Study: In 2013, a study was conducted to investigate the accuracy of the HIT system used in football helmets. The study focused on the helmet fit in high school aged football players and the assessment of the appropriate helmet size for the Hybrid III, the gold standard dummy used for impact testing. Twenty-four FlexiForce™ sensors were designed into a nylon skullcap worn by volunteers to measure the pressure between the player's head and helmet padding to determine how tightly the players wore their helmets and how evenly they fit their heads. The sensors were also used to measure the pressure between the Hybrid III dummy and both a medium and large Riddell helmet. The pressure was transmitted from the head to the sensor via thin plastic shims adhered to the sensors. Each sensor was calibrated three times with dead weights and a custom signal conditioning system was fabricated on a printed circuit board while the data analysis was conducted in Matlab.

Nylon Cap with FlexiForce Sensors

Results: Researchers analyzed the fit of the helmet by computing the average and max pressure of all the sensor data from each volunteer and collected a pressure distribution mapping of the helmet pressure. They also conducted linear impact testing on both the medium and large sized Riddell helmets on the Hybrid III dummy. The large helmet on the Hybrid III was more representative having average pressure and max pressures in the 39th and 35th percentile of the volunteer data while the medium helmet tests produced peak pressures and high levels of discomfort. This study verified the rationality of manufacturer’s suggestion to use the large helmet for Hybrid III testing, however most studies use a medium helmet.

Conclusion: When the wrong size helmet is used for acceleration testing, for example the medium Riddell helmet on the Hybrid III dummy, the results are less accurate. The measurement of head acceleration in football must be accurate in order to properly report the severity of on-field collisions. The consequences of these inaccuracies result in the risk of concussions being undetected. As this topic becomes increasingly more popular, the football and concussion community need to invest in further research of concussion detection and helmet fit in order to reevaluate existing data and future studies.

Benefits of FlexiForce™ Sensors

• Ultra-thin sensor construction and flexibility means minimal interference/disturbance to normal action
• Accurate response gives your customers and end users confidence in the performance of your product
• Knowledgeable, experienced technical staff help you develop the most effective, economical sensor based on your specific requirements. All manufacturing takes place at ISO 9001 compliant & 13485 registered Tekscan headquarters.
• 100% factory inspection ensures your sensors meet established performance specifications

Getting Started with FlexiForce Sensors

FlexiForce sensors are available off-the-shelf in packs of four or eight for testing and prototyping. Visit our online store to place an order, or contact us to discuss customization options with one of our engineers.

Citation: Ron Jadischke, David C. Viano, Nathan Dau, Albert I. King, Joe McCarthy, On the accuracy of the Head Impact Telemetry (HIT) System used in football helmets,Journal of Biomechanics, Volume 46, Issue 13, 3 September 2013, Pages 2310-2315, ISSN 0021-9290, http://dx.doi.org/10.1016/j.jbiomech.2013.05.030.