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Repetitive Head Impacts: A Major Concern At All Levels of Sports

Research now strongly suggests that CTE result of accumulation of undiagnosed subconcussive head trauma

Is better detection the answer?

One approach to the problem of sub-concussive blows that escape detection via conventional means is to find new enhanced detection methods: If functional impairment could be detected on the sports sideline, a player, like those exhibiting more obvious concussion signs or complaining of symptoms consistent with concussion, could be removed from play.

As Dr. Leverenz told MomsTEAM after publication of the first Purdue study, the limitation of screening tools currently being used to assess neurocognitive function on the sports sideline, such as the Standardized Assessment of Concussion (SAC) and the Sports Concussion Assessment Tool 3 (SCAT3), is that they test verbal memory, not the visual memory which he and the Purdue researchers found impaired in the functionally, but not clinically impaired, players who experienced at least short-term neurologic trauma from RHI.

All too often, even hits hard enough to cause an athlete to display signs of concussion that can be observed by sideline personnel, or which cause the athlete to experience symptoms of concussion, go undetected, either because the signs are too subtle to be seen or are simply missed by sideline personnel or because the athlete fails to report them (a 2010 study[7] of Canadian junior hockey players, for example, found that, for every concussion self-reported by the players or identified by the coaches or on-the-bench medical personnel, physician observers in the stands picked up seven) - a persistent problem that, given the "warrior" mentality and culture of contact and collision sports, is not going to go away any time soon, if ever. 

One way to increase the chances of detection may be to equip players with impact sensors to alert sideline personnel to head impact exposure, either from a single, forceful hit, or from less forceful but repetitive blows, that has the potential to result in brain injury, which could help medical staff identify athletes who should be removed for evaluation on the sports sideline and, if found to have a suspected brain injury, referred for further evaluation and banned from a return to play.[6] 

Are reducing full-contact limits or hit counts a solution?

But better detection does nothing to prevent such brain trauma, or at least reduce the risk, in the first place.  No matter how good the technology, no matter how good we get at identifying suspected concussions, the essential problem remains: the hits themselves. 

As a result, an increasing number of experts are urging that the focus be on reducing the risk of concussions and sub-concussive brain trauma by reducing exposure to concussive and sub-concussive hits that athletes sustain during contact and collision sports.  

Limiting contact practices in football to one session per week, or eliminating contact practices altogether, for example, would, according to a 2013 study[10] by researchers at the University of Michigan, result in an 18% to 40% reduction in head impacts respectively over the course of a high school football season.

The Michigan study pointed to recent research suggesting that the number of head impacts sustained may play a more important role in putting an athlete at risk of developing CTE than clinically evident concussions.  Among them were the Purdue and Rochester studies of athletes in high school and college football [1,8,9,12,13, 31-38] and ice hockey, [8] which, as noted above, found subtle changes in cerebral function in the absence of concussion symptoms or clinically measurable cognitive impairment which researchers linked to the volume of head impacts, and a much publicized case-study autopsy of a collegiate football player, Owen Thomas, with no reported history of concussions, which revealed early signs of CTE. [14]

"If verified," lead author, Steven P. Broglio, PhD, ATC, of Michigan NeuroSport and Director of the NeuroSport Research Laboratory at the University of Michigan, writes, these reports "would support the use of head impact numbers to limit the head trauma volume experienced by an athlete each season."

Broglio recognized that "contact sport athletes appear to be at a greater risk for developing CTE,"  but was careful to note the absence of studies "indicating the relationship between head impacts, concussions, and other factors (eg. genetic profile) that may trigger the disease pathway."

He described the goal of reducing the overall number of head impacts that high school football players sustain in a season as "logical" and "appealing," but noted that, "until the risk factors for chronic traumatic encephalopathy (CTE) are better defined by carefully designed and controlled research," and research determines "what the advisable limit to head impact exposure should be," employing contact limits or establishing "hit counts" will remain "educated guesses, at best."

Indeed, the 2014 University of Rochester study [23] suggests that, "rather than monitor total head hits, as [was initially suggested [by Sports Legacy Institute in its much publicized Hit Count program], it may be more effective to monitor those hits that are most likely to produce [white matter] changes, which Bazarian and his colleagues found were when the number of helmet impacts resulting in a peak rotational acceleration of 4500 rads/sec2exceeded 30-40 for the season, and when the number of helmet impacts resulting in a peak rotational acceleration .6000 rads/sec2 exceeded 10-15 for the season. 

Two of the Purdue studies [36,37] suggested that it might be possible to reduce risk of brain trauma by gradually increasing the amount of contact in the football pre-season to allow time for players' brains to adjust, and one, by finding that players who sustained more than 50 hits per game, were much more likely than those who sustained fewer hits to be "flagged" by ImPACT and/or fMRI results as having neurocognitive deficits or altered brain activity, suggested that players be limited to a certain number of plays per game (a hard rule to implement, given the prevalence of two-way players in the high school game).  

A 2016 study by Broglio [46] found that a rule change limiting full-contact high school football practices appears to have been effective in reducing head-impact exposure for all players, with the largest reduction occurring among lineman.  The study found that impacts were reduced from an average of 592 impacts per player per season before the rule change to an average of 345 impacts per player per season, or a 42% decline in impact exposure

Although Broglio and his colleagues viewed the results as "promising", they were careful to note that the restrictions on full-contact practices in football were being implemented despite a "lack of clarity surrounding the relationship between repeated head impacts in high school athletes and long-term neurocognitive dysfunction.

Bobby Hosea teaching tackling in The Smartest Team documentary

Question of balance

Finding a way to reconcile two competing demands - minimizing contact in practice in order to reduce the number of concussions sustained and the number of hits players sustain over the course of a week and a season that emerging science, now more than ever, suggests may have a deleterious cumulative effect on a player's cognitive function over the long term, while at the same time maximizing the amount of time in practice learning how to tackle and block without head-to-head contact - time that is needed to maximize the protective effect of proper tackling on the number of head-to-head hits players sustain in game action, which can not only result in concussion, but catastrophic neck and spine injuries - is challenging, but clearly not impossible.

"As a scientist, I am not in a position to make policy," Broglio told MomsTEAM, but "we can't just reduce [the number of contact practices] without looking at the whole picture. We don't know if 18% means anything, or how much less [in terms of the number of impacts] is meaningful."

If he were making policy, however, Broglio would "lean more towards the cautious side" in limiting contact practices, which is not to say that he doesn't think "that a football program could be successful" with some limits on full-speed contact practices.  Pointing to rugby, where players practice tackling without helmets without increased risk of head injury in games, he "didn't necessarily buy" the argument advanced by some experts that limiting contact practices would expose football players to increased injury risk in games.

As Broglio writes in his 2013 study, however, his view comes with a very important caveat: only if "extra emphasis on the appropriate tackling technique [is] put in place to ensure that the highest level of safety was maintained during games." 

While the recent movement to limit full-contact practices is intended to make the game safer, some experts agree with Broglio that caution should be the bywordA March 2013 review of current risk-reduction strategies in the British Journal of Sports Medicine [11] reminds state high school athletic associations and legislatures that, in enacting rules, such as limits on full-contact practices, they "need to carefully consider potential injury 'trade-offs' associated with the implementation of injury-prevention strategies, because every change may have certain advantages and disadvantages. That is, by reducing one risk or danger, additional risks may be created." In other words, as the Michigan study points out, limits on full-contact practices could create additional risk of injury to players because they haven't spent enough time learning to tackle properly. 

The results of at least two recent studies, however, suggest that reductions in full-contact practices can be accompished safely without putting players at additional risk, while researchers continue looking for the head trauma "holy grail": a threshold - whether it is number of hits per week, over the course of the season, of a certain force, or to a certain part of the helmet  (e.g. facemask, top of the head) above which players are at an unacceptably high risk of permanent brain injury.

A 2013 study by researchers at Wake Forest Baptist Hospital and Virginia Tech [24] showed that reducing the number of head hits in practice did not, as some had predicted [25] lead to higher force impacts during games. 

And, more recently, a 2015 study [39] reported that comprehensive coach education in teaching "heads up" tackling and practice contact restrictions, such as implemented by Pop Warner, can be effective in reducing the rate of concussions in youth football. 

The challenge is to determine whether a critical number of head hits exists above which this type of brain injury appears, and then to get players and coaches to agree to limit play when an athlete approached that number.    

As the recent Purdue studies demonstrate, science is coming closer than ever before to determining that number,   

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Originally posted April 6, 2012; most recently July 30, 2016