For much of the twentieth century, girls in many American states played a version of basketball with players confined to half the court. The rules encoded assumptions about their bodies.
The design divided the court and the players
Teams fielded more players than the familiar five, with each player restricted to one half of the floor and forbidden to cross the center line during play.
Some versions limited dribbling to a set number of bounces before passing, and restricted contact and movement in ways the boys' game did not.
The practical effect was that no player ran the full court, which was the explicit intention rather than an incidental consequence of the format.
The justification was physiological and mistaken
Prevailing beliefs held that sustained exertion was harmful to girls, particularly to reproductive health, and rules were written to limit continuous running.
These beliefs were assumptions rather than findings, and they were applied selectively, since girls performing demanding physical labor on farms and in factories attracted no similar concern.
The pattern is familiar in the history of women's sport: a restriction is introduced as protection and persists long after the premise has been abandoned.
The format nonetheless built enormous programs
In several states, particularly rural ones, girls' basketball drew large crowds and served as a central community event, with state tournaments that filled arenas.
Those programs gave girls competitive athletic careers at a time when few other sports were available to them, which complicates any simple account of the rules as pure limitation.
Coaching, officiating and administration grew around those tournaments as well, creating a set of jobs and expertise in girls' sport that existed almost nowhere else at the time.
Conversion was contested by the players' own communities
When states moved to the full-court game, resistance came partly from within, because the six-player format was the game those communities knew and had built traditions around.
The change also reduced the number of roster places, since fewer players take the floor, which meant fewer girls in a program that had been unusually inclusive.
Transitions ran at different speeds in different states, so for a period a player's experience of the sport depended entirely on which side of a state line she lived.
What the sequence illustrates
A rule justified by a claim about bodies shaped what a generation of athletes could do, and the claim was never the reason the rule survived as long as it did.
Once a format has stadiums, tournaments and loyalties attached to it, the argument stops being about physiology entirely and becomes about institutions.
That is why changing it took decades after the medical premise had collapsed, and why the eventual argument was made in terms of opportunity rather than in terms of evidence.