You can stand very straight and still feel held together by effort.
You can also be moving, turning, even swaying, and feel that the whole body belongs to the same movement.
That difference is where this essay begins.
Through ippon blade, I have kept returning to the relationship between weight, support and the freedom to respond. “Axis” is the word I use for the connection I seek in practice. Understanding it takes us from the foot’s small movements to the habits through which we live.
Where the weight goes
Lift an arm. Turn your head. Reach for something just beyond your hand.
The shape of the body changes, and its weight is redistributed. Even an ordinary gesture changes the problem of remaining upright. We make these adjustments so often that the work usually disappears from attention.
The center of mass is the point that represents the average location of the body’s mass. Near the Earth’s surface, we can also speak of the center of gravity. It changes as the body changes shape; it is not a fixed spot hidden behind the navel.
The line of gravity is the vertical line through that center. It continues downward even when we lean. The line does not lean with the body.
When I speak of an axis in ippon blade practice, I am describing the organization we feel through the feet, pelvis, rib cage and head. The word gives us a way to attend to how the body supports itself and moves. It is a practical image, distinct from the measured line of gravity.
The lower abdomen, solar plexus and space between the eyebrows can also serve as points of attention. In Japanese body traditions, these are associated with the three tanden. They are not three anatomically fixed centers of mass. Their value in practice is in how they help us sense the relationship between regions of the body.
Underneath this changing body is the base of support: the area enclosed by the outer boundaries of contact with the supporting surface. With both feet on the floor, it includes the space between them. In ippon blade, the relevant ground contacts are the teeth. Each has a real contact area, narrow in the front-to-back direction; “one point” is a shorthand for the experience, not a mathematical description.
The center of pressure is the location on that surface where the combined ground reaction force is represented as acting. It moves as pressure changes. It is not simply the geometric middle of the support area.
During quiet standing, the body continually adjusts the relationship between pressure and weight. During walking, the support itself changes as we step. The center of mass does not have to remain above the current support at every instant: momentum and the next contact matter too.
A sense of axis therefore has to include the next movement. A body arranged beautifully for a photograph may still struggle to take a step.
The foot is a living arch
The foot meets load by changing. Its bones move in relation to one another, its tissues take tension, and its muscles contribute to support and control.
The heel, the ball of the big toe and the ball of the little toe give us a useful three-point reference for sensing the foot. Between and around them are the longitudinal and transverse arches. These references help us notice load distribution; they do not mean that every step should place exactly one third of our weight on each point.
In the truss model, the bones of the arch carry compression while tissues beneath the arch, including the plantar fascia, resist its spreading through tension. Under load, the foot can deform and store elastic energy. Muscles, ligaments and the movement of multiple joints all contribute.
The windlass mechanism describes how extending the toes winds the plantar fascia around the metatarsal heads and influences the shape of the arch. It helps explain one part of foot function. A moving, loaded foot is more complex than a rigid arch operated by a single cable; the fascia itself can stretch, and muscles remain involved. Research on the interaction of these mechanisms shows why the simple model is not the whole story.
Neither mechanism is a separate reflex that automatically puts the center of mass in the right place.
In practice, the foot’s inversion and eversion, plantarflexion and dorsiflexion form part of a three-dimensional response. These movements involve the ankle and other joints of the foot. The Chopart joint complex lies across the midfoot; the Lisfranc complex joins the tarsal bones to the metatarsals. Their contributions occur within the movement of the whole foot, rather than as isolated hinges we must command one by one.
When I refer to loading through the tarsal center, I mean a functional reference used in our practice. It includes the relationship among the tarsal bones and the foot’s arch. It should not be reduced to a claim that the tooth sits directly beneath the talus or the vertical line of the shin.
The foot still meets a platform when wearing ippon blade. What changes most visibly is the platform’s contact with the ground. That distinction matters: the sensation comes through the relationship among the foot, the wooden structure and the surface beneath it.
From there, a small change at the foot can invite a response through the knee, hip and trunk. The rest of the body has a part in how that invitation is answered.
The ground answers every step
The ground reaction force is present before we give it a name.
When we apply a contact force to the ground, the ground applies an equal and opposite contact force to us. This is Newton’s third law. Through the feet, those forces become part of standing, walking, accelerating and stopping. The action and reaction act on different bodies.
Gravity and ground reaction force are not that action–reaction pair. Both act on our body. During quiet standing they can approximately balance overall; during movement, the ground force changes in direction and magnitude. It can have horizontal as well as vertical components. During a flight phase, when neither foot touches the ground, there is no ground reaction force.
This distinction makes “moving with gravity” more interesting, not less.
Gravity does not become a free engine that carries us indefinitely across level ground. Muscles do work, tissues store and return energy, and contact with the ground supplies the forces needed to change the motion of the body. The timing and coordination of those contributions can feel remarkably different from one step to the next.
The instruction “do not kick” belongs to that experience. It asks us to stop adding a harsh, deliberate push that disturbs the movement. It does not ask the leg muscles to switch off or claim that forward motion needs no force.
A runner can feel carried while still doing substantial physical work.
The same care is needed with the word “rebound.” Ground reaction force is the contact force from the surface. Elastic recoil is energy released by tissues or materials that have deformed. Stretch reflexes are neural responses. They interact during movement, but the words name different things.
In the body, internal forces include muscle and tendon forces and the forces transmitted through joints. The nervous system organizes activity; breathing and fatigue influence how we perform it. Calling all of these a single “internal energy” may sound vivid, but it makes their roles harder to understand.
What I seek in practice is something tangible: the feeling that support and movement continue into one another, without having to restart the whole body at every step.
An upright pelvis that can still move
“Set the pelvis upright” can be a helpful instruction. It can also become another way to hold oneself rigidly.
A person hears it, pulls the abdomen tight, lifts the chest and braces the back. The outline may look orderly. Breathing and the next step may become more difficult.
In TENARI practice, an upright pelvis means finding support while retaining the ability to move. Anterior and posterior tilt are available movements. Neither has to become a permanent identity or an angle held through the whole day.
When seated, the sitting bones offer a direct reference for support. When standing, body weight passes through the hips and legs toward the ground; the sitting bones are no longer the contact points. Their direction can still be a useful image, provided we do not mistake the image for the supporting anatomy.
The knees also need room to participate. Bending a knee does not automatically collapse the pelvis, and locking the knees is not a requirement for an axis.
The psoas major is important in our teaching because it links the lumbar region with the thigh and contributes to hip movement and the relationship between the trunk and legs. Its work occurs alongside that of many other muscles. It does not independently lift the rib cage, govern every pelvic movement or create the entire body’s coordination.
Our emphasis is on reducing unnecessary bracing, especially the habit of tightening the front of the abdomen to manufacture stability. In this practice, keep the abdomen responsive and allow breathing to continue. There is no need to deliberately raise abdominal pressure simply to stand on the axis.
That instruction is about how we approach the task. The body still uses muscular activity and pressure regulation. Deep and superficial muscles cooperate; neither group is something to eliminate.
Rather than securing a perfect position and then trying to move from it, we explore a position that already allows movement. The usefulness of the alignment becomes apparent in what happens next.
The part of movement we do not command
You decide to reach for a cup. You do not issue a separate conscious order to every muscle needed to keep you upright while you do it.
Movement combines intention with processes that work outside moment-to-moment awareness. Vision, the vestibular system, sensation from the feet and information from muscles and joints all contribute. The body both anticipates a task and responds as it unfolds.
Stretch reflexes and automatic postural responses belong to this activity. Learned coordination also becomes less demanding of conscious attention with practice. These are related aspects of movement, not interchangeable names for the same process.
Primitive reflexes have a more specific meaning in neurodevelopment. Examples such as the infant grasp and Moro responses belong to early development and change as the nervous system matures. They are not a general name for every useful automatic response in an adult. The aim of ippon blade practice is not to revive infant reflexes.
What matters here is the capacity to respond without having to narrate every adjustment.
On a narrow support, a person may initially attempt to manage everything at once: toes, knees, pelvis, shoulders. That is understandable. But the attempt itself can become so demanding that there is little attention left for the actual movement.
Practice gives us a chance to simplify the task. We can notice one relationship, make a small adjustment, and observe what the rest of the body does. Conscious attention and automatic response begin to cooperate more usefully.
Learning is still required. Simply wearing ippon blade does not guarantee that this coordination will appear.
The freedom that interests me is the ability to remain attentive without having to interfere with every part.
More than one way to move
A quiet sliding step and an open, athletic stride can both be skilled movements. They solve different problems.
We can use counter-rotation between the shoulders and pelvis, or explore closer coordination along the same side. We can lengthen a stride, shorten it, change rhythm or lower the amount of visible movement. The task, terrain and the person determine what is useful.
In our practice, Nanba includes exploration of same-side coordination. It can involve bringing a shoulder into the movement and allowing a wave through the trunk. It can also be quieter, with the elbows dropping and little visible undulation. Repeating a rigid rule about which hand must accompany which foot misses those possibilities.
“Single axis” and “two axes” are useful teaching expressions for the felt organization of movement through the center or through the alternating sides. They do not replace the mechanical definition of the body’s center of mass, and they are not fixed categories of person.
These patterns can be learned across cultures. Nationality does not determine someone’s muscle-fiber composition or prescribe the way they should move.
The same openness matters when discussing heel, midfoot and forefoot contact. In walking or running without ippon blade, the first contact varies with speed, surface, footwear and the task. Looking only at that instant tells us little about the complete step.
With ippon blade, the tooth is the usual ground contact. Foot pressure on the platform and contact between the tooth and the ground are different relationships. Trying to imitate a familiar shoe-based foot strike by repeatedly driving the front of the wooden platform into the ground misses the point of the structure.
A useful movement remains available for change. You should be able to slow down, redirect it, or choose another pattern when the situation asks for one.
When a method becomes a cage
A method becomes familiar because we repeat it. Repetition can give us skill, confidence and a dependable starting point.
It can also become difficult to notice when the starting point has turned into a boundary.
The runner who trusts a particular shoe, the practitioner devoted to a traditional form, the athlete who measures progress in strength: each has learned something real. Trouble begins when preserving the explanation becomes more important than observing the next movement.
I recognize that impulse in myself. Once I have invested in an idea, I want the world to keep confirming it.
The body offers a useful interruption. An explanation may continue winning an argument long after it has stopped helping us move. A step still has to meet the ground. Fatigue still changes the task. Another person still has a different body.
Strength training, endurance work, relaxation and precise technique can all belong in the same life. Developing one quality does not require declaring the others mistakes. We can also acknowledge what a method has given us while noticing what it has not yet taught us.
That is why I do not want ippon blade to become another fixed image of the correct body.
The consistency I value is the willingness to return to observation. I want to know whether I can still feel, respond and change when the situation changes.
That requires more honesty than repeating a form we already know how to perform.
What it means to return
For much of my life, I tried to become someone I thought would be accepted. Effort and comparison became difficult to separate.
Through nature, barefoot running and single-tooth geta, I began to encounter moments when that demand quietened. I could attend to the next step without turning it into a verdict on who I was.
That experience is the background to the phrase “return to your axis.”
I use “neutral” to describe the room to respond before a familiar habit decides everything. Neutrality leaves our feelings, preferences and intentions intact. It does not demand that we erase the self or accept someone else’s authority over our sensations.
There is no single inner personality that everyone must uncover. A person can be ambitious, playful, reserved, competitive or contemplative and still learn to notice when an old response no longer fits the moment.
The physical practice makes this concrete. We can feel where we have started gripping. We can notice a held breath, a fixed knee, a shoulder that is working harder than the task requires. Sometimes a small change opens another possibility.
That does not turn posture into a moral judgment. A tense body is not evidence of a flawed character. Our condition includes fatigue, pain, experience and circumstances as well as intention.
Returning is something we do repeatedly. We become absorbed in a task, meet a limit, notice it and adjust. The axis is valuable because it helps us continue that conversation with ourselves.
Kata, craftsmanship and freedom
I understand kata as a way of making useful relationships repeatable.
A form can hold knowledge that would otherwise be difficult to transmit: timing, direction, the relationship between support and movement. Practicing it lets us encounter those relationships with the body.
But copying the outline is only the beginning. A form becomes useful when we can feel what it is organizing and adapt that understanding to the task in front of us.
My own route into this inquiry was through barefoot running, mountains, teaching and long-distance practice in single-tooth geta. I was not setting out to reproduce a particular martial school. I wanted to understand how movement could remain connected under changing conditions.
That inquiry became tangible in the development of ippon blade with Mokuen.
Wood has grain, weight and limits. A tooth has a position and a height. The platform must meet a foot. The straps must hold it in a way that allows the intended movement. Those relationships cannot be settled by an attractive outline alone.
The golden ratio and the Japanese Yamato proportion informed the design of MIROKU and ZEN respectively. We brought those proportional ideas into the practical work of dimensions, materials, prototypes and repeated use.
The body then had to answer. The design had to be felt in standing, walking, running and teaching, and revisited through what those experiences revealed.
I see the same responsibility in a kata and in a crafted pair of ippon blade: a form has to remain in contact with the life it is meant to serve.
The room to play
A perfectly motionless human body is not the model for living balance.
Even in quiet standing, small adjustments continue. Breathing changes the shape of the trunk. Pressure shifts under the feet. The nervous system keeps working with information from inside and outside the body.
The word “play” has two meanings that meet here. It is the pleasure of exploration, and it is the small amount of room that lets a relationship move without becoming loose or locked.
Too much stiffness leaves little room to respond. Too little support can make the movement difficult to manage. Practice lets us explore the usable space between them.
On a level surface, the consistency of the ground makes small changes in our own movement easier to compare. A familiar step can be repeated, adjusted and felt again. The apparent simplicity can reveal a great deal.
Uneven terrain asks something different. Slopes and changing surfaces require decisions that cannot be settled once and repeated indefinitely. The body has to respond to what is actually there. That adds demands and risk; it is not a shortcut around learning on stable ground.
Both experiences have depth. One makes a relationship easier to examine. The other asks how well it can adapt.
This is also why play matters beyond exercise. Curiosity gives us a reason to try a smaller change, another rhythm, another way of approaching the same task. We remain involved because there is something to discover.
A practice that leaves room for discovery has somewhere to go tomorrow.
From support to expression
At first, much of our attention may be occupied by remaining upright.
As a movement becomes familiar, attention can widen. We begin to notice rhythm, direction, the surrounding space and the people with whom we are moving. We have more room to choose what to express.
An axis is useful when it gives that choice somewhere to begin.
It can appear in a quiet step or a vigorous run, in yoga, in a change of direction, in a movement whose pleasure has no audience. The outward forms differ, but each involves a body finding support and making something possible from it.
This is the connection I see between physical practice and a way of living. We can become so occupied with defending a position that we lose the room to act from it. Returning to support can make movement possible again.
That is a personal philosophy drawn from practice. Its value is in whether it helps us attend more honestly to our own experience.
The words should eventually lead us back to something we can feel: pressure beneath a foot, the movement of the pelvis, breathing that continues through a gesture, the possibility of taking the next step.
The axis comes alive there.
Afterword: what I put into a single tooth
ippon blade holds years of movement, making, teaching and questions that remain open.
I began by trying to find a way of moving that I could live with. Along the way, I met people whose experience changed the work, and whose hands helped give it form.
What I hope to share is the possibility of having that relationship with your own body: learning from it, taking responsibility for it, and allowing it to surprise you.
A single tooth makes the point of contact conspicuous. What follows from that contact is much larger than the wooden structure itself. It involves the whole person and the ground beneath them.
Return to your axis.
There is still a world to move through.
About the author
Ten Kodaira (TEN) is the founder and inventor of ippon blade and a representative of TENARI. His work grew through nature guiding on Iriomote, barefoot movement, mountain practice, instruction and 100 km ultramarathons in single-tooth geta. He developed ippon blade with the woodcraft artisan Mokuen and continues the project with Ayari and Mokuen from Haruno, Shizuoka, Japan.
Read the personal story: We Run to Be Born.
For a reference you can return to alongside practice, see Q&A: Foundations & Philosophy and Q&A: Movement & Body Mechanics.