On Jūjutsu and Stiffness:

The Paradox of Learning the Art of Flexibility

It’s not just beginners who are stiff when learning budō (武道), the seasoned practitioner too can become stiff when learning a new movement.

We’ve all been there:
“I can’t do that.”
“I’m not that flexible, I can’t get into that position.”
“I feel too tight to move.”

Sometimes, both beginners and advanced practitioners are already physically flexible, and yet still can’t get into the right position. So what gives? Why can’t we just relax and move with minimal effort and maximum efficiency?

Jūjutsu (柔術) is often mistranslated as “the gentle art.” More accurately, it refers to the art of flexibility, adaptability, and strategic yielding. The character 柔 (jū) is not limited to gentleness, it conveys suppleness, pliability, and the ability to bend without breaking: to dissipate or redirect incoming force through controlled movement, rather than oppose it with brute strength. When reduced to “gentle,” the term risks sounding passive, yet in practice, it denotes a dynamic, elastic quality of harmonizing with an opponent’s energy while maintaining control (Zoughari, 2010).
The second character, 術(jutsu), means art, method, or applied technique, a discipline internalized through rigorous training.

Jūjutsu is therefore not limited to empty-hand fighting, it is a movement system that applies to weapons, tactics, positioning, timing, and perception. It's a method of movement based on natural principles. It is deeply contextual and adaptive, one learns to move with minimal tension, using posture and spacing to control opponents. Suppleness, not strength, is the root of control, a principle emphasized in classical martial systems (Zoughari, 2010). 

Hall (2012) explains that by the Edo period, jūjutsu became a generic label for grappling methods used in classical martial art ryuha, including throws, pins, and joint locks, often derived from battlefield kumiuchi tactics. Karl Friday (1997) adds that these systems were rarely standalone; they were deeply embedded in the curriculum of full warrior training, designed to support armed techniques and broader combat strategy.

Jūjutsu, then, is not merely “gentle” it is a refined, adaptive, and intelligent approach to martial movement, embodying strategic yielding and functional pliability developed through centuries of embodied practice.

So if we are meant to move with suppleness, to display flexibility and pliability then why do we have the movement characteristics of a house brick? 
​That, my fellow buyū (武友), is not exactly your fault, it’s how we learn to move.

The Learning Process: Why Tension Appears First
When we attempt a new movement, whether it’s a kata (型) we’ve never done before, or a familiar waza (技) performed under new constraints like fatigue, added load such as a weighted vest, wearing yoroi (鎧), or even using a different weapon such as a yari (槍) instead of ken (剣) we often find ourselves using far more muscular effort than necessary. This isn’t a failure of flexibility or coordination; it’s a natural adjustment strategy.

This early stiffness isn’t just psychological, it reflects how the nervous system manages uncertainty. Biomechanically, it’s linked to what Franklin & Franklin (2023) describe as internal model uncertainty. When the brain isn’t confident how a movement will unfold, it increases muscle co-contraction, tightening opposing muscle groups to stabilize the joints and reduce motor error. This is a control strategy, not a panic response: the system tightens up temporarily while it calibrates its predictions and fine-tunes coordination through trial and error.

It’s important to distinguish this from the stretch reflex, which is a fast, automatic response triggered by sudden muscle lengthening. That reflex acts like an emergency brake, protecting muscles from overstretching and potential injury. While both the stretch reflex and co-contraction increase muscular tension, they arise from different processes, one reflexive and spinal, the other strategic and cortical. As Behm (2019) notes, stretch responses can be amplified by fear or unfamiliarity, but with repetition and increasing confidence, both forms of tension tend to diminish.

Even without visual feedback, as in Franklin’s visual clamp experiments, people still adapt successfully, relying on proprioceptive and internal cues. Movement refinement doesn’t depend on watching yourself, but on the nervous system gradually tuning control strategies through repeated exposure (Franklin and Franklin, 2023).

This process mirrors what Rob Gray (2022) describes as “freezing degrees of freedom” in early learning, a way to reduce variability and gain control. As skill develops, the system naturally “unfreezes” these constraints, allowing for smoother, more efficient movement. Moinuddin et al. (2021) further emphasize that while external feedback can help, sustainable skill development depends on how well internal sensory systems adjust over time.

That initial tension? It’s not poor technique, it’s a functional adaptation. You’re not failing to move like a martial artist. You’re learning to.

Kata as Constraint-Based Learning
Kata in classical martial arts is often misunderstood as fixed choreography, but it functions more accurately as a structured constraint, a deliberate narrowing of options that accelerates neuromuscular refinement. When repeated under conditions like low kamae (構え), narrow stances, or strict timing, kata places the nervous system in a constrained environment that demands adaptation through repetition and feedback.

Zoughari (2010) explains that the term kata (型 or 形) historically denotes a mold or ideal form, both a vessel of transmission and a container for movement principles. In classical martial systems, kata represents codified sequences designed not simply to preserve technique, but to refine physical expression over time through embodied repetition. These forms serve not as performance, but as tools for internalizing movement patterns and combat strategies in context.

Motor learning research supports this approach. Franklin and Franklin (2023) describe how uncertainty in movement triggers increased muscle co-contraction, a temporary stiffening to stabilize joints and reduce error. Rob Gray (2022) refers to this as “freezing degrees of freedom” in early learning, with gradual “unfreezing” as internal models improve. Moinuddin et al. (2021) emphasize that durable skill development hinges on internal feedback processing, the same sensory refinement kata cultivates. Behm (2019) notes that with repetition and reduced fear, unnecessary tension gives way to confident, adaptable control. Kata transmits not only technique but tacit knowledge, a felt sense of timing, distance, and energy flow refined through repetition. Kata creates pressure within boundaries. It doesn’t just teach movement, it teaches how to learn movement.

Suppleness Is Earned. 
So, if your shoulders are tight, your hips are stubborn, or your waza feels clunky, it’s not because you’re doing something wrong. What you’re feeling is your nervous system responding to something new, it’s sorting out uncertainty and protecting itself until it understands the task. This is exactly what Franklin and Franklin (2023) observed: when faced with novel or unpredictable conditions, the brain increases muscle co-contraction, literally tightening up the system to reduce the risk of error. That stiffness isn’t a failure, it’s a sign that the system is gathering information, adjusting, and gradually finding its feet.


Kata gives the nervous system a repeatable, structured environment to work in, allowing these rough edges to wear down through informed repetition. Over time, that unnecessary tension—the grip your nervous system has on unknown patterns, begins to release. Control becomes more refined, and movement grows smoother and more adaptable. This is not immediate, and it’s not supposed to be. The process is visible in Franklin & Franklin’s findings: “once the motor memory is learned, the co-contraction and feedback gains are gradually decreased, but often remain higher than in the null environment, suggesting tuning to these novel dynamics”.

Feeling stiff is normal. It’s not proof of poor practice or lack of promise. It only becomes a problem if nothing changes after months and years of focused, corrective work. When the conditions are right, when practice is consistent and attentive, the excess tension will give way to suppleness and stability. That’s not a gift; it’s the result of adaptation.

The goal isn’t to move like someone else. The goal is to create the right context for your own system to adapt. That requires time, feedback, and a willingness to go through awkward phases before you can move freely or with control. In the long run, jūjutsu teaches that flexibility... real, functional flexibility, is earned, not granted.

Stiffness is not a failure, it's a phase. In the early stages of learning, tension is not only normal, it's functional. But it should not be permanent. With adequate time, thoughtful practice, and repetition in a structured context, that tension will give way to freedom. The key is to avoid frustration when stiffness appears, and instead recognize it as a sign of learning in progress. Don’t try to bypass this phase, move through it. Supple, efficient movement is not something you copy from others; it’s something your nervous system earns. With keiko (稽古), you will loosen. With diligence, you will flow.

稽古次第で未熟も上手になる
Keiko shidai de mijuku mo jōzu ni naru
“With practice, even the unskilled become skillful.”




Gray Anderson
正中線道場
July 2025
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Behm, D.G. (2019) The Science and Physiology of Flexibility and Stretching: Implications and Applications in Sport Performance and Health. London: Routledge.


Friday, K.F. (1997) Legacies of the Sword: The Kashima-Shinryu and Samurai Martial Culture. Honolulu: University of Hawai‘i Press.

Franklin, S., & Franklin, D. W. (2023). Visuomotor feedback tuning in the absence of visual error information. Neurons, Behavior, Data Analysis and Theory, 3. https://doi.org/10.51628/001c.91252



Gray, R. (2022) How We Learn to Move: A Revolution in the Way We Coach & Practice Sports Skills. Champaign, IL: Human Kinetics.

Hall, D.A. (2012) Encyclopedia of Japanese Martial Arts. Tokyo: Kodansha International.

Moinuddin A, Goel A, Sethi Y. The Role of Augmented Feedback on Motor Learning: A Systematic Review. Cureus. 2021 Nov 18;13(11):e19695. doi: 10.7759/cureus.19695. PMID: 34976475; PMCID: PMC8681883.

Zoughari, Kacem. The Ninja: Ancient Shadow Warriors of Japan (The Secret History of Ninjutsu). Tuttle Publishing, 2010.
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Zoughari, K.  ‘The Origin of Jujutsu’, Seishin Ninpō Dōjō Blog, 29 March. Available at: https://seishinninpodojo.wordpress.com/2010/03/29/the-origin-of-jujutsu-by-dr-kacem-zoughari/