Recurve shooting technique by skill level: Simsek 2014

Twenty-seven Turkish recurve archers split into three groups of nine, elite, mid-level and novice, with surface electromyography on nine muscles of the drawing side and two high-speed cameras on the hand holding the string. The fall of the clicker fires an electrical signal recorded alongside the muscle signal, and the analysis windows are the four hundred thousandths of a second before the click and the eight hundred after.

On muscle activation the differences between groups come out significant, with p below 0.05, for the extensor digitorum communis, the flexor digitorum superficialis, the middle and posterior deltoid, the middle trapezius and the lower trapezius. The anterior deltoid and the pectoralis major work the same way at every level. The upper trapezius appears in both lists, among the significant and among the non-significant, in the same sentence of the article.

The description in the discussion is more informative than the abbreviations. The novices, in the four hundred thousandths before the click, activate the forearm flexors and extensors beyond their own maximum reference value; at release the flexor activity falls gradually and the extensor activity rises. The mid-level archers sit at lower percentages, but both activities tend to rise as soon as the clicker falls. The elite archers have lower percentages than either other group and an activation that falls away gradually. On the proximal side, in the final phase of the draw the elites engage the posterior deltoid and the middle trapezius more than the others, while the lower trapezius is more active in the mid-level archers and the novices.

On the kinematic side, the joint angles of fingers, wrist and elbow and their changes over time do not differ between the three groups, with p above 0.05. The authors write that a difference is detected all the same in a graphical sense.

The conclusion is that as the level rises the weight of the string is carried by the proximal muscles, while those at the beginning and those halfway tend to draw with the distal musculature.

Proceedings of the thirty-second international conference on biomechanics in sports, four pages, 268 to 271.

Three groups of nine: elite, mid-level, novice. Informed consent, procedures conforming to the declaration of Helsinki and approval from the local ethics committee. A standardised fifteen-minute warm-up, five of active upper-body movement, five of stretching and five of shooting. A single test session, of six shots.

Before the shots, the maximum isometric voluntary contraction was obtained for each of the nine muscles, serving as the reference for expressing activity as a percentage. The nine are the flexor digitorum superficialis, the extensor digitorum communis, the anterior, middle and posterior deltoid, the upper, middle and lower trapezius, and the pectoralis major.

Recording with a sixteen-channel wireless system, pass band between 20 and 500 hertz, sampling at 2000 hertz, maximum inter-electrode impedance of 6 kilohms and common mode rejection of 95 decibels. The snap of the clicker triggers a five volt logic signal recorded alongside the muscle signal: from its rising edge come the four hundred thousandths of a second before, as the pre-clicker interval, and the eight hundred after. The signals were full-wave rectified and filtered with a moving average over a window of one hundred thousandths of a second.

For the kinematics, two high-speed cameras at 500 frames per second, set at seventy degrees to one another at a height of one and a half metres, record full draw, aiming and release. The successful trials were digitised automatically with seventeen markers; the article names eight of them, among which the distal phalanx, the distal and proximal interphalangeal joints, the metacarpophalangeal joint, the ulnar styloid, the lateral epicondyle, the triceps insertion and the greater trochanter.

The analysis uses descriptive statistics for the groups, the mean of each participant's six shots, and one-way analysis of variance to compare activity between groups in each time interval, followed by Tukey pairwise comparison. Threshold at p below 0.05.

In describing the electromyographic data the article speaks of twelve shots per participant, while the protocol gives six.

Every difference in this study is a percentage of each person's maximum contraction, and one line of the discussion says that reference did not hold: the novices activate flexors and extensors beyond their own maximum value during aiming. An activation above one hundred per cent of the measured maximum means the maximum was measured too low, which is exactly what happens in people unused to producing a maximal effort on request. Since the comparison between groups runs entirely through that normalisation, part of the main result, that novices use the distal musculature more, may come from the reference rather than from the movement. Nothing in the article allows that part to be estimated.

The article contains not one number beyond the thresholds. No amplitude, no mean, no F value, no measure of effect, no interval: there are two lists of abbreviations, one with p below 0.05 and one with p above. Nine muscles compared across several intervals with an analysis of variance, and no mention of any correction for the number of comparisons.

And the two lists do not stand together. The upper trapezius appears in both within the same sentence, among the muscles with significant differences and among those without. The list of muscles compared names eight and leaves out the lower trapezius, which then turns up among the significant ones. The number of shots is six in the protocol and twelve in the description of the data. These are drafting inconsistencies that four pages of proceedings never resolve, and they leave a reader with no way of knowing which version was used.

The kinematic part also has to be taken for what it says. The angles of fingers, wrist and elbow do not differ between groups, with p above 0.05, and the article adds that a difference is detected in a graphical sense. A non-significant result does not become a result because a curve looks different, so the kinematics should be read as a null. As a null, for that matter, it is interesting.

The explanation the authors give for the proximal side was never measured. They write that the elites bring the scapula towards the spine forming an angle of forty-five degrees thanks to the horizontal force of the middle trapezius and the rhomboids: the rhomboids were not among the nine muscles, they lie beneath the trapezius and surface electrodes do not reach them, and no scapular angle was recorded. That sentence is a theoretical reconstruction, not a measurement. In the same way, separating the upper, middle and lower trapezius with surface electrodes invites cross-talk between neighbouring portions, and the article does not discuss it.

The conclusion, too, is sharper than its own data support. The weight of the string passing to the proximal muscles holds for the posterior deltoid and the middle trapezius, but the lower trapezius is proximal as well and goes the other way, being more active in the mid-level archers and the novices. The picture is therefore a shift between different proximal muscles rather than a simple more-proximal in the experts.

Of the participants nothing is known: no age, no sex, no years of practice, no draw weight, and the word elite is never defined. There is no score, so nothing links the activation to accuracy. One session, six shots, nine people per group.

Finally there is a hypothesis announced and not reported: the introduction says reaction time is expected to be shorter as the level rises, and in the results reaction time never appears.

The picture this study describes is one a coach recognises at once, and it is worth keeping even without the numbers. The novice draws with the fingers and the forearm, to the point of exceeding their own reference maximum while aiming; the mid-level archer sits lower but stiffens further still at the click; the elite archer sits lower than either and their activity, instead of rising, falls away gradually. Put in the terms of a shooting hall: in the strong archers the hand is not doing the work, and at release it lets go rather than adding.

On the back side the reading is finer than drawing with the back. In the final phase of the draw the elites engage the posterior deltoid and the middle trapezius more than the others, that is they bring the scapula towards the spine horizontally; the other two groups use the lower trapezius more, which brings it downwards. So it is not more back against less back, it is one part of the back instead of another. The geometric explanation the authors give, with the forty-five degrees and the rhomboids, was not measured and remains a line of reasoning.

There is also a null result worth knowing: across the three levels the angles of fingers, wrist and elbow at release do not differ detectably. If there were a release geometry belonging to the stronger archers, twenty-seven archers would have been the place to see it. What separates the levels in these data is how much and when the muscles switch on, not the shape of the movement.

What this card draws from it is no exercise and no threshold. There are no percentages to reach, because the values are not published and because the reference they were computed against did not hold in the novices. The registry keeps this work as a cross-sectional comparison across three levels, with good instrumentation and bare reporting, useful for the direction of the shift from distal to proximal and for the null on the kinematics, and not for any measurement.