A doctor once told me this as actual medical advice once.

Doing a work physical a few years ago, during the infamous turn your head and cough test, I started to whistle tunelessly, to defuse a socially awkward situation. My doctor looked up with his eyebrows knitted together in a shocked accusing look. "Never do that." he said, blowing his already sub-par bedside manner. After the test was completed by the book, he actually stopped a moment and laughed. I suppose the confused look on my face was enough to prompt an explanation.

The turn your head and cough test checks for hernias. One specific type of hernia can be very readily discovered by this test; the inguinal hernia. It is a protrusion of a loop of intestine into the groin or scrotum through a hole in the lower abdominal wall. It is common in baby boys and older men. You can get a inguinal hernia in one of two interesting ways. You can be born with a inguinal canal, or you can rupture your lower abdominal wall by straining or lifting heavy objects.

Either way, a loop of intestines suddenly arrives between your two best friends and you are very uncomfortable.

The doctor then explained why whistling is a bad idea. Hernias are usually muscle related. More specifically, a muscle is disrupted and the organ or tissue it was containing slips into a space it shouldn't. When you whistle, you are using both the large intercostal muscle under your ribs as well as changing the pressure in your abdominal cavity. Along with that, the muscles of the front of your abdomen (think six-pack) constrict. When you urinate, the muscles of groin relax to allow the flow of urine from your bladder, which is also shrinking. I'll let you do the math.

In what I am sure is a story that he shouldn't have told me, he detailed the plight of a confused guy who would whistle while peeing. I suppose he really enjoyed it or something. Anyway, this poor fellow would start to urinate and whistle, only to have a searing pain appear suddenly. When he constricted the muscles of his groin in response to the pinched loop of guts getting irritated, it slipped back, just out of pain territory. After three or four similar incidences, he finally went to the doctor. A quick trip to the hospital and he was back to his old self.

I remain tuneless in the bathroom.