Question

Each muscle fiber can either contract or expand depending upon the demands placed upon it at any given moment. true or false

Answer 1

Muscles can only contrast.

Answer 2

Answer: Muscles can only contract.

Explanation: Muscles can only contract. They cannot actively extend, or lengthen. Therefore, pairs of muscles must work in opposition to move bones in opposite directions. For example, the biceps and triceps muscles of the upper arm work in resistance to bending and extending the arm at the elbow (see Figure below).