title: Context dependence of manual grasping movements in near weightlessness.
abstract: BACKGROUND
  We have shown before that human subject grasping performance differs in an everyday-like context with that observed in a laboratory context. The purpose of the present study was to determine whether reported deficits in weightlessness are more pronounced when grasping is performed as part of everyday-like behavior rather than as an isolated laboratory-type response.
  
  
  METHODS
  The grasping performance of 12 participants (ages 29 +/- 5 yr) during periods of near weightlessness in parabolic flights was compared. Subjects performed a typical laboratory task (L) where grasping was repetitive, externally triggered, purposeless, and attention-attracting, and an everyday-like task (E) where the movements were part of a rich behavioral pattern, internally initiated, purposeful, and little attended. We registered typical kinematic, force, and gaze parameters, and calculated their within-subject means and variation coefficients.
  
  
  RESULTS
  A global parameter comparison showed that the effects of weightlessness on grasping movements were task-dependent: means were more affected in task E (RMS scores 1.29 +/- 0.07 in L compared with 1.74 +/- 0.15 in E) and variation coefficients in task L (RMS score 4.92 +/- 0.53 in L compared to 3.00 +/- 0.22 in E).
  
  
  CONCLUSIONS
  The results suggest that the effects of weightlessness observed under laboratory conditions can under- or overestimate the effects that emerge during everyday routines.
authors.affiliation: Institute of Physiology and Anatomy, German Sport University Cologne, Am Sportpark Müngersdorf 6, 50933 Cologne, Germany. f.steinberg@dshs-koeln.de
authors.forename: Fabian
authors.initials: F
authors.lastname: Steinberg
authors.forename: Otmar
authors.initials: O
authors.lastname: Bock
mesh_terms: D000328:Adult; D001288:Attention; D001696:Biomechanical Phenomena / Q000502:physiology; D053483:Eye Movement Measurements; D005403:Fixation, Ocular / Q000502:physiology; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D008297:Male; D009068:Movement / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology*; D018474:Weightlessness Simulation; D055815:Young Adult