German soldiers have discovered a surprising side effect after training with an elite military battalion - man boobs.
Researchers found that a group of soldiers who precision military drills at official ceremonial functions have reported growing breasts on their left side, reports the German Herald.
Many of the drills involve thumping a rifle against the left side of their chests and that's stimulated production of the hormones that cause man boobs, according to LiveScience.
"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."
Man boobs, or gynecomastia as its officially known, have been reported in nearly 75 percent of battalion members who expressed concerns over their budding chests.
Krapohl said the research team found significant differences between the affected battalion and a healthy test group. Those in the Guard Battalion in Berlin had lower testosterone levels and higher body mass indexes (BMI), or a measure of body fatness, reports Live Science.
Here's a video of the German soldiers performing the chest-thumping drills.
Affected soldiers are beign treated individulally for the condition. Military leaders said they will change the battalion's drills if necessary.