Biology · KS3 Y7 · Human Body Systems

Antagonistic muscles

Antagonistic musclesFree1:23Heddy Score 3 of 7, below the standard
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What you need to know

  • Flexion bends a joint and makes its angle smaller; extension straightens it and makes the angle bigger.
  • Muscles can only pull, so a joint needs a pair of muscles to move it one way and then back again.
  • At the elbow the biceps contracts to bend the arm while the triceps relaxes, and the triceps contracts to straighten it while the biceps relaxes.
  • Two muscles working against each other like this are called an antagonistic pair.

In this clip

Runs 1:23, from 0:49 to 2:12 of the full video.

Heddy Score3/7, Below the standard
See the seven stars
  • Trusted source · passed. The creator's own upload, live and playable here.
  • On the map · not judged yet. A teacher watched it: it mainly teaches this map topic.
  • Spec-true · not judged yet. Accurate, and right for the current UK specification.
  • Focused · passed. One idea, short enough to watch in one go.
  • Accessible · passed. Good captions, clear sound and pictures.
  • Safe for children · not judged yet. Right for 11 to 16 year olds, with no sales pitch.
  • Proven · not judged yet. Earned from our students: they learn from it, find it helpful and watch it to the end.
★ passed · ☆ pending · ✕ failed
Our students

Not enough students yet

Our own students' answers. These are what move ★7 Proven.
On YouTube

1.13M views · 33.7K likes · Siebert Science 514K subscribers

As reported by YouTube on 2026-11-01. Not part of the Heddy Score.
How the Heddy Score works

Why we picked it

A short whiteboard explanation of the biceps-triceps pair that shows exactly why muscles work in antagonistic pairs.

Siebert Science on YouTubechecked 2026-10-22

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