Sensitivity of the results produced by the inverse dynamic analysis of a human stride to perturbed input data.

The results of the inverse dynamic procedures used in gait analysis are known to be highly dependent on the quality of the kinematic and dynamic input data and on the biomechanical model anatomical data. In this paper the sensitivities of the system response to imprecision in the input data and biomechanical model were calculated. It was shown that the gait analysis results were very sensitive to the identification of the point of application of the external forces. The quality of the results was less sensitive to errors made during motion reconstruction and to uncertainties in the biomechanical anatomical data. In this study it is also shown that the adopted inverse dynamic analysis method, based on natural coordinates, effectively shielded any error made on a particular kinematic chain from propagation to other branches of the biomechanical model.