What causes muscle fibers to get shorter?
friction acetic acid heat or cold sweating electrically resistance Damages them exercise
A B C D E F G H
Exercise causes muscles to contract.
muscle fibers get shorter during exercise
What causes muscle fibers to get shorter? (A) friction (B) acetic acid (C) heat or cold (D) sweating (E) electrically (F) resistance (G) Damages them (H) exercise