Last month in kinesiology class in massage school we learned that the muscles that contract in a movement are called the agonist muscles. The muscles that relax and lengthen to allow for the movement are called the antagonist muscles. Afterwards, I looked up the word agon: it is ancient Greek meaning a contest or competition.
As I mused on this, I repeated to myself "Agon, agon, that sounds familiar . . ." Then I remembered George Balanchine's famous modern ballet called Agon, set to music by Igor Stravinsky. Below is a video of New York City Ballet's performance of Agon. At the very least, forward to the 6:22 mark and watch Allegra Kent and Arthur Mitchell's stunning duet. There is a dynamic tension throughout their pas de deux, while they coordinate their agonist and antagonist muscles together exquisitely.