Joint Movements and Antagonistic Muscle Action
Joints let the body move, and muscles pull on bones in pairs to make it happen. Learn the types of joint and their movements, how antagonistic muscles work together, and the difference between concentric and eccentric contraction.
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Muscles, bones and movement
Your bones cannot move on their own. Muscles pull on them across joints to create movement, and they work in pairs so that one pulls while its partner relaxes. In this module you learn the types of joint and the movements they allow, how these muscle pairs work, and the different ways a muscle can contract.
Agonist and antagonist
Four terms run through the whole topic. Learn them first.
Two kinds of joint
The shape of a joint decides how it can move. Compare the two main types.
Match the movement
- Flexion
- Extension
- Abduction
- Adduction
- Bending a joint to make the angle smaller
- Straightening a joint to make the angle larger
- Moving a limb away from the midline of the body
- Moving a limb back towards the midline of the body
Name the movement
A person bends their arm at the elbow, making the angle at the joint smaller. What movement is this?
- Flexion
- Extension
- Abduction
- Rotation
Match the structure
- Hinge joint
- Ball-and-socket joint
- Tendon
- Ligament
- A joint like the elbow or knee, allowing flexion and extension
- A joint like the hip or shoulder, moving in all directions
- A tough band that attaches a muscle to a bone
- A tough band that attaches a bone to another bone
Muscles work in pairs
Muscles can only pull, not push, so they work in antagonistic pairs. When you bend your elbow, the biceps is the agonist and contracts, while the triceps is the antagonist and relaxes. When you straighten your elbow again, the two muscles swap roles.
Flexion, extension and the agonist
Bending a joint to decrease its angle is _____. Straightening it is _____. The muscle that contracts to cause a movement is the _____, while the muscle that relaxes is the _____. A tendon attaches a muscle to a _____.
Antagonistic pairs
Which statements about antagonistic muscle action are true? Choose all that apply.
- Muscles work in pairs
- The agonist contracts to cause the movement
- The antagonist relaxes while the agonist works
- Both muscles contract hard at the same time
- Only one muscle is ever involved in a movement
Find the hinge joints
Tap the two joints that are hinge joints.
- The elbow
- The knee
- The hip
- The shoulder
Type of contraction
During the upward phase of a bicep curl, the biceps shortens as it contracts. What type of contraction is this?
- Concentric
- Eccentric
- Isometric
- Extension
Order the bicep curl
Put the phases of a bicep curl in order.
- The biceps contracts and shortens, a concentric contraction
- The elbow flexes and the weight is lifted
- The biceps lengthens under tension, an eccentric contraction
- The elbow extends and the weight is lowered under control
Name it
Read each description and choose the correct term.
- A footballer bends their knee to prepare to kick the ball. What movement is this?
- A gymnast lowers slowly into a squat, the thigh muscles lengthening under control. What type of contraction is this?
- A swimmer moves their arm out to the side, away from the body. What movement is this?
Explain the action
Explain antagonistic muscle action at the elbow during a bicep curl. Name the agonist and the antagonist and say what each does.
- Name the agonist and the antagonist at the elbow
- Say what happens to each muscle as the elbow flexes
- Use the words concentric and eccentric to describe the lifting and lowering phases