It is estimated that millions of mild traumatic brain injuries (mTBIs) occur each year, and studies show that these injuries can have more long-term neurological consequences than previously thought. High impact sports provide a unique real-world opportunity to study the biomechanical inputs that lead to mTBI and helmet-based instrumentation can be used to estimate the kinematics of head impacts in sports. In Chapter 1, we evaluate two helmet-based measurement systems that use different approaches to estimate kinematics by impacting a helmeted anthropometric test device (ATD) in a laboratory setting. The relationships between the helmet sensor system and reference ATD measures are evaluated. In Chapter 3, we explore the effect of real-world impact and usage variations on the relationships between helmet system and ATD-measured head impact kinematics. The factors varied include the interface between the head and the helmet, repeatability of sensor/helmet systems, helmet geometry/construction, effective mass of the torso, and impacting surface. In Chapter 4 we assess the effect of helmet-based sensor performance on brain injury metrics calculated using finite element analysis. This is done by using helmet system and ATD data from the laboratory impacts as inputs into a finite element head model and comparing outcomes. Chapter 5 discusses the implications of the findings on the implementation of helmet-based systems in real-world scenarios.