title: Force control of isometric elbow flexion with visual feedback in cold with and without shivering.
abstract: BACKGROUND
  Exposure to cold impairs manual performance through effects on muscle tissue and control mechanisms. The purpose of this study was to assess the influence of increased muscle tone and shivering on ability to maintain required force during isometric flexion over a wide range of effort levels.
  
  
  METHODS
  Lightly clad male subjects (n = 6) were exposed to thermoneutral air (TN, 27 degrees C) for 30 min, or to cold air (CA, 10 degrees C) for 30 min followed by a cold drink (1 L, 8 degrees C) to cause vigorous shivering (SH). At the end of each condition, subjects performed isometric elbow flexion at 10, 20, 40, and 80% of individual maximal voluntary contraction (MVC) for 10 s each, using digital visual feedback to control the force. We analyzed mean force output (F), the coefficient of force variation (FCv), information transmission (F/SD), and the coefficient of force auto-correlation (Ra), and the averaged electromyogram (aEMG) from elbow flexors, elbow extensor, and pectoral girdle muscles.
  
  
  RESULTS
  Compared with TN, CA with increased muscle tone raised the aEMG by 5-30% but did not impair any of the force characteristics. In SH, F was not affected, while FCv and Ra were significantly increased at 10% MVC, while aEMG increased by 30-400% depending on the specific muscle and MVC level.
  
  
  CONCLUSIONS
  Neither thermoregulatory muscle tone nor shivering influenced the control of force output during isometric elbow flexion, except that at the lowest MVC (10%) the force output was more variable during shivering.
authors.affiliation: Dept. of Human and Animal Physiology, Petrozavodsk State University, Petrozavodsk, Russia. meigal@petrsu.ru
authors.forename: Alexander Yu
authors.initials: AY
authors.lastname: Meigal
authors.forename: Juha
authors.initials: J
authors.lastname: Oksa
authors.forename: Ludmila I
authors.initials: LI
authors.lastname: Gerasimova
authors.forename: Esa
authors.initials: E
authors.lastname: Hohtola
authors.forename: Yuri V
authors.initials: YV
authors.lastname: Lupandin
authors.forename: Hannu
authors.initials: H
authors.lastname: Rintamäki
mesh_terms: D000328:Adult; D003080:Cold Temperature; D004576:Electromyography; D005246:Feedback; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D012768:Shivering / Q000502:physiology*; D013647:Task Performance and Analysis