Posture and draw weight in archery: Ji 2024 study

The same 13 university students as in the paper in Frontiers in Medical Engineering (7 men and 6 women, from novice to expert) shot recurve bows of 25 and 32 pounds at 10 and 15 yards, five arrows per condition. Using inertial sensors and a digital human model, the authors estimated, at the moment just before release, the compression on the L4/L5 disc and the angles of the shoulders, elbows and trunk.

With the 25 lb bow, mean compression was 558.46 and 530.92 newtons in the women and 662.19 and 631.11 in the men, at the two distances; with the 32 lb bow it was 576.27 and 552.05 in the women and 890.60 and 797.03 in the men. The authors sum up the difference as about 100 N with the lighter bow and over 250 N with the heavier one, and note that every value stays below the 3,400 N they take as the safety limit.

With the 32 lb bow the women leant their trunk back much more than the men (-17.02 and -17.47 degrees against -5.24 and -4.58, with p = 0.001 and 0.0002) and flexed the right shoulder, on the string side, less (30.96 and 27.31 against 46.63 and 44.38 degrees, p = 0.024 and 0.032). With the 25 lb bow the men held the left shoulder, on the bow side, more abducted (p = 0.048 and 0.045). The correlation between compression and trunk flexion rose from 0.30 with the lighter bow to 0.45 with the heavier one.

Participants, aged 18 to 30, came mostly from the university archery club, which provided the range and the equipment; the individual table classes them as 5 novices, 4 intermediates and 4 experts. The lower target had its centre 100 cm above the ground. Each person shot five arrows in each of the four combinations, after a free warm-up at every change of bow, supervised by a certified coach.

The Xsens MVN Awinda system, with 17 sensors, recorded the movement, which was streamed in real time to a model built from each participant's measurements in Siemens' JACK software. For the pose just before release, the force on the string hand was treated as horizontal, along the arrow, and the force on the bow hand as equal and opposite, plus the weight of the bow; string force was measured with a digital force gauge. From posture and forces the software calculated lumbar compression. The comparisons were a two-way analysis of variance, t tests by sex and by task, and correlations.

The limits of the companion paper apply here too. Compression is calculated by a model and depends on the forces assigned to the hands, and the force gauge readings are not reported. The text gives the weight of the two bows as 11 and 15 kg, which match the draw weights expressed in kilograms rather than the mass of a recurve bow: if those figures went into the calculation of the force on the bow hand as they stand, the estimated compression would be inflated. The 3,400 N comparison comes from a standard designed for lifting loads at work.

Thirteen participants are few, and the groups are not comparable: all four experts were men, four of the six women were novices, and one man weighed 117 kg. The sex differences, which the authors attribute to muscle strength without measuring it, may therefore also come from experience, body mass or a 32 lb bow that is too heavy for someone who has only just started. Distances of 10 and 15 yards are far from competition distances, and scores were not recorded. The study shares its participants and the 25 lb, 10 yard condition with the paper in Frontiers, which reports exactly the same values for that condition: in the registry the two papers count as one. A third paper by the same group, from 2025, gives different values for the 25 lb bow at 10 yards, which in the Frontiers paper correspond to the high target condition.

The most interesting observation for anyone who shoots concerns the trunk: with the 32 lb bow the women in the sample, most of them novices, leant back by about 17 degrees, against 5 for the men. Coaches usually read that as a sign of a bow that is too heavy for the archer, and the authors themselves advise choosing draw weight according to one's own strength. The study measured neither strength nor score, though, so it cannot say how much that posture costs in accuracy.

The lumbar load figures need caution: they are model estimates with possible errors in the inputs, obtained with light bows on a few students, and the model calculates only compression, not the other loads that leaning back involves. The closing recommendations (train strength, keep the back straight, keep the shoulders in a natural position, point the drawing elbow straight away from the target with the forearm parallel to the ground) are general advice that this paper does not test.