The capacity of a mechanical model to reproduce experimental characteristics of a human body was always a main indicator for evaluation of model merits. In doing so, the question as to how many models can reproduce these experimental data with the same exactness remained beyond the examination. In other words, the question of uniqueness (as well as existence) of the model construction problem remained open. This induced to direct our attention to constructing a theory of identification for human body mechanical models. As the first steps in this study, several theorems relative to existence and uniqueness of an identification problem solution were proved. In particular, it has been shown that even if a mechanical model structure is given, one can find several sets of model parameters which result in one and the same amplitude frequency characteristic, conventionally used as a criterion. At the same time, it was shown that the different parameter values bring to different results when constructing a vibroprotection system. It was established that the mechanical model parameters determined uniquely if both a transfer function and an input mechanical impedance of a human body are known. Besides, mechanical models of a new class, that is systems, possessing the multi-joint deformable links, were proposed to use. Some advantages of such models for reproduction of experimental characteristics were illustrated.