This is Shihan Kano’s words on what is seiryoku-zenyo found at the Kodokan.
“Seiryoku-Zenyo (maximum efficient use of energy) applies to all types of endeavours, and it is to fully utilise one’s spiritual and physical energies to realise an intended purpose.
Seiryoku-Zenyo is the most effective use of the power of the mind and body. In the case of Judo, this is the principle upon which attack and defence are based, and what guides the process of teaching as well. Simply, the most effective use of mind and body may be described as the maximum efficient utilisation of energy. In summary, this can be described as “maximum efficiency”.
This idea of the best use of energy is one of the central tenets in Judo, but it is also important for achieving various aims in one’s life.” *1
“This concept of the best use of energy is the fundamental teaching of Judo. In other words, it is most effectively using one’s energy for a good purpose. So, what is ‘good’? Assisting in the continued development of one’s community can be classified as good, but counteracting such advancement is bad… Ongoing advancement of community and society is achieved through the concepts of ‘Sojo-Sojo’ (help one another; yield to one another) or ‘Jita-Kyoei’ (mutual benefit). In this sense, Sojo-Sojo and Jita-Kyoei are also part of the greater good. This is the fundamental wisdom of Judo.
Kata and Randori are possible when this fundamental wisdom is applied to techniques of attack and defence. If directed at improving the body, it becomes a form of physical education; if applied to gaining knowledge, it will become a method of self-improvement; and, if applied to many things in society such as the necessities of life, social interaction, one’s duties, and administration, it becomes a way of life…
In this way, Judo today is not simply the practice of fighting in a dojo, but rather it is appropriately recognised as a guiding principle in the myriad facets of human society. The practice of Kata and Randori in the dojo, is no more than the application of Judo principles to combat and physical training… From the study of traditional Jujutsu Kata and Randori, I came to the realisation of this greater meaning. Accordingly, the process of teaching also follows the same path. Furthermore, I recognised the value of teaching Kata and Randori to many people as a fighting art and as a form of physical training. This not only serves the aims of the individual, but by mastery of the fundamental wisdom of Judo, and in turn applying it to many pursuits in life, all people will be able to live their lives in a judicious manner.
This is how one should undertake the study of Judo that I founded. However, in actuality there are many people throughout the world living their lives on the basis of Judo principles without knowing that this is the real essence of Judo. If the Judo that I espouse is propagated to society at large, the actions people undertake will become Judo without even thinking about it. I believe that if more people gain an understanding of the guiding principles of Judo, this philosophy will also help guide their lives. Thus, I implore you all to make great efforts, and initiate this trend in society.” *2
* 1 Kano Jigoro, “The Best Use of Energy”, Taisei, Vol.1, No.1, 1922.
* 2 Kano Jigoro, “Jujutsu and Judo, Recognising the Distinction of Judo”, Judo, Vol.7, No.2, 1936.