# Evaluation of Snowboarding Helmets in Mitigation of the Biomechanical Responses of Head Surrogate
## 4 Discussion
They also suggested that the effectiveness of an anti-rotational liner depends on its integration inside a helmet. [PERSON] et al. [6] studied the impact performance of bicycle helmets during oblique impacts. They found that helmet design had a profound impact on helmet performance. Our work shows that a comfort liner indeed plays a critical role in reducing angular kinematics. The results with the comfort liner suggest that bicycle helmets should also incorporate a comfort liner. The computational simulations showed that the side orientation created a heterogeneous pattern in the spatiotemporal evolution of the strain field, encompassing regions of the temporal cortex/lobe, corpus callosum, midbrain, thalamus, and amygdala. For the front orientation, the spatiotemporal evolution of the strain pattern was relatively homogenous, encompassing motor, sensory, and emotional regions. Abnormalities in these regions have been often seen in neuroimaging investigations of mild TBI (e.g., see [70; 71] and the references therein). Our results are comparable (Table 6) with other snowboarding investigations in the literature [22; 23; 24] for similar impact velocities. The peak values and pulse durations of head kinematics obtained in this work are consistent with the reported data in the literature. [PERSON] et al. [23] recreated a snowboarding impact scenario by impacting the headform (no-helmet and with-helmet configurations) on the snow surface at an impact velocity of 4.1 m/s. They measured the peak linear acceleration of 82 g for the no-helmet configuration. They reported peak angular accelerations of 7291 rad/s2 (pulse duration: 9 ms) and 4056 rad/s2 (pulse duration: 12 ms) for the conventional and anti-rotational helmet, respectively; the anti-rotational helmet reduced angular acceleration by ~45% compared to the conventional helmet. Similarly, [PERSON] et al. [24] reconstructed a snowboarding impact scenario by impacting the headform (no helmet) on the snow surface at an impact velocity of 5.3 m/s. They obtained a peak linear acceleration of 120 g (pulse duration: 6 ms). In another investigation, [PERSON] et al. [22] recreated a snowboarding impact scenario by impacting the helmeted headform on a rigid anvil. They investigated the performance of conventional and anti-rotational (MIPS and WaveCel) snowboarding helmets at an impact velocity of 4.8 m/s. They obtained peak linear acceleration, peak angular velocity, peak angular acceleration in the range of 60-65 g, 8-20 rad/s, 1800-4100 rad/s2, respectively, for the conventional and anti-rotational helmet. The obtained peak values and pulse durations of head kinematics in this work were commensurate with the data reported by [PERSON] et al. [23] and [PERSON] et al. [24]. However, some of the quantitative discrepancies in head kinematics were observed between the data reported by [PERSON] et al. [22] and this work. Despite quantitative differences, the qualitative trends were similar. For example, [PERSON] et al. [22] found a significant reduction in peak angular kinematics (60-70%) in the anti-rotational helmet compared to the conventional helmet. We also found a 50-70% reduction using the anti-rotational helmet compared to the conventional helmet. This quantitative difference in head kinematics may be attributed to differences in the test setup (linear impactor vs. drop tower setup) and impact orientation (normal vs. oblique impact). A few investigations [21; 38] have reported that anti-rotational helmets may not reduce angular kinematics significantly. [PERSON] et al. [38] compared the performance of four different anti-rotational bicycle helmets with a conventional bicycle helmet. They found that MIPS and SPIN helmets, equipped with shearing pads, significantly reduced the angular kinematics. The other two helmets, one with viscoelastic padding and the other with elastic dampers, had an insignificant effect on the angular kinematics. [PERSON] et al. [21] evaluated the performance of conventional and anti-rotational bicycle helmets (i.e., SPIN and MIPS).