Validation of Computationally Estimated Human Body-Seat Contact Forces During Sitting

Internal loads such as muscle and spinal disc forces are used for the evaluation and the design of seats. Such loads can be non-invasively estimated by employing musculoskeletal models which use body posture and contact forces as inputs. Estimations of the human-seat contact forces can be used as an alternative to complex, time consuming and expensive experimental measurements. However limited evidence exists on the validation of these contact forces estimations. Therefore, this study investigated how well modeling procedures can estimate the human-seat contact forces. Participants with different anthropometric dimensions performed a wide range of sitting postures using a multi-adjustable experimental seat. The postures of the participants were recorded using a full body marker protocol. Additionally, the contact forces were measured at the seat pan, back rest, feet and arm rests. Subsequently, subject specific musculoskeletal models were developed to estimate the contact forces via an optimization routine, using the recorded kinematics and the positions of the force platforms as inputs. The computed contact forces were compared against the experimentally obtained ones. Good agreement was observed between the simulated and the measured seat pan and back forces, supporting the use of the musculoskeletal modelling approach for investigating sitting biomechanics related questions.