Tenbindori (天坪鳥) is one of the core principles in the study of body techniques, Taijutsu (體術), and focuses on understanding and managing the forces acting on the human body.
In this guide, we’ll explore the basics of balance management and how to apply them in more complex forms within shibari.
The Module 1 of the course, particularly the section on "POSTURE," serves as the reference for this guide, especially the topic of "Mobility" (link at the bottom of the page).
Let’s quickly revisit some key concepts we’ll be working with in this guide.
Ground Reaction Force (GRF)
Ground Reaction Force (GRF) refers to the force the ground exerts back on our body in response to the force we apply to it.
This concept is based on Newton’s Third Law, which states that for every action, there is an equal and opposite reaction.
The goal of this first module is to understand and begin using this energy to facilitate movement and body management in shibari.
Anatomically Neutral Posture
Anatomically neutral posture is the position where the body is optimally aligned, minimizing unnecessary muscle tension and maximizing movement efficiency.
Balance and Equilibrium
- Equilibrium: A static physical state that tends to maintain itself.
- Balance: A dynamic state where the distribution of forces is adjusted to maintain stability or equilibrium.
What’s happening in this video?
The exercise demonstrates how to apply Tenbindori.
- First step: Take a neutral, stable posture and check that you can maintain it with ease, even when subjected to external forces.
- Second step: Apply the technique and use specific mechanisms to "trick" the brain into breaking the balance in a controlled, manageable way.
The goal isn’t to break the balance to create chaos or a fall, but to learn to manage it without losing control.
Back Support Point
This support point is not arbitrary; it’s one of the "key points" in anatomy.
- The hand should rest on the pillow aligned with the thumb (thenar and hypothenar eminences), allowing fine wrist movement control.
- The support point is located in the middle of the back, along the spine, near the lowest part of the shoulder blades.
- There isn’t a universally fixed point; it’s important to experiment and provide feedback to find the optimal position.
With this support, we aim to achieve the following:
- The one providing support offers a stable point of reference.
- The one being supported actively transfers part of their weight, avoiding dead weight.
Both should feel it:
- The one being supported experiences a reduction in apparent weight.
- The one providing support may feel a slight increase in weight but without a significant load.
Movement from the Core
Once the support is established, the person providing support will make a slight upward movement with their arm, gently moving forward in a smooth and progressive manner.
Observe the effect on the person being supported. If the technique is executed correctly, their body will tend to lift proportionally, bringing them onto their toes.
We begin these exercises with an upward movement because it’s the simplest and safest way to verify that the technique is working.
Once this is achieved, feel free to experiment and progress with caution and enjoyment.
What’s going on here?
Transfer of Ground Reaction Force (GRF)
By establishing a support point managed through the core of the person holding the position, part of the Ground Reaction Force (GRF) from the supported person is transferred to the person providing the support.
This gives the person providing support more energy to move the other person efficiently.
Shifting Balance
- The person being supported transfers part of their GRF to the person holding them, shifting their balance in that direction.
- Their brain adjusts their balance line, moving it from the center of their body to the wrist of the arm providing support.
Leveraging Kuzushi (Unbalance)
- As the movement begins, physics allows the body to start shifting with even a slight gesture.
- Simultaneously, the brain of the supported person tries to correct the balance.
- However, by attempting to correct from an incorrect equilibrium point, they can’t stabilize.
- In that moment of "error" or unbalance (kuzushi), the person managing the movement must capitalize on it, guiding the shift in a controlled, effective manner, without applying excessive force.