title: Responsiveness of exercise parameters in children with inflammatory myositis.
abstract: OBJECTIVE
  Juvenile dermatomyositis (DM) is an inflammatory myopathy in which the immune system targets the microvasculature of the skeletal muscle and skin, leading to significant muscle weakness and exercise intolerance, although the precise etiology is unknown. The goal of this study was to investigate the changes in exercise capacity in children with myositis during active and inactive disease periods and to study the responsiveness of exercise parameters.
  
  
  METHODS
  Thirteen children with juvenile DM (mean+/-SD age 11.2+/-2.6 years) participated in this study. Patients performed a maximal exercise test using an electronically braked cycle ergometer and respiratory gas analysis system. Exercise parameters were analyzed, including peak oxygen uptake (VO2peak), peak work rate (Wpeak), and ventilatory anaerobic threshold (VAT). All children were tested during an active period of the disease and during a remission period. From these data, 4 different response statistics were calculated.
  
  
  RESULTS
  The children performed significantly better during a remission period compared with a period of active disease. Most exercise parameters showed a very large response. The 5 most responsive parameters were Wpeak, Wpeak (percent predicted), oxygen pulse, VO2peak, and power at the VAT.
  
  
  CONCLUSIONS
  We found in our longitudinal study that children with active juvenile DM had significantly reduced exercise parameters compared with a remission period. Moreover, we found that several parameters had very good responsiveness. With previously established validity and reliability, exercise testing has been demonstrated to be an excellent noninvasive instrument for the longitudinal followup of children with myositis.
authors.affiliation: Department of Pediatric Physical Therapy & Exercise Physiology, University Hospital for Children and Youth, University Medical Center Utrecht, Utrecht, The Netherlands. t.takken@umcutrecht.nl
authors.forename: Tim
authors.initials: T
authors.lastname: Takken
authors.forename: Janjaap
authors.initials: J
authors.lastname: van der Net
authors.forename: Raoul H H
authors.initials: RH
authors.lastname: Engelbert
authors.forename: Suzanne
authors.initials: S
authors.lastname: Pater
authors.forename: Paul J M
authors.initials: PJ
authors.lastname: Helders
mesh_terms: D002648:Child; D003882:Dermatomyositis / Q000503:physiopathology*; D005080:Exercise Test; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male