The Wachbataillon unit performs precision military drills at official ceremonial functions, the German Herald reports. Many of their drills involve smacking their rifles against the left side of the soldiers’ chests. And all that pounding on the same spot has stimulated the production of hormones that cause man boobs to grow.

“There is a very significant link between the activity in the … battalion and the development of the breast on the left side,” Dr. Bjorn Krapohl, director of plastic surgery at the military’s main hospital in Berlin, told the Herald. “They need to change the way they drill.