Research on German soldiers has shown that enlarged breasts are an unfortunate side-effect of gun-toting

The rhythmic impact of a rifle wielded by a military man can puff up his chest. This sometimes leads to worry, or worse. Though soldiers might appreciate a good pair of breasts, what would happen if they themselves grew a pair? Or if they grew just one?

Some men do experience this affront. A study called Gynecomastia in German Soldiers: Etiology and Pathology, published last year in the journal GMS Interdisciplinary Plastic and Reconstructive Surgery, analysed the plight of 211 male German soldiers who suffered from, or at least exhibited, one or two enlarged breasts. The ailment has a medical name: gynecomastia.

The study's authors, Prof Björn Dirk Krapohl, Dr Dietrich Doll, and four colleagues at Bundeswehrkrankenhaus, the German Armed Forces Hospital in Berlin, played detective. They set out "to investigate the increased incidence of left-sided gynecomastia in members of the German Ministry of Defense Guard Battalion who perform ceremonial duties in Berlin … A possible explanation is the mechanical impact of the carbine against the left side of the body during the drills that these soldiers regularly perform as part of their ceremonial duties".

The doctors compared those patients with other enlarge-breasted men who had not spent years frequently and intensively slapping rifles into their left breast.

They noticed a stark difference.

Seventy-five percent of the gynecomastiacal Guard Battalion chest-slappers had an enlarged left – only the left, not the right – breast.

The other patients – the non-chest-slappers – as a group showed neither sinister nor dexter breastedness. One third of them did have an enlarged left breast only. But another third of them had only a big right breast. The third third had a big pair.

The doctors suggest that this ritual breast-beating damages the tissue so much that "surgical resection of excess breast tissue is the only effective treatment".

This medical investigation, with its tight focus on one possible cause of gynecomastia, smacks of an old national stereotype: that Germans over-indulge their love of military precision.

An earlier medical inquiry, also performed by military physicians in Germany, looked at a different possible cause of gynecomastia, in soldiers from a different nation. Their homeland, far from Germany in both place and spirit, was famed at that time for its fascination with marijuana.

Two doctors at the US Army Hospital in Nuremberg published, in 1977, a study called Gynecomastia and Cannabis Smoking. They examined 11 low-ranking, abnormally big-breasted American soldiers. Some of those swell-chested fellows admitted to smoking marijuana. Others did not.

The report ends with a clear, sober statement: "Our epidemiologic evidence does not support [any] relationship between chronic cannabis use and gynecomastia."

The cannabis report, seen in retrospect, is incomplete. It makes no mention of how many of the toking soldiers had just one enlarged breast, let alone which.

(Thanks to James Harkin for bringing the chest-slapping to my attention.)

• Marc Abrahams is founder of the Ig Nobel prizes and editor of the bimonthly Annals of Improbable Research