Some saddle designs are more damaging than others, scientists say. But even so-called ergonomic seats, to protect the sex organs, can be harmful, the research finds. The dozen or so studies, from peer-reviewed journals, are summarized in three articles in September's Journal of Sexual Medicine.

In a bluntly worded editorial with the articles, Dr. Steven Schrader, a reproductive health expert who studies cycling at the National Institute for Occupational Safety and Health, said he believed that it was no longer a question of "whether or not bicycle riding on a saddle causes erectile dysfunction."

Instead, he said in an interview, "The question is, What are we going to do about it?"