Re: kendo's gruelling challenge
The point of this video (for me) was that the "mind" takes us beyond the body to the sword. These practitioners believe that they can improve their technique far past the ages of 17, 25 and 35.
The "physical body" for a male is at its prime at the ages of 15--19. After that, its about maintenance. Yet,the experiences of the "older practitioner" gives him the advantage of "judgment" as he makes a decision.
The weapon (the sword) uses slight imperceptible movements. It relies less and less on the body in gross movements and more and more on "fine motor movement". This is the domain of the "brain/mind".
As such, the 46 year old, training for haichi-dan, continues to improve his outward technique through the "extension" of his mind through his sword. He takes his body beyond the external to the internal.
Watch carefully, how the bodies of these practitiioners become outwardly softer as they age. But, how the technique "seems" to "be there" as if by magic.