title: Changes in passive mechanical properties of the gastrocnemius muscle at the muscle fascicle and joint levels in stroke survivors.
abstract: OBJECTIVE
  To investigate the ankle joint-level and muscle fascicle-level changes and their correlations in stroke survivors with spasticity, contracture, and/or muscle weakness at the ankle.
  
  
  METHODS
  To investigate the fascicular changes of the medial gastrocnemius muscle using ultrasonography and the biomechanical changes at the ankle joint across 0 degrees, 30 degrees, 60 degrees, and 90 degrees knee flexion in a case-control manner.
  
  
  METHODS
  Research laboratory in a rehabilitation hospital.
  
  
  METHODS
  Stroke survivors (n=10) with ankle spasticity/contracture and healthy control subjects (n=10).
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  At the muscle fascicle level, medial gastrocnemius muscle architecture including the fascicular length, pennation angle, and thickness were evaluated in vivo with the knee and ankle flexion changed systematically. At the joint level, the ankle range of motion (ROM) and stiffness were determined across the range of 0 degrees to 90 degrees knee flexion.
  
  
  RESULTS
  At comparable joint positions, stroke survivors showed reduced muscle fascicle length, especially in ankle dorsiflexion (P< or =.048) and smaller pennation angle, especially for more extended knee positions (P< or =.049) than those of healthy control subjects. At comparable passive gastrocnemius force, stroke survivors showed higher fascicular stiffness (P< or =.044) and shorter fascicle length (P< or =.025) than controls. The fascicle-level changes of decreased muscle fascicle length and pennation angle and increased medial gastrocnemius fascicle stiffness in stroke were correlated with the joint level changes of increased joint stiffness and decreased ROM (P<.05).
  
  
  CONCLUSIONS
  This study evaluated specific muscle fascicular changes as mechanisms underlying spasticity, contracture, and joint-level impairments, which may help improve stroke rehabilitation and outcome evaluation.
authors.affiliation: Rehabilitation Institute of Chicago, Chicago, IL 60611, USA.
authors.forename: Fan
authors.initials: F
authors.lastname: Gao
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Grant
authors.forename: Elliot J
authors.initials: EJ
authors.lastname: Roth
authors.forename: Li-Qun
authors.initials: LQ
authors.lastname: Zhang
mesh_terms: D000328:Adult; D000368:Aged; D000843:Ankle Joint / Q000503:physiopathology; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D005260:Female; D006429:Hemiplegia / Q000150:complications / Q000175:diagnosis / Q000534:rehabilitation*; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D007719:Knee Joint / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D018485:Muscle Fibers, Skeletal; D009128:Muscle Spasticity / Q000000981:diagnostic imaging / Q000209:etiology / Q000534:rehabilitation*; D018908:Muscle Weakness / Q000503:physiopathology; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000503:physiopathology*; D011336:Probability; D012680:Sensitivity and Specificity; D020521:Stroke / Q000150:complications / Q000175:diagnosis; D000071939:Stroke Rehabilitation; D017741:Survivors; D014463:Ultrasonography