A Kinematic Rating System for evaluating helmet performance

Adopting a helmet has been very helpful in reducing the risk of head injury in activities with a high risk of impact to the head. However, the main focus of most helmet standards is protecting the head against skull fracture through a pass or fail criterion that only measures the linear acceleration of the head during impact. Yet, it is known that most impacts result in both linear and rotational acceleration to the head. A pass-or-fail criterion does not inform the consumers how well a helmet performs. In recent years, Virginia Tech Summation of Tests for the Analysis of Risk (STAR) rating system was introduced to provide more insight into a helmet performance. The STAR rating system quantifies the risk of concussion based on the linear and rotational performance of a helmet. However, the science behind concussion is not fully understood, and in addition to helmet performance, the risk of concussion is closely related to other factors such as age, sex, genetic, the direction of an impact, and previous head trauma. The STAR rating also does not include all crucial factors in assessing a helmet performance, and therefore, it may not provide an accurate performance or risk of injury assessment for a given helmet. In this work, a Kinematic Rating System (KRS) was developed to evaluate helmet performance based on how well a helmet reduces crucial factors such as linear acceleration, rotational acceleration, and rotational velocity. KRS is an effective tool that provides an accurate assessment of the performance of a helmet compared to when the head is not protected by a helmet. KRS requires the helmet of interest to be tested against a 45º anvil at 6.5 m/s impact speed. Various football, hockey, and cycling helmets were tested according to the KRS, and the results were compared with the STAR rating system. In some cases, the performance reported by the STAR rating system were found to have significant discrepancies with the results obtained by the KRS. This is because the STAR rating system does not consider all the crucial factors while evaluating a helmet, such as the magnitude and duration of the acceleration pulse.