscular system: The anatomical system of a species that enables it to move.

paralysis: The loss of the ability to move in part or much of the body.

skeletal muscle: The voluntary muscles attached to our skeleton, which enable our bodies to move.

smooth muscle: Involuntary muscles found in the walls of our body's organs.

Assessment

Pre-Lesson Assessment

Question/Answer: Ask the students and discuss as a class:

• Are the muscles in our bodies important? Why? (Possible answers: Our muscles enable our bodies to move and operate; to create physical motion.)
• Do engineers have any interest in the human body? (Answer: Yes, engineers want to understand how the body works so they can design and create devices to help fix problems that can occur.)

Post-Introduction Assessment

Question/Answer: Ask the students and discuss as a class:

• Why might biomedical engineers be interested in the human muscular system? (Answer: Because our muscular system can have problems and injuries that require help. Biomedical engineers can help by designing devices to aid in the recovery of our damaged muscles.)

Lesson Summary Assessment

Biomedical Engineering and Muscle Movement: Have students pick a basic motion that involves skeletal muscles. Ask them to write down which muscles are being used, what might happen if one of the muscles was injured, and how biomedical engineers might help fix the muscle. Have each student describe and explain their biomedical situation to the class.

Review: Using what they learned, have students describe how the body is a system of multiple interacting subsystems.

Lesson Extension Activities

Continue the class discussion by posing the following questions for students to think about and then discuss together:

• Why do you think people in some cultures carry loads on their heads? (Discussion points: With this technique, the load is distributed down the back and supported by the skeletal system without producing a force around any joint, which muscles must counteract. This method uses fewer muscles and relies more on the support of the skeletal system; hence, your muscles do not tire as quickly.)
• (Use the classroom door to demonstrate a simple lever) Why is it easier to open the door if I push on the edge of the door far away from the hinge, compared to pushing on the door close to the hinge? (Discussion points: Engineers call this "leverage." Leverage is when less force is needed to produce the same amount of work. Less force is needed if we use a longer lever. That means less muscular force is required if we push at a spot farther away from the hinge.)

Artificial muscle implants are been studied for use by astronauts orbiting in space and persons on Earth with muscle-degeneration diseases. Have students research the effects of muscles in space and discuss how artificial muscle implants might help with this problem.

(For more advanced students) Using the Mechanics of Muscle Motion Handout (which requires the use of basic algebra), have students calculate the maximum amount of weight the average student can lift; W = (ℓF)/d. Assume reasonable values for the variables (for example, d = 0.25 m [9.84 in], ℓ= 0.0325 m [1.28 in], maximum bicep strength: F = 240 N [54.0 lbs]).

References

Copyright

Contributors

Supporting Program

Acknowledgements

The contents of this digital library curriculum were developed under a grant from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education and National Science Foundation GK-12 grant no. 0338326. However, these contents do not necessarily represent the policies of the Department of Education or National Science Foundation, and you should not assume endorsement by the federal government.