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" Over the past eight years, all the bone-crunching tackles, hard hits on the blitz, head-on collisions and even celebratory helmet slaps endured by the Virginia Tech football team have produced more than pain. They&amp;#039;ve produced data.  It&amp;#039;s all a part of a study published this month in the Annals of Biomedical Engineering to rank how well football helmets prevent concussions. This is the first time such information has been made publicly available, according to study co-author Stefan Duma, who studies biomechanics at Virginia Tech. To Duma, the rating system for helmets is like the sports version of the crash-test rating given to cars.  Researchers hit the field for the first data-collecting phase of the study. Each football season of the past eight years, the scientists fit 60 or more Hokie players&amp;#039; helmets with accelerometers to measure the force of each hit to the head during every practice and game. The accelerometers wirelessly transmitted the data to scientists on the sideline, who matched them to any observed concussions and often went back over game film with players to pinpoint when injuries happened.  The second phase was the kind of abusive lab test PM loves: Duma and colleagues strapped a dummy head into each test helmet and dropped them onto an anvil from different heights and in different orientations. Spring-loaded accelerometers mounted in the center of the head\u2014a fluid-filled compartment meant to simulate the brain\u00AD\u2014measured the linear acceleration, or straight-line force (measured in g&amp;#039;s) caused by the blow. Head acceleration after a hard hit is closely correlated with rates of concussions. And by dropping the helmeted dummy heads onto anvils and comparing the numbers to the on-field measurements, the researchers then came up with the helmet&amp;#039;s Star value (Summation of Tests for the Analysis of Risk). The idea, Duma explains, is that the Star value represents the risk of concussion for one season of college football.      The head-dropping tests used the protocol developed by the National Operating Committee on Standards for Athletic Equipment (Nocsae), which measures linear acceleration in dummy heads. But this standard is meant to prevent against catastrophic injury like skull fractures. It doesn&amp;#039;t directly measure a helmet&amp;#039;s ability to prevent concussions\u2014and that&amp;#039;s what the researchers attempted to do in this study, according to study co-author and Virginia Tech biomedical engineer Steven Rowson. &amp;quot;The Nocsae standard looked at skull fractures\u2014we wanted to further develop that standard to protect against concussions,&amp;quot; Rowson says. The new rating system gave top marks to the Riddell Revolution Speed, which was assigned the only five-star grade. Five other brands scored a four-star grade: the Schutt ION 4D, Schutt DNA Pro+, Xenith X1, Riddell Revolution and Riddell Revolution IQ. Interestingly, Duma says, a more expensive helmet wasn&amp;#039;t necessarily a safer one. For example, at $169.95, the Schutt DNA Pro+ was one of the cheapest helmets but achieved a four-star rating. Adams A2000 Pro Elite helmet received the lowest rating of any tested (&amp;quot;not recommended&amp;quot;), but costs $199, he says.  Duma and Rowson make it clear that no helmet is perfect. &amp;quot;We don&amp;#039;t want anybody to think that if they have a certain helmet on they are risk-free,&amp;quot; Duma says. And the study has limits. Most important, the tests didn&amp;#039;t account for rotational forces within the head following hits, called rotational acceleration. Steven Broglio, a kinesiologist who studies concussions at the University of Michigan, says these twisting forces are just as important in concussion research as the straight-line forces that researchers measured. However, the accelerometers in the study couldn&amp;#039;t measure rotation in three dimensions, Duma says. &amp;quot;But I think it&amp;#039;s a good first attempt,&amp;quot; Broglio says. &amp;quot;It&amp;#039;s nice that this data is out in the open, and hopefully it will push manufacturers to develop better helmets.&amp;quot;  However, other scientists\u2014particularly rival concussion researchers\u2014didn&amp;#039;t think much of a study that didn&amp;#039;t measure the rotational forces. Robert Cantu is a clinical professor of neurosurgery at Boston University School of Medicine and chair of Nocsae&amp;#039;s scientific advisory committee, and Nocsae is currently spending millions to investigate those rotational forces. He argues that any football helmet rating system that doesn&amp;#039;t incorporate these forces within the head is misleading. &amp;quot;This study has serious limitations, and I think it&amp;#039;s a disservice to rank these helmets based on such limited data, because it&amp;#039;s implying one helmet is better than another,&amp;quot; he says. &amp;quot;From this data, you can&amp;#039;t make these statements.&amp;quot;  But, Rowson says, this system is only a first step in a plan to evaluate helmets. &amp;quot;As we learn more about rotational impacts and other factors, we expect to develop a better way of quantifying impacts,&amp;quot; he says. "^^<http://www.w3.org/2001/XMLSchema#string>
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