You are presented with the question "Weigh lifting requires muscles" and the following answer choices: 
- to move people
 - Energy.
 - stamina
 - it needs them
 - shortening
 - hydration
 - sensory neurons
 - Energy

Now knowing that muscle contraction occurs when muscle fibers get shorter and isometric exercise is a sustained contraction of large muscles, such as weight lifting, choose the best answer.


 

     shortening    