Measuring head impacts: accelerometers and other sensors.

Understanding the biomechanics of head injuries is essential for the development of preventive strategies and protective equipment design. However, there are many challenges associated with determining the forces that cause injury. Acceleration of the skull is often measured because it is relatively easy to quantify and relates to severity of impact, but it is difficult to relate those measurements to the type and extent of injury that occurs. Experimental work in the laboratory has used either human cadavers or volunteers. Cadavers can be instrumented with high-grade sensors that are tightly coupled to the skull for accurate measurements, but they cannot exhibit a functional response to determine a threshold for brain injury. Volunteers can also be instrumented with high-grade sensors in controlled laboratory experiments, but any head accelerations they experience must be well below an injurious level. Athletes participating in contact sports present a unique opportunity to collect biomechanical data from populations that have increased exposure to head impacts and a higher risk of head injury than the general population. Recent advances in sensor technology have allowed for more accurate measurements from instrumented athletes during play, but it is challenging to tightly couple the instrumentation to the skull to provide meaningful measurements. Because of the challenges associated with on-field measurements, it is important to consider the type of sensor used and its accuracy in the field when evaluating head impact data from athletes.