In kinbaku, ebi usually means the person sits cross-legged and curls forward, bent like a shrimp. That forward shape comes from an Edo-period torture position. Gyaku-ebi turns it around. The English name is reverse shrimp tie: the body is arched backward.
English sources often fold this into hogtie, or treat the two words as the same tie. In the picture books they are two different things. A hogtie gathers the four limbs into one bundle behind the back. Gyaku-ebi arches the back. They often end up on the same person. The line each one wants through the body is different.
The classic placement is face down. The chest starts on the mat, and the arms are fixed behind the back with a gote, a takate-kote, or a box-tie chest harness. The knees bend, and the ankles fold back toward the buttocks. A rope leaves the ankles, runs up along the spine, passes through the wraps of the chest harness, and is drawn back. The load misses the wrist wrap and sits on the wider wraps around the chest. The closer the ankles come to the head, the deeper the curve in the lower back. Taken up fully, the chest lifts, the belly is pulled flat, and the throat is open.
How the body sits, compared with a forward shrimp
Set beside a forward curl, gyaku-ebi leaves the body much more exposed. In ebi the face points toward the knees and the front of the body closes. In gyaku-ebi the chest, the belly, and the throat all face out. The hands are behind the back and cannot touch or cover those places. The position lifts the buttocks, and the waist and hips sit high. A crotch rope added here bites deep into the crease of the thigh and pulls the eye there.
How deep the arch is decides how much the person can still move. A shallow gyaku-ebi only folds the lower legs toward the buttocks. The waist barely arches, and the person can still roll onto a side or inch along the mat. Draw the ankles up beside the back of the head and the body is locked down, with almost nowhere to go. The same arc can be made while kneeling upright, but the person has to hold their own balance, and it does not last. The usual places are face down or on the side. On the side, the pressure on the chest eases a little, and breathing is easier than when the whole body is planted face down.
In pictures, and off the floor
In SM photographs and performances, gyaku-ebi is often used so the posture itself keeps the person there. Once they are tied, the shape holds without a further restraint, and that self-supporting tension is the main pull of the picture. A rope between the teeth shows up often, saliva running down it. The bit is not required by the position. It sharpens what the picture is suggesting. Hung, the tie is gyaku-ebi tsuri: the legs are often suspended apart, and the body moves toward the arched hang of suruga-doi. A suspended reverse shrimp and the same tie on the floor do not share a risk level. Nerve injury in the upper arm, and a wrist that will not lift afterward, belong to the suspension. A floor gyaku-ebi should not be turned into a hang on the way through.
Risk, and taking it off
This is between adults who have already agreed. How deep the arch goes is settled before the rope is pulled. The tie asks for flexibility, and for strength in the belly and the upper body. Face down, with a chest harness and the lower back arched, positional asphyxia is a real outcome. The hands are behind the back, so the person cannot tap anyone. Agree the stop in the voice: one sentence, or a repeated hum. The person tying watches whether the chest is still rising, and whether the color of the face changes. Someone in this tie is not left alone. A larger chest needs a lift under the shoulders or the hips, so the chest and the face are not sealed against the mat, and the head has to be able to turn to one side. An old injury in the lower back means the arch stays shallow. A sharp pain from the spine means stop. Stretch hard just before the tie and then take it in deep on the spot, and the looseness can fade halfway through. The lower back and the shoulders suddenly cannot hold the shape.
If the pull from the ankles loads the wraps on the arms, the nerves of the upper arm can be injured and the wrist will not lift afterward, so the connecting rope belongs on the chest harness. Do not cinch the ankles straight into the wrist wrap and then haul. When a Western hogtie joins them that way, the force goes into the wrist joint. Do not add a rope around the neck to force the arc deeper. Folding the knees up near the head hurts as well.
On time: a shallow arch on something soft can be held for a while. Drawn tight to the level of a torture tie, the lower back, the shoulders, and the breath hit their limit quickly, and the hold is much shorter than a decorative tie done sitting. To take it off, support the legs first, let the back come down flat slowly, then untie the ankles and the upper body. Do not cut the connecting rope. The person can drop hard onto the mat. On the floor the shape usually takes two or three ropes. Under the body, use tatami, a futon, or a pad. Do not leave someone directly on a hard floor for long.
