Tanren [鍛錬] or the Sanchin Kata (Its true purpose)

The characters/ideograms mean, “Tempering; forging; hardening; disciplining; training.” The first character means, “forge; discipline; train,” the second character means, “tempering; refine; drill; train; polish.” 

Tanren is a term used with the term “kata [方].” The tanren kata can be any or all kata in the martial arts but one kata stands out as a true tanren kata, Sanchin. This form is a body and mind conditioning kata. It has a breathing technique that is both natural yet controlled deep rhythmic diaphragmatic breathing process. It is a process of both hardening and softening the body at certain moments that are governed by the movements within the kata as related or inter-connected to the breathing methods used in that kara. 

This kata trains the mind to work the body from its center, the hara. It is this combination of movement, breathing and a systematic hardening-n-softening with a process of sequential locking and sequential unlocking that brings a special outcome from its practice in training and in application. This process is alluded to from the ken-po goku-i, i.e., one terse koan like statement of, “the manner of drinking or spitting is either soft or hard.” 

It is a  core kata in the Goju-ryu system because it actually teachings the student all the fundamental principles of martial systems necessary to achieve proficiency in karate. 

It teaches us about control, control of the mind, body and spirit. It teaches us about efficiency, the power paradox, Ratio, natural action, reciprocity, training truth, breathing, posture, centerline, spinal alignment, Axis both minor and major, structure, heaviness and relaxation, wave energy, centeredness, body-mind, void, both centripetal and centrifugal force, sequential locking and relaxation, rooting, techniques vs. technique, compliment, economical motions, active movement, complex forces, live vs. dead energy, speed, rhythm, timing, balance, natural and unnatural motion, weak link, mind, mushin, kime, oneness, zanshin and being, character and so much more. (Note: to define and interconnect the above principles to your practice of sanchin read more through the book of martial power)

Sanchin not only teaches these principles but how to bring them all together holistically and wholeheartedly into that “one” complete kata that once mastered transitions to the other kata as each is learned. Learning this one kata may take a considerable amount of time but the benefits outweigh that requirement especially when learning additional kata, i.e., once you learn the principles and learn to apply them then learning the remainder of your system comes “faster.” A real paradox not well understood by those who have trained with sanchin taking a lesser position in the training and practice of karate. 

Once a person’s sanchin with all its ancillary aspects becomes second nature than all others can be incorporated to give a bit more depth and breadth to a system of karate. 

Sanchin as a tanren kata is the basis for learning about “chinkuchi,” or that explosive power applied when applied correctly with all principles aligning as a technique is applied in that moment. 

Sanchin tanren is a complex type of kata that does not necessarily translate into any type of applicable bunkai. Yes, many attribute bunkai to that kata but that is a side order for that kata. Its true purpose is to teach you the essence that makes karate or any martial system work - its principles. Of all the kata this one is unique in this as it does not need to be practiced with applicable bunkai. Its core is to teach you those aspects that make “any martial art” a true combative and/or self-defense system. 

Notes: The fundamental and key things to remember as well are Sanchin tensing is to be tense, not tight as to be rigid. It is about flow, rhythm and a certain cadence that makes it work. The breathing and hara control the entire kata pulling all the principles together into that one wholehearted dynamic kata. The overall kata is best compared to “dynamic tensioning” or what early health pioneers called, “Isometrics.” This is something to keep in mind when pursuing the kata. Leave its supposed applications as to fighting or self-defense as secondary or to other kata and leave the true essence that is sanchin remain focused on its principles. Even the health and fitness achieved practicing this kata is secondary to the principles taught.

Note 2: Another important trait of proper sanchin practice is the tensing and relaxation. Stay away from "prolonged tensioning." It is far more important and beneficial all the way around if you apply proper and adequate positive relaxation and dynamic tensioning with breathing, etc. as described here.