A Dynamic Model of the Human Body in the Vertical Direction

Abstract

This paper presents a dynamic model of a human spine subjected to vertical vibrations. The lack of information regarding the negative load of the spine obstructed the development of an adequate dynamic model. The spine can be considered the resilient load-bearing member, and the mass of the upper body can be considered to be resting on top of the column. The described situation refers to the case in which the acceleration is applied in such a manner that the body is pushed down into the seat. The natural frequency, the dumping coefficient and also the critical levels of the force from the spinal direction are calculated. Fig. 1 presents a biomechanical model of the human body under vertical vibration. In all cases analyzed was thesteptype excitation. It was considered that the response tosteptype excitation has greater practical importance than theweightresponse because a large class of real signals that are external dynamic disturbances of the human body can be treated easily with the help ofstep-type function (Heaviside functions) or combinations thereof. Fig. 2 presents the force response for differents excitation times: (a) τ1=0.01s; (b) τ1=0.10s; (c) τ1=1.00s. There is a transient increase of transient regime with increasing of model time constant value.Key words:biomechanical model, vertical vibrations, force response, transient regime.