title: Lower limb muscle strength impairment in late-onset and adult myotonic dystrophy type 1 phenotypes.
abstract: Lower limb strength has never been characterized separately for late-onset and adult myotonic dystrophy type 1 (DM1) phenotypes.
  
  
  
  The purpose of this study was to: (1) describe and compare lower limb strength between the 2 DM1 phenotypes; and (2) compare the impairment profiles obtained from 2 assessment methods [manual (MMT) and quantitative (QMT) muscle testing] among 107 patients.
  
  
  
  Both MMT and QMT showed more pronounced weakness in the adult phenotype. In the late-onset phenotype, although MMT showed normal strength, QMT revealed a loss of 11.7%-20.4%. Participants with grade 1 or 2 on the Muscle Impairment Rating Scale had weakness detected using QMT, which suggests earlier muscle impairment than MMT alone would suggest.
  
  
  
  To avoid muscle wasting, physical activity recommendations should be made for the late-onset phenotype and in the early stages of the disease for the adult phenotype. MMT is not recommended for use in clinical trials. Muscle Nerve 56: 57-63, 2017.
authors: Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Québec, Canada.
authors: Émilie
authors: É
authors: Petitclerc
authors: Faculty of Medicine, Rehabilitation (Physiotherapy) and Radiology Department, Université Laval, Québec City, Québec, Canada.
authors: Luc J
authors: LJ
authors: Hébert
authors: Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Québec, Canada.
authors: Jean
authors: J
authors: Mathieu
authors: Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Québec, Canada.
authors: Johanne
authors: J
authors: Desrosiers
authors: Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Québec, Canada.
authors: Cynthia
authors: C
authors: Gagnon
mesh_terms: D000328:Adult; D000368:Aged; D004576:Electromyography; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D035002:Lower Extremity / Q000294:innervation*; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology*; D018908:Muscle Weakness / Q000209:etiology*; D018482:Muscle, Skeletal / Q000503:physiopathology*; D009223:Myotonic Dystrophy / Q000150:complications*; D012720:Severity of Illness Index; D055815:Young Adult
keywords: lower limb; myotonic dystrophy type 1 (DM1); outcome measures; phenotype comparison; quantitative muscle testing; strength