title: Body Sway as a Possible Indicator of Fatigue in Clerical Workers.
abstract: BACKGROUND
  Fatigue has a strong impact on workers' performance and safety, but expedient methods for assessing fatigue on the job are not yet available. Studies discuss posturography as an indicator of fatigue, but further evidence for its use in the workplace is needed. The purpose of the study is to examine whether posturography is a suitable indicator of fatigue in clerical workers.
  
  
  METHODS
  Thirty-six employees (Ø 34.8 years, standard deviation = 12.5) participated in postural tasks (eyes open, eyes closed, arm swinging, and dual task) in the morning and afternoon. Position of their center of pressure (COP) was registered using a Nintendo Wii Balance Board and commercial software. From registered COP time series, we calculated the following parameters: path length (mm), velocity (mm/s), anterior-posterior variance (mm), mediolateral variance (mm), and confidence area (mm(2)). These parameters were reduced to two orthogonal factors in a factor analysis with varimax rotation.
  
  
  RESULTS
  Statistical analysis of the first factor (path length and velocity) showed a significant effect of time of day: COP moved along a shorter path at a lower velocity in the afternoon compared with that in the morning. There also was a significant effect of task, but no significant interaction.
  
  
  CONCLUSIONS
  Data suggest that postural stability of clerical workers was comparable in the morning and afternoon, but COP movement was greater in the morning. Within the framework of dynamic systems theory, this could indicate that the postural system explored the state space in more detail, and thus was more ready to respond to unexpected perturbations in the morning.
authors.affiliation: German Sport University Cologne-Institute of Physiology and Anatomy, Cologne, Germany.
authors.forename: Ina
authors.initials: I
authors.lastname: Völker
authors.affiliation: German Sport University Cologne-Institute of Physiology and Anatomy, Cologne, Germany.
authors.forename: Christine
authors.initials: C
authors.lastname: Kirchner
authors.affiliation: German Sport University Cologne-Institute of Physiology and Anatomy, Cologne, Germany.
authors.forename: Otmar Leo
authors.initials: OL
authors.lastname: Bock
authors.affiliation: IfADo-Leibniz Research Centre for Working Environment and Human Factors, Dortmund, Germany.
authors.forename: Edmund
authors.initials: E
authors.lastname: Wascher
keywords: fatigue; posturography; workplace