title: Mechanical and neural changes in plantar-flexor muscles after spinal cord injury in humans.
abstract: METHODS
  Cross-sectional study.
  
  
  OBJECTIVE
  To determine the effect of injury duration on plantar-flexor elastic properties in individuals with chronic spinal cord injury (SCI) and spasticity.
  
  
  METHODS
  National Rehabilitation Center for Persons with Disabilities, Japan.
  
  
  METHODS
  A total of 16 chronic SCI patients (age, 33±9.3 years; injury localization, C6-T12; injury duration, 11-371 months) participated. Spasticity of the ankle plantar-flexors was assessed using the Modified Ashworth Scale (MAS). The calf circumference and muscle thickness of the medial gastrocnemius (MG), lateral gastrocnemius and soleus were assessed using tape measure and ultrasonography. In addition, the ankle was rotated from 10° plantar-flexion to 20° dorsiflexion at 5 deg s(-1) with a dynamometer, and the ankle angle and torque were recorded. After normalizing the data (the initial points of angle and torque were set to zero), we calculated the peak torque and energy. Furthermore, angle-torque data (before and after normalization) were fitted with a second- and fourth-order polynomial, and exponential (Sten-Knudsen) models, and stiffness indices (SISOP, SIFOP, SISK) and AngleSLACK (the angle at which plantar-flexor passive torque equals zero) were calculated. The stretch reflex gain and offset were determined from 0-10° dorsiflexion at 50, 90, 120 and 150 deg s(-1). After logarithmic transformation, Pearson's correlation coefficients were calculated.
  
  
  RESULTS
  MAS, calf circumference, MG thickness, peak torque and SIFOP significantly decreased with injury duration (r log-log=-0.63, -0.69, -0.63, -0.53 and -0.55, respectively, P<0.05). The peak torque and SIFOP maintained significant relationships even after excluding impacts from muscle morphology.
  
  
  CONCLUSIONS
  Plantar-flexor elasticity in chronic SCI patients decreased with increased injury duration.
authors: 1] Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan [2] Department of Rehabilitation for the Movement Functions, Research Institute, National Rehabilitation Center for Persons with Disabilities, Saitama, Japan.
authors: K
authors: K
authors: Yaeshima
authors: Division of Functional Control System, Graduate School of System engineering and Science, Shibaura Institute of Technology, Saitama, Japan.
authors: D
authors: D
authors: Negishi
authors: Division of Functional Control System, Graduate School of System engineering and Science, Shibaura Institute of Technology, Saitama, Japan.
authors: S
authors: S
authors: Yamamoto
authors: Department of Rehabilitation for the Movement Functions, Research Institute, National Rehabilitation Center for Persons with Disabilities, Saitama, Japan.
authors: T
authors: T
authors: Ogata
authors: Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan.
authors: K
authors: K
authors: Nakazawa
authors: Department of Rehabilitation for the Movement Functions, Research Institute, National Rehabilitation Center for Persons with Disabilities, Saitama, Japan.
authors: N
authors: N
authors: Kawashima
mesh_terms: D000328:Adult; D000842:Ankle / Q000473:pathology / Q000503:physiopathology; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D035002:Lower Extremity / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009128:Muscle Spasticity / Q000209:etiology / Q000473:pathology / Q000503:physiopathology*; D018482:Muscle, Skeletal / Q000473:pathology / Q000503:physiopathology*; D013119:Spinal Cord Injuries / Q000150:complications / Q000473:pathology / Q000503:physiopathology*; D013997:Time Factors; D019415:Torque; D055815:Young Adult