Preparing for her semifinal bout at last year's world championships in Barbados, U.S. women's lightweight boxing champion Quanitta "Queen" Underwood felt the sting of a sucker punch.

Dressing at her hotel for the fight, Ms. Underwood opened the new uniform semifinalist contestants had been given for the competition and found a surprise: a skirt, instead of the baggy shorts she and many other female boxers prefer.

The...