## 1 Introduction  
Fall-related injuries among the elderly and children are an enormous health concern worldwide [1]. For seniors over the age of 65, especially in high-risk environments such as long-term care, around 60% of elders fall at least once per year [2], which can cause injuries including hip fracture [3] and traumatic brain injury (TBI) [4]. Similarly, the annual average number of emergency department visits for adolescents under 14 years old in the United States exceeded 200,000, with 9.8% having a TBI due to falls from 2001 to 2013 [5]. Considering the alarming rise in incidence and fatality rates of fall-related TBI [6, 7], it is imperative to design and implement effective intervention strategies to contain the social and economic impact of the prospective increase in fall-related TBI incidence over the coming decades [8]. Currently, a common approach that is particularly relevant for high-fall-risk environments is to reduce the stiffness of the ground surface in order to attenuate the contact forces applied to the body during a fall impact [9, 10]. An energy-absorbing floor (EAF) is a passive intervention structure with the intention of reducing the incidence and severity of fall-related injuries [11]. Evidence shows that some low stiffness surfaces like soft foam could influence balance maintenance and balance recovery abilities and cause a rise in fall risk [12]. Thus, EAF is generally designed to achieve a dual stiffness response characterized by minimizing deformation during movements and enhancing the energy absorption at the higher loads associated with fall-related impacts [13] without increasing the fall risk. A typical design pattern consists of a continuous top surface that overlays a series of support columns, which deform after reaching a critical load threshold. Previous studies have suggested that certain commercially available EAFs could potentially reduce the risk of injury among the elderly without increasing the likelihood of falls based on statistics from incident reports [14]. [PERSON] and [PERSON] [13] investigated the flooring system on headform impact dynamics based on a mechanical drop tower and indicated that EAFs (SmartCells, SofTile, and Kradal) provided more protection than commercial carpet with a 20-80% reduction in impact force and an approximately 60-70% attenuation in HIC. Certain models of products have also exhibited a reduction in the femur impact force by up to 50% based on hip impact simulator tests [11] without substantially impairing balance in older women. However, there is a lack of biomechanical research concerning the impact process of pedestrian falls, as well as the absence of quantitative evaluation methods for the protective effectiveness of floor strategies. There is a need to conduct a detailed simulation analysis of impact dynamics at the human tissue level for the improvement of injury prevention strategies and corresponding protection effectiveness. Finite element (FE) models and instrumented headforms have been increasingly used to investigate head impact dynamics and optimize the performance of safety gears, including ground surfaces [15]. The advantage of an FE head model is that it can be modeled in detail to investigate the effect on brain tissue level [16] and can match the anthropometric characteristics of human heads [12]. Various FE brain models have been developed for brain injury research, all with varying levels of anatomical detail, material properties, and boundary conditions between different anatomical regions of the brain [17; 18; 19; 20]. [PERSON] et al. [21] presented a comprehensive summary of most of these models, such as the Global Human Body Model Consortium (GHBMC) [22], Imperial College model (IC) [23], KTH model [24], PIPER 18-year-old model [25], Total Human Model for Safety (THUMS) [26], etc. Previous research suggested that the intracranial responses could be different depending on which FE model is used [27].