title: Prior heat stress effects fatigue recovery of the elbow flexor muscles.
abstract: BACKGROUND
  Long-lasting alterations in hormones, neurotransmitters, and stress proteins after hyperthermia may be responsible for the impairment in motor performance during muscle fatigue.
  
  
  METHODS
  Subjects (n = 25) performed a maximal intermittent fatigue task of elbow flexion after sitting in either 73° or 26°C to examine the effects of prior heat stress on fatigue mechanisms.
  
  
  RESULTS
  The heat stress increased the tympanic and rectal temperatures by 2.3° and 0.82°C, respectively, but there was full recovery prior to the fatigue task. Although prior heat stress had no effects on fatigue-related changes in volitional torque, electromyographic (EMG) activity, torque relaxation rate, motor evoked potential (MEP) size, and silent period (SP) duration, prior heat stress acutely increased the pre-fatigue relaxation rate and chronically prevented long-duration fatigue (P < 0.05).
  
  
  CONCLUSIONS
  These findings indicate that prior passive heat stress alone does not alter voluntary activation during fatigue, but prior heat stress and exercise produce longer-term protection against long-duration fatigue.
authors.affiliation: Physical Therapy and Rehabilitation Science, Carver College of Medicine, 1-252 Medical Education Building, University of Iowa, Iowa City, Iowa 52242-1190, USA.
authors.forename: Masaki
authors.initials: M
authors.lastname: Iguchi
authors.forename: Richard K
authors.initials: RK
authors.lastname: Shields
mesh_terms: D000328:Adult; D004550:Elbow / Q000502:physiology*; D004576:Electromyography / Q000379:methods; D005260:Female; D018869:Heat-Shock Response / Q000502:physiology*; D006801:Humans; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D020127:Recovery of Function / Q000502:physiology*; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation / Q000379:methods; D055815:Young Adult