Arm length, strength and archer accuracy: Noor 2023

In 26 archers from a club in Bandung shooting at 30 metres, the authors measured arm length, leg length, a figure they call body mass index and arm strength, and related them to a shooting score. The mean score is 148.62 with a standard deviation of 20.36, from a minimum of 111 to a maximum of 176. The correlations: arm length r = 0.576 (p = 0.002), body mass index r = 0.631, arm strength r = 0.793, leg length r = 0.234 (p = 0.249), the only one that does not reach significance.

The picture changes when the four measures go into a regression together: only arm strength stays related to the score (p = 0.002), while arm length (p = 0.896), leg length (p = 0.414) and body mass index (p = 0.250) lose any relation. The abstract puts this correctly; the paper's conclusion does not, and goes back to saying that arm length, body mass index and arm strength all contribute strongly and significantly, which is the opposite of what the same paper's regression shows.

So there is one thing a reader can take away: among these 26 people, those who pushed and pulled harder on the dynamometer also had the higher score, and leg length had nothing to do with it.

The study is observational and cross-sectional: everything is measured once, with no intervention. The participants are 26 archers active in the provincial sports organisation of Bandung, described as eighteen-year-old males shooting at 30 metres; archers with a history of arm or leg injury liable to affect accuracy, or with balance disorders, were excluded.

That is where the information about the instruments stops, and it matters. The paper does not say which dynamometer measured arm strength, in what position, or over how many attempts. For the shooting score there is no statement of how many arrows it covered, on what face, or in how many ends: the paper calls it primary data collected directly by the researchers and reports only its mean, median and range.

The descriptive values are these: arm length 77.00 ± 5.19 cm (median 77.5, from 67 to 86), leg length 89.12 ± 5.14 cm (median 90, from 79 to 98), body mass index 42.82 ± 17.34 (median 44.1, from 16.9 to 80.6), arm strength 33.39 ± 11.20 in units that are never stated (median 36.8, from 12 to 47.6). The analysis comprises a Shapiro-Wilk normality check, Pearson correlations and a linear regression with the four measures together.

The measure called body mass index cannot be a body mass index: the mean is 42.82, the minimum 16.9 and the maximum 80.6, values that do not exist in a group of young archers. What was actually measured, body mass in kilograms perhaps, the paper does not say, so the correlation of r = 0.631 cannot be interpreted.

The correlation table has its significance column copied from the coefficient column: for body mass index it reports r = 0.631 and p = 0.631, for arm strength r = 0.793 and p = 0.793, while in the text the same two values have p = 0.001 and p = 0.000. The normality check says arm strength is not normally distributed (p = 0.030), and the Pearson correlation is computed anyway.

The sample is 26 people from a single club, all male and all the same age, so the range of stature and strength is narrow and nothing transfers to women, to younger archers or to other distances. The design is cross-sectional, and the word influence in the title is not earned: nothing was changed. Above all there is the score, which is never described: without knowing how many arrows and on what face, there is no judging how stable the measure is that every correlation rests on. And the paper's conclusion contradicts its own regression.

The finding that survives is predictable and narrow: among 26 archers from an Indonesian club, measured once at 30 metres, dynamometer strength went with the score, and when all the measures are considered together it is the only one that holds. Arm length, which looked to matter in the simple correlations, matters no longer once strength is accounted for; leg length never mattered at all.

This is not an argument for strength training, because nobody trained anything here and an association in a small group does not show that raising strength raises the score. Nor is it an argument for selecting archers on body measurements, since the result runs against the direction of the title. And the figure the paper calls body mass index cannot be used for anything, because the values reported do not belong to that scale.

For an archer the honest reading is that this study adds little: it repeats, roughly, that archers with stronger arms tend to score better in a club-level group, and it does so with a score we are not even told the number of arrows for.