Trunk muscles in archers: Azhar 2021 study

In 28 Indian male archers aged 18 to 28, split into beginners (9), trained archers (10) and elite archers (9), the activity of two deep trunk muscles, transversus abdominis and lumbar multifidus, increased with level. Measured with surface EMG over 10 shots and expressed as a percentage of maximal voluntary contraction, transversus activity during the release phase averaged 12.15% in beginners, 23.89% in trained archers and 32.85% in elite archers; multifidus activity in the same phase was 8.63%, 13.28% and 15.46%. The co-contraction index between the two muscles followed the same pattern: between 8.19 and 14.65 in beginners depending on the phase, and between 21.67 and 27.50 in the elite group.

The differences between groups were significant for all three measures, but between trained and elite archers only transversus differed, while multifidus and co-contraction were similar. Across the phases of the shot only transversus changed, with a significant difference between anchor and release (from 22.90% to 32.85% in the elite group); multifidus and co-contraction stayed roughly constant from set-up to follow-through. There were no differences from one shot to the next.

The archers came from the Jawaharlal Nehru Stadium in New Delhi: beginners had less than six months of practice, trained archers between a year and a half and three years with some competition, and elite archers at least three years and national or international competition. Anyone with low back pain in the previous six months was excluded. Electrodes were placed on one side only, opposite the bow arm: for transversus 2 cm forward and inward from the anterior superior iliac spine, for multifidus beside the spine at the level of the posterior iliac spines. The reference maximal contraction was recorded with a forced exhalation followed by drawing in the abdomen for transversus, and with prone trunk extension against resistance for multifidus, as the mean of three 5-second trials.

Each archer shot 10 arrows in 200 seconds at 10 metres, in the laboratory, after a ten-minute warm-up. The shot was split into five phases, marked by verbal cues: set-up, draw, anchor, release and follow-through. The analysis is a three-way ANOVA (group, phase and shot) followed by pairwise comparisons.

The study measures how much the muscles are active, not how well the archers shoot: there is no score, and the conclusion that trunk stabilisation exercises are needed does not follow from these data. Higher activation in the elite group could be a training adaptation, but it could also reflect heavier bows or different physiques: draw weights are not reported, nor is the type of bow. Ten metres is not a target archery competition distance, even though the paper presents 10 arrows in 200 seconds as the standard protocol of international events.

There is also a known technical limitation: at that site a surface electrode cannot separate transversus abdominis from internal oblique, so the signal is very likely a mix of the two. The tables contain several inconsistencies: units given as millivolts for percentage values, an F of 200 with p = 0.941, p values that differ between text and table (0.031 against 0.311 for the group by shot interaction, p ≤ 0.001 against 0.089 for multifidus between trained and elite archers), and a phase by shot interaction described in the same sentence as both significant and not significant. The sample is made up only of young men, measured on one side.

The study describes something plausible: in more experienced archers the deep trunk muscles work harder, and together, throughout the shot, and transversus rises at the release. It does not show that strengthening them improves shooting, since nobody was trained or followed over time, nor that higher activation is an advantage: it could simply mean more effort to hold a heavier bow.

Anyone who already does trunk work as part of their conditioning finds no reason here to stop, and no evidence that it adds points. Finding that out would take a study with an exercise programme and a control group, which the authors themselves suggest as the next step.