title: Estimation of maximal work rate based on the 6-minute walk test and fat-free mass in chronic obstructive pulmonary disease.
abstract: OBJECTIVE
  To propose a predictive equation of the maximal work rate (Wmax) in patients with chronic obstructive pulmonary disease (COPD) based on the product of 6-minute walking test (6MWT) and fat-free mass (FFM) and to compare it with a previously proposed equation based on the product of 6MWT and body weight (BW).
  
  
  METHODS
  Descriptive (cross-sectional) study.
  
  
  METHODS
  University-based rehabilitation center.
  
  
  METHODS
  Patients with COPD (N=53; 30 men; forced expiratory volume in 1 second, 45%±15% predicted).
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  Three Wmax were produced: Wmax_real (obtained from the maximal cycle ergometry test), Wmax_BW (estimated from the product of 6MWT and BW), previously proposed by Hill et al. (Arch Phys Med Rehabil 2008; 89(9):1782-7); and Wmax_FFM (estimated from the product of 6MWT and FFM).
  
  
  RESULTS
  The equation derived from a regression model to estimate Wmax_FFM was as follows: -27.9717+3.7792*(6MWT*FFM). Wmax_real correlated better with Wmax_FFM (r=.64) than with Wmax_BW (r=.54). There was no difference between Wmax_FFM (median [interquartile range], 41 [29-50] W) and Wmax_real (40 [20-50] W, P=.88), whereas Wmax_BW (60 [52-69] W) significantly overestimated Wmax_real (P<.0001).
  
  
  CONCLUSIONS
  In patients with COPD, Wmax is better estimated by an equation including the product of 6MWT and FFM than by a previously proposed equation including the product of 6MWT and body weight.
authors.affiliation: Departamento de Fisioterapia, Universidade Estadual de Londrina, Paraná, Brazil.
authors.forename: Vinícius
authors.initials: V
authors.lastname: Cavalheri
authors.forename: Nídia Aparecida
authors.initials: NA
authors.lastname: Hernandes
authors.forename: Carlos Augusto
authors.initials: CA
authors.lastname: Camillo
authors.forename: Vanessa Suziane
authors.initials: VS
authors.lastname: Probst
authors.forename: Dionei
authors.initials: D
authors.lastname: Ramos
authors.forename: Fábio
authors.initials: F
authors.lastname: Pitta
mesh_terms: D001823:Body Composition; D003430:Cross-Sectional Studies; D005080:Exercise Test / Q000379:methods*; D017079:Exercise Tolerance; D005260:Female; D006801:Humans; D008297:Male; D026741:Physical Therapy Modalities; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology* / Q000534:rehabilitation*; D012047:Rehabilitation Centers; D016138:Walking