肌肉成对工作
Muscles Work in Pairs
解释肌肉以拮抗对的形式工作：一块收缩，另一块放松，从而产生运动；以肱二头肌和肱三头肌作为主要例子。
Explain that muscles work in antagonistic pairs — one contracts while the other relaxes — to produce movement, using the bicep and tricep as a key example
学习证据 / Evidence
- 解释为什么肌肉只能拉、不能推
- 描述手臂弯曲和伸直时肱二头肌与肱三头肌的变化
- 举出另一组拮抗肌的例子
- Explains why muscles can only pull, not push
- Describes what happens to the bicep and tricep when the arm is bent and straightened
- Gives another example of an antagonistic muscle pair
评估问题 / Assessment
如果{{name}}弯曲并伸直自己的手臂，能否解释为什么需要两块不同的肌肉——一块用于弯曲，一块用于伸直——并说明分别是哪块肌肉？
If {{name}} bent and straightened their arm, could they explain why two different muscles are needed — one to bend and one to straighten — and which muscle is which?