Head Impact Sensor

Head Impact Sensors. What are they and what do they do?

You may not be familiar with these products, but chances are that you are already seeing them attached to lacrosse helmets and girls' eyewear. They are small devices that are designed to measure impact forces. Some models have light indicators that identify forces above a certain threshold. Marketers are telling you that this device will help you determine if your son or daughter sustained contact that could cause a concussion.

But are these manufacturer claims valid? Is the technology sound? And regardless of the science involved, can these devices really be used to monitor the safety of game participants?

US Lacrosse asked four of its medical and safety experts, members of the Sports Science and Safety Committee, to weigh in on these devices. What should athletes, parents and coaches know? Do users have a false sense of security by using these products?

Our experts:

  • Trey Crisco, PhD, Professor of Orthopedic Research, Brown University
  • Bruce Griffin, PhD, Director of Health and Sport Safety, US Lacrosse
  • Andrew Lincoln, ScD, MS, Director of MedStar Sports Medicine Research Center
  • Margot Putukian, MD, Director of Sports Medicine, Princeton University

Their answers to 10 key questions below about impact sensors.

Crisco: Sport sensors are similar to the impact sensors in automobiles that sense an impact and can deploy air bags. Sport sensors measure sudden motion from a hit. The severity of the hit, as measured by the sensor, is often reported in g’s, where one g is equal to the acceleration due to the earth’s gravity.

Griffin: Impact sensors come in many forms. The most common form that consumers may be seeing are the type that attach to the outside of the lacrosse helmet. There are other sensors that attach directly to the skin, attach to goggles in girls’ lacrosse, and others that are digitized mouthguards. All these products have the same functionality, which is to measure impact forces.

Putukian: Impact sensors can measure forces transmitted to the head or protective headgear. These forces are generally measured as occurring in two ways: linear and rotational forces.

Griffin: A hit count is the total number of hits to the head that an athlete sustains. The issue with a hit count is that we don’t yet know, through controlled scientific data, whether there is any clear correlation between a hit count and significant injury to the athlete. Minimizing the number and severity of hits to the head makes intuitive sense, but at this time, we don’t know what the threshold number of hits would be to be considered “safe” and how that number might vary from player to player. For example, are 1000 small hits “safer” than five big hits, or are five hits worse than two hits of the same impact force?

Putukian: We simply do not know. Some may be more accurate than others. There is ongoing research to determine the accuracy of these devices.

Crisco: Most sensing systems will give an accurate measurement in the lab. But depending on the type of sensor and where the sensor is located (within the liner, on the back of head, or on the helmet shell), the sensor’s measurements may or may not be an accurate measure of the severity of the impact to the head.

Putukian: These devices determine the extent of forces applied to the head, but there is no correlation between the impact of a hit and the likelihood of concussion. In fact, some research has demonstrated no correlation at all. The diagnosis of concussion is based on clinical information and made by a qualified healthcare provider familiar with the evaluation and management of concussion. It is noteworthy that some concussions can occur due to impact to the body with no direct contact with the head.

Crisco: No. Even the most sophisticated sensor systems can only provide an indication for clinical assessment.

Putukian: No, it is not. At best, these devices may help doctors understand the mechanisms of concussion injury. There are much more compelling methods to reduce the risk of concussion, including education, use of proper technique, fair play, enforcement of game rules, and qualified medical care and counseling.

Lincoln: Impact sensors may be useful to identify high level impact forces, but that would not prevent a concussion.

Crisco: The more sophisticated sensor can potentially be a useful tool for qualifying concussion risk by identifying players with abnormal exposures. An effective management strategy, however, must also include risk mitigation and concussion education strategies.

Putukian: Yes, there are, especially since the ‘jury’ is still out on whether these sensors are potentially worth it. Certainly, the factors mentioned above (in question 5) are known ways to keep your athlete safe.

Griffin: If the cost of the sensors for a team were considered, as opposed to individual purchases, those dollars could be applied to having a considerable number of games and practices covered by a certified athletic trainer on site. This would not only allow for better treatment for concussions and other injuries, but could provide an expert in preventative care.

Putukian: Impact sensors may be useful in measuring the location, number and forces that occur in sport, but there is no current data that supports the use of impact sensors as a method of identifying players who should be assessed for concussion given the lack of data correlating the impact force with clinical measures. Educating athletes, parents and coaches regarding the signs and symptoms of concussion is likely more important than the use of sensors.

Lincoln: Impact sensors represent a potentially useful research tool to better understand the physical exposures associated with lacrosse and other sports. This may also be useful in understanding the total impacts players may experience over multiple seasons and at different levels of play.

Griffin: No, we do not recommend for general use. If the time comes when these sensors and this product is proven to aid in the diagnosis, treatment, or management of concussions, US Lacrosse will make a recommendation concerning this product. We value and support their use in ongoing research under the oversight of an Institutional Review Board.

Lincoln: The sensors can be useful to determine how many impacts to the head occur, where they occur, and how much energy is transferred. All of this information may be useful in evaluating whether safety measures are effective.