They are caused by rapid contraction and relaxation of the muscles.

Fibrillation is the rapid, irregular, and unsynchronized contraction of muscle fibers.

In response to irritation, the body forces air through the airways by a rapid and strong contraction of the muscles of respiration-a cough.

Insufficient length minimizes the length of the muscles needed for powerful and rapid muscular contraction.

What happens during the fight-or-flight response is an example of rapid fascial contraction.

The wings are moved by the rapid muscular contraction and expansion of the thorax.

The hitter uses arm swing, wrist snap, and a rapid forward contraction of the entire body to drive the ball.

And it intensified the belief that the Federal Reserve would move soon to cut interest rates again to arrest what could become a rapid economic contraction.

You may start shivering, which is an involuntary, rapid contraction of the muscles.

There was a tremour from the bag and a rapid contraction that she could feel with the back of her hand.