Muscle pairs at the elbow

In the picture

1. 1Short, bulging red muscle on the front of the bent upper arm
2. 2Long, thin blue muscle along the back of the same bent upper arm
3. 3Curved arrow at the bent elbow, marking where the forearm swings
4. 4Short, bulging red muscle along the back of the straight arm, with its blue partner long and thin at the front

Examples

• Lifting a backpack off the floor
• Bringing a cup up to your mouth

Quiz: Muscle pairs at the elbow (Age 12)

1. 1

   When you bend your arm at the elbow, what happens to the muscles in your upper arm?

   • The muscle at the front shortens while the muscle at the back lengthens.
   • Both the front and back muscles shorten at the same time.
   • The muscle at the front lengthens while the muscle at the back shortens.
2. 2

   What does the lengthening partner muscle do while the other muscle shortens?

   • It resists slightly, making the movement smooth instead of jerky.
   • It relaxes completely so the joint can move freely.
   • It shortens too, adding extra force to the movement.
3. 3

   Which statement best describes how muscles at a joint usually work?

   • They work as opposing pairs: when one shortens, the other lengthens.
   • They work alone, with one muscle doing all the movement.
   • They work in pairs by both shortening to move the joint.

The answers, each with its explanation, are in the app. This lesson has left the free week, so its quiz is part of the subscription.