Flexion

SubFamily

屈曲(Kukkyoku)

Traditional

Translation: flexion

Overview

Wrist flexion locks force the hand forward (palmar flexion), compressing the wrist joint and stressing the dorsal ligaments and extensor tendons. [1],[2] Nikkyo (二教, second teaching) in aikido is a classic wrist flexion lock that applies inward pressure on the wrist while controlling the elbow. Figure-four flexion locks, Z-locks, and two-on-one flexion grips are common BJJ variations. [3],[4]

Also known as
Wrist Flexion Lock[1]Palmar Flexion Lock[2]

History & Origin

Nikkyo is the second foundational technique in aikido's curriculum, inherited from Daito-ryū Aiki-jūjutsu. [1],[2] Wrist flexion locks have been used in Japanese martial arts for centuries as both standing control techniques and ground submissions. [3],[4]

Effectiveness

Wrist flexion locks are highly effective pain compliance techniques, forcing a tap through intense wrist joint pressure. [1] They are particularly effective as surprise submissions in BJJ, catching opponents who post their hands during transitions. [2]

Lineage

Wrist flexion locks originate from Japanese jūjutsu and aikido, where nikkyo (second teaching) is a foundational technique inherited from Daitō-ryū Aiki-jūjutsu. [1] They were adopted into BJJ and submission grappling as opportunistic submissions. [2]

Competition Record

Wrist locks are legal at brown and black belt in IBJJF competition and fully legal in ADCC and MMA. They are increasingly popular as surprise submissions at high-level BJJ competition. [1]

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Biomechanical Mechanism

Primary ActionHyperextension of the elbow joint — the hips drive upward against the posterior humerus while controlling the wrist
Joints InvolvedElbow (extension beyond normal ROM), wrist (stabilized), shoulder (isolated and controlled)
Force VectorPosterior-to-anterior force on the upper arm with fixed distal anchor at the wrist creates a lever arm across the elbow
Leverage PrincipleHips act as the fulcrum — the longer the lever (full arm extension), the less force needed to hyperextend

Position & Entry

From top positionIsolate the arm, control the wrist, and apply hyperextension pressure against the elbow using body positioning
From guardSecure wrist control, pivot to create the angle, and apply elbow hyperextension from the bottom position

Videos

Thoracic Flexion vs Thoracic Spine Flexion

0
Flexion·Neal Hallinan

When PRI talks about "Thoracic Flexion" they do not mean "flexion of the thoracic spine". In PRI-speak, the thoracic spi

1 video

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Ratings

Danger Rating

Risk of injury to the person this technique is applied to

5
High5/10

Wrist flexion locks force the hand palmward, stressing dorsal ligaments and extensor tendons

Difficulty

Skill level needed to execute this technique reliably

Advanced
Competition Legality

Whether this technique is allowed under major competition rule sets

Legal
IBJJF — Legal at all belt levels
IBJJF Rules Book v6.0, June 2024PDF
ADCC — Legal — all submissions legal in ADCC
ADCC Rules Update, April 2025PDF
Unified MMA — Legal submission technique
Unified Rules of MMA, August 2025PDF
FIAS Sport Sambo — Legal
FIAS International Sambo Competition RulesPDF
FIAS Combat Sambo — Legal
FIAS Combat Sambo RulesPDF

Training Notes

Wrist flexion locks bend the hand forward — forcing the palm toward the inner forearm, attacking the extensor tendons and the dorsal carpal ligaments (Danaher, New Wave Jiu Jitsu, 2020)
The flexion lock is less common than the extension lock but equally effective: it attacks the wrist from the opposite direction, often catching opponents who defend the extension
Flexion locks work by cupping the back of the opponent's hand and driving it toward the inner forearm — the wrist joint cannot resist this direction of force
The sankyo wrist lock in aikido is a flexion-rotation combination: the wrist is flexed while the forearm is rotated — creating a compound lock on multiple structures
Flexion locks appear when the opponent reaches behind you or when their hand is positioned palm-up — the natural hand position creates the entry
The flexion lock is often combined with a figure-four grip: one hand pushes the back of the hand forward while the other controls the forearm
Flexion wrist locks from guard: when the opponent pushes on your chest with a flat hand, curl the hand forward for the flexion lock

Common Mistakes

!Applying flexion without controlling the forearm — the forearm must be anchored; otherwise, the arm simply moves with the hand
!Not recognising the palm-up hand position — flexion locks require specific hand orientation; don't attempt when the palm faces down
!Using the same grip as for extension — flexion requires pressing the back of the hand forward, not pulling the fingers back; different mechanics
!Applying with fingers only — use the palm of your hand against the back of theirs for adequate force distribution
!Not combining with extension threats — the opponent defending flexion opens themselves to extension; flow between the two
!Forcing the lock when the wrist is already flexed — the lock needs the hand in neutral or slightly extended position to have range to flex
!Not training the less-common flexion direction — most wrist lock training focuses on extension; flexion creates surprise opportunities

Related Techniques

Counter Techniques

Setup Chain

1Control the Armisolate and grip the target arm
2Position the Hipsalign hips perpendicular to the arm for maximum leverage
3Pinch Kneessqueeze knees together to prevent arm extraction
4Extend for the Finishbridge hips up while pulling the wrist down to hyperextend the elbow

Sources & References

Primary Source

Aikido — Nikyo (二教); Kisshomaru Ueshiba, 'Aikido'

1BookAikido — Nikyo (二教); Kisshomaru Ueshiba, 'Aikido'

Japanese terminology sourced from Aikido — Nikyo (二教); Kisshomaru Ueshiba, 'Aikido'

2SyllabusAikido Terminology

Aikido technique naming conventions

Standard Japanese martial arts terminology (kanji/hiragana)

4OtherJapanese Martial Arts Standard Terminology (武道用語)

Established Japanese martial arts naming convention — native Japanese term (和語/漢語)

5CitationAikido — Nikyo (二教); Kisshomaru Ueshiba, 'Aikido'

Japanese terminology sourced from Aikido — Nikyo (二教); Kisshomaru Ueshiba, 'Aikido'

Community

Athletics

Requires

fine motor control, grip sensitivity, quick hand transitions

Favours

dexterous hands with strong fingers

Key muscles

forearm flexors and extensors, intrinsic hand muscles

Sub-techniques

Arm-Drag

Genus

The arm-drag wrist lock applies wrist flexion — bending the wrist toward the inner forearm — using an arm-drag grip as the controlling mechanism. [1,2] The attacker uses a standard arm-drag motion to isolate the opponent's arm, then repositions the grip to fold the wrist inward while controlling the elbow. [1] The arm-drag entry is effective because it simultaneously disrupts the opponent's balance and exposes the wrist for the lock. [1,3] This technique bridges the gap between wrestling-style arm drags and submission-oriented wrist manipulation. [1]

4 species·4 techniquesExplore

Chin-down

Genus

The chin-down wrist lock from seated guard is a flexion-based wrist submission where the attacker, working from a seated or guard position, traps the opponent's hand and forces the wrist into acute flexion by pressing the back of the hand toward the inner forearm. [1] The 'chin-down' designation refers to the specific grip configuration where the attacker's thumbs press down on the back of the opponent's hand, mimicking the motion of pushing someone's chin toward their chest. [1,2] From seated guard, the attacker isolates one of the opponent's posting hands during a pass attempt, cups the hand, and applies downward flexion pressure against the wrist joint. [2] This creates intense stress on the radiocarpal and midcarpal joints, threatening ligament damage and compelling the tap. [2,3]

4 species·4 techniquesExplore

Figure-Four

Genus

The figure-four wrist lock from seated guard is a flexion submission where the attacker uses a figure-four grip configuration to isolate and bend the opponent's wrist from a bottom guard or seated position. [1] The attacker grabs the opponent's hand with one hand, then threads the other arm around the wrist to grip their own forearm, creating a powerful figure-four lever. [1,2] This interlocking grip provides superior mechanical advantage compared to simple two-hand grips, as the figure-four structure distributes force efficiently and prevents the opponent from pulling free. [2] From seated guard, the attack typically arises when the top player posts a hand on the mat or the attacker's body during guard passing, exposing the wrist. [2,3] The figure-four lock allows finishing with relatively small movements. [3]

4 species·4 techniquesExplore

Gooseneck

Genus

The flexion gooseneck wrist lock bends the wrist forward (toward the inner forearm) while curling the fingers backward, creating a gooseneck shape in the flexion direction. [1,2] The attacker grips the opponent's fingers and palm, pushes the wrist into flexion, and curls the fingers back toward the back of the hand. [1,3] The combined wrist flexion and finger extension creates compound joint stress that is extremely painful. [1] This is commonly used in self-defense, law enforcement wrist control, and as a submission from various grappling positions. [1,4]

1 species·1 techniquesExplore

Two-On-One

Genus

The two-on-one wrist lock from seated guard is a flexion submission where the attacker uses both hands to control and bend a single wrist from a seated or guard position. [1] Both of the attacker's hands wrap around the opponent's hand and wrist, with one hand cupping the fingers and the other pressing against the back of the hand, driving the wrist into forced flexion. [1,2] The two-on-one grip provides raw strength advantage and is the simplest wrist lock configuration — no interlocking or figure-four mechanics are needed, just direct bilateral pressure. [2] This attack is commonly opportunistic, catching an opponent's posting hand during a guard pass attempt or when grips are momentarily exposed. [2,3] The simplicity makes it accessible but also easier for the opponent to resist with a strong fist. [3]

4 species·4 techniquesExplore

Z-Lock

Genus

The Z-lock wrist lock from seated guard is a flexion-based submission that uses a distinctive Z-shaped arm configuration to hyperextend the opponent's wrist joint from a bottom guard or seated position. [1] The attacker threads their forearm behind the opponent's wrist in a weaving pattern that creates a Z-shape when viewed from the side — the attacker's arm bends at the elbow, wraps behind the opponent's wrist, and the hand hooks back to create three connected segments. [1,2] This configuration generates exceptional leverage because the Z-shape creates two fulcrum points acting on the wrist simultaneously. [2] From seated guard, the Z-lock catches opponents who post carelessly or extend their arms during passing attempts. [2,3] The Z-lock is considered an advanced wrist lock variant due to the precise positioning required to establish the weaving grip. [3]

4 species·4 techniquesExplore

Frequently Asked Questions

What's the difference between thoracic flexion and thoracic spine flexion?

Thoracic spine flexion involves flexing the thoracic spine while maintaining an extended lower lumbar spine, whereas thoracic flexion can refer to just compressing or jamming the thoracic spine down without that spinal positioning distinction. Neal Hallinan emphasizes this is a critical concept to understand, especially when working with PRI (Postural Restoration Institute) techniques.

How does the Flexion work?

Wrist flexion locks force the hand forward (palmar flexion), compressing the wrist joint and stressing the dorsal ligaments and extensor tendons. Nikkyo (二教, second teaching) in aikido is a classic wrist flexion lock that applies inward pressure on the wrist while controlling the elbow.

Where does the Flexion come from?

Nikkyo is the second foundational technique in aikido's curriculum, inherited from Daito-ryū Aiki-jūjutsu. Wrist flexion locks have been used in Japanese martial arts for centuries as both standing control techniques and ground submissions.

Is the Flexion legal in competition?

IBJJF: legal — Legal at all belt levels; IJF: banned — Only elbow joint locks (kansetsu-waza) permitted in judo — all other joint lo…; ADCC: legal — Legal — all submissions legal in ADCC; Unified MMA: legal — Legal submission technique; FIAS Sport Sambo: legal — Legal; FIAS Combat Sambo: legal — Legal

How dangerous is the Flexion?

Danger rating 5/10. Wrist flexion locks force the hand palmward, stressing dorsal ligaments and extensor tendons

How do I set up the Flexion?

The standard setup chain: Control the Arm → Position the Hips → Pinch Knees → Extend for the Finish.

How do I defend against the Flexion?

Standard counters include: Clasp Hands — grip own wrist to prevent arm extension / Stack — drive forward to compress the attacker and relieve elbow pressure / Hitchhiker Escape — rotate the thumb toward the mat and roll to extract the arm.

What are the variants of the Flexion?

Common variants: Standard wrist lock (kote gaeshi) (two-handed rotational lock on the wrist); Gooseneck wrist lock (flexion lock bending the wrist down toward the forearm); Standing wrist lock (applied during grip fighting or a standing exchange); Ground wrist lock (catching the opponent's posted hand from mount, side cont…).

How effective is the Flexion in competition?

Wrist locks are legal at brown and black belt in IBJJF competition and fully legal in ADCC and MMA. They are increasingly popular as surprise submissions at high-level BJJ competition.

What are common mistakes when doing the Flexion?

Top errors to watch for: Applying flexion without controlling the forearm — the forearm must be anchored; otherwise, the arm simply moves with… / Not recognising the palm-up hand position — flexion locks require specific hand orientation; don't attempt when the p… / Using the same grip as for extension — flexion requires pressing the back of the hand forward, not pulling the finger… / Applying with fingers only — use the palm of your hand against the back of theirs for adequate force distribution.

What are other names for the Flexion?

The Flexion is also known as Kukkyoku, Wrist Flexion Lock, Palmar Flexion Lock.