Modeling How Skeletal Muscles Work

Skeletal muscles work in pairs. When you straighten your leg, the muscles on
the front of your thighs contract while the muscles behind your thigh relax.
In this activity, you will model how muscles work in pairs.

Side view of the elbow joint model Top view of the elbow joint model

1.	Think It Over

What do the elastic bands represent in your model? The cardboard strips?

The elastic bands in the model represent the tendons in our arm. The cardboard strips represent the bones and the paper represents the muscle.

Where are two places on the human body, other than the arm, where muscles work in pairs to move our bones?

The main muscle groups of the thigh are the hamstrings and the quadraceps. The This works similar to the bicep and triceps muscles where the hamstrings pull and the quads push the lower leg. The calf and tibialis anterior also work together to plantar and dorsi flex the foot.

Explain the limitations of this model.

This model has many limitations. The most obvious of which is the materials involved. The use of cheap, less dynamic materials limit the accuracy of my model. For example, the rubber bands which represent tendons do not attach on different bones, but rather the opposites sides of a long bone. However, to show the dynamics of tendon movement, the rubber bands have to be attached to separate bones to show contraction. Additionally, in these models, contraction occurs when you move the bone, but in the human body, it works the other way around. The bone moves due to tendon and muscle contraction. The use of these materials also limits the accuracy in the fact that they do not represent real bone, tendon, and muscle shapes. Our humerus is not flat, and our forearm actually consists of two bones: the ulna and radius. So while this model roughly represents the elbow joint, the materials involved do not fully capture the anatomy nor the bone-muscle-tendon interactions.