How muscles work
Muscles can get shorter. This is called contraction. When muscles contract, they produce a pulling force.
Look at the diagram of the muscles in the arm (https://drive.google.com/open?id=1hortiJsX628gejcdax0vl-ZGpbiQBOit các bạn sao chép link trên để xem ảnh). When the biceps muscles contracts, it pulls on the radius and scapula.
The pulling force is transmitted to these bones through the strong tendons.
The radius is pulled upwards, towards the scapula. The arm bends.
Question 1: Predict what will happen if the biceps stops contracting, and the triceps contracts.
Question 2: Explain why it is important that tendons do not strect.