There also is no time limit for bathroom breaks — compared with the five minutes allowed for injury timeouts — because there is not uniformity in how far courts are from bathrooms.

“The rule is there to provide for a need for the players,” said Steve Simon, the chief executive of the WTA. “It is not meant to be strategic or a momentum changer.”

He said the breaks had been causing “undue delay, which was not good for either television or for the fans who had to sit through them.”

“There’s a certain subjectivity to this whole thing,” he added. “We have to be sensitive to feminine issues and to gastro issues. We’re not going to put anyone in an uncomfortable position.”

The Association of Tennis Professionals, which governs men's matches, follows a similar protocol, though the men are allowed two bathroom breaks during a best-of-five match (the women have just one break but play shorter matches, needing to win two sets out of three). The U.S. Open and other Grand Slam tournaments, which all have their own rule books, follow the WTA and ATP guidelines regarding bathroom breaks.

The breaks are prevalent even at the lower rungs of the sport, where they border on the absurd.

At one pro circuit tournament in Lexington, Ky., this summer , Yuxuan Zhang, who was ranked just outside the top 200, lost the first set of her quarterfinal match, 6-1, in only 24 minutes. Instead of recovering in her courtside chair during the two-minute changeover, she left for the bathroom. She returned nearly 10 minutes later, saying the bathroom was far away from her court. She lost the second set, 6-0, after another 33 minutes.