Practical application of fundamental principles in the field of body management and control techniques.
In this exercise, we’ll explore how two of these foundational elements—muscle activation and balance—work together.
Both concepts are thoroughly explained in this first module, particularly in the sections on "Posture" and "Mobility."
Combining these two elements is key to achieving and maintaining an optimal posture (shisei).
Understanding these techniques requires a dual approach. On one hand, there’s the rational side, where we analyze how physics and biomechanics function, and on the other, the intuitive side, where we "feel" how forces interact with the body.
Integrating both perspectives is crucial for effectively applying and adapting these techniques to different situations, making them truly your own.
The video is an updated version, featuring better quality and more detailed explanations than the one we shared previously.
What’s happening in the video?
The video demonstrates how the body’s structures respond differently depending on which muscles are engaged at any given moment.
Recognizing this distinction is vital for managing the body in shibari.
For example, when moving an arm backward. If we grab it haphazardly, touching areas that activate muscles with opposing functions, we can still move the arm, but the motion will feel unnatural, making it harder to maintain activation and stabilize the posture.
This issue stems from the fact that muscles have specific roles and are designed to move in particular directions. If a muscle’s job is to extend the arm when activated, it’s counterproductive to engage it when we want to bend the arm.
At the same time, muscles often work in pairs (agonist-antagonist): one contracts while the other resists.
This exercise is best practiced by alternating roles. It’s fascinating for both participants to observe and understand what happens in each of the three scenarios we’ll explore.
First scenario
We begin standing in an anatomically neutral position, facing each other at a distance that allows us to reach each other’s hands with arms extended.
One person extends their arm forward, palm facing the other.
The position of the hand—flexed slightly upward—influences the muscular response. This is a subtle trick we use in the exercise. With the wrist flexed, the arm is predisposed to retract or bend toward the body.
In this first scenario, when the hand is struck (gently, with controlled force), the body absorbs the energy. Without specific muscle activation, the kinetic energy causes the body to shift as a whole.
The person receiving the strike, feeling displaced from their center of balance, will instinctively correct their posture by leaning or stepping if the shift is too great.
If the force is excessive, they might even lose their balance and fall.
Second scenario
Next, we’ll focus on activating a specific set of muscles while ignoring the rest. To do this, we lightly stroke the outer part of the arm, following the "pinky line," being careful not to touch the hand, wrist, or inner arm.
When we repeat the strike, the activated muscles now absorb all the energy. How?
The muscles on the outer arm connect to the lateral muscles along the ribs, which in turn link to the opposite glute and legs.
As a result, the impact on the hand travels through this chain of muscles to the ground. According to the laws of physics (Newton!), the ground returns the energy, which travels back up to the hand, neutralizing the kinetic force of the strike.
The body remains steady, without swaying or shifting.
It’s important for both participants to reflect on the sensations: how the person striking notices the difference and how the person receiving perceives the energy’s absorption and redirection.
Third scenario
Between exercises, you can switch roles or relax the muscles to avoid carryover effects.
This time, we’ll activate only the inner muscles of the arm.
When the strike lands, the arm bends, absorbing the energy through this movement. In other words, the elbow becomes a "leak point."
The energy doesn’t reach the body or the ground; instead, it dissipates as the arm flexes. Any remaining energy may cause the body to shift, but without the ability to manage it, as in the first scenario.
Why?
Because the activated muscles are responsible for bending the arm, so they naturally fulfill that role.
Without control over this movement, a strong enough impact could lead to injury.
Activation mechanism
Rubbing the skin over the muscles triggers their activation.
This happens because, in the brain, the areas responsible for processing touch and movement are closely linked. When one is stimulated, the other is influenced by its electrical activity, prompting movement. For this motion, the inner arm muscles must engage.
The muscular system operates in an agonist-antagonist relationship, meaning one group of muscles performs a movement while the opposing group resists or counteracts it (e.g., biceps and triceps).
If we activate the biceps (the outer arm muscles), the impact is absorbed and redirected through the antagonist muscles without bending the arm.
Conversely, activating the inner arm muscles causes the arm to bend upon impact, dissipating the energy as movement and creating a leak point at the elbow.
This simple exercise helps us understand how the body functions and how its responses change depending on which muscles are engaged.
Now it’s your turn to reflect on how this knowledge can be applied to your practice of shibari.