Ground forces and skill level in archers: Simsek 2019

Twenty-seven recurve archers, all male and right-handed, shot at 18 metres while standing on a force plate, and the study compares how much the body swayed during the phases of the shot across three levels of experience. The groups, of nine archers each, were formed on FITA score: the beginners averaged 1.4 years of shooting and 915.2 points, the intermediate group 6.6 years and 1150.3 points, the elite group 8.7 years and 1244.5 points. Reaction time to the clicker also fell with level: 167.2 ms in the beginners, 140.0 in the intermediate group and 111.6 in the elite.

The elite group had the lowest values of the two horizontal forces, fore and aft and sideways, in every phase, but the differences between groups were not significant. The only significant difference concerns the range of movement of the centre of pressure, the point under the feet where the push on the ground is concentrated: it was smaller in the elite than in the beginners, while the intermediate group sat in between without differing from either. These values appear only in graphs, with no figures in the text or a table. From the graphs the authors also describe a pattern shared by all three groups: sway is smallest during the draw and at full draw and largest just after the clicker drops.

The archers came to the laboratory twice, first for body measurements and to get used to the force plate, then for the test. After a 15-minute warm-up (5 minutes of upper-body movement, 5 of stretching and 5 of shooting at short range) they shot at 18 metres on the 40 cm face, with their own bow and arrows, but all with a square stance imposed by the study. Before shooting they stood still for 10 seconds on the line with their equipment, to record a reference posture. The instruction was to aim for the 10, with no time limit, and only successful shots were analysed.

The force plate (Kistler 9281EA) recorded at 2000 Hz and forces were normalised to body weight; a high-speed camera at 500 frames per second filmed the archer from the side. A switch on the clicker lit an LED on the archer's belt and sent a signal to the plate, so every shot is aligned to the clicker dropping: the window analysed runs from 400 ms before to 800 ms after. The centre of the target was lined up with one axis of the plate, so that one force represented the fore and aft push and the other the sideways push. Groups were compared with a one-way analysis of variance followed by Tukey's test.

The paper does not say how many shots were recorded per archer or what counted as a successful shot, and it does not report the centre of pressure values, which can only be read off the graphs. Clicker reaction time is in the table, but how it was measured is not described. Some figures do not add up: the intermediate group should lie between 1100 and 1150 points, yet its mean is 1150.3, so some of its members were above the elite threshold; draw weight is given in kilograms (34.8, 35.5 and 44.0), values that make sense only as pounds.

The discussion goes beyond the results: it states that the hypothesis is supported by a significantly different use of forces, which did not in fact differ, and credits the elite with less asymmetry between the legs, which a single plate under both feet cannot measure. Reading the sideways force as weight shifting from one foot to the other is also the authors' interpretation. The study is cross-sectional, men only, at 18 metres, with the same stance for everyone, which for archers who usually shoot with an open stance was not their normal position. The elite group also had more years of shooting and heavier draw weights, and the visual force feedback training the authors recommend was not tested.

The study adds one more data point to a familiar picture: better archers sway less on their feet, but here the difference shows only between the extremes, the elite and beginners with little more than a year of shooting. Between the intermediate and elite groups the force plate did not separate the archers, and the horizontal forces did not differ in any phase. It therefore does not show that reducing sway raises scores, nor that balance training helps anyone shoot better: it compares different people at a single point in time.

For coaches the more interesting finding is when the body moves most, just after the clicker drops, which held at every level: the peak comes with the clicker and the release, not during the draw. The difference in clicker reaction time, more than 50 ms between beginners and elite, should be treated with caution too, because the paper does not explain how it was measured.