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

Abstract

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.

Comparative Analysis for the Measurement of Head Accelerations in Ice Hockey Helmets Using Non-Accelerometer Based Systems

“…The sensors have been developed to trigger above 50g which represent 8% of impacts in hockey [13]. Further, the sensor trigger range is where the risk of head injury begins to increase to 25% at 66g and 50% at 80g [15].…”

“…This value was chosen due to the mechanical constraints of the force switch itself and as a design requirement to avoid spurious and erroneous sensor activation including small 10-30g impacts and impulses which are not the target activation points of interest for high risk impact events. The activation threshold was also chosen based on data from Gwin indicating 92% of hockey impacts were below 50 g [13] and 97% of football impacts were below 40 g linear acceleration recorded by Rowson [14].…”

Hockey STAR: A Methodology for Assessing the Biomechanical Performance of Hockey Helmets

“… 39 These accelerometer arrays have previously been described in detail, but briefly, each helmet contains six single-axis linear accelerometers that are oriented tangentially to the head and integrated into foam inserts which allow the sensors to maintain contact with the head during impact. 25 The median number of head impacts per player per season experienced by collegiate athletes was 287 for males and 170 for females. 57 The median number of impacts per player per season for youth athletes was 223.…”

“…The exposure for each impact location was weighted by how often they occur in data collected in the literature. 7 , 25 , 39 , 57 The front, side (left and right combined), and back were approximately 30% each, with the remaining 10% of impacts to the top of the head. These values were used to weight exposure by impact location.…”

A fluidics-based impact sensor

“…Another need for an accelerometer is in sports. In many contact sports, injuries (e.g., head injuries, concussions) often arise from physical contacts, such as in American football [ 9 ], rugby [ 10 , 11 ], ice hockey [ 12 , 13 ], basketball, soccer [ 14 , 15 ], judo [ 16 ], and many others. Today, MEMS-based sensors have been developed specifically for these sports [ 17 ], and are sold in the market [ 11 , 18 , 19 ].…”