Impact characteristics of two American football helmet models

Few studies have compared the impact characteristics of modern American football helmet types. The purpose of this study was to measure and compare the collision biomechanics of the common Vicis Zero1 (2.27 kg) and Riddell Speedflex (2.09 kg) helmets. Linear drop tests were conducted from 1.52, 1.98, 2.59, and 3.05 m with a Hybrid III headform. The helmets were positioned crown-down and dropped in a manner that resulted in minimal pre-collision rotation. An 8-camera motion capture system recording at 300 Hz was used to verify that contact occurred to the region of the helmet immediately superior to the top of the facemask for each trial. Impact kinetics were recorded via a force plate sampling at 1800 Hz. Peak and mean accelerations (g) were calculated from initial contact until peak vertical ground reaction force (VGRF) was reached. Independent t-tests and effect sizes (Hedge’s g) were performed. The Speedflex helmet resulted in greater peak VGRF, peak acceleration, and mean acceleration (p = 0.045, <0.001, and <0.001, respectively). Effect sizes were medium for VGRF (0.73) and large for peak (48.07) and mean (2.28) accelerations. These data indicate that the Zero1 helmet, which has a compliant outer shell, may lead to greater athlete safety by resulting in peak forces and accelerations of less magnitude as compared to helmets with rigid shell designs.