The Penn State Safety Floor: Part I—Design Parameters Associated With Walking Deflections

Abstract

A new flooring system has been developed to reduce peak impact forces to the hips when humans fall. The new safety floor is designed to remain relatively rigid under normal walking conditions, but to deform elastically when impacted during a fall. Design objectives included minimizing peak force experienced by the femur during a fall-induced impact, while maintaining a maximum of 2 mm of floor deflection during walking. Finite Element Models (FEMs) were developed to capture the complex dynamics of impact response between two deformable bodies. Validation of the finite element models included analytical calculations of theoretical buckling column response, experimental quasi-static loading of full-scale flooring prototypes, and flooring response during walking trials. Finite Element Method results compared well with theoretical and experimental data. Both finite element and experimental data suggest that the proposed safety floor can effectively meet the design goal of 2 mm maximum deflection during walking, while effectively reducing impact forces during a fall.

Characterization of the protective capacity of flooring systems using force-deflection profiling

“…Previous studies involving quiet stance and backwards perturbations in elderly individuals revealed clinically insignificant differences in postural sway between some safety floors and traditional floors [15,23]. In order to examine a more dynamic task scenario, the flat-foot stage of single-leg stance during a natural cadence gait-cycle was simulated in this study to contribute to existing literature on locomotor adaptations, footfall deflections and toe-floor clearance distances while walking on compliant surfaces [22,24,25]. In addition, this approach corresponds to recommendations that "future research into the role of floor compliance in balance in older adults should include studies of walking" [33].…”

“…Control of balance is dependent on the central nervous system continually integrating visual, vestibular, and somatic sensory information about the surrounding environment, orientation of body parts, and forces acting on the body [20]. Soft foam surfaces detrimentally affect somatic sensory inputs from proprioceptive muscle spindles and cutaneous receptors in the foot and ankle, leading to a delayed or misguided balance control response [21,22]. Thus, a crucial design element for effective safety floors is the ability to provide substantial force attenuation without allowing deflections that may impair balance control during gait and stance activities.…”

Effects of body configuration on pelvic injury in backward fall simulation using 3D finite element models of pelvis–femur–soft tissue complex

“…To develop new intervention strategies such as impact attenuating safety floors (Casalena et al, 1998;Laing et al, 2006), more data are needed on the dynamics of backward fall and injury locations for various fall configurations.…”

Impact properties of floor coverings and their role during simulated hip fractures

“…A study into the design of a safety floor stated that it must reduce peak impact forces in a fall and also remain relatively rigid under normal walking conditions with less than 2 mm deflection [16,17]. Under impact conditions from a fall, the floor would deform much more than 2 mm to absorb the greater kinetic energy.…”

“…Such materials have limited damping properties when there are high impact energies involved as in a typical fall. There is an increasing amount of research into the impact properties of floor coverings [16,17,18]. The aim of this work is to describe a new technique for accurate simulation of typical impact conditions and a method for analysis of results.…”