Despite these trends, Murray said, many are not even aware that kids' recess time had been dwindling.
"Most of the time when I talk about this issue with people, pediatricians and parents alike, they're shocked that there is even an erosion of recess," he said.
Murray said at least some of the explanation for this trend lies at the feet of policymakers' best intentions to improve the country's schools -- specifically, the No Child Left Behind Act. The program launched in 2002 to increase children's performance in such areas as math and reading, and effectively increased the amount of school time devoted to these subjects. As a necessary consequence, this forced cutbacks in time devoted to other school activities: art and music instruction -- and, most dramatically, unstructured recess time.
"As schools are evaluated more and more on science and math scores, they have looked for opportunities to get more academic time in," Murray said. "Some of the other [subjects and activities] have definitely taken a hit."
It is a sacrifice, Fromme said, that deserves a second look.
"Though the argument that more time needs to be spent in teaching essential academic topics is valid, the time should not be taken from recess," Fromme said. "The argument needs to be how to optimize the time that is spent in the classroom, and recess is part of that answer.
"Which is more effective: 60 minutes in class with half the attention, or 45 minutes with 100 percent focus? If recess can create the latter, then its existence is actually more valuable than its absence."