title: Sonographic evaluation of the effect of long-term exercise on Achilles tendon stiffness using shear wave elastography.
abstract: OBJECTIVE
  This study aimed to assess the feasibility of using quantitative shear wave elastography (SWE) to assess the stiffness (Young's modulus) of Achilles tendon and to investigate the effect of long-term weight-bearing exercise on the stiffness of human Achilles tendon by comparing the frequent and infrequent exercise groups.
  
  
  METHODS
  Case-control study.
  
  
  METHODS
  A total of 36 healthy subjects aged 19-25 were recruited. Subjects were categorized into frequent and infrequent exercise groups dependent on their level of lower limb weight bearing exercise. B-mode and shear-wave ultrasound examination of Achilles tendon were performed. Measurements of the Achilles tendon stiffness were conducted with the foot position standardized by an ankle fixer. To evaluate inter and intra-operator reliability of Young's modulus measurements, each subject was scanned by three operators and each operator scanned the subject three times.
  
  
  RESULTS
  The intra-operator reliability of Young's modulus measurements ranged between 0.803 and 0.845. The inter-operator measurement reliability was 0.585. Result showed that Achilles tendon on non-dominant ankle in frequent-exercisers (median: 320.1kPa) was significantly stiffer than that in infrequent-exercisers (median: 296kPa) (p<0.05), whereas there was no significant difference in Achilles tendon stiffness on dominant ankle between the two groups (p>0.05).
  
  
  CONCLUSIONS
  Shear wave elastography is feasible for assessing the Achilles tendon's stiffness in vivo. The stiffness of Achilles tendon of frequent-exercisers was significantly higher than that of infrequent-exercisers on non-dominant ankle but not on dominant ankle. With the use of an ankle fixer, there was high repeatability and moderate reproducibility in SWE measurement of Achilles tendon stiffness.
authors.affiliation: Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Hong Kong Special Administrative Region.
authors.forename: Wai-Lam
authors.initials: WL
authors.lastname: Siu
authors.affiliation: Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Hong Kong Special Administrative Region.
authors.forename: Chi-Ho
authors.initials: CH
authors.lastname: Chan
authors.affiliation: Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Hong Kong Special Administrative Region.
authors.forename: Cheuk-Hei
authors.initials: CH
authors.lastname: Lam
authors.affiliation: Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Hong Kong Special Administrative Region.
authors.forename: Chu-Man
authors.initials: CM
authors.lastname: Lee
authors.affiliation: Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Hong Kong Special Administrative Region. Electronic address: htmying@polyu.edu.hk.
authors.forename: Michael
authors.initials: M
authors.lastname: Ying
mesh_terms: D000125:Achilles Tendon / Q000000981:diagnostic imaging* / Q000502:physiology*; D000328:Adult; D000843:Ankle Joint / Q000502:physiology; D016022:Case-Control Studies; D004548:Elasticity; D054459:Elasticity Imaging Techniques; D015444:Exercise; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D015203:Reproducibility of Results; D055070:Resistance Training; D018709:Statistics, Nonparametric; D014463:Ultrasonography; D055815:Young Adult
keywords: Elastic modulus; Elasticity imaging techniques; Exercise physiology; Physical activity; Ultrasonography