Anyone who has been shooting for a few years asks it sooner or later, often in front of a mirror: the drawing arm looks bigger, one shoulder sits higher than the other, and you start to suspect that thousands of arrows shot from the same side are building a crooked body. That leads to the practical question of whether to train the other side as well, in the gym or even with the bow in the opposite hand.
The studies answer in two steps. Electromyography shows clearly that shooting loads the two sides differently. Whether that load leaves a lopsided body is a separate question, and the answer changes with the region: in the arms, and above all in the fingers, a difference between sides does turn up, while in the trunk and spine it does not. That is why, in the registry, the claim that the asymmetric shooting action creates muscle asymmetries is contested: studies on archers point in opposite directions, largely because they look at different parts of the body.
A different load on each side
The premise holds, even if it is less simple than it is usually made out to be. In five elite Russian recurve archers, with eighteen muscles measured on both sides over 180 shots, the drawing side dominated in most muscles, above all in the finger flexor of the forearm, with an asymmetry coefficient of 0.86 on a scale where zero is parity and one means a single side doing all the work. The bow side, however, was more active in serratus anterior, pectoralis major and latissimus dorsi. In nine recreational archers, using an extremely light bow, the two arms worked at similar overall levels but with different muscles: the drawing arm relied more on latissimus dorsi and biceps, the bow arm on the lateral deltoid and triceps.
Which side works harder therefore depends on the muscle and on the phase of the shot, and the claim that in the shot the drawing side works harder than the bow side is itself contested. That the two sides do different jobs, on the other hand, comes up in every study. These are measurements of how the muscles work during the shot, though, not of how the body is built at rest: the step from one to the other looks obvious, since a muscle loaded more on every arrow ought to grow more, but it has to be measured, and those who have measured it have not always found the same thing.
Arms, hands and fingers
The most thorough study is recent and small: thirteen registered Turkish archers aged 11 to 18, all right-handed and with at least two years of experience, measured side by side with a hand-held dynamometer and a long series of posture and mobility tests. The drawing arm turned out stronger in every strength test, but the size of the differences varied widely. In the large shoulder and elbow movements the gap ranged from small to moderate: elbow flexion, the most uneven of the group, measured 224.7 newtons against 196.6. In whole-hand grip it stayed small, 30.4 kg against 28.8. In the finger pinches, on the other hand, it became very marked: these pinch the thumb against the other fingers, which is not how the string is hooked, but they measure the strength of the part of the hand that holds the string in the shot.
In the same archers the drawing side also had shorter external rotators of the shoulder, a slightly shorter pectoralis minor and a shoulder blade sitting further from the spine, and the arm was thicker above the elbow, 23.7 cm in circumference against 23.3, though not below it. The study has no comparison group, however, and that is its main limitation: all thirteen were right-handed, and a right-hander's right hand is stronger than the left even without a bow.
The other studies help to separate shooting from handedness, without quite managing it. In twenty young Malaysian archers the grip gap between the two hands was 6 kg, against 1.3 in sedentary peers, but nobody tested that gap statistically, and the archers were heavier. In ten Japanese university archers, by contrast, the drawing hand gripped only slightly harder than the other, with no significant difference. Finally, in seventeen Indonesian beginners the drawing arm already carried more muscle mass before they started: part of the asymmetry found in archers, then, was there before the bow.
The discipline seems to matter too, but on both sides. In 37 pre-elite Taiwanese archers, 19 recurve and 18 compound, the recurve archers had stronger horizontal shoulder abductors on both sides, 19.0 against 15.4 kilograms-force on the drawing side and 19.1 against 15.4 on the bow side, while the upper trapezius was practically identical in the two disciplines. The claim that recurve archers have stronger shoulders than compound archers is reported, with two caveats: the recurve group had more men and weighed more, and a comparison made at a single point in time cannot say whether the equipment creates the difference or whoever chooses it brings it along. For the question of this article one detail matters: the differences lay on both sides, not on one.
Trunk and spine
In the trunk the measurements point the other way. In fifteen young elite Israeli archers, aged 17 on average and training at least seven three-hour sessions a week, ultrasound measured the thickness of the deep muscles: multifidus in the back, transversus and internal oblique in the abdomen. It was the same on the dominant and non-dominant sides, at rest and when contracted, and the differences between sides, 5-8% in multifidus and 15-19% in the abdominals, did not reach significance. The side bridge, by contrast, varied a great deal from one athlete to the next, with an average difference between the two sides of 44.8%, calculated without regard to which side was the stronger. In the thirteen Turkish archers, the side bridge held for 63.1 seconds on the drawing side and 59.4 on the bow side, a difference the statistics cannot tell apart from chance.
The oldest evidence comes from kyudo. In the early 1970s a Japanese orthopaedic survey examined and X-rayed the thirty practitioners with the most marked complaints, out of 122 who had answered a questionnaire, and despite the asymmetric shooting posture it found no scoliosis, either cervical or lumbar. It is a measure of the spine rather than the muscles, taken in people who had complaints, but it points the same way as the recent studies.
A symmetrical trunk, for that matter, is not the same as a highly developed one. The only study that has measured archers' trunk muscles alongside those of other athletes did so with magnetic resonance imaging in 352 Japanese athletes of national and international level, 88 of them archers: for the same height, adult male archers had a smaller psoas, erector spinae and lateral abdominals than wrestlers, and female archers had smaller lateral abdominals than table tennis players and gymnasts. Compared with peers who do no sport, however, the young athletes in the same study, archers included, had cross-sections 50-66% larger in the lateral abdominals, psoas and erectors, although that comparison relies on values published elsewhere. The claim that archery does not build the trunk muscles the way other sports do is reported: a single cross-sectional study, with small subgroups.
Does shooting widen the gap?
Almost all of these studies capture archers at a single moment, and finding out whether shooting creates the asymmetry means looking at the same people before and after. The closest thing to an experiment is a Malaysian randomised trial: thirty-four sedentary young men, half of whom shot three times a week for twelve weeks, 42 arrows a session with a 35-40 lb bow at 10 m. In the shooting group grip strength rose in both hands, and by similar amounts; the bow hand, which started weaker, even caught up a little. In twelve weeks shooting made them stronger, and in the registry the claim that shooting a bow builds strength in people who start out sedentary is reported, but it did not widen the gap between sides.
A systematic review reports a similar result on a different measure: in 36 beginners in traditional archery, 84 sessions over twelve weeks improved the precision of an arm movement to a similar degree on both sides, and the difference between the dominant and the other side stayed where it was. It measures movement control rather than muscle. The only before-and-after data pointing the other way come from the seventeen Indonesian beginners: eight weeks of bow training, with draws on a device of about 10 kg, resistance bands and their competition bow, increased muscle mass in both arms, and in the girls the gap widened a little, from 0.98 against 0.87 kg to 1.12 against 0.94, while in the boys it stayed where it started. There was no comparison group, and nobody tested that gap statistically. These are a few weeks in any case, against a competitive archer's years, and nobody has followed the same archers for years, measuring both sides.
Shooting from one side or from both
On the question of training the other side there is a study designed for it, from Germany. Seventy-five adult competitive archers, aged 47 on average with about ten years of experience: 25 who had been training on the non-dominant side as well for at least a year, 4.6 years on average, and 50 who shot from one side only, matched two to one for age, sex, training hours and years of practice. Neck and shoulders were measured with an ultrasound-based motion analysis system, an inclinometer on the shoulder blade and a simple test: bringing the fists towards each other behind the back and measuring how far apart they stay.
Only the one-sided archers showed differences between their two shoulders: in arm rotation, in the rotation of the shoulder blade as the arm rises to the side, and in the fist test. In that test the drawing side came out as the more mobile, with the fists 18.0 cm apart against 22.0 on the bow side, while in those who trained on both sides the values were close, 19.3 and 20.9. The neck, on the other hand, did not change: no difference between groups or between sides in any of the three planes of movement, and a range about 20 degrees above the reference threshold for age. That is why the claim that neck mobility stays good in competitive archers, even in those who always shoot from the same side is reported.
On the shoulders, the claim that training both sides reduces the asymmetries caused by shooting is reported, and no more than that. The comparison is made at a single point in time: we do not know whether the archers who train on both sides reduced an asymmetry or never developed one, nor whether those who choose to do it differ from the others in some other way. The authors themselves suggest a simpler explanation, namely that archers who shoot from both sides spend less time, with each shoulder, in the extreme positions of the shot. And nobody has tested whether compensatory exercises in the gym, the kind people usually have in mind when they talk about evening things out, reduce the differences between an archer's two sides.
Does shooting from the other side help the good side?
There is also a different argument for shooting with the other side, which concerns learning more than the body. A group at the University of Oldenburg randomly split forty right-handed beginners into four groups, who shot sixty arrows over three days at a target 10 m away, dividing them between the two sides in different proportions. Measured on the dominant side, the score rose by almost 20% in those who had split their arrows evenly, by 15% with three quarters of the arrows on the dominant side, by 9% with three quarters on the other side, and by just under 8% in those who had shot only with the dominant side. At a new distance, 15 m, the one-sided group shot 9% worse than in the initial test, while the bilateral groups shot 4% better.
For beginners, the claim that practising with the non-dominant side as well improves the side they shoot with is reported, and it is the most limited evidence that can still be called that: the work came out as two pages in the German federation's magazine, with tests of three arrows per side, without the number of archers per group or any statistical test between groups. Stated in general terms, without restricting it to beginners, the same idea is contested, because in the German study of competitive archers the 25 who also trained on the other side did not shoot better than the rest: 14.5 points against 15.7, a non-significant difference, in a test of nine arrows at 15 m that lacks the precision to pick up small differences.
Where the studies stop
Almost every study compares the right side with the left in right-handed people, and so folds the effect of the dominant hand and the effect of shooting into a single number. The samples are small, thirteen, fifteen, twenty archers, nearly always young, and when an asymmetry appears at 15, after two years of shooting, the data we have cannot say whether by 30 it will have grown, stayed the same or shrunk. Nobody, moreover, has set an archer's asymmetry against their score, so we do not know whether a difference between sides costs anything on the target, or whether correcting it gains anything.
What I take from it for the shooting line
With the data available, the answer to the opening question is calmer than the worry suggests. Shooting loads the two sides differently, and in the archers measured the arms, and above all the fingers, do differ between right and left; but in the trunk, where the concern usually centres, the measurements find no difference between sides, and in the only experiment with a group that did not shoot, twelve weeks of shooting did not widen the gap between the two hands. I draw three points from this, bearing in mind that none of them comes from an experiment on experienced archers.
The first concerns the hands. A difference in strength between the drawing hand and the bow hand is not in itself a warning sign: some of it would be there in anyone with a dominant hand, and the most marked part lies in the fingers, which is where shooting asks most of the drawing hand. No study has linked that difference to poorer shooting.
The second concerns physical preparation. Training both sides in the gym has good general reasons behind it, since a strength programme is built on both sides anyway, but the idea that it corrects an asymmetry created by shooting has not been put to the test. If you want to know where you stand, you can measure yourself and repeat the same tests every few months: grip with both hands, the side bridge on both sides, the distance between the fists behind the back one way and the other. These are the tests used in the studies above, and the comparison that counts is with your own numbers from a few months earlier, not with another archer's. The rest of the gym work is covered in the article on specific strength for archers, while pain is a separate matter, dealt with in the one on injuries.
The third concerns the bow in the opposite hand. For a beginner, shooting some of the arrows from the other side costs little, and the only experiment, weak as it is, suggests that it takes nothing away from the side they shoot with. For an archer with an established technique no study has found an advantage in score, and the comparison between those who train on both sides and those who train on one sees no difference on the target; if anything, it sees one in the shoulders. So I treat it as a training variation, useful for feeling the shot from another side, rather than an obligation, bearing in mind that it needs a second bow suited to the opposite hand and the time to tune it.