The influence of helmet size and shape on peak linear decelerations when impacting crash pads

Abstract

During training and competition in short track speed skating, skaters commonly fall on the ice and slide into crash pads that line the boards of the rink. Skaters wear helmets to protect their heads from such impacts. Nevertheless, concussion injuries are not uncommon, especially from impacts into the crash pads. Basic mechanical principles suggest that, all other things being equal, smaller sized and rounder shaped helmets should reduce peak impact forces when hitting relatively soft crash pads. This study validates these assumptions and determines the magnitude of these effects using drop tests and a 3D accelerometer. Hemispherical head forms of various radii, each weighing approx. 4.5kg, were dropped from four heights (0.3-4.0 m) onto a crash pad. Peak linear decelerations were recorded. In one set of tests, complete hemispheres were used, highlighting the effect of helmet size (radius). In a second set of tests, another set of hemispheres of various radii were sliced to produce caps each with a diameter of 8” but each with a different radius of curvature. Impact tests at four drop heights using these caps revealed the effect of helmet shape. Size was found to be more important than shape, with the greatest effects being in the 10-20cm radius range, a range which is relevant to helmets used in the sport today.