title: Impact of habitual exercise on the strength of individuals with myotonic dystrophy type 1.
abstract: OBJECTIVE
  It remains unclear whether habitual physical activity can attenuate the rate of progressive muscle strength loss in individuals with myotonic dystrophy type 1 (DM1). The aim of this study was to identify whether there were any strength differences between DM1 patients who were habitually active or sedentary.
  
  
  METHODS
  Knee extension, handgrip, and elbow flexion quantitative strength measurements were investigated in the DM1 patients using isokinetic dynamometry. Strength was compared between the patients who followed self-selected formal exercise plans for at least 1 yr, those who were sedentary (controls), and those who initiated or terminated a formal exercise routine.
  
  
  RESULTS
  Physically active DM1 patients with midrange CTG repeat size (100-500 CTG repeat sizes) had significantly stronger handgrip and knee extension and elbow flexion torques as compared with their sedentary counterparts with the same CTG repeat range. The DM1 patients who began a formal exercise routine experienced a significant improvement in knee extension torque measurements (+24.3%) in comparison with those who were habitually active or sedentary.
  
  
  CONCLUSIONS
  These data suggest that there is an association between physical activity and strength. This may be shown to be a useful tool for the management of this condition. Further investigations into the relationships between physical exercise, muscle weakness, and genetic factors are needed before evidence-based recommendations can be made.
authors.affiliation: From the Departments of Pediatrics (LIB, LGM, MAT) and Medicine (MAT), McMaster University, Hamilton, Ontario, Canada.
authors.forename: Lauren I
authors.initials: LI
authors.lastname: Brady
authors.forename: Lauren G
authors.initials: LG
authors.lastname: MacNeil
authors.forename: Mark A
authors.initials: MA
authors.lastname: Tarnopolsky
mesh_terms: D000328:Adult; D018450:Disease Progression; D004551:Elbow Joint / Q000503:physiopathology; D015444:Exercise / Q000502:physiology*; D005260:Female; D018737:Hand Strength; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology*; D009223:Myotonic Dystrophy / Q000503:physiopathology / Q000534:rehabilitation*; D016059:Range of Motion, Articular; D012189:Retrospective Studies; D019415:Torque; D019680:Trinucleotide Repeat Expansion