As U.S. children play team sports in greater numbers and with growing intensity, their risk of getting a concussion has grown but the science of preventing, diagnosing and treating this increasingly frequent brain injury remains maddeningly incomplete, experts warned.

Although concern over traumatic brain injury has spawned high-tech imaging techniques, helmet-mounted accelerometers and sideline concussion tests, these have yet to show they can reduce sports-related concussions, the Institute of Medicine concluded in a 286-page report.

Simple steps — including enforcing game rules and fair-play policies in place — show signs of reducing a range of sports-related injuries, including concussions, the panel said. For instance, several studies have found that enforcing penalties for helmet-to-helmet contact in football and blindside hits in hockey and La Crosse reduce concussions as well as the smaller impacts that rattle the brain, with more uncertain consequences.

“Oftentimes the simplest solution is the best solution,” said University of California, Los Angeles neurosurgeon Dr. Mayumi Prins, one of the report’s authors. The science that could guide prevention efforts and better care “has a long way to go,” she added.

A year in the making, the report also concludes that young athletes have embraced a culture of competitive sports and are reluctant to report symptoms of brain trauma out of fear that it will keep them on the sidelines.

By setting children up for a slower recovery from concussion and putting them at greater risk of further injuries, this “culture of resistance” endangers their well-being, the report said.

State laws, rule changes in youth sports leagues and public health awareness campaigns have begun to have a positive effect, the panel said. But, it added, “the culture shift is not complete.”

Students should be the target of “large-scale efforts to increase knowledge about concussions and change the culture surrounding concussions,” the group recommended.

Sports- and recreation-related brain injuries affect between 1.6 million and 3.8 million people a year.