Kramer was on campus last week taking an intensive six-week course in Croatian, strategically getting her language requirement out of the way over the summer rather than spreading it out over three quarters during the school year.

“If you know what to expect for preseason, you know you have to kick your butt in the off-season,” Kramer said. “If you don’t, you’re out of luck: You have to accept the consequences of not making lineups, not being able to compete as much as you want.”

So each day Kramer, whose events include the vault and the floor exercise, arrives at the gym before 8 a.m. and does what she termed, pun unintended, a “flexible” workout for a few hours. She prefers the “nice open gym” at U.C.L.A. as opposed to the gym she would use near her childhood home a couple of hours away, one that she would need to share with local club teams.

Peter Roby, formerly Northeastern’s athletic director and a member of the Knight Commission, which works to reform college sports, said the trend had paid dividends, especially in football and men’s basketball, in the form of higher graduation rates, as athletes effectively have more time to take and pass the required classloads. But he also sounded a note of caution.

“If the athletes don’t have the chance to take time off, that’s where they start to get burned out, injuries start to happen,” he said. “And that’s why you may have athletes who feel they should be paid — because they never get any time off.”

The year-round phenomenon in some of these sports is relatively recent, said Kathy DeBoer, the executive director of the American Volleyball Coaches Association. These days, she estimated, three-quarters of women’s college volleyball teams have most or all of their players on campus for much of the summer.