Archery biomechanics: Vendrame 2022 review

A systematic review of 41 studies on the biomechanical assessment of archery, published between 1986 and 2021. The authors searched Scopus, PubMed and Web of Science up to 15 July 2021 and sorted the studies by parameter measured, instrument used and result. Of the studies included, 83% appeared in indexed journals and 17% in conference proceedings; by field, 67.5% belong to sport science, 17.5% to human health and physiology and 15% to sports engineering. Almost half (46%) compare groups of different skill levels, usually experts and beginners, while the rest look at a single group, and in 17 of those 22 cases the group is experienced archers.

Eight parameters were collected: duration of the shot phases, muscle activity, postural stability and bow sway, clicker reaction time, body configuration and tremor, heart rate and cardio-pulmonary measures, hand kinematics and grip force. Body sway holds up best: in nine studies out of ten it behaved as an indicator of performance, with experts steadier than beginners and, among elite archers, higher scores when sway was smaller. One study goes the other way and argues that for elite archers stabilising the orientation of the arrow matters more than reducing movement of the centre of mass. On aiming duration the five studies that measured it do not agree: one, on four elite archers, found two who shot worse as the hold lengthened and two who did the opposite; another found arrows more accurate with longer aiming; two found a negative correlation.

On the muscles, the fourteen studies using surface electromyography describe differences between levels: beginners recruit the biceps rather than the back muscles while drawing and tire sooner, while experts bring in the posterior deltoid and middle trapezius and keep the trunk muscles contracted after the release as well. Two studies, though, conclude that performance does not go with the intensity or the type of activation but with the ability to repeat the same pattern on every arrow. On clicker reaction time all four studies agree that a later loose goes with worse scores; in top archers that time is of the order of 150 ms, cannot be seen by eye and, in the authors' view, is already near its physiological limit, so much so that two studies point to the variability of the reaction time from arrow to arrow as a better predictor than its mean. Four studies on elite archers found no link between heart rate and score, while those comparing experts with beginners report lower rates and greater parasympathetic activity in the experts. On the force applied to the bow grip, the single study included found no difference either between levels or with fatigue.

The authors conclude that every experienced archer develops a personal strategy of muscle activation, timing and posture, and that the most promising candidate as a performance indicator is the repeatability of the movement from one arrow to the next. They also flag a gap: of the six studies found on athletes with a disability, only one dealt with the biomechanics of the shot, and only that one entered the review.

The search closed on 15 July 2021 across three databases, Scopus, PubMed and Web of Science, with strings crossing "archer*" against a list of terms on instruments and parameters (force platform, motion capture, stereophotogrammetry, inertial sensors, accelerometer, gyroscope, electromyography, kinematics, postural control, muscle activity, heart and respiratory rate, biomechanics, performance, score, injury, variability), plus a second branch with terms on disability and para sport. Titles and abstracts were read independently by two reviewers, and disagreements were settled in a meeting with the other authors. Only English-language papers on human participants, with or without a disability, were accepted.

After duplicates were removed, only work on target archery was kept. The authors excluded studies that were purely psychological or about arousal, pharmacological studies, those devoted solely to optimising equipment, purely methodological papers developing sensor systems or analysis methods for talent scouting, studies with a single participant and assessments made by visual inspection alone. What remained eligible was work investigating a movement of the archer or a technical aspect tied to the quality of the shot, that is, studies correlating a feature with the score or comparing different skill levels.

Quality was assessed with the Standard Quality Assessment Criteria for Quantitative Studies, a 14-item tool in which each criterion scores 2 if met, 1 in part and 0 if not. Three items, those on random allocation and on blinding of participants and investigators, were dropped as not applicable to this kind of study; the rest were divided into research outline (four items), user study design (three) and results analysis and reporting (four). Each category receives a score from the ratio of total obtained to maximum possible, with thresholds at 0.5 and 0.75 separating low, medium and high quality. From each paper the authors extracted journal and year, aim, sample size and skill level, experimental set-up, parameters, sensors and significance of the results, collected in a table that also records bow type, shooting distance and the muscles instrumented.

The synthesis is descriptive: the authors count the studies that find a parameter relevant and those that do not, but they do not pool the results in a meta-analysis and report no effect sizes, so a study on two archers weighs the same in that count as one on forty. The authors themselves write that the picture turns out contradictory and that a direct comparison between results is hardly feasible, given the differences in protocol and instrumentation.

The inclusion criteria also decide what the review cannot say. English-language papers only: much of the Japanese, Korean, French and Turkish literature stays outside. No studies on a single participant, none that are purely psychological or about arousal, none devoted to equipment, no methodological papers on sensors, so anyone looking for tuning, materials or mental preparation will not find their survey here. The search closes in July 2021, so later work is absent.

On quality, the weakest category is the design of the studies on participants, because of thin description of the archers and the set-up: bow type, target size and shooting distance are not always stated, and many studies have fewer than five participants, with two to eight in the work on phase durations. The authors also note that restricting attention to the high-quality studies does not change the proportions between supportive and unsupportive results, which means the quality filter does not help in deciding. The assessment tool, moreover, was used without three of its fourteen items.

Two points of internal accuracy. In the data extraction table the 1990 Clarys study appears three times, once for each of its experiments, so the rows of the table and the count of 41 studies do not line up. At one point a reference does not match: the claim about who first recorded the sound of the clicker with a microphone is attributed to Heller but points in brackets to Callaway and colleagues.

The review works as a map rather than an answer: it says which questions have been asked about the archer's movement, with which instruments, and how often the answers contradicted one another. For someone who shoots, the sturdiest result concerns body sway, which behaved as an indicator of performance in nine studies out of ten; on aiming duration, by contrast, the five available studies point in opposite directions, so the belief that holding longer, or shorter, adds points does not rest on this literature.

A few numbers are worth keeping as reference points. Clicker reaction time in top archers is of the order of 150 milliseconds, so it cannot be seen with an ordinary camera and, on the authors' reading of the studies, sits close to its physiological limit: among archers who are already strong, the variability from arrow to arrow separates them more than the mean value does. Heart rate, across the four studies on elite archers, showed no association with the score.

The general conclusion has a concrete consequence for how measurements are read. Experienced archers differ from one another in muscle activation, timing and posture, so comparing one's own measurements with those of a single champion taken as a model says little, and what separates the better archers in these studies is how closely each arrow resembles their own, not someone else's. A declared gap remains too: on the biomechanics of para-archery only one included study exists, so on that technique the registry has almost nothing to cite.