title: Muscle strength, muscle mass, and physical disability in women with systemic lupus erythematosus.
abstract: OBJECTIVE
  Data describing relationships between muscle strength, muscle mass, and physical disability among individuals with systemic lupus erythematosus (SLE) are limited. The present study examines the relationship of muscle strength and muscle mass with physical disability among adult women with SLE.
  
  
  METHODS
  A total of 146 women from a longitudinal SLE cohort participated in the study. All measures were collected during an in-person research visit. Lower extremity muscle strength was assessed by peak knee torque of extension and flexion and by chair-stand time. Total lean body mass, appendicular lean mass, and fat mass (kg/m(2) ) were measured by whole-body dual x-ray absorptiometry. Self-reported physical disability was assessed using the Short Form 36 health survey (SF-36) physical functioning subscale, and the Valued Life Activities (VLA) disability scale. Spearman's rank correlation coefficients tested the correlations between muscle strength, muscle mass, and disability scores. Regression analyses modeled the effect of lower extremity muscle strength and mass on SF-36 and VLA disability scores controlling for age, SLE duration, SLE disease activity measured with the Systemic Lupus Activity Questionnaire, physical activity level, prednisone use, body composition, and depression.
  
  
  RESULTS
  On all measures, reduced lower extremity muscle strength was associated with poorer SF-36 and VLA disability scores. Trends persisted after adjustment for covariates. Muscle mass was moderately correlated with muscle strength, but did not contribute significantly to adjusted regression models.
  
  
  CONCLUSIONS
  Lower extremity muscle strength, but not muscle mass, was strongly associated with physical disability scores. While further studies are needed, these findings suggest that improving muscle strength may reduce physical disability among women with SLE.
authors: University of California, San Francisco.
authors: James S
authors: JS
authors: Andrews
authors: Laura
authors: L
authors: Trupin
authors: Gabriela
authors: G
authors: Schmajuk
authors: Jennifer
authors: J
authors: Barton
authors: Mary
authors: M
authors: Margaretten
authors: Jinoos
authors: J
authors: Yazdany
authors: Edward H
authors: EH
authors: Yelin
authors: Patricia P
authors: PP
authors: Katz
mesh_terms: D000328:Adult; D001823:Body Composition / Q000502:physiology*; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D006233:Persons with Disabilities; D005260:Female; D006306:Health Surveys / Q000379:methods; D006801:Humans; D008137:Longitudinal Studies; D008180:Lupus Erythematosus, Systemic / Q000000981:diagnostic imaging* / Q000453:epidemiology / Q000503:physiopathology*; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology*; D011859:Radiography