The concept of Hard-Soft enters many a conversation regarding martial arts technique. I’m sure I need not elaborate too much on this point—most of us understand the notion—that yin/yang enters into training in the form of rigid force and flexible movement. This, in theory, makes for well rounded budo.
But taken a step further, the concept of hard and soft can be embraced and benefited from at an even higher level: the balance between the physical and the mental. It is not by chance that many experienced external artists at some point in their journey begin to explore the path of the internal arts such as meditation, qi gong, or tai chi. I think at some point, after proficiency is achieved both technically and physically, the external art is complemented by an understanding of the inner workings.
Here is a good summary of the idea:
“‘….Some years ago, (A Sensei) chose two students who were as evenly endowed with natural talents as possible. One he trained purely on calisthenics and work-outs, taught him all the tricks. The other he gave less physical training, but made him do zazen religious meditation every day for half an hour when he awoke and again before his evening work-outs, squatting like Buddha, forcing all his internal organs into proper alignment, breathing “right down to his toes” and clearing his mind. After six months, both came up for their black belt test and he matched them.… The thinker made mincemeat of the muscle boy.’ (Jay Gluck, Zen Combat)
“The same point of view was expressed by a high-ranking instructor of (aikido)…when he warned against qualifying as “lazy” those students who devote a greater proportion of their time on the mat to sitting or standing in evident concentration, as compared to those who are busily engaged in techniques, physical exercises, and so forth. This instructor had also realized that the former could often perform better under stress than the latter because they had been working to develop those inner factors of stability, control, and power which are considered to be the necessary foundation for correct outer technique.”
–(Secrets of the Samurai, Ratti/Westbrook)