SUMMARY

High-tone extensor thrusts, or involuntary muscle contractions experienced by many children with cerebral palsy, can cause problems that are not addressed by current seating systems. This thesis presentation is concerned with the development of a dynamic seating system to better accommodate individuals who exhibit high-tone extensor thrusts. The first part of the presentation is focused on obtaining a general understanding of an extensor thrust from a mechanical perspective. To achieve this goal, an analytical dynamic model of a human subject undergoing an extensor thrust on a rigid chair is created. This model is validated experimentally, and inferences about the nature of extensor thrusts are made from the simulation and experimental data. The next section outlines the development of a Simple-Hingeback Seating System which allows the occupant to lean back during an uncontrolled extensor thrust event. This system is also capable of maintaining its rigidity during an intentionally-induced episode, enabling the occupant to communicate or interact with his/her environment. The design of this system is influenced by the results obtained from the rigid seat study, as well as by numerical simulation results gathered with a commercial dynamic simulation software package (Working Model 2D). The improved seatback performance is characterized through experimentation. Additionally, other possible dynamic seating systems are explored, with inferences made about possible benefits and drawbacks of each design.