Heart rate variability in novice archers: Tok 2020

In 39 Turkish university students at the end of their first archery course, heart rate variability (HRV) was recorded at three points: seated at rest, during a set of 10 arrows, and during recovery. Across the whole group the only component that changed was high-frequency (HF) power, usually read as parasympathetic activity: it rose from rest to shooting, and in recovery it was no longer significantly different from rest (F = 6.90, p = 0.002, eta squared 0.15). Low-frequency (LF) power and the LF/HF ratio showed no significant differences between the three points (p = 0.055 and p = 0.084).

The authors then split the sample at the median score, 76 points out of 100: judging by the degrees of freedom, 22 archers at or above the median and 17 below. In the lower-scoring group no component changed. In the better group both LF and HF changed; for HF the pairwise comparisons confirm the rise from rest to shooting, while for LF no pairwise comparison survives the Bonferroni correction. Between the 27 men and the 12 women the changes relative to rest were almost identical.

Mean LF and HF values at the three points appear only in the figures, not in the text or in a table, so the direction of the changes and their statistics are known but not their size.

The participants were 39 students at Celal Bayar University in Manisa, aged 18 to 27 (mean 23.5), with no archery experience before a 14-week course. The test took place during the course's final exam, between 9 and 11 in the morning with no spectators, and course credit required at least 60 points: a setting with some pressure, though not a competition. The sessions were run by one of the authors, a former international archer. Each student had 6 practice shots to adjust the sight, then shot 10 arrows in 4 minutes at 18 metres on an 80 cm face, at their own pace; only the first 10 counted.

HRV came from a three-electrode chest ECG (a Nexus-10 system with Biotrace software, sampling at 1,024 Hz). Recordings covered 4 minutes seated at rest, the 4 minutes of shooting, and recovery, measured after a further 4 minutes of rest following the set; how long this last recording lasted is not stated. Beat-to-beat intervals were cleaned of artefacts by eye and split by Fourier transform into the two bands, LF from 0.04 to 0.15 Hz and HF from 0.15 to 0.40 Hz. The three points were compared with repeated-measures analysis of variance; to compare men and women the authors expressed the shooting and recovery values as a percentage of the resting ones.

Breathing was not controlled, as the authors acknowledge: in shooting the breath is slowed and held, and the HF band depends heavily on breathing rate. The rise in HF during shooting may therefore reflect the way the archers breathed rather than a shift in autonomic balance. Reading LF as sympathetic activity is also contested in the HRV literature, and is even less secure during physical activity.

The sample consists of beginners on their first course, shooting at 18 metres with equipment that is not described: bow type and draw weight are not given. The split into better and worse shooters rests on 10 arrows, a very noisy basis for ranking an archer, and the fact that one group changed while the other did not does not show that the two groups differ from each other: there is no direct comparison between them. In their practical applications the authors speak of increased sympathetic activity in the better archers, yet for LF the pairwise comparisons found no differences.

There are also small inconsistencies: the age range is 21 to 27 in the abstract and 18 to 27 in the methods, and the abstract says recovery was measured immediately after shooting while the methods describe a 4-minute rest first. There were only 12 women, and the menstrual cycle, which affects HRV, was not taken into account.

For archers the study offers little that can be used directly. It shows that during a set of 10 arrows a beginner does not show the cardiac response typical of physical effort, in which HF falls: here it rises, probably in part because shooting imposes slow, controlled breathing. This fits the idea that archery is a precision task more than an endurance one, at least at 18 metres and in beginners.

The link with score is weak: two groups split on 10 arrows, with no direct comparison between them and values visible only in the figures. The authors suggest that coaches could look at HRV during shooting to see how an archer controls their breathing; this is an idea to be tested, not a conclusion of the study, which says neither what values to look for nor what to do with them. For anyone measuring HRV with an app there is one useful point: breathing during shooting shifts the numbers, so a reading taken while shooting cannot be compared with one taken at rest in the morning.