Purpose

The inside heel hook (from cross ashi / saddle) is the highest-risk submission in the leg lock system. It loads the knee’s internal rotational stability — the ACL, MCL, and posterior capsule — through internal tibial rotation. These structures can fail under small amounts of force applied quickly, and may give no pain signal before structural damage occurs. The drill is cooperative and uses partial rotation only; the full finish arc is not trained here.

Prerequisite: Both practitioners must have completed DRILL-LL-02 (Heel Hook Rotation Mechanics) and DRILL-LL-08 (Tap-Release Reflex) before this drill may begin. Coaches should confirm this explicitly.

Joint load description: The inside heel hook applies internal tibial rotation force to the knee. The load vector is: the heel rotates inward (toward the partner’s body centreline) while the attacker’s hip connection — established through the saddle/cross ashi position — prevents the femur from rotating with the shin. This differential rotation loads the ACL and medial structures. The rotational range before structural engagement is small — as little as 15–20 degrees of differential shin rotation can produce significant ligament load. Partners must tap at the first awareness of any knee movement or sensation: not at discomfort, not at pain, but at the first moment of awareness.

Partner Communication Protocol

Stated aloud and confirmed by both players before the first rep. Both practitioners must verbally confirm each point:

Dual-signal tap: Partner provides both a physical double tap (on the attacker’s body or mat) AND a verbal “tap” simultaneously. Both signals are required — the attacker does not proceed until both are clearly received.
Attacker stops rotation at tap — not after: The rotation ceases the instant the tap is received. The attacker does not complete the movement, does not assess whether the tap was “early,” does not adjust the grip. Rotation stops at tap.
Grip releases after rotation stops: Rotation stops. Then grip releases. Never simultaneously.
Ten-second pause after every rep. Mandatory. Both players remain still. This gives the partner’s knee time to return to neutral and both practitioners time to re-establish awareness of each other before the next rep.
No bridging by the partner. Under any circumstances while the inside heel hook grip is established. Internal bridging loads the partner’s own ACL through the same rotation the attacker is applying. If escape is needed, tap.
Partner controls the rotation depth. The partner says “further” to allow the attacker to progress through the rotation arc. Without this explicit signal, the attacker holds at the current position. The default is stillness; movement requires permission.

Setup

Both players in cross ashi (saddle) with hip connection confirmed: attacker’s thighs pinching the partner’s near thigh, attacker’s hip pressed into the entanglement, partner’s inside heel exposed on the internal line.

Inside heel hook grip: Both hands cup the inside of the partner’s heel — the palm faces the inside of the foot, fingers wrap around the Achilles to the outside. The grip position is slightly different from the outside heel hook — the hands rotate to cup from the inside.

Execution

Step 1 — confirm saddle and hip connection: Both players confirm the cross ashi position. Attacker confirms hip connection is active (not passive).

Step 2 — establish the grip and announce “grip on.” Partner confirms.

Step 3 — rotation to 20%: Attacker begins internal rotation to 20% of the arc — approximately the range where the partner can first feel the heel is moving. Hold.

Step 4 — partner controls progression: Partner says “further” to allow the next 10% of rotation. This step-by-step permission structure ensures the partner is always aware and in control.

Step 5 — stop at 40% maximum. The drill reaches 40% of the full finish arc at most. This is well within a safe mechanical range when applied slowly and with communication — and it is sufficient to establish the correct torso rotation habit.

Step 6 — rotation stops, ten-second pause, then grip releases and entanglement releases.

Six reps. No increase in speed or arc across reps in this drill.

Coaching Notes

Mechanical coaching: The inside heel hook requires the same fundamental technique as the outside heel hook — torso rotation, not arm squeeze. The difference is the rotation direction and the heel cup position. Practitioners who have correct outside heel hook mechanics often invert the rotation direction incorrectly for the inside variant. Cue: “turn your torso toward the partner’s head, not away from it.”

Safety coaching: The inside heel hook is the submission most likely to produce training injuries precisely because its entry (cross ashi) is now widely trained, but the finish mechanics and communication protocols are not proportionally developed. Coaches are responsible for the environment in which this drill is used. The prerequisites (DRILL-LL-02 and DRILL-LL-08) are not suggestions — they are the minimum preparation for this drill. A practitioner who has not demonstrated reliable tap-release behaviour in less dangerous contexts should not be doing this drill.

The partner-controlled rotation (step 4) is the key safety structure of this drill. It inverts the normal dynamic — the attacker does not control the pace; the partner does. Practitioners who resist this inversion (“I know where to stop”) are not ready for this drill.

Common Errors

Proceeding without partner “further” signal: Attacker continues rotation without waiting for partner permission. This bypasses the drill’s safety structure. Stop the rep immediately and re-state the protocol.

Grip release before rotation stop: Attacker releases the heel cup while still rotating inward. The rotation continues momentarily — often enough to load the medial structures. Stop rotation first. Always.

Skipping the ten-second pause: Both players reset within seconds. The pause is the safety structure, not the drilling. Coaches must actively enforce the ten-second pause as part of the drill mechanics.