Science

Common mistakes in muscles and movement

3 mistakes learners make with muscles and movement, each one named and explained.

All common mistakes

A muscle can only pull, so movement in two directions needs two muscles.

A muscle given an action it cannot cause

What it looks like

A muscle at the elbow is described as rotating the shoulder or as causing no movement at all.

Why it happens

Muscles are learned as names on a diagram rather than as a pull between two specific points.

A worked example

Question. What the biceps does when it contracts

A common answer. it rotates the shoulder

The answer. it bends the elbow

Why. A muscle can only move the joint it crosses.

Put the two side by side

A muscle is anchored at two points.
It can only affect the joint between them.

Find both ends of the muscle. The joint in between is the only one it can move.

Muscles thought to push as well as pull

What it looks like

You answer that muscles push, or that they push and pull equally.

Why it happens

It feels like pushing when you press against something, so the word matches the sensation.

A worked example

Question. How a muscle moves a bone

A common answer. by pushing it

The answer. by pulling it

Why. A muscle can only get shorter, and getting shorter pulls.

Put the two side by side

Contracting shortens the muscle and pulls the bone.
Relaxing lets it be stretched, which does not push anything.

A rope can pull but never push. A muscle works the same way, which is why they come in pairs.

The partner muscle credited with the action

What it looks like

The biceps contracting is said to straighten the arm rather than bend it.

Why it happens

The two muscles are always named together, so which one does which action is easy to swap.

A worked example

Question. The biceps contracts

A common answer. the arm straightens

The answer. the arm bends at the elbow

Why. The biceps sits on the front of the upper arm, so pulling it shortens the front.

Put the two side by side

Biceps contracts: the arm bends.
Triceps contracts: the arm straightens.

Feel where the muscle is. It pulls the bone towards its own side.

WAJD spots these patterns in your child's answers and names the one behind their wrong answers, instead of just marking them wrong.

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