Arm length and archery score: Rabbani 2023 study

At a university club in Jakarta the authors measured arm length, VO2max and plank hold, and related them to the score over 60 arrows at 18 metres shot with the Indonesian standard bow, analysing the data with a path analysis. The mean score is 555.13 out of 600, with a standard deviation of 26.01 and values between 495 and 594; arm length is 73.96 ± 2.25 cm, VO2max 46.46 ± 2.88, and the plank hold 269.30 ± 25.68 in units the paper never states and which the context makes seconds.

All three factors come out related to the score, with very different weights: the path coefficient for VO2max is 0.520 (p < 0.001), for the plank hold 0.266 (p = 0.022), and for arm length 0.253 (p = 0.017). VO2max and arm length are also related to the plank hold, with coefficients of 0.511 (p = 0.011) and 0.399 (p = 0.040), and through that route the authors compute indirect effects on the score of 0.138 and 0.106.

The striking figure is the weight given to VO2max, which would account on its own for 27% of the variation in score in a static task at 18 metres. The paper makes no attempt to explain by what mechanism maximal oxygen uptake would act on the score in a task of this kind.

The study calls itself quantitative, with a survey method and a correlational design, on athletes of the Fortius club at Jakarta State University. The number of participants appears twice with two values: 24 in the abstract, 23 in the results section.

The shooting test is a score at 18 metres with the Indonesian standard bow, in two sessions of ten ends of three arrows, for a total of 60 arrows and a maximum of 600 points. Arm length is the distance from the acromion to the tip of the middle finger, taken with an anthropometer. VO2max is estimated with the progressive shuttle test, the bleep test, although the abstract calls it a Balke test, which is a different protocol. What is called core stability is the plank hold.

The analysis is a path analysis over seven hypotheses: three direct effects on the score, two effects on the plank hold and two indirect effects. For each one the paper gives the coefficient, the p value and a percentage contribution obtained by squaring the coefficient. There is nothing on age, sex, years of practice or draw weight, the correlation matrix is not shown, and the period in which the data were collected is not stated.

The design is cross-sectional and everything is measured on one occasion, so the word influence in the title and the causal language of the path analysis are not earned: a path analysis imposes a structure of causes on the data rather than deriving one from them.

The sample is too small for that kind of analysis: with twenty-three people and four variables the coefficients rest on very little information, and their intervals, which the paper does not report, would be wide. The number of participants is itself uncertain, twenty-three or twenty-four depending on where you read, and the group's age, sex and experience are unknown.

Some of the arithmetic uses the coefficients of other paths. The contribution of the plank hold is computed in the printed formula from 0.520, which is the VO2max coefficient, even though the result (7.07%) is the square of 0.266. The total effects are summed using the coefficients towards the plank hold instead of those towards the score: 0.399 plus 0.106 for arm length and 0.511 plus 0.138 for VO2max, where 0.253 and 0.520 should stand in first place.

Two substantive limitations remain. VO2max, the strongest predictor, is more plausible in a static task at 18 metres as a general marker of how much an athlete trains than as a cause of the score, and the study does not separate the two. And the shooting is done with the Indonesian standard bow, a school bow of fixed draw weight, so the values transfer neither to Olympic recurve nor to compound. The introduction, finally, announces an intervention of psychological exercises that appears nowhere in the study.

For an archer the content is an association in a small group: among twenty-three university athletes shooting at 18 metres with the standard bow, those with a higher VO2max and those who held a plank longer also had the better score, and VO2max came out much more strongly related to the score than the other two factors. Arm length counts for little and cannot be changed anyway.

Before making anything of it, it is worth asking where that link can come from. VO2max is measured with a shuttle run, and in a university group the better runners are often those who train more in general: the number may describe the amount of training rather than a mechanism acting on the shot. The study does not separate the two, because it measures everything in the same period and changes nothing.

What is left is an observation rather than a pointer: it does not show that improving aerobic fitness raises the score, it does not say how much plank work is needed, and the setting, a school bow at 18 metres in a university club, is not that of a competition with an Olympic recurve. The one thing that can be stated is that in this group the three measures were not independent of the score, and that the one most strongly related to the result was also the least specific to archery.