Slow breathing for archers: Russo 2017 review

This is a narrative review by three authors from an Australian pain clinic on what happens in the body of healthy people when they breathe slowly, which the authors define as 4 to 10 breaths a minute, against the usual 10 to 20. It presents no new data: it brings together studies on breathing, circulation and the autonomic nervous system.

The thread of the review runs as follows. As breathing slows, each breath gets larger and gas exchange becomes more efficient; heart rate and blood pressure swing more in time with the breath; heart rate variability (HRV) and the sensitivity of the reflex that regulates blood pressure increase, peaking at around 6 breaths a minute, the so-called resonant frequency, which nonetheless varies from person to person. On the autonomic nervous system, the studies cited point to a shift towards the parasympathetic side, the one associated with recovery; the authors stress that slow breathing does not switch off the sympathetic system but appears to make it more responsive and better balanced. They propose 6 to 10 breaths a minute, with deeper breaths driven by the diaphragm, as an "optimised" pattern, and note that no adverse effects in that range have been reported in the literature.

The authors searched Medline for studies of breathing at 4 to 10 breaths a minute in humans, excluding those involving respiratory loads, breathing devices, other breathing techniques, meditation, yoga, exercise or diet, and widened the search to basic physiology as they wrote. They do not say how many studies they found or by what criteria they selected or assessed them, and they do not pool the results numerically.

Each section starts from the physiology of normal breathing and then moves to the effects of slow breathing, in this order: the respiratory system, the cardiovascular system, the interaction between heart and breathing (HRV, the blood pressure reflex, respiratory sinus arrhythmia) and the autonomic nervous system. A closing table summarises the effects, using italics to separate those documented from those hypothesised.

Like any narrative review, it depends on the authors' choices: with no stated criteria there is no knowing how complete it is or how much weight small studies carry. Many of the effects summarised come from short laboratory trials with people sitting or lying down and breathing at a set pace; the authors themselves note that recordings during sustained practice are scarce. Some mechanisms, such as the origin of respiratory sinus arrhythmia, are presented as still debated, and the ratio of low to high HRV frequencies, used to describe sympathetic and parasympathetic balance, is called a qualitative index by the authors themselves.

The closing table mixes measured effects and hypotheses, separated only by italics, and the reference to health and longevity is the authors' outlook rather than something the review demonstrates. Sport is not covered: there are no studies of athletes, of precision tasks or of breathing during effort.

For archers the review is useful as physiological background, not as a method. It explains why a few slow, deep breaths quickly change heart rate and HRV, and where the figure of about 6 breaths a minute comes from: the rate at which, in laboratory studies, HRV and the blood pressure reflex peak. It says nothing about shooting: it does not deal with aiming, with holding the breath during the draw or with performance, and it does not show that higher HRV before an end leads to better arrows.

In the registry it counts as background on the physiology of slow breathing in healthy people. Claims linking breathing, HRV and shooting need studies that measure archers while they shoot.