The use of atemi notwithstanding, our Senseis classically taught that to clench the fist was to rob the aikidoka of her power by redirecting her ki back in upon herself.  Mumpower Sensei sternly trained us that upon encountering the faintest notion of threat, our primary response was to assume 'the martial face' and to spread the fingers, opening the hands; prior even to raising them.  Hands and face are partners in intimacy and the expression of human personality.  What young tyke has escaped the adoration of his Auntie or Grandma without  having his cheery little face touched by her wise and loving hands?  And so it is that the summit of sophistication and dignity in the extensive repertoire of human martial achievement, known as Aikido, should flex the hands and the face but not the biceps.

How true it is that the finer points of Philosophical Aikido rely on openness and generosity, not only as fundamentals of the Teachings, but for proper execution of the techniques, as well.  The human biceps being paired flexives; to work them is to assume the kinesthetic equivalent of the clenched fist: symbolically ungenerous and functionally recursive with regard to ki.  Indeed, proper extension is possibly the essential, sine qua non, for aiki waza.  As the student advances into some degree of personal mastery in the art, she will discover more and more the importance of hand ki and its requisite extension until, at a certain stage in her  esoteric advancement, the Teachings become distilled into the finer subtleties of digital ki, as extensions of her energetic psyche.