title: Electrophysiologic evaluation of muscle fatigue development and recovery in late polio.
abstract: OBJECTIVE
  To study aspects of fatigue in late-polio patients and healthy controls. We hypothesized that late-polio subjects would develop more peripheral fatigue, assessed with surface electromyography (EMG), and that no major differences would exist between the two groups in neuromuscular junction transmission.
  
  
  METHODS
  Case-control study.
  
  
  METHODS
  University hospital laboratory.
  
  
  METHODS
  Ten patients with a history of polio (mean age, 54 yrs, SD = 5; mean time since polio onset, 49 yrs, SD = 7) and a matched control group (mean age, 52 yrs, SD = 8).
  
  
  METHODS
  A protocol with a stepwise force increase up to 80% of maximal voluntary contraction ending with an 8-minute recovery period was performed twice, first with surface EMG and then with electrical stimulation and surface-recorded evoked M-response.
  
  
  METHODS
  Surface EMG analysis of voluntary activity and evoked M-response.
  
  
  RESULTS
  No significant differences existed between groups in the relative decrease during the fatigue protocol. The recovery of force was slower in the late-polio subjects. A reduction in the root mean square (RMS) value during recovery was seen in the polio group, although a normalization of the mean power frequency (MPF) was seen in both groups.
  
  
  CONCLUSIONS
  The weakness during the fatigue procedure was not caused by neuromuscular blockade, because electrical nerve stimulation evoked a normal response. The weakness after exercise was the result of a slow recovery that may reflect both central and peripheral fatigue.
authors.affiliation: Department of Rehabilitation Medicine, Göteborg University, Sweden.
authors.forename: K S
authors.initials: KS
authors.lastname: Sunnerhagen
authors.forename: U
authors.initials: U
authors.lastname: Carlsson
authors.forename: A
authors.initials: A
authors.lastname: Sandberg
authors.forename: E
authors.initials: E
authors.lastname: Stålberg
authors.forename: M
authors.initials: M
authors.lastname: Hedberg
authors.forename: G
authors.initials: G
authors.lastname: Grimby
mesh_terms: D016022:Case-Control Studies; D004558:Electric Stimulation; D004576:Electromyography; D004594:Electrophysiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction; D018763:Muscle Fatigue / Q000502:physiology*; D016262:Postpoliomyelitis Syndrome / Q000175:diagnosis / Q000503:physiopathology*