Modeling three-dimensional hip and trunk peak torque as a function of joint angle and velocity

Healthcare costs for treating back pain have risen to 50 billion dollars a year in the past decade. In attempt reduce the risk of back pain; ergonomists use digital human modeling to assess the risks involved in functional tasks. However, current models are limited to analyzing the strength in static position. The overall goal of this study is to provide three-dimensional strength surfaces incorporating both static and dynamic strength for digital human models. Fifteen male and twenty-one female subjects were recruited. The study required two visits, were hip strength testing was performed in one visit and trunk strength testing was performed in the other visit. Hip strength was tested by completing flexion and extension isometric tests and isokinetic tests. Trunk flexion and extension strength was also measured by isometric and isokinetic tests. Isometric and Isokinetic tests were completed for trunk left and right rotation too. The data was analyzed using custom made MATLAB (Mathworks, Inc) programs and the three-dimensional strength surfaces were generated using SigmaPlot (SYSTAT Software, INC). The maximum peak torques were as followed: Hip flexion male 183Nm(57), hip flexion female 106 Nm (38), hip extension male 181 Nm (71), hip extension female 130 Nm (52), trunk flexion male 182 Nm (40.3), trunk flexion female 111.8 Nm (32), trunk extension male 328.5 Nm (52), trunk extension female 197.5 Nm (58), trunk right rotation male 71.6 Nm (20), trunk right rotation female 43 Nm (14), trunk left rotation male 71 Nm (24), and trunk left rotation female (43 Nm (17). Correlations were found between the hip and trunk joints, and the flexion and extension motion. Implementing this data into digital human models will provide realistic static and dynamic human strength parameters. Ultimately, this will help ergonomists predict and reduce high risk back injuries.