title: Models of the apparent mass of the seated human body exposed to horizontal whole-body vibration.
abstract: BACKGROUND
  Many environments contain vibration with simultaneous vertical and horizontal components. Mathematical lumped parameter models of the mechanical impedance of the seated human body have previously been defined for exposure to vertical vibration. This paper proposes models for the response of the seated body when exposed to horizontal vibration.
  
  
  METHODS
  Four target functions were derived from previously reported measurements of the apparent masses of seated subjects exposed to fore-and-aft and lateral vibration at both 0.5 and 1.0 ms(-2) r.m.s. Parameters were optimized for six different three degree-of-freedom models to fit the modulus of the model responses to the four target functions.
  
  
  RESULTS
  The modulus and phase of the apparent masses optimized for all combinations of vibration magnitude and direction were close to the responses previously measured and reported in the literature. Fitted parameters for all models with elements in series showed at least one element with a parameter that tended to zero.
  
  
  CONCLUSIONS
  Models with three parallel single degree-of-freedom systems with a rigid support generally gave the closest representation of the apparent mass of the seated body exposed to horizontal vibration. More experimental data on the effect of gender, posture and magnitude of vibration on the apparent masses of seated subjects would be useful to enable these models to be improved.
authors.affiliation: Department of Technical Hygiene, National Institute for Working Life, Umeå, Sweden.
authors.forename: N J
authors.initials: NJ
authors.lastname: Mansfield
authors.forename: R
authors.initials: R
authors.lastname: Lundström
mesh_terms: D000328:Adult; D015982:Bias; D001696:Biomechanical Phenomena; D015992:Body Mass Index; D005260:Female; D006801:Humans; D008297:Male; D008954:Models, Biological; D017711:Nonlinear Dynamics; D016273:Occupational Exposure / Q000009:adverse effects / Q000032:analysis; D011187:Posture; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012727:Sex Characteristics; D014732:Vibration / Q000009:adverse effects*