We continue our series on nonverbal communication in shibari, focusing this time on the body as the channel for transmission.
The term tension (張力 chōryoku) encompasses two techniques: tension in the body (activation) and tension in the rope. The combined use of both becomes a key element for communication and session management, serving as the channel or medium through which communication flows.
It’s the tool that allows us to modulate, from the body of the person tying, the body of the person being tied.
“Body tension” is best understood when interpreted as activation.
This mechanism in our body is easy to observe: muscle activation causes a muscle to “harden” when it’s engaged and “soften” when it relaxes.
A Bit of Biomechanics
Muscles are responsible for executing body movement through contraction and extension. There are different types, but the format of this class doesn’t allow us to delve into too much detail, though we’ll touch on a few key points.
From a biomechanical perspective, it’s important to know that our bodies are designed to move in patterns deemed the most efficient and safe. We’ve evolved through movement, and our muscles have specialized to perform specific actions and motions.
However, our modern lifestyles often stray far from these optimal movement patterns, and it’s common to develop postural habits.
As a result, when we ask our body to perform a movement, our brain often resorts to familiar but flawed patterns instead of the optimal ones.
For example, if we typically round our back when bending down to pick something up or tie our shoes, it’s likely that, without thinking—say, when performing a suspension—we’ll bend the same way.
This means the lumbar spine ends up bearing the load instead of the glutes, which are designed for that task.
This is what we call compensations, defined as using a muscle or structure for a motor function it wasn’t designed for, instead of the one that was.
Compensations are highly dangerous and must be monitored and corrected, both in the person tying and the person being tied.
When constructing different shibari figures, it’s crucial to understand how they work biomechanically to ensure the right muscles and structures are bearing the weight and forces, and that the distribution of those forces is as optimal as possible.
While we won’t discuss ligaments in this class, one thing to keep in mind is that compensations tend to put a lot of strain on them, and ligaments don’t recover easily.
This isn’t to say you should avoid moving through all possible ranges of motion. On the contrary, exploring different movement patterns is beneficial.
However, when adopting a position that involves bearing weight or applying various forces, the closer we are to optimal postures and patterns, the better our body will distribute those weights and forces, reducing the risk of injury.
Regarding muscles, we need to understand when a muscle is active versus inactive, and that our body is designed to bear weight with active muscles and stable joints.
In everyday life, the body’s stabilizing muscles protect and provide stability to joints.
This is something to remember in shibari practice when constructing figures, whether by directly engaging those muscles during the session or reinforcing them with ropes.
Agonism and Antagonism
This is a bodily mechanism where, when one muscle contracts, another extends.
For example, when you extend your arm, some muscles relax to allow the extension, while others contract to control and stabilize the movement.
You can verify this by touch.
That’s why it’s good practice for the person tying to touch the body of the person being tied, checking muscle activation and engaging or relaxing muscles as needed at each moment.
Generally speaking, an active muscle feels firm, while an inactive one feels soft.
In shibari, tension is critical: tension in the rope and tension in the body.
A rope without tension doesn’t transmit, but neither does an inactive muscle—one without tension.
In fact, any muscle that isn’t active becomes dead weight.
It’s often easier to notice tension during muscle contraction.
However, activation is just as important during extension. This is because, broadly speaking, a movement results from the combined action of the agonist and antagonist muscles involved.
While this is a complex topic, we can simplify it: agonist muscles are those that contract to execute a movement when activated. For example, when lifting your leg to walk, the quadriceps act as agonists, contracting to raise the femur.
Antagonist muscles, on the other hand, stretch when activated to support and stabilize the movement. In the same example, the glutes and hamstrings at the back of the leg act as antagonists.
Management
During a shibari session, we must induce this activation in the person being tied, as the person tying controls the session’s resources. We can’t expect the person being tied to generate it consciously.
Moreover, if we’re tying someone who tends to compensate in their daily movements, those compensations will likely carry over into shibari, and their body won’t automatically engage the necessary muscles.
To address this, we can use the skin as a communication tool, applying gentle stimuli like caresses, light taps, or small pinches, always remembering that pain causes the brain to deactivate muscles as a protective measure.
This activation is agonist to the movement, meaning the muscle we’re stimulating prepares for contraction, while the antagonists prepare for extension.
This is important because stimulating the wrong muscle group can activate the body for the opposite movement, making it harder to construct the figure and distribute forces and weights properly.
Other methods at our disposal include increasing blood flow to the area to engage the vascular system or initiating a movement so the muscle follows, ensuring it’s done correctly.
Never with Pressure, Force, or Pain
The body’s defense mechanisms deactivate muscles in the presence of pain.
This is to prevent more serious injuries. The immediate effect is that tension disappears, and with it, the ability to communicate with the body of the person being tied.
If we apply too much pressure or if there’s excessive activation causing the body to “lock up,” the technique won’t work.
One way to modulate the tension applied or established in the body is for the person tying to manage all their movements from the core.
Activation in the Person Tying
The person tying must manage both the activation of the person being tied and their own.
The body of the person tying cannot be relaxed or unbalanced. All movements must originate from the core.
To interact and communicate this way with the person being tied, we must engage the abdominal, lumbar, pelvic, and gluteal muscles (among others), collectively known as the core.
Only then can we modulate the body of the person being tied from our own body.
Biomechanically, this is because the core muscles provide strength, power, and stability, while the further we move from the spine, the more we rely on fine motor skills, precision, and dexterity.
In other words: if the person tying grips too hard, squeezes, or handles roughly, they’ll first get a proportionally symmetrical response from the body of the person being tied. But more importantly, they’ll lose control and precision over that person’s movements.
Remember: It’s a Dialogue
Touching, activating, moving, approaching, or stepping back are all forms of communication.
Think about being in a public space—waiting in line at the supermarket or at a bus stop—when someone stands too close to you. You react, don’t you?
It’s the same in shibari. Even before physical contact, we’re already communicating.
It might happen that the person tying approaches, touches the person being tied… and gets no reaction. No response!
Well, that’s communication too. It could mean they’re calm and waiting, understanding they need to stay relaxed to facilitate the tying, or simply that they’re not at all impressed by what’s happening.
Whatever it is, we’ll figure it out later. Assuming one explanation over another is risky. But the person tying can adjust their next move to see what response follows, and so on.
Understanding this mechanism is key in erotic shibari. If you leverage it, you’ll achieve far more compelling results.
Feeling the Activation
Exercises from previous lessons will teach you to “feel” activation. Practically speaking, during a session or scene, we can’t keep stopping to check or ask if everything’s as it should be.
Nor can we assume everything’s fine.
The person tying must develop the skill to identify, through touch and observation, whether the anatomical response of the person being tied is appropriate.
It’s not magic—it’s technique. And to master it, you need to practice beforehand, with good feedback from the person being tied.
We must understand, then, that “tying tightly” is just a narrative device and should be used sparingly. A session of constantly tying tightly creates a flatline—like an EEG. Nor is a sustained crescendo viable—it’s the same, only worse over time.
Tying tightly or cinching ropes is merely a narrative tool in the language of shibari. It should be treated as such. Intensity—both physical and emotional—doesn’t depend on how tight the ropes are.
Ropes that are too tight (or too loose) hinder communication, dialogue, and, ultimately, emotional expression....
Managing tension in the rope and the body is the key.
This tension isn’t generated through brute force as riggers, but through activation itself, modulated by intention to match the intensity required at each moment of the session.
The same principle applies to force with the rope: too tight, and it’s uncomfortable; too loose, and it can be dangerous.
When creating a complex figure, we must thoroughly understand the technique behind its construction to properly adjust the tension and pressure of each rope across the three stages every figure goes through: during construction, once completed, and when in use.
Let me briefly explain:
Think of a complex figure, like kanuki shibari or a multi-rope TK, for example. When we apply each rope, we do so with controlled strength or intensity—not randomly or by chance.
As we build the figure, ropes overlap, pulling on one another, and the body moves… tensions shift.
And when we start using the figure, subjecting it to forces and movements…Do you understand how the ropes in your ties behave under tension?
We must recognize, then, that “tying tightly” is just a narrative device and must be used judiciously.
A session of constant tight tying produces a flatline—like an EEG.
A sustained crescendo isn’t viable either—it’s the same, only progressively worse.
When using force, we need precision and control.
If a rope is tight, it should be intentional, with a clear purpose and real control over that tension—a deliberate choice, not a fluke or an “it just happened.”
Adapting is essential: adjusting intensity, force, and movements to the person being tied, to ourselves, and to the moment. In that order: the first limit is the person being tied, the second is our own capabilities, and the third is the present moment.