title: The effect of changes in joint angle on the characteristics of physiological tremor.
abstract: BACKGROUND
  Physiological tremor, as a whole, can be influenced by changes in muscle activity. However, the origin of low-frequency physiological tremor oscillations has yet to be conclusively determined. It is possible that by experimentally manipulating muscular activity, a better determination of the origin of those low-frequency oscillations can be achieved. It was demonstrated that changes in joint angle modify characteristics of muscular activity. As such, we hypothesize that changes in wrist-joint angle will alter the characteristics of low-frequency physiological tremor oscillations.
  
  
  OBJECTIVE
  Assess the influence of changes in joint angle of the wrist on characteristics of physiological finger tremor.
  
  
  METHODS
  Physiological finger tremor was recorded (n = 25) using a laser displacement system while the arm and hand were supported. The relative angle between the dorsum of the hand and the forearm was altered between conditions (135°, 180°, 225° and 270°), while the hand and the finger remained parallel to the ground. EMG of the extensors and flexors were also recorded.
  
  
  RESULTS
  Tremor amplitude was significantly altered by changes in wrist-joint angle. This was especially the case for lower frequency oscillations. In addition, electromyography properties of forearm muscles were also significantly modified by changes in wrist-joint angles.
  
  
  CONCLUSIONS
  This study demonstrates that changes in wrist-joint angle modify the characteristics of physiological finger tremor. This should be taken into account when interpreting tremor data as well as when developing tools to minimize tremor.
authors.affiliation: Département des Sciences Biologiques, Université du Québec à Montréal, Montréal, Québec, Canada.
authors.forename: Benoit
authors.initials: B
authors.lastname: Carignan
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Daneault
authors.forename: Christian
authors.initials: C
authors.lastname: Duval
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D004576:Electromyography; D005260:Female; D005385:Fingers / Q000503:physiopathology*; D005542:Forearm / Q000502:physiology; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology; D016059:Range of Motion, Articular / Q000502:physiology*; D014202:Tremor / Q000503:physiopathology*; D014955:Wrist Joint / Q000502:physiology*