Volume 6, Issue 6 (June 2009)
In situ Measures of Head Impact Acceleration in NCAA Division I Men’s Ice Hockey: Implications for ASTM F1045 and Other Ice Hockey Helmet Standards
A pilot study was performed to measure head impact accelerations in collegiate men’s ice hockey during the 2005–2007 seasons using helmets instrumented with Head Impact Telemetry System technology to monitor and record linear head accelerations and impact locations in situ. The objectives of this study were (1) to quantify the relationship between resultant peak linear head acceleration and impact location for in situ head impacts in collegiate men’s ice hockey, (2) to quantify the frequency and severity of impacts to the facemask, and (3) to determine if in situ impacts occurred such that the peak resultant linear head acceleration was higher than the peak resultant linear headform acceleration from a 40-in. linear drop (as in ASTM F1045–99) on the same helmet at a similar impact location. Voluntary participants (n=5 and 7 for years 1 and 2, respectively) wore instrumented helmets which monitored head impact accelerations sustained by each player during all games and practices. Head impact data were grouped by impact location into five bins representing top, back, side, forehead, and facemask. Forehead impacts represented impacts to the helmet shell as distinguished from facemask impacts. Additionally, a sample instrumented helmet was impacted in the laboratory at forehead, side, rear, and top impact locations (40-in. drop, three trials per location, test setup as specified in ASTM F1045-99). The mean peak resultant linear headform acceleration for each impact location was determined for analysis. Of the 4,393 recorded head impacts, 33.2 % were to the back of the helmet. This percentage increased to 59.2 % for impacts above 70 g. Facemask impacts accounted for 12.2 % of all impacts but only 2.4 % of impacts above 70 g. Over two seasons, five in situ impacts occurred such that the peak resultant linear head acceleration was greater than the mean peak resultant linear headform acceleration for a corresponding impact location in the laboratory. This study found that the most common impact location in ice hockey, particularly for impacts with higher peak linear accelerations, was the back of the head and demonstrated that facemask impacts were typically of a lower magnitude. The five impacts or ∼0.4 per player/season that exceeded the peak linear acceleration associated with 40-in. laboratory drops suggested that the impact energy specified in ASTM F1045 may not reflect the highest energy impacts seen in situ.