Muscle asymmetry in recurve archers: Pukhov 2025

Five Russian recurve archers holding the Master of Sport title each shot 36 arrows at 18 metres while the electrical activity of 18 trunk and arm muscles was recorded on both sides of the body. All of them held the bow in the left hand and the string in the right. For each muscle the author calculated an asymmetry coefficient, the difference between right and left divided by their sum: close to 0 means equal activity on both sides, positive values more activity on the right, negative values more on the left.

Over the whole shot the strongest asymmetry was in the forearm of the drawing hand: 0.86 for flexor digitorum superficialis, 0.64 for brachioradialis and for flexor carpi radialis, 0.43 for extensor digitorum. Also more active on the right were the long head of biceps (0.58), erector spinae (0.38), tensor fasciae latae (0.35), posterior deltoid (0.33) and middle trapezius (0.27). More active on the left, the bow side, were serratus anterior (-0.46), pectoralis major (-0.38 and -0.36 in its two portions), latissimus dorsi (-0.27) and upper trapezius (-0.22).

The phases change the picture. During the draw, the muscles that raise and point the bow were more active on the left, between -0.18 and -0.23: upper and lower trapezius, middle deltoid and serratus anterior. From anchor to the clicker falling, and then up to the release, left serratus anterior rose further, to -0.66 and then -0.83; lower trapezius became symmetrical (-0.03) at the release and more active on the right (0.31) in the following half second; middle deltoid went from -0.20 during the draw to 0.09 and 0.10, reaching 0.22 after the release.

Each archer shot 6 ends of 6 arrows at 18 metres, 180 shots in all. Surface EMG was recorded with a 16-channel ME-6000 biomonitor at 2,000 Hz, synchronised with a Qualisys three-dimensional motion capture system at 500 Hz that tracked landmarks on the arms and bow and was used to split the shot into phases. An opto-mechanical sensor mounted between the grip and the sight signalled the clicker falling and the arrow leaving.

Four phases were analysed: the draw, from raising the bow to the drawing hand reaching anchor; the clicker phase, from anchor to the clicker falling; the release, from the clicker falling to the fingers opening; and the follow-through, the half second after that. The set-up before raising the bow and the relaxation phase after the shot were left out as too variable. The asymmetry coefficient was calculated on the signal amplitudes of the two sides, with thresholds taken from the Russian literature: up to 0.10 counts as symmetry, above 0.40 as marked asymmetry. Means are given with their standard error, and comparisons use the Mann-Whitney test.

There are five archers, all with the same orientation, at a single distance (18 metres), and no data link the asymmetry to score or shot quality. The most important limitation is methodological: the paper does not say that amplitudes were normalised, for example to each muscle's maximal contraction. Raw signal amplitude also depends on electrode position, skin and the tissue beneath it, so part of the difference between right and left may not come from what the muscles are doing.

Other points remain unclear. A 16-channel device is reported with 48 leads, and the coefficient is calculated on 24 pairs for 18 muscles, without explaining how the recordings were split; the Mann-Whitney test treats measurements from the same archers as independent; and which differences are significant can only be seen from asterisks on a figure. The conclusion that the right deltoid predominates in the later phases rests, for the clicker phase and the release, on values of 0.09 and 0.10, which by the author's own thresholds count as symmetry. The paper is in Russian, in the journal of a Russian sports university.

The study puts numbers on what recurve archers feel: the movement is asymmetric, with the string hand working mainly through the forearm and arm, and serratus anterior, pectoralis and latissimus predominating on the bow side. The most interesting figure concerns serratus anterior on the bow arm: its predominance on the left side grows from the draw through to the release, just as the force of the bow on the hand is at its highest, and the author reads it as the work that holds the shoulder blade steady against the push of the bow.

It does not say whether more or less asymmetry is an advantage or a fault, since there is no comparison with scores or with less experienced archers, and it says nothing about whether balancing the two sides through physical conditioning is useful. It is a description of five very experienced archers, useful as a reference, not a model to copy.