title: Effects of repeated ankle stretching on calf muscle-tendon and ankle biomechanical properties in stroke survivors.
abstract: BACKGROUND
  The objective of this study was to investigate changes in active and passive biomechanical properties of the calf muscle-tendon unit induced by controlled ankle stretching in stroke survivors.
  
  
  METHODS
  Ten stroke survivors with ankle spasticity/contracture and ten healthy control subjects received intervention of 60-min ankle stretching. Joint biomechanical properties including resistance torque, stiffness and index of hysteresis were evaluated pre- and post-intervention. Achilles tendon length was measured using ultrasonography. The force output of the triceps surae muscles was characterized via the torque-angle relationship, by stimulating the calf muscles at a controlled intensity across different ankle positions.
  
  
  RESULTS
  Compared to healthy controls, the ankle position corresponding to the peak torque of the stroke survivors was shifted towards plantar flexion (P<0.001). Stroke survivors showed significantly higher resistance torques and joint stiffness (P<0.05), and these higher resistances were reduced significantly after the stretching intervention, especially in dorsiflexion (P=0.013). Stretching significantly improved the force output of the impaired calf muscles in stroke survivors under matched stimulations (P<0.05). Ankle range of motion was also increased by stretching (P<0.001).
  
  
  CONCLUSIONS
  At the joint level, repeated stretching loosened the ankle joint with increased passive joint range of motion and decreased joint stiffness. At the muscle-tendon level, repeated stretching improved calf muscle force output, which might be associated with decreased muscle fascicle stiffness, increased fascicle length and shortening of the Achilles tendon. The study provided evidence of improvement in muscle tendon properties through stretching intervention.
authors.affiliation: Department of Health Care Sciences, The University of Texas Southwestern Medical Center at Dallas, Dallas, TX, USA.
authors.forename: Fan
authors.initials: F
authors.lastname: Gao
authors.forename: Yupeng
authors.initials: Y
authors.lastname: Ren
authors.forename: Elliot J
authors.initials: EJ
authors.lastname: Roth
authors.forename: Richard
authors.initials: R
authors.lastname: Harvey
authors.forename: Li-Qun
authors.initials: LQ
authors.lastname: Zhang
mesh_terms: D000843:Ankle Joint / Q000503:physiopathology*; D055119:Elastic Modulus; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015915:Motion Therapy, Continuous Passive; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000503:physiopathology*; D013314:Stress, Mechanical; D020521:Stroke / Q000503:physiopathology*; D000071939:Stroke Rehabilitation; D013710:Tendons / Q000503:physiopathology*