Heart rate and attention in archery: Vrbik 2015

Eight archers from a Zagreb club, four recurve and four compound, each shot 15 arrows at 18 metres wearing a heart rate chest strap and an EEG headset with a single electrode on the forehead, which produces two scores from 0 to 100 that the manufacturer calls "attention" and "meditation". Values were read 2 seconds and 1 second before release, at release and 1 second after.

The compound archers averaged 9.17 points per arrow against 8.80 for the recurve archers, with a higher heart rate (111.48 beats per minute at release against 103.18) and a higher attention score (62.45 against 45.37), while the meditation score was similar, around 55. In both groups heart rate was higher at release than in the two seconds before it, and peaked one second after it.

The least expected finding concerns the score of individual arrows: in both groups the 10s came with a faster heart rate than the 8s. At release the recurve archers averaged 97.86 beats on arrows scoring 8, 104.92 on 9s and 107.00 on 10s; the compound archers 101.25, 110.12 and 118.50. The attention score went the other way and was higher on the 8s than on the 10s, with its highest value, 83.5 at release, on the only four compound arrows that scored 8.

Testing took place in an ordinary indoor hall, one archer at a time, on the 40 cm triple face. After 9 warm-up arrows each archer shot 5 ends of 3 arrows with no particular instructions, knowing only that heart rate and brain waves were being recorded. The group comprised 3 women and 5 men, aged 26.34 on average (standard deviation 12.85), with 7.76 years of shooting and a season's best of 553.5 in the World Archery 18 m indoor round; seven were right-handed and one left-handed.

Heart rate came from a Polar RS800CX monitor; the mental scores from a NeuroSky MindWave Mobile headset with a dry electrode at Fp1 and the reference on the ear, which computes attention and meditation once a second with the manufacturer's own algorithm. Two webcams filmed the archer, to fix the moment of release, and the heart rate monitor's display, whose clock was synchronised by hand with the computer. Arrows scoring 6 and 7 were left out of the comparison by score because there were too few of them. Differences between bow types and between scores were analysed with analysis of variance.

The statistics treat the 120 arrows as 120 independent observations, when they come from eight people: with four archers per group, the differences between recurve and compound may come from the individuals rather than the bow, and the very small p-values are inflated as a result. The link between heart rate and score may likewise reflect who was shooting better, rather than what happened on each arrow.

The attention and meditation scores come from an unpublished commercial algorithm, working on a single frontal electrode close to the eyes and the facial muscles, and the paper does not show how far they match what their names suggest. Heart rate is read second by second, so it says little about variability, although the discussion refers to it. The compound table repeats the same meditation values twice for arrows scoring 10, and they do not match those in the other table. The title speaks of expert archers, but the average level, 553 indoors, is that of a good club archer, and the shooting was done at 18 metres in training, without the pressure of competition.

The most concrete figure is heart rate during the shot: on average between about 95 and 120 beats per minute in club archers, higher at release than in the two seconds before and higher still a second after. In this small group a faster heart rate did not go with poorer arrows, if anything the reverse; that is no reason to try to raise it, but it is a reason not to assume that lowering it improves the score.

On using consumer EEG headsets to measure concentration in training, the study offers no solid ground: the scores move, but it is not clear what they measure, and on these arrows the highest "attention" went with the lowest scores.