Shoulder muscles in compound archers: Mat Salleh 2024

Twenty-four compound archers from a Malaysian state team, 10 men and 14 women aged 14 to 22, shot nine arrows at 18 metres wearing six surface EMG sensors: middle and posterior deltoid and middle and lower trapezius on the drawing side, triceps and anconeus on the bow arm. Split by score into three groups of eight (elite, intermediate, junior), they showed no significant difference in the activation of any of the six muscles, and the same applies to the comparison between men and women.

Mean values, expressed as a percentage of maximum voluntary contraction, lay between 15 and 36%. In the elite group the highest were anconeus (35.6%) and middle trapezius (32.0%), in the juniors again anconeus (31.5%) and middle trapezius (29.5%), and in the intermediate group posterior deltoid (27.1%) and lower trapezius (26.5%). The largest difference, not significant, concerns lower trapezius: 27.3% in the elite group and 15.6% in the juniors (p 0.12). The authors also report that 74.64% of the archers used posterior deltoid, 68.61% middle trapezius, 55.89% anconeus and 49.6% lower trapezius, without explaining how these percentages were calculated.

The archers shot with their own bows and arrows on the range, after their usual warm-up of three ends at 10 metres, at a vertical compound triple face (given as 3 x 20 cm) at 18 metres, with about 30 seconds between shots. The EMG system was a wireless Delsys Trigno, and electrodes were placed according to a reference atlas after the skin had been cleaned and shaved. For each archer the mean of the nine shots was calculated and then the group mean; the three groups were compared with one-way analysis of variance, while the test used for men and women is not stated.

Groups were assigned by score: 341 to 360 for elite, 321 to 340 for intermediate and 301 to 320 for junior. The methods do not describe how the reference maximum contraction was measured, which phase of the shot was analysed (draw, aiming or release), or the type of release aid used.

Eight archers per group is too few to detect moderate differences, and the standard deviations often reach half the mean or more, so the absence of significant differences says little. The groups are also less distinct than they should be: according to the methods the intermediate archers scored between 321 and 340 and the juniors between 301 and 320, but the table gives them mean best scores of 347.1 and 329.5, outside those ranges. The text also says the best score refers to 30 metres, whereas the test was at 18.

The EMG signal is averaged over the whole shot without separating phases, and the maximum contraction test used to normalise it is not described; the coefficient of variation quoted refers to injured and uninjured conditions that do not exist in this study. The percentages of archers using a muscle are not defined. In the discussion anconeus and middle trapezius are said to be significantly activated in the elite and junior archers, but no comparison was significant. On the bow arm only triceps and anconeus were measured.

The study is one of the few to look at shoulder muscles in compound archers, but it reaches no findings that change anything for someone who shoots: between archers of different levels, and between men and women, mean activation of the six muscles measured did not differ. The clearest descriptive finding is that at 18 metres, with their own compound bows, these archers were working at between 15 and 36% of their maximum contraction, and that anconeus, a small elbow muscle on the bow arm, was among the most active.

The authors take this to mean that a compound should be shot by relying on bone structure rather than muscle, and they link anconeus to bow-arm stability at draw weights of 45 to 60 pounds. These are their interpretations, not measurements: the study did not record draw weight, elbow position or the accuracy of individual shots. Higher lower trapezius activity in the elite archers than in the juniors is a trend that larger studies may or may not confirm, not a finding.