title: Tension-referenced measures of gastrocnemius slack length and stiffness in Parkinson's disease.
abstract: It is not known how passive muscle length and stiffness contribute to rigidity in Parkinson's disease. The objective of this study was to compare passive gastrocnemius muscle-tendon slack length and stiffness at known tension in Parkinson's disease subjects with ankle rigidity and in able-bodied people.
  
  
  
  Passive ankle torque-angle curves were obtained from 15 Parkinson's disease subjects with rigidity and 15 control subjects. Torque-angle data were used to derive passive gastrocnemius length-tension data and calculate slack length and stiffness of the gastrocnemius muscle. Between-group comparisons were made with linear models.
  
  
  
  Gastrocnemius muscle-tendon slack lengths (adjusted between-group difference, 0.01 m; 95% CI, -0.02 to 0.04 m; P = 0.37) and stiffness (adjusted between-group difference, 15.7 m-1; 95% CI, -8.5 to 39.9 m-1; P = 0.19) were not significantly different between groups.
  
  
  
  Parkinson's disease subjects with ankle rigidity did not have significantly shorter or stiffer gastrocnemius muscles compared with control subjects. © 2016 International Parkinson and Movement Disorder Society.
authors.affiliation: Faculty of Engineering, University of New South Wales, Sydney, NSW, Australia.
authors.forename: Benedict
authors.initials: B
authors.lastname: Tan
authors.affiliation: Sydney Medical School, University of Sydney, NSW, Australia.|Brain and Mind Centre, University of Sydney, NSW, Australia.
authors.forename: Kay L
authors.initials: KL
authors.lastname: Double
authors.affiliation: Sydney Medical School, University of Sydney, NSW, Australia.
authors.forename: John
authors.initials: J
authors.lastname: Burne
authors.affiliation: Sydney Medical School, University of Sydney, NSW, Australia.
authors.forename: Joanna
authors.initials: J
authors.lastname: Diong
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000842:Ankle / Q000473:pathology / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009127:Muscle Rigidity / Q000473:pathology / Q000503:physiopathology; D018482:Muscle, Skeletal / Q000473:pathology / Q000503:physiopathology; D010300:Parkinson Disease / Q000473:pathology / Q000503:physiopathology
keywords: Parkinson's disease; ankle; muscle and tendon; rigidity; stiffness