Make your own bicep!

Biomedical engineers try to understand how the body works so they can fix it with artificial parts when it gets damaged. One of the important types of body parts is muscle. When a muscle is stretched too much, or strained, it might need a biomedical device to get better. Sometimes a device can act like a muscle and help your strained muscles rest and heal faster. Try out this activity to make an artificial bicep!

The Experiment

Materials:

6 rubber bands different sizes)
5 feet of thin rope
1 foot of string
paperclips
scissors
a small spring scale
a ruler

Try it out:

1. Make a shoulder harness by making a figure 8 out of a piece of rope. Put one loop of the 8 around your shoulder and the other one around your chest.
2. Make a second loop of rope to go on your wrist.
3. Connect the two loops with rubber bands. You can tie different rubber bands together, or use things like paperclips to connect them. Use your imagination!
4. Test out your artificial muscle by putting on the shoulder harness but not the wrist loop. Put the spring scale on the wrist loop and stretch the rubber bands until they are as long as your arm. Measure the force of the rubber bands using the spring scale.
5. Now measure how far the rubber bands stretch by pulling the wrist loop down just like before and measuring the length of the rubber bands. Now raise the wrist loop until the rubber bands aren't stretched and measure that length. If you subtract the second distance from the first, you'll find out how much your rubber bands stretched.
6. Try out different ways of attaching rubber bands, or different sizes. Which bicep is the strongest? Which one stretches the most?
7. Put on the wrist loop and try bending or unbending your arm. How does the artificial bicep move when you move your arm?

What's happening

Muscles work by pushing and pulling each other to make parts of your body move. Muscles are special because they work in pairs. When you flex your arm, your bicep contracts, or shrinks, and your tricep stretches out. When you relax your arm, your bicep stretches and your tricep contracts. Every muscle in your body works the same way.



What happens when one of the pair of muscles is injured? You can't move your body part properly because the stretching and contracting doesn't match up. Bioengineers try and find devices that help your muscles heal faster or help them rest so that you can use your muscles soon. When you made an artificial bicep out of ropes and rubber bands, the rope acted like the partner for your tricep. That way your bicep can rest and heal faster. 

If you thought this was cool...

This experiment is related to bioengineering. You can find out more here.
You can learn more about muscles and how they work by studying anatomy or physiology. The ideas of forces, tension, and compression are from physics, and are also related to mechanical engineering.