Approximately 100,000 concussions are diagnosed each year in Canadian hospitals, and approximately two-thirds are sports-related. Prevention of concussions is a major focus for Canadians and has been taken up by a variety of sports equipment manufacturers. A Canadian design and technology company, AEXOS Inc. (Waterloo, Ontario Canada), has developed a compression shirt designed to reduce whiplash and rotational acceleration/deceleration during impacts in sports. The effectiveness of this technology has been assessed through computer modeling and laboratory testing. However, its effectiveness has not been assessed in sports environments with athletes. Furthermore, there has been little research evaluating the usability of this equipment. This company is interested in researching the effectiveness of its technology in attenuating the magnitude of head accelerations during contact sports and evaluating its usability. We have been performing research evaluating the magnitude of heading impacts in varsity football, and their neurological consequences, for the past five years. We evaluated the effectiveness of the HALO technology by comparing the magnitude of the head impacts from players wearing the HALO technology compared to historical data of matched impacts when the players were not wearing HALO technology. In specific, a set of 41 head impacts was identified from the 2018-2019 varsity football season for two players that completed eight games without the HALO compression shirt and four subsequent games wearing the HALO compression shirt. The with/without HALO impacts were matched based on criteria such as play type, impact surface, and size of the opponent. The peak linear acceleration and peak angular velocity were measured for these impacts using wireless sensors in the players’ helmets (GFT3, GForceTracker, Markham, Ontario).
A paired-samples t-test was used to determine whether there was a statistically significant mean difference between the linear accelerations and rotational velocities of the helmet when players were wearing the HALO compared to when they were not. Data are presented as mean ± one standard deviation. Some outliers were detected. These values were within the range of head impact magnitudes we have measured over the past five seasons, so they were retained in the analysis. Data were normally distributed, as assessed by visual inspection of a Normal Q-Q plot, which means that it is appropriate to perform a paired samples t-test analysis. Effect size (d) of the paired samples t-test was calculated to reflect the practical importance of the differences (Cohen, 1988). An effect size of small, medium and large as indicated by values of 0.2, 0.5, and 0.8 respectively.
The peak linear helmet accelerations for the matched impacts with and without the HALO collar is presented in Figure 1. Visual inspection reveals that there is considerable variability, but that the head impact severity is reduced for the majority of head impacts. On average, the linear accelerations of the helmet were reduced by 31.1% when wearing the HALO collar (33.56 ± 23.91 g) compared to not wearing it (48.21 ± 29.66 g). This 14.65 g average difference was statistically significant (95% CI, 5.92 to 23.38; t(40) = 3.39, p = .002) and had a medium effect size (d = 0.53) indicating that it has moderate practical importance.
The peak angular helmet accelerations for the matched impacts with and without the HALO collar are presented in Figure 2. Visual inspection reveals a smaller effect of wearing the HALO collar for the angular velocities compared to the linear accelerations. While the helmet angular velocity is reduced for the majority of head impacts, it is also apparent that there is a clear set of impacts that are larger with the HALO collar. The average rotational velocities of the helmet were reduced 15.5% when wearing the HALO collar (716.20 ± 423.92 deg/s) compared to when not wearing it (847.80 ± 274.45 deg/s). This average decrease of 131.61 deg/s was not statistically significant (95% CI, -22.93 to 286.16; t(40) = 1.72, p = .093) and had a small effect size (d = 0.27) indicating that it has a noticeably smaller practical importance than the linear accelerations, but not so small as to be trivial. In summary, analysis of the helmet impact magnitudes for matched set of impacts reveals that the HALO collar resulted in significantly reduced peak helmet linear accelerations (31.1% reductions), and smaller reductions in peak helmet angular velocities (15.5%). The reduction in linear accelerations is considered to have moderate practical importance. The reduction in angular velocity is considered to have limited practical importance.
Figure 1. Comparison of linear acceleration (g) of the player helmet for matched impacts without HALO collar and with HALO collar. Black lines indicate the matched impacts that had a reduced linear acceleration from wearing HALO collar, red lines indicate the matched impacts that had an increased linear acceleration from wearing HALO collar. On average, the magnitude of the linear acceleration while wearing the HALO collar was reduced 31.1%, which was statistically significant and was of limited practical significance and has moderate practical importance.
Figure 2. Comparison of rotational velocity (deg/s) of player helmet for matched impacts without HALO collar and with HALO collar. Black lines indicate the matched impacts that had a reduced rotational velocity while wearing HALO collar, and red lines indicate the matched impacts that had an increased rotational velocity while wearing HALO collar. On average, the magnitude of the rotational velocity while wearing the HALO collar was reduced 15.5%, which was not statistically significant and was of limited practical significance.