Worldwide, short track (ST) speed skaters are incurring a notable number of concussions when hitting the padding that surrounds the dasher boards in their training and racing environments. Recent findings regarding the influence of helmet shape and size on peak linear deceleration values suggest that these factors matter in ST speed skating where impacts take place against compliant surfaces. This work expands upon the initial findings in several ways. In both of these studies, two types of test articles were dropped in free fall from various heights onto a crash pad. The “shape” test articles were cylindrical missiles with an end-cap of fixed area but variable radius of curvature. The expanded polystyrene end-caps had diameter values of 8, 12, 15.6, 24, and 30 in. (20.3, 30.5, 39.6, 61.0, and 76.2 cm). The “size” test articles were expanded polystyrene hemispheres of these same five diameters. Wireless 3D accelerometers (MicroStrain) were used to record acceleration while an Olympus iSpeed 2 high speed camera (1000 fps) recorded impact velocity. In the current work, impact velocities up to 12 m/s were employed. Peak linear deceleration, Head Injury Criterion (HIC), and peak jerk were determined for every impact condition. The influence of impact position on the crash mat (side, end, middle, and corner) was characterized with differences of up to 30 % in peak deceleration and 60 % in HIC values being measured between middles and corners. Penetration depths into the middle of the crash pad were also measured. Current results present a more complete picture of how helmet size and shape can affect some variables implicated in concussions. Smaller helmets produce lower peak deceleration and HIC values, and higher penetration depths. Rounder helmets penetrate more deeply into pads. At high impact speeds, the thickness and stiffness of pads likely affect the optimal helmet shape and size.
helmets, impact, size, shape, acceleration, jerk, HIC, penetration
Faculty of Science and Technology, Mount Royal Univ., Calgary, AB
Faculty of Science & Technology, Mount Royal Univ., Calgary, AB
Schulich School of Engineering, Univ. of Calgary, Calgary, AB