Study Leader Explains Crash Test Dummy Head Trials
Joint US Lacrosse-NOCSAE study measures stick-to-head impacts in girls, women's lacrosse
|Dr. Trey Crisco, a member of the
US Lacrosse Sports Science and Safety Committee, led a July 26
"crash test dummy" research session at Brown University, where
several female lacrosse players, aged 12 to 28, were asked to take
36 swings at a headform.
© Mike Cohea/Brown University
We recently visited Dr. Trey Crisco at the Bioengineering Lab in the Department of Orthopaedics at Rhode Island Hospital and Brown Medical School in Providence, Rhode Island. Through a study funded by NOCSAE (National Operating Committee on Standards for Athletic Equipment) and US Lacrosse, Crisco is testing and measuring head accelerations from stick checks in girls and women's lacrosse.
Late last month, after five months of product development, design and setup, finally came "game day" for Crisco and his team. Several female lacrosse players, aged 12 to 28, were asked to take 36 swings at a customized crash test dummy headform, which was fitted with an accelerometer that captured the resulting movement. The sticks were also fitted with sensors to measure stick speed and accelerations. Designated spots on the front, side and top of the headform were marked as targets for the players. Measurements were recorded on each swing and are being analyzed.
Crisco, a member of the US Lacrosse Sports Science and Safety Committee and the director of the bioengineering lab at Brown, is also the father of three daughters, ranging in age from 13 to 22, who have all played or are still playing lacrosse. He has coached girls' youth lacrosse for 12 years and was the goalie coach and junior varsity coach at Yale University during his graduate school years. He wholeheartedly supports maintaining the unique culture of girls' and women's lacrosse.
LM: Walk us through the logistics of setting up this head acceleration study?
TC: The primary aim of this part of our study is to understand the relationship between stick checks and head accelerations. This grant that we received through both US Lacrosse and NOCSAE is just one piece in trying to understand what the potential injury mechanism is for head injuries in girls' lacrosse. Previously, there have been epidemiological studies and surveillance studies that have found that the majority of head injuries in girls' lacrosse occur from the stick. These are inadvertent, obviously, and could be a result of follow-throughs from shots, or fore checks. Unlike the boys' game, where head injuries are dominated by body-to-body or head-to-head contact, in the girls, we don't see that; but we are seeing the stick impacting the head. So the goal of this study was to get an understanding of the relationship between the severity of the stick checks and the resulting head accelerations.
Do we know that certain rates of acceleration equal certain severities of injury?
That's the holy grail of concussion studies, to document the relationship between head acceleration and concussion. We're not there yet. We know that above 90Gs or 120Gs, you are more likely than not to get a concussion, but there's not a definitive threshold. It's unlikely that there will be across all people because people are different and there's variability. But there are other factors, like where you get hit and what your previous exposures were. We're still in the process, through other studies, of coming up with that relationship.
Were the stick speeds used by the subjects in the study similar to real-game stick speeds?
We had the girls in this study check the head form at medium severity and then again with their most aggressive motion. We would never expect to see those types of accelerations in a game, so we are being conservative. We have a pretty good idea of where college stick speeds are. This study will give us a pretty good idea of where youth girls' stick speeds are. The impacts that we are measuring are at the upper end of the severity.
How much does player age matter in the relevancy for this study?
From our related studies in other sports, we know that the only thing that is going to differ is the speed of the stick. All the other factors, like player size, reduce to stick speed. When we finish collecting the data, we'll have an entire spectrum of data, going from youth to college, and then we'll be able to see what those differences are, but we think that the severity of the impacts will vary by stick speeds and not by group. Clearly, stick speeds increase by age and experience.
Tell us about the locations of the sensors that were built into the head forms to collect the data.
What we wanted to do was to correlate head impact severity with stick speed. From a previous pilot study, we knew that the response from the head form was the same for impacts in the front as to the back, the left was the same as the right, and the top was different than both. So we were able to reduce it down to hit the side, the front and the top, and we believe that will give us the entire envelope of resulting accelerations that we'd see. We think that the location of the hit will cause differences in acceleration.
Do you expect to see a difference between the use of two different head forms?
There are several head models that are currently out there. These are head forms that are used in helmet testing in automobile crash testing. The NOCSAE head form is a silicone-coated, urethane-filled-with glycerine cavity. The ASTM [known until 2001 as American Society for Testing and Materials] head form is a solid steel, solid magnesium head form. We would expect differences between the head forms, but neither one is a perfect model for a human. We're using both in order to capture as much variability as we can with these head forms. I don't think the differences are going to be as pronounced as the differences by stick speed.
Tell us a little more about the overall timetable for this study.
We received notice of the funding award in February through NOCSAE. Prior to that, US Lacrosse also provided donations so that we could start earlier. We spent the past five months developing the system, building the electronics, and writing the software. The experiment itself consists of tracking the full motion of the stick in 3D and measuring the acceleration of the head form on the model of a neck. We had to develop the software to track the stick, then we had to take the sensors and modify them and their electronics to use in this application, then we had to design and develop the neck that supports these head forms because they don't have necks when they are used in helmet testing. Then we put it all together and that's when we started looking at different impacts. We also had to validate all the test apparatus. Then we started a pilot study where we generated some data.
How long will you continue to collect data from players you have brought into the lab?
Every swing by one of these players is basically a separate data file. We'll have thousands of data files that we'll have to go through. It will take us anywhere from two to four weeks to analyze the data. We'll then have a good idea of what we have and we'll evaluate whether or not we have to do more testing. If not, it will probably take us another two to three months to pull together the data in a form that's presentable.
Who gets the report?
The report will be filed with NOCSAE. They usually are not interested in a presentation, just in a report. Then we'll provide the data to US Lacrosse's Sports Science and Safety Committee, and then also to the ASTM committee that is working on whether a headgear standard is feasible and what it will be. The information from this study will really help inform them.
What is the next step once the data is reviewed?
The ASTM process for protective sports equipment has been an open process, so manufacturers, scientists, governing bodies are all able to comment on the development on a standard. That standard will be based upon some of the data we are collecting and other studies, and will then provide design specifications for headgear. How a manufacturer designs the headgear is rarely dictated by ASTM – so if they want to make it out of wood or bubblegum – it doesn't matter. As long as it meets the performance standard. So then it's up to manufacturers to come up with a reasonable and cost-effective way to produce a product that meets the standard. That standard still doesn't carry any weight unless a governing body adopts it and puts it in the rulebook.
Do we know if the standard that is developed from this data will address concussions?
Right now, our understanding of the causes of concussion is very limited, and there is no data out there that has demonstrated a strong correlation between concussion and an engineering variable that could be used in a design or specification. This study will provide an understanding of what head accelerations you should see, but it's not going to help decide whether girls should or should not wear helmets, and it's not going to come up with the criteria to prevent concussion. It's one small step in understanding what the exposure is (to possible concussion).
Are there any other elements of this study that you can tell us about?
The other part of the study that we are still working on is to take our sensors that have been used in football and ice hockey studies and develop a research headgear. It needs to be something light that also measures head acceleration to measure what we see as girls run around on the field during realistic game situations. We're hoping that during some scrimmages we'll be able to collect data on what the on-field accelerations would be. From previous measurements in football and ice hockey, we don't expect those accelerations to be very high at all. In the study that we are doing here in the lab, the checks that the girls are delivering to the head forms are far, far more excessive than what they would do on the field.