Updated: Aug 16, 2022
Sai is often one of the core introductory weapons in most Kobujutsu/Kobudo systems. Often introduced after the Bo it presents multiple new challenges for students. It is often the first “dual weapon” requiring independent co-ordination of each weapon whilst in transit. The primary methods of power generation are perhaps more subtle than that of the Bo; where leverage and the unison of your hands make achieving a modest level of power quite straight forward. In contrast, beginners with the Sai often lack any power transmission and then in pursuit of this often overpower the arms and shoulders which, with only a short amount of intense training, quickly leads to fatigue.
The metallic nature of the weapon often makes it feel less natural and smooth than that of wood. I’ve known more than one student whom, despite initial excitement for the study of Sai, have ended up being grateful for Tonfa. Sai is a long-term weapon. Unlike Tonfa and Nunchaku which love to move for you, freely and without much effort, Sai must be moved. Done wrong, even light Sai become torturous in prolonged training.
As you commence a study of Sai, you are really commencing a study of distance. For a student who has already covered the basics of Bo kumite, Sai kumite requires a very specific development in your ability to close and control distance which fundamental Bo kumite often precludes. This is a direct result of the transition from symmetry in weapon range to asymmetry. Sai, as the first of the short-range weapons, embellishes this principle of closing distances, which carries through a multitude of later weapons but develops first and foremost with Sai Kumite.
Like overcoming the advantage of a boxer with a longer reach, Sai kumite requires the same considerations. There is a critical range where the Bo can easily strike you but you can’t return a strike and remaining there is asking for trouble. Moreover, there is a second important reason why closing and controlling the distance is so important; fundamentally the Sai is at a mechanical disadvantage compared to the Bo. Any technique is only a strong as its weakest characteristic and whilst the material strength of Sai is high, it suffers with a severe deficit of leverage.
In contrast to the Bo, which is just short of a 6 foot lever with a mobile fulcrum enabling the generation of massive power and speed, Sai can hardly be considered a comparable force multiplier. If rotation is occurring at the wrist as the pivot point, then that results in a very short lever indeed. It is the weakness of the wrist which accounts for the greatest proportion of power loss with Sai. Therefore, in the various grips of the Sai (primarily being that of Honte mochi, Gyakute mochi and Tokui mochi), the alignment of the Sai and the forearm is generally quite important. There are also many situations where an acute angle is required but if the correct positioning isn’t matched with the desired function, then the result is total breakdown in power transmission.
If alignment is important most of the time, but there are some “exceptions” there must be something more fundamental than the angle at the wrist in governing power transmission. It turns out it's not just the angle of the wrist to the Sai that matters, but the angle between the Bo and Sai which is most significant.
If you stood along a straight embusen, immediately opposite your opponent with a Sai out extended in your hand and crossed it with a Bo, everyone can understand that the person holding the Bo (with two hands) could easily power the Sai out of the way. Now rotate that same person through 90 degrees and magic happens. Now the Sai can effortlessly withstand pressure from the Bo. This shows the optimum positioning you’re always looking for with Sai against Bo. Where ever you can you want to create lines of defense that act perpendicular to the attack line of the opponent. It isn’t always possible of course but if you strive for the ideal, you’ll find that any angle close to 90 degrees will do the trick. It is for this reason you should be highly suspect of Sai kumite which is overtly linear.
These two central problems for Sai kumite, that of the distance problem and the leverage deficit problem must be overcome and managed in effective kumite. By exploiting strategic angles, closing the distance to reduce the effects of your opponent’s leverage and limit their mobility with the weapon you can overcome the initial mechanical weaknesses of the Sai and use it in a highly efficient and devastating way.
Part 2 will explore more deeply some of the tactical principles which can be used to overcome these central problems.