128 - Softer foam in bicycle helmets reduces the impact force in a simulation model

Poster Number: 128
Publication Number: 128.329

Davis J. Wong, University of Hawaii, John A. Burns School of Medicine, Kaneohe, HI, United States; Brianna-Marie A. Hollister, University of Hawaii, John A. Burns School of Medicine, Waipahu, HI, United States; Brennan E. Yamamoto, Applied Research Laboratory, University of Hawaii, Honolulu, HI, United States; Loren G. Yamamoto, University of Hawaii, John A. Burns School of Medicine, Honolulu, HI, United States

Background: Bicycling accidents are a leading cause of unintentional injury in children, resulting in many emergency department visits and associated costs. Efforts to increase bicycle helmet use have resulted in fewer head injuries and decreased bicycle-related mortality. Currently, most bicycle helmets are lined with crushable expanded polystyrene (EPS) foam, designed for a single hard impact. However, soft/rubbery foams are typically used in helmets designed for sports with a high risk of head injury, such as football, hockey, and skateboarding.

Objective: This study compared the linear acceleration generated from an impact to a manikin's head wearing an off-the-shelf “standard” bicycle helmet (stdBH) compared to a modified bicycle helmet (modBH) (original foam replaced with softer polyolefin foam).

Design/Methods: Pairs of 5 different bicycle helmets from a wide price range ($20-$90) were tested (standard versus modified). The head impact was simulated by striking the test bicycle helmet placed onto the head of a Century BOB boxing manikin, with a conventional football helmet (4.6 kg additional weight added) swung from a 1.2 meter rope and released from an angle of 45º serially for multiple data points as in Figure 1. The manikin's bicycle helmet was struck by the football helmet in the frontal, left parietal, and occipital locations for 12 trials each. Each of three accelerometers located at the manikin’s forehead, apex of the head, and right ear collected data on linear acceleration in the X, Y, and Z planes.

Results: Mean linear acceleration in G's (9.8 m/sec/sec) was obtained from the three accelerometer locations on the manikin's head for each striking position. The mean linear accelerations across the 5 different helmet pairs are summarized in the graphs (Figure 2). For each of the three striking locations, there were statistically lower striking forces sustained with the modified softer foam bicycle helmet (modBH) compared to the standard bicycle helmet (stdBH). The greatest reductions were observed in the apical accelerometers when the manikin was struck from the occipital and parietal locations.Conclusion(s): These results suggest that softer foams in bicycle helmets may reduce injury from bicycle accidents. Further research on this topic can lead to the development of safer and more effective bicycle helmets.
Figure 1: Simulating a Bicycle Helmet ImpactA weighted football helmet was tied to a basketball rim and dropped at a 45 degree angle in line to strike a bicycle helmet.
Figure 2: Frontal, Parietal, and Occipital StrikesFigure 2A. Frontal Strikes at the three head locations (accelerometer locations). Scattergram of mean G's for each helmet type. Bars show the mean of these means and the error bars show the 95% confidence interval of these means. Figure 2B. Parietal Strikes (same parameters as Figure 2A). Figure 2C. Occipital Strikes (same parameters as Figure 2A).