Contraction produces tension, a pulling force, in a muscle and its tendons. When that tension acts across a joint, it can rotate a bone. An antagonistic pair provides opposing actions, such as elbow flexion and extension. The muscles coordinate their activity; a real movement need not mean one muscle is completely inactive.
The human body · Discover & try
How can a pair of muscles move a joint both ways?
Reading level 3 of 5 · IndependentChange
Word help
Tendon
Tissue transmitting a muscle’s pull to bone.
Antagonistic pair
Muscles or groups that can produce opposing actions.
Watch · Try · Explain
See how it works
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A conceptual opposing pair. Shapes and angles are illustrative; real movement includes stabilisation and coordinated muscle activity.
What to look for
- Reverse the action.
- Notice which side shortens and which lengthens.
Explain what you noticed
A different virtual joint needs to reverse its movement. Which strategy fits the muscle principle?
Keep this idea: Opposing muscle pulls can move a joint in opposite directions.
Follow the sources
- NIH NIAMS — Health Lesson: Learning About Muscles
- NIH National Cancer Institute — Structure of Skeletal Muscle
Source material checked 2026-10-28. Explanations and activities by Nepedia. Source links do not imply endorsement.
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