Sleep, mood and accuracy in kyudo: Yoshioka 2024

Fifteen university kyudo archers shot twenty arrows in the morning on two or three separate days, and for each archer the morning with the highest hit rate was compared with the one with the lowest. On the good mornings the proportion of arrows on target was 83.7% (standard deviation 16.5), on the poor ones 61.7% (17.5); the feeling of having shot well, marked on a 100 mm line, followed the result, 58.0 against 30.2 mm.

The night before the good mornings the archers had slept less, not more: 286.7 minutes against 349.7, with sleep efficiency of 88.7% against 94.1%. Time to fall asleep and time awake after falling asleep did not differ, and the sleep questionnaire filled in on waking showed no difference at all. On the POMS2, completed a few minutes before shooting, none of the seven scales separated the two mornings: the closest was vigour, lower on the good mornings (46.8 against 50.8 points, p = 0.09). The two sleep differences, significant on their own, did not stay so once that vigour was taken into account: sleep time goes from F = 6.57 with p = 0.02 to F = 3.11 with p = 0.10, efficiency from F = 5.77 with p = 0.03 to F = 2.74 with p = 0.12.

In a secondary analysis of the 10 archers for whom the following night was also recorded, the night a few hours before shooting, the direction reverses: on the good mornings there were fewer awakenings and higher efficiency. The authors conclude that kyudo archers may shoot better in less than optimal sleep and mood conditions, and note that this does not sit well with much of the literature on athletes' sleep, while it does resemble two earlier kyudo studies in which the archers who hit more targets showed greater autonomic activation before shooting.

The archers belonged to the kyudo club of the University of Tsukuba and were recruited through personal contacts. Of the 22 who started, 5 with less than a year of practice and 2 whose sleep recording failed were excluded, leaving 15 in the analysis (11 men and 4 women, mean age 19.9), all of whom had shot an official competition within the year, training 5.8 days a week for 3.7 hours a day, shooting 52 arrows a day with a self-reported hit rate of 61.1%.

The study ran for eight days, from 6 to 13 November 2022. Sleep was recorded for seven nights with a sensor placed under the mattress at chest height (Nemuri SCAN), which reads body movement minute by minute and gives time in bed, sleep latency, time awake after sleep onset, total sleep time and efficiency; each morning the archers also filled in a sleep questionnaire (OSA MA). Shooting sessions were two or three per archer, on the days each was available, always at the same time fixed in advance between 8.30 and 11.00, with waking at least an hour before, a breakfast bar of about 200 kilocalories, nothing else to eat or drink but water, no smoking and no alcohol in the preceding twelve hours. On arrival at the range the archers completed the short form of the POMS2, shot, and then marked how well they felt it had gone.

The shooting was twenty arrows at a 36 cm target set at 28 metres, in five ends of four, which is the format of university team matches, with the pace left to the archer. It did not rain on any of the mornings; mean temperature on the testing days was 12.4 degrees and mean wind 1.8 metres per second. The comparisons are paired t tests, with a one-way repeated measures analysis of variance used to repeat the sleep comparison with vigour taken into account.

The authors list five limitations: the study is observational, so it does not establish the direction of the relationship; sleep is measured as quantity, in time, and says nothing about its quality, for which polysomnography would be needed; the archers are few and the women fewer still; the kyudo range is outdoors from the shooting line to the target, so the weather on each morning may have affected the hits; and the athletes came from the same club but from different years and faculties, with different university timetables.

To that can be added that the comparison does not set two conditions against each other, but the best and the worst of two or three mornings: no archer scored the same on every assessment, and a gap of twenty-two percentage points between two mornings can hold a good deal of chance, given that it rests on twenty arrows. The sleep of the night before is a single night. The paper does not say whether the people running the tests knew the results, and the analysis of the night closest to the shooting covers only 10 of the 15 archers. Nothing was manipulated: nobody slept short on purpose. The text is in Japanese, with the abstract and tables in English.

The study is about kyudo, twenty arrows at 28 metres on a 36 cm target, and about how many arrows stay in the target: it does not measure Olympic target scores and it is not about competition, but about a morning's practice. Its result runs against what the authors expected, since the mornings with more hits came after shorter, less efficient nights, and with a slightly lower reported sense of vigour.

It does not follow that sleeping less helps anyone hit the target. The link between sleep and hits disappears once mood is taken into account, nobody changed their sleep on purpose, and the authors themselves ask for an intervention study to check the idea. What remains worth knowing for an archer is this: in this group a short night was not followed by a worse morning, and the belief that a poor night dooms the session finds no support here. The authors float the idea that in kyudo a degree of arousal, rather than complete calm, goes with accuracy, but they rest it on two earlier studies and a statistical trend, not on a measurement.