In Japanese budo, as well as in any activity, there are six words when someone refers to the intensity of training: keiko, renshu, shunren, tanren, kufu, and shugyo. Although the first four can be translated respectively as, practice, training, discipline, and forging, there are no English words for an adequate translation of the last two. ‘’Shugyo’’, which may literally translated as ‘’austere training’’, is the highest physical and deepest spiritual training possible.

The Japanese term "shugyo", generally translated as "austere training," seems to have been originated with the training of the Samurai during the "Pax Tokugawa," an unprecedented period of internal peace from the mid-1600 through the mid-1800. Its purpose is to "forge the spirit," remaking a practitioner’s character through hard physical and mental training. As the heirs of the feudal samurai, modern budo-ka have incorporated shugyo into their training regime. This applies to all budo arts, karate, judo, aikido, kendo, iaido, kyudo etc.

Shugyo may include various forms of practice, kihon waza, kata, free practice (kumite, randori or jigeiko), however what is common is the austerity of training. Kihon waza or kata practice include big numbers of repetition and free practice (kumite, randori, jigeiko) may include long hours against different or even multiple opponents. It will also include mental training, meditation and other forms of similar practice. From the diary of an aikido club we read: ‘’…For us, austere training was 20 minutes of shiko (sumo leg strengthening exercise) on a hardwood floor; it was ukemi (falling practice) on a hardwood floor; it was ritsuzen (a Japanese form of standing meditation)…’’

Refining the self in shugyo is like forging a sword. Fire, water, and iron are folded upon each other, pounded by the hammer over and over again, to create the cutting edge. In a similar way the natural form of the body will be developed, the structures of mind will emerge from the Unconscious and a person will move beyond his physical and mental limits. Without shugyo, all realizations are passing highs. If a person trains to attain enlightenment as an end, frustration and despair is inevitable for the Way is endless. But if you accept life as shugyo and continually refine breath, posture, and awareness through practice, then one day you will clearly realize that "Training is enlightenment, and enlightenment is training."

Shugyo is experiential. It is impossible to describe (like Lao Tsu's Tao -"the Way," which is the same character as the –do in karate do, Kendo, etc- in his Tao Te Ching), although we do try to, and is extremely difficult to begin to explain it to anyone who has not experienced it. During the Edo period (1603-1868) in Japan, as the various bujutsu (martial arts) were evolving into koryu budo (classical martial ways), shugyo became a developmental stage for the bushi (samurai), replacing the rigors of life-and-death combat with those of hard training and mental discipline. Today shugyo is a quaint anachronism to some, while still an absolute necessity to others. However, in order to "pierce the veil" into the essence of budo, it becomes an essential "rite of passage."