Force plates, senior and junior national archers: Ely 2026

Twenty recurve archers from the Brazilian national teams, thirteen from the senior squad and seven from the junior squad, shot eighteen arrows at 70 metres outdoors at the federation's centre in Rio de Janeiro, with one foot on each of two force plates. The study compares the two groups on how far the centre of pressure moves under each foot while aiming, forwards and backwards and sideways, and on score.

On none of the four centre of pressure measures do the groups differ. Under the foot of the dominant leg, which for a right-handed archer is the right, forward-backward displacement is 21.49 millimetres in the seniors and 19.73 in the juniors, lateral displacement 5.54 and 5.56; under the other foot 21.10 and 19.66 forwards and backwards, 3.65 and 3.17 sideways. All p values lie between 0.47 and 0.98, and if anything the seniors move slightly more. In both groups the forward-backward displacement under each foot is about four times the lateral one.

Score, on the other hand, separates the groups: 8.67 points per arrow for the seniors against 7.85 for the juniors (p = 0.009, Cohen's d 1.38), with scores far more consistent from one archer to the next among the seniors (coefficient of variation 3.97% against 11.58%). The seniors also had more years of practice, 14.4 against 5.7, and more body mass, 78.9 against 64.4 kilograms. Taking these two variables into account, the estimated difference in score stays almost the same, 0.79 points instead of 0.82, but the confidence interval widens until it touches zero (from -0.01 to 1.58, with p = 0.052). The authors state plainly that finding no difference in stability does not mean the two groups are equivalent.

The data were collected between March and May 2025 at the Brazilian confederation's training centre, as part of the teams' routine assessments. The seniors were seven men and six women with a mean age of 28, the juniors two boys and five girls aged 17.4; all trained between 20 and 50 hours a week. Height, body mass, age and years of practice were reported by the athletes on an online form.

After two warm-up ends to adjust the sight, each archer shot three ends of six arrows at 70 metres on a 122-centimetre face, with the feet in their own shooting stance and one on each of two Vald plates at 500 Hz. For each arrow the centre of pressure was analysed over the stabilisation phase, from when the bow settles in the aim to the instant before the release, with a filter that removes frequencies above 5 Hz; each archer's value is the mean of their arrows, in millimetres, not normalised for body mass. The dominant leg is the one on the side of the drawing hand.

The groups were compared with the t test or the Mann-Whitney test, with effect sizes, and then with an analysis of covariance that takes body mass and years of practice into account, which the authors present as an exploratory check.

There are seven juniors, and with groups this small the study does not have the power to detect modest differences: no sample size calculation was done beforehand, because the sample was made up of every athlete available. Wind, which at 70 metres outdoors moves both archer and bow, was measured neither arrow by arrow nor end by end, and may have masked differences between archers. Eighteen arrows are few compared with a qualification round.

The centre of pressure is measured under each foot separately. The choice shows how the two legs work, but it is not the whole-body sway that other studies measure on a single plate: the shift of weight from one foot to the other, which moves the body sideways, does not appear in the displacement under a single foot, and a foot's forward-backward displacement is naturally larger than its lateral one, because the foot is longer than it is wide. The paper does not define precisely the measure it reports, which it calls mean centre of pressure oscillation, nor does it say how the plates were oriented relative to the target. The two groups differ in age, body mass and years of practice, and comparing categories does not reveal which of these matters for the score; men and women, and a left-handed archer, sit in the same groups.

Among archers from the same national set-up, the seniors score more than the juniors but are no steadier underfoot. Anyone coaching young archers already at that level can take this from it: the step that separates a good junior from a senior international, in this sample, does not show on the force plate, and a stability measure taken on its own is not enough to say where the room for improvement lies. The authors point to technique, competitive experience and emotional control as possible explanations, without having measured them.

The result does not say that stability is unimportant. It says that among archers who are all elite already, differences in sway, if there are any, are smaller than twenty people and eighteen arrows outdoors make it possible to see.