Koshi

I am obsessed with developing proper koshi. My iai teacher, Kiyama Hiroshi, has been kicking my butt about my koshi for decades, and I’m getting so monomaniacal about it that I wonder why he hasn’t pushed me harder. Whenever I see him, he always makes point to remind to work on my koshi. He is over 90, and still has powerful koshi.

Kiyama Hiroshi Shihan Photo Copyright Peter Boylan 2013

So what is koshi? That’s a little tough, because koshi not a clearly defined medical term. Koshi includes the lower back, hips, waist and pelvis. It may be a little vague, but it’s a really good term for a critical area of the body when doing good budo.  That’s because the koshi is the platform that the upper body rest upon.  If the koshi isn’t solid, everything else will wibble-wobble around without any power or control.

Kiyama Sensei always tells me ”腰を入れて” or “put my koshi in”/”use my koshi.” This is subtly different from what people mean when they say “use your legs” or “put your back into it”. Proper use of the koshi is something more fundamental. Good koshi isn’t just about giving power, though it does that. It also gives stability in a way that is critical for being able to use the power in both your legs and your upper body.

When I swing a sword, thrust with a jo, or throw someone in judo, the quality of the technique is limited by how well I can use my koshi. It is the platform that the technique rests upon. When I swing a sword, does the weight and movement of the sword disrupt my balance and stability? If my koshi isn’t solid, it will. On the other hand, if my koshi is solid, I can increase the power and effect of my swing significantly by small movements of the koshi. The koshi ties my whole body together and allows me to direct all the power of my body into the swing of the sword, the thrust of the jo or a throw in judo.

koshi is related to what exercise instructors and trainers refer to as the “core.” The koshi combines the muscles of the lower back and the lower abdomen and ties them together with the pelvis and hips. The lower back muscles have to work with the abdominal muscles as a single unit. They can’t be fighting each other, and one can’t be overpowering the other. These muscles then attach to the pelvis from above to create a single, solid platform.

The stability of that platform is critical in whatever form of budo you are doing.  Most beginners using a sword will tend to sway back and forth like a metronome when they swing the sword. As a beginner swings the sword down, her body is pulled forward from its balanced position. As she raises the sword back over her head her body comes back to center and sometimes even sways past center to the rear.  Without a stable koshi, the beginner has no balance and no control.

The same problem arises when thrusting with a jo.  A martial artist who doesn’t know how to apply her koshi tends to thrust with just her arms, or worse, tries to power the thrust by tipping her upper body into the thrust. This doesn’t increase the power of the thrust, but it does leave her badly off balance and unable to do anything until she has pulled her upper body back over her koshi.

On the other hand, if you power a weapons thrust by driving forward with the legs and transmit that movement and leg power through the koshi to the upper body to the arms and then the weapon, you get a very powerful technique that can actually pick up and move someone (if you can find an uke who is willing to suffer through this). The koshi has to be rock solid for this to work. If there is some point where the hips, pelvis, abdomen and lower back aren’t properly connected, the moment your thrust encounters solid resistance everything will fall apart. Without a solid koshi, when you thrust into a solid partner (someone with great koshi!), your own energy will force your upper body to bend back, away from the target, even as your legs and hips are driving forward. This is disasterous.  The thrust loses any effect on the target and instead knocks you backward and off balance.

Koshi is fundamental. Nowhere is this more true than in empty hand arts. I was watching some budo demonstrations on youtube, and what consistently stood out to me was that nobody had good koshi.  Everyone demonstrating had weak koshi.  Their bodies were all over the place.  Whenever tori threw uke or took him to the ground in a pin or joint control, tori was leaning into the technique instead of driving with his legs and koshi.

I’m a judoka. If you lean into a throw or a pin, it becomes trivially simple for uke to take control from you and reverse the situation. With a judoka that can mean that three-quarters of the way through the technique, when you are sure uke is going down, you suddenly find yourself in flight going over and past uke before you hit the ground.

So how do you develop koshi? The most obvious first step is to have a solid core. That’s not complicated or mysterious.  There are thousands of sites and videos that detail exercises for building a strong core. I’m not going to spend time going over that ground. I will talk about learning to feel and use your koshi well. The first check is to stand up.

Just stand up, close your eyes and feel where your head and shoulders are in relation to your hips. Because the koshi are so fundamental to everything we do, small changes in the angle and relationship between your koshi and the rest of your body can have outsized effects on your stability and technique.  Where are your hips and pelvis? Odds are if you dropped a plumb line from the base of your neck, your hips would be a little behind it.  

That’s not where you want it. You want your hips and pelvis under your shoulders and your shoulders under your head. Take a look at the video of Kim Taylor above. He does a strike with the tsuka of the sword yet his shoulders and head are never in front of his koshi. All the power of his koshi is punching right through the end of the tsuka. The same thing happens when he turns and does the thrust with the sword. He doesn’t over extend his arm.  He doesn’t lean forward from the waist. He pushes the sword forward from his koshi.

That’s where the real power comes from.  Find where your koshi is, and then adjust it to where it should be. Can you feel the difference? Get familiar with that feeling. Really learn how it feels to stand like that. Now try walking.

It’s more difficult than we expect to move from our koshi when we walk because we have all sorts of habits from everyday life. These make walking difficult to do without paying a lot of attention to it. The upside is that walking is something we do all the time. We don’t have to go to the dojo, and we don’t need a skilled uke to practice moving with good koshi. We can practice this any time we walk, even at work.

The first thing to practice is just walking while maintaining a stable, connected koshi. This is the first step towards having a solid koshi to apply to budo. When you walk, do your head and shoulders stay over your koshi? Or are you a citizen of the 21st century whose head is permanently tilted forward and down, ready to check your iPhone at a moment’s notice? Can you duplicate the feeling of stability you have when standing still with a solid koshi while walking normally?  Once you get that, you’ll be ready to start introducing good koshi into your budo.

Koshi alone isn’t everything, but without good use of koshi, it’s difficult to progress in your practice. 


I want to give a bow of thanks to Deborah Klens-Bigman more editing and advice on this one. You can read her excellent martial arts blog at http://resobox.com/author/deborah-klens-bigman/