title: Effect of 6-minute walk test on neuromuscular properties of patients with chronic obstructive pulmonary disease.
abstract: OBJECTIVE
  The objective of this study was to evaluate the neuromechanical properties of the knee extensor muscles before and after the 6-minute walk test (6MWT) in chronic obstructive pulmonary disease (COPD) patients and control subjects.
  
  
  METHODS
  COPD patients from the Department of Pulmonology of the Hospital de Clinicas de Porto Alegre and age- and sex-matched control volunteers without COPD were included in this study. Body composition and lower limb strength assessed by maximal voluntary isometric contraction (MVIC) of the knee extensors) were assessed before and after the 6MWT. The total reaction time (TRT), premotor time (PMT) and motor time (MT) were assessed using surface electromyography of the rectus femoris and vastus lateralis knee extensor muscles.
  
  
  RESULTS
  Eighteen patients COPD patients (10 men, FEV136 ± 12% of predicted) and 8 control subjects (5 men, FEV182 ± 7% of predicted) were included. COPD patients had lower muscle strength before (21.77 ± 7.86 kg) and after the 6MWT (11.16 ± 4.70 kg) compared with control subjects (33.50 ± 14.01 kg before; 29.25 ± 16.66 kg after). After the 6MWT, COPD patients showed a significant reduction in the MVIC and a significant increase in the TRT and PMT, which did not occur in control subjects. The reaction time parameters were higher in COPD patients after the 6MWT compared with control subjects. The TRT (r = -0.535, P < 0.005) and PMT (r = -0.549, P < 0.005) were inversely correlated with the MVIC after the 6MWT.
  
  
  CONCLUSIONS
  Neuromuscular changes associated with upper motor neuron activation contribute to MVIC impairment in COPD patients after performing a functional test.
authors.affiliation: Postgraduate Pulmonology Program, Federal University of Rio Grande do Sul, UFRGS.
authors.forename: Juliana Saraiva
authors.initials: JS
authors.lastname: Pereira
authors.affiliation: Program of Human Movement Sciences, Faculty of Physical Education and Physiotherapy, Federal University of Rio Grande do Sul.
authors.forename: Fernando de Aguiar
authors.initials: FA
authors.lastname: Lemos
authors.affiliation: Postgraduate Pulmonology Program, UFRGS.|Federal University of Rio Grande do Sul.
authors.forename: Fábio Cangeri
authors.initials: FC
authors.lastname: Di Naso
authors.affiliation: Program of Human Movement Sciences, Faculty of Physical Education and Physiotherapy, Federal University of Rio Grande do Sul.
authors.forename: Renata
authors.initials: R
authors.lastname: Krüger
authors.affiliation: Faculty of Physical Education and Physiotherapy, Federal University of Rio Grande do Sul.
authors.forename: Alice
authors.initials: A
authors.lastname: de Oliveira
authors.affiliation: Service of Pneumology, Hospital de Clinicas de Porto Alegre, Postgraduate Pulmonology Program, UFRGS.
authors.forename: Marli Maria
authors.initials: MM
authors.lastname: Knorst
authors.affiliation: Postgraduate Program in Respiratory Sciences and Human Movement Sciences, UFRGS.|Physiotherapy Service of Hospital de Clinicas de Porto Alegre.
authors.forename: Alexandre Simões
authors.initials: AS
authors.lastname: Dias
mesh_terms: D000368:Aged; D004576:Electromyography / Q000379:methods; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000503:physiopathology; D009469:Neuromuscular Junction / Q000503:physiopathology*; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D012129:Respiratory Function Tests / Q000379:methods; D000070857:Walk Test / Q000379:methods*
keywords: chronic obstructive pulmonary disease - electromyography - muscle strength - six-minute walk test