Sports Medicine Research: In the Lab & In the Field: When Practice Becomes Injurious (Sports Med Res)
Monday, October 14, 2013

When Practice Becomes Injurious

Estimation of head impact exposure in high school football

Broglio SP, Martini D, Kasper L, Eckner JT, Kutcher JS. Am J Sports Med. Ahead of print.

Take Home Message: Limiting or eliminating contact football practices may reduce the number of head impacts sustained by athletes by 18 to 39% over the course of a season.

Sub-concussive impacts, those not resulting in a concussion injury, have been shown to contribute to cognitive impairment. On average a high school football athlete receives 50 head impacts a week, which may lead to future cognitive impairment. It may be desirable to reduce the number of impacts by changing rules related to practices and games but it is unclear if this will be sufficient since we don’t know how many impacts occur during contact and noncontact practices. Therefore, Broglio et al compared the number and magnitude of head impacts resulting from games, contact practices, and non-contact practices to estimate the effect of limiting contact practices on head impact exposure in high school football. The authors utilized the HIT System to measure head impacts and followed 42 high-school athletes (18 lineman; 2 quarterbacks; 13 wide receivers, center backs, and safeties; and 9 tight ends running backs, linebackers) over 6 seasons. On average athletes received 774 head impacts per season. Linemen sustained the highest number of impacts per athlete (~1076 impacts); followed by tight ends, running backs, and linebackers (~779 impacts); wide receivers, center backs, and safeties (~417 impacts); and quarterbacks (~356 impacts). A typical athlete sustained about 2 head impacts per non-contact practice, ~11 head impacts per contact practice, and ~24 head impacts per game. The magnitudes of linear acceleration of the head impacts were also higher in games (~26.9g) compared to both contact (~25.2g) and non-contact practices (25.7g). There were no differences in the magnitude of linear acceleration between positions. However, the tight end, running backs, and linebackers received higher magnitudes of rotational acceleration compared to the other player groups. Head impacts suffered during a game had the highest magnitude of rotational acceleration (~1769.1rad/s/s) compared to contact (~1645.8rad/s/s) and non-contact practices (~1570.1rad/s/s). The authors estimated that limiting a team to 1 contact practice per week would reduce head impacts 18% (138 less head impacts per season). Eliminating all contact practices would reduce head impacts by 39% (301 less head impacts per season) across all players.

The number and magnitude of head impacts reported in this study were similar to previous past studies. This demonstrated that the frequency and magnitude of head impacts have been alarmingly high, and could benefit from a rule change. A change in the amount of contact-practices would be especially beneficial for linemen, who received the most number of head impacts. Additionally, it would support tight ends, running backs, and linebackers who received the highest magnitude of head impacts compared with players at other positions. However, all athletes could benefit from less contact. It was estimated that if there were no contact-practices that would eliminate 31 head impacts per week, where the average number of head impacts would go from 50 to 20 head impacts per athlete per week. However, it is not known if this decrease in head impacts would be large enough to have a protective effect. An 18% reduction may not be large enough to prevent long-term cognitive impairment but then again this reduction over 8 years may be beneficial to an athlete who plays high school and then college football. Future studies will need to measure and evaluate if reducing head impacts leads to less cognitive impairment over the course of 1 season, 1 year, 4 years, or longer. Due to the large number and magnitude of head impacts that occur during a game focusing on safe tackling techniques (e.g., not leading with the head) as well as reducing the number of overall head impacts may also be necessary to decrease the number of high-load head impacts an athlete sustains. Overall, we may need to focus on reducing the number and severity of head impacts in games and practices but we also need to better understand how many hits we need to prevent to have a benefit.

Questions for Discussion: Do you think reducing the number of head impacts in football could lower the risk of long-term cerebral dysfunction? Do you think having 1 or no contact practices would still get the athlete ready for a game?

Written by: Jane McDevitt PhD
Reviewed by: Jeffrey Driban

Related Posts:


Broglio SP, Martini D, Kasper L, Eckner JT, & Kutcher JS (2013). Estimation of Head Impact Exposure in High School Football: Implications for Regulating Contact Practices. The American Journal of Sports Medicine PMID: 24001576

9 comments:

Amanda Brown said...

This does bring up a very important issue that many athletes, especially football players are experiencing long term effects of concussions. I believe that reducing the number of head impacts per week would decrease the risk of long term effects. However, this is the case because it lowers the number of potential times to receive a concussion. If an athlete does not have a concussion, then they are not going to experience the long term effects associated with concussions. Although this sounds like a good idea in concussion management, I don't believe it is practical to eliminate contact practices. The athletes would then only experience contact in games which could lead to many other problems and injuries. I think the most important thing right now is for coaches to teach and correct proper technique. Also, as athletic trainers we need to be able to recognize any time where there is a possibility of a concussion occurring and then manage the situation appropriately. Concussion management has improved greatly in the past few years, but there is still a lot of room for improvement. Much more research needs to be done on concussions and their long term effects on cognitive function and brain health.

Liz said...

I think we also need to look at how many sub-concussive hits can equal one concussive hit. We may not have the technology right now to determine that but I think there are still effects from those sub-concussive hits that could potentially be detrimental later on. In regards to contact practices, I believe that they are necessary in order to prepare athletes for games. I think they have to know what it feels like to get hit so they know what to do in the game when it happens. Safe hitting is a skill that needs to be practiced just like any other skill that is practiced. Does it need to be practiced every day? Probably not but it does need to be practiced enough that players know how to hit safely and know how to safely receive a hit.

Jane McDevitt said...

Liz- I agree looking at sub-concussive hits are very important, and can potentially lead to a concussion. There has been research on this topic. blowshttp://www.sportsmedres.org/2011/11/rotational-head-kinematics-in-football.html

I do feel it is necssary to practice hitting and safe hitting is a skill that needs to be practiced. You make a valid point that it should be practiced, but it maybe it does not need to be practiced everyday.

Jess Schlesman said...

I find this article to be very interesting because I have always thought it to be odd that football players can only participate in one game a week due to the strain it puts on one's body however, during practice each day they are experiencing similar, game-like situations. Though I do think it's important for the players to practice safe hitting techniques so when would be a good time to practice tackling and how often? When they do practice hitting is it necessary to practice on other players or would hitting sleds or pads benefit the players just as much?

Jane McDevitt said...

Jess-

That is a good point. I wonder if hitting sleds or pads would be just as beneficial as hitting other players. I do not believe that has been investigated. I think that could be a very good option that could result in less head impacts players sustain.

Becca Burkhart said...

Head injuries are a rising problem with sports. Since there are now more youth participating it means a larger population is being effected by head injuries. I think it would also be interesting to do research on whether hitting sled or pads would be just as beneficial as hitting other players and decrease head impacts during practice. I also wonder if research would show that having all no-contact practice would decrease the long term effects associated with head impacts.

Jason Shermer said...

Very interesting article, I wonder if any studies exist on any beneficial effects (outside of negative concussion effects) that happen from the frequency, for example the body adapting and thickening the protective layers of the brain. Obviously I'm not contradicting this article, but I wonder if lessening the frequency of impacts too much will cause the less often impacts to be more detrimental, and if there is an achievable medium?

Jane McDevitt said...

Becca- My only fear with no contact practices is that they they will not be able to practice correct technique and that has such a big effect on not just head injuries but other orthopedic injuries.

Jason-I do not believe their are any studies that look at the beneficial effects of head impacts. There are 3 meningeal layers the protect the brain (dura mater, arachnoid mater, and pia mater); however, I do not believe they become thicker and more protective due to head impacts.

Alex Ruxton said...

Concussions are important and need to be reduced but I don't think eliminating contact would be completely beneficial. Yes, non-contact practices would reduce the amount of times a player gets hit but that's not how the games are played. I would fear that the techniques of blocking and tackling would suffer if not practiced over the course of a season. Maybe hitting sleds and pads can help maintain proper technique and form but they are usually not moving when the athlete is practicing. In a game everyone is moving and I feel that if all the contact was taken out of practice then the technique would suffer and result in injury. I think teaching the players the correct way to tackle is more important. Way to often players launch themselves or hit someone to high. I think one of the things coaches can try in practice is to remember that your practicing with your own teammates so try not to hurt them. Something does need to be done though to try to and reduce the amount of concussions in sports.

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