Back pain and posture in archers: Jeon 2016 study

Fourteen archers with at least four years of practice and pain in the spine or pelvis were compared with nineteen people without pain, measuring the shape of the back and isokinetic trunk strength.

The figure the authors highlight is lateral trunk inclination: 2.5 degrees in the male archers and 3.8 in the female ones, against 2.1 and 0.5 in the comparison group, with a significant group by sex interaction (p of 0.033) and a group main effect (p of 0.008). On the pelvis, by contrast, obliquity, torsion and rotation do not separate the two groups, and the only difference concerns sex (pelvic rotation, p of 0.006). On the spinal curves, kyphosis does not differ, while the lordosis angle is smaller in the archers (p of 0.019 for group and 0.002 for sex): 29.2 degrees in the men and 32.4 in the women of the archery group, against 30.2 and 42.6 in the comparison group.

Isokinetic strength at 60 degrees per second shows a significant interaction for the flexors (p of 0.010) and the extensors (p of 0.001). The male archers' extensors come to 158.8 newton metres against 240.9 for the comparison men, while the female archers are at 130.9 against 116.6 for the comparison women. The flexors are 196.3 and 148.5 in the archers, 222.5 and 118.0 in the comparison group.

The authors present the results as baseline data for building exercise programmes against the imbalances that one-sided movements bring. They measure nothing about shooting.

A cross-sectional study of 33 participants: 14 archers, 6 men and 8 women, with at least four years of practice and pain in the spine or pelvis, and 19 people in the comparison group, 8 men and 11 women. None had musculoskeletal disease or neurological problems; all signed informed consent in line with the Declaration of Helsinki.

The shape of the back was recorded with a posterior trunk measuring system, Formetric 4D, chosen as an alternative to radiological examination. The technique is rasterstereography: a halogen light projects a grid onto the back and the software reconstructs the surface in three dimensions. The authors state mean deviations of 0.15 mm for the surface analysis and within 3 degrees for lateral spinal deviation. For the measurement each participant undressed far enough to expose the posterior superior iliac spines and stood upright about two metres from the camera; there are four landmarks, the seventh cervical vertebra, the sacrum point and the two iliac spines.

Trunk strength was measured on a Humac Norm isokinetic dynamometer with a trunk adapter, with straps and a belt holding the pelvis. For each person the range of motion was calibrated to the largest pain-free arc, to avoid hyperextension and hyperflexion. After a familiarisation trial, three repetitions were recorded at 60 degrees per second, deliberately few so as not to introduce fatigue.

The analysis, in SPSS 20, uses a two-way analysis of variance with group and sex as factors, looking for both main effects and the interaction, with the threshold at 0.05.

The two groups differ greatly in age and the paper never mentions it. The archers average 16.2 years for the men and 16.4 for the women, the comparison group 23.6 and 22.3: a seven-year gap, that is adolescents against young adults. An extensor strength difference like the one between 158.8 and 240.9 newton metres in the men is what you would expect between a sixteen-year-old and a twenty-three-year-old, and attributing it to archery is not possible with these data. The same goes for the comparison on lordosis.

The archery group was selected because its members had pain. The comparison is therefore not between people who shoot and people who do not, but between adolescents with spinal or pelvic pain and young adults without pain. Pain, moreover, is an inclusion criterion and is never quantified: there is no scale, no duration, nothing on how intense it was.

The paper describes the comparison group only as healthy subjects, without saying whether they played any sport or what work they did: calling them non-athletes goes beyond what the text states. The numbers are small, from 6 to 11 people in each of the four cells, and the standard deviation of the flexors in the male archers, 5.4 newton metres across six people, is too small to be plausible.

The details that would make the study specific to archery are missing: the bow discipline, the draw weight, the exact years of practice and above all which side each person drew on, which in a study about asymmetric loading is the central fact. Rasterstereography describes the surface of the back rather than the bones, and no shooting outcome was measured. The design is cross-sectional: it says how these people stand today, not what archery does to a back over time.

The question this study is called on to answer is whether archery, a one-sided movement, leaves a mark on the spine. What it measures is narrower: fourteen adolescent archers who already have pain lean sideways slightly more than nineteen young adults who do not, about 0.4 degrees more in the men and 3.3 in the women. On the pelvis and the spinal curves the two groups do not separate consistently.

Since the archers are seven years younger and were chosen precisely because they had pain, nothing here shows that archery bends a back out of shape, or the opposite. It serves as descriptive data and as an example of what can be measured without radiographs.

For an archer with back or pelvic pain there is nothing to take away: the study proposes no exercises, follows nobody over time and does not say whether the inclination can be corrected. Pain that does not pass needs assessing by a doctor or a physiotherapist, and a study on 33 people is no substitute for that.