Motare in kyudo as focal dystonia: Ogiso 2023

In kyudo, motare is the name given to being unable to let the arrow go when you want to, once you have reached kai, the full-draw position in which you keep drawing very slightly until the release comes. Four neurologists in Gifu set out to check whether motare has the features of a task-specific focal dystonia, and to do so compared three practitioners who had it with three who had hayake, the opposite problem, in which the arrow leaves earlier than intended, and with three who had neither.

In the three with motare, the interview found the elements looked for in a dystonia. The problem was stereotyped in all three, meaning it always appeared in the same way, and specific to the task, since none of them had trouble with everyday activities outside kyudo. In two, motare improved when the instructor touched the forearm, the upper arm or the shoulder, which is the so-called sensory trick; in one it improved in morning competitions, shortly after waking. In one case the onset had followed an increase in the bow's draw weight.

In the three with hayake, none of these signs. The problem was specific to the task, but with no morning benefit, no sensory trick and no stereotypy, since the symptoms varied from one occasion to the next; in one, onset followed a change in the way of drawing, in another a run of consecutive hits, and one reported being able to hold it back to some extent on purpose.

On surface electromyography, two of the three with motare felt the block during the recording, one in all three trials and one in two out of three. In one of them an abnormal co-contraction of the forearm flexors and extensors appeared, starting about a second before entering kai, with a frequency that fell after some five seconds in kai, until it disappeared and gave way to the release. Nothing in the biceps or triceps, and in the other six participants no co-contraction in any muscle. That in the same person, holding the same posture, the co-contraction appeared in one trial and not in another is why the authors read it as a sign favouring dystonia rather than a voluntary movement.

Between July 2021 and July 2022 the authors contacted forty university kyudo clubs looking for practitioners reporting problems with the release, and heard back from thirty-three. From there came the nine participants of the study: three with motare, three with hayake and three controls. They were aged 20 to 28, two women and seven men, all right-handed, with between 4 and 10 years of kyudo behind them; one had a previous injury to the left forearm, but from before he started practising. None had a personal or family history of neurological disease, and at the examination before the recording none of the nine showed dystonia or tremor.

The interview covered neurological history, family history, injuries and the four elements associated with task-specific focal dystonia: the trigger that set off the onset, morning benefit (defined as improvement in morning competitions, shortly after waking), the sensory trick and stereotypy.

Surface electromyography was recorded for all nine in the electrophysiology laboratory of Gifu University Hospital, with disc electrodes on the biceps brachii, triceps brachii, forearm flexors and forearm extensors, three trials each. The drawing movement was performed without the kyudo robe and without the glove, and with a rubber bow, a simplified training implement different from the competition bow. The study was approved by the ethics committee of the Gifu University School of Medicine.

The sample is three cases per group, all in their twenties, and the finding in the title is more fragile than it sounds: co-contraction, the only instrumental measure compatible with a dystonia, appeared in one participant out of nine. In the two remaining motare cases the authors record stereotypy, task specificity and a sensory trick, but no morning benefit and no abnormality on electromyography, and they write themselves that those two are not explained by dystonia alone and that psychological factors or other mechanisms may be involved.

The authors list their limitations precisely: few participants, ages confined to the twenties, recordings made with clothing, equipment and surroundings unlike actual shooting, no clear criterion for defining co-contraction, data collection and analysis not blinded, so that no reasoning is possible about the relationship with years of practice or technical level, no experimental provocation of the sensory trick, and very few trials per person. They ask for studies on more cases, of a wider age range, and in surroundings close to a dojo with the target in front of the archer.

To this can be added that motare and hayake were established from what the participants reported, with no independent measure, and that the three controls serve only to show the absence of the signs, not to estimate how often those signs occur in people who shoot normally. The caption of the electromyography figure reports a high pass filter at 5,000 hertz and a low pass at 10, that is, the two labels reversed. The paper is in Japanese, with the abstract and table in English, and presents itself as a short report rather than a full study.

What this study adds for someone who shoots is a distinction, not an explanation. Two problems that practice tends to lump together under the same label behave differently when questioned the way a neurologist questions a dystonia: those who cannot release show a problem that is always the same, which sometimes loosens if somebody touches their arm and in one case was better in the morning, while those who release too early show none of this and can hold it back to some extent on purpose. In kyudo hayake is common, and an earlier study by the same group found it in 53.8% of practitioners against 4.6% for motare.

This does not mean that a blocked release is a neurological problem, nor that an early release is a problem of the mind. The only co-contraction observed comes from one participant out of nine, and the authors say explicitly that the other two motare cases are not explained this way. Anyone who recognises their own problem in one of these descriptions does not have a diagnosis here: the paper is a working hypothesis built on nine people, and a block that does not go away is something for a doctor to assess.

Outside kyudo the translation is not automatic. The rubber bow used in the recordings is not a bow, there was no target and no glove, and in kyudo the kai is a prolonged and codified phase with no direct equivalent in recurve shooting. It remains useful to know that in one case the onset of motare followed an increase in draw weight, and that in one case of hayake it followed a change in the way of drawing: those are two coincidences reported by two people, not a mechanism.