The Ability of an Aftermarket Helmet Add-On Device to Reduce Impact-Force Accelerations During Drop Tests

Abstract

Context: The Guardian Cap provides a soft covering intended to mitigate energy transfer to the head during football contact. Yet how well it attenuates impacts remains unknown. Objective: To evaluate the changes in the Gadd Severity Index (GSI) and linear acceleration during drop tests on helmeted headforms with or without Guardian Caps. Design: Crossover study. Setting: Laboratory. Patients or Other Participants: Nine new football helmets sent directly from the manufacturer. Intervention(s): We dropped the helmets at 3 velocities on 6 helmet locations (front, side, right front boss, top, rear right boss, and rear) as prescribed by the National Operating Committee on Standards for Athletic Equipment. Helmets were tested with facemasks in place but no Guardian Cap and then retested with the facemasks in place and the Guardian Cap affixed. Main Outcome Measure(s): The GSI scores and linear accelerations measured in g forces. Results: For the GSI, we found a significant interaction among drop location, Guardian Cap presence, and helmet brand at the high velocity (F10,50 = 3.01, P = .005) but not at the low (F3.23,16.15 = 0.84, P = .50) or medium (F10,50 = 1.29, P = .26) velocities. Similarly for linear accelerations, we found a significant interaction among drop location, Guardian Cap presence, and helmet brand at the high velocity (F10,50 = 3.01, P = .002, ω2 = 0.05) but not at the low (F10,50 = 0.49, P = .89, ω2 < 0.01, 1–β = 0.16) or medium (F5.20,26.01 = 2.43, P = .06, ω2 < 0.01, 1–β = 0.68) velocities. Conclusions: The Guardian Cap failed to significantly improve the helmets' ability to mitigate impact forces at most locations. Limited evidence indicates how a reduction in GSI would provide clinically relevant benefits beyond reducing the risk of skull fracture or a similar catastrophic event.

Sport-Related Concussion: Evaluation, Treatment, and Future Directions

“…Although several companies market helmets that claim to protect against concussion, a lack of published scientific literature exists, due in part to the proprietary nature of the products of helmet companies. Studies have been published that evaluate several innovations, such as tethering a helmet to shoulder pads [109] or introducing an additional layer on top of a helmet, but show limited scientific evidence supporting the clinical benefit of implementing these new designs. Specifically, Breedlove and colleagues evaluated the Guardian Cap and demonstrated that the device reduced force at velocities high enough to cause skull fracture, but failed to mitigate impact forces at the low and medium velocities typically involved in concussion [110].…”

A football helmet prototype that reduces linear and rotational acceleration with the addition of an outer shell

“…The study of laboratory-based design of novel helmets for football has been sparse. 2,25 Nakatsuka and Yamamoto 25 added a soft cushion layer to the helmet exterior in an attempt to reduce the magnitude of head impacts. One helmet had a foam pad fixed to the crown and struck a second helmet with a foam pad fixed to the side, and after 90 total impacts, the foam layer of both helmets significantly reduced head impact–severity measures.…”

“…25 However, the study was limited by the low forces (30 g ) used, lack of rotational acceleration testing, and absence of a statistical analysis. Most recently, Breedlove et al 2 found that the addition of an outer cap to a commonly used football helmet did not reduce rates of linear acceleration significantly after subjecting it to 18 total tests on 6 locations at 3 different velocities.…”

“…Second, collaborations with industry to evaluate current equipment should be pursued by researchers and/or sports safety-promoting organizations. An example can be seen with the helmet add-on device Guardian Cap, studied by Breedlove et al, 2 who tested it in a controlled setting. Third, the power of professional sports organizations should be used to award both industry and independent researchers for collaborative and transparent helmet research.…”

“…The few innovations that have been reported include designing a personalized helmet, 15 tethering the helmet to the shoulder pads, 22 and implementing helmet add-on devices. 2 Linear acceleration can be attenuated through a thicker, heavier helmet shell; however, this generally comes at the expense of decreased comfort, higher magnitudes of rotational acceleration caused by increased rotational momentum and duration of acceleration, and increased force because of increased mass.…”