Naifu-kinniku (literally: “knife-and-muscles”) is a variant of the outside shutō block, which is apparently unique to Goshin-Jutsu. Whereas outside shutō blocks are linear, two-beat motions (i.e, ♫, “1-2”), naifu-kinniku is a circular, one-beat motion (i.e., ♪, “1”), which makes them intrinsically faster. This is because a naifu-kinniku consists of two simultaneous motions:
- The opposite-side hand swats the opponent’s technique aside with a circular pressing block variant, before pulling back to the hip, and floor-sanding motion. Since this “pre-block” is more of a slap or swat, it does not require counter-rotating the hip.
- The same-side hand follows a similar circular path, but a half-beat out of time; it's much like waxing a car, and ends with your same-side shutō contacting the opponent.
[video of a naifu-kinniku, fast and slow, from the front and side]
Timing is critical to avoid crossing your arms. Crossing your arms creates a vulnerability, because a fast and observant opponent can push on your lead arm to pin both of your arms to your chest, leaving you momentarily helpless.