title: Achilles Tendon Properties of Minimalist and Traditionally Shod Runners.
abstract: BACKGROUND
  Tendon adapts to load through alterations in its composition and mechanical properties. Mechanical adaptation to increased load often involves increases in cross-sectional area (CSA), stiffness, and modulus. Runners exhibit these adaptations.
  
  
  OBJECTIVE
  To determine if runners wearing minimalist shoes had larger and stiffer Achilles tendons (AT) than traditionally shod runners.
  
  
  METHODS
  Cross-sectional study of well-trained, traditionally and minimally shod runners.
  
  
  METHODS
  Laboratory assessment of trained runners.
  
  
  METHODS
  23 men (11 traditional, 12 minimalist) and 8 women (6 traditional, 2 minimalist). Runners wearing minimalist shoes had 4.2 ± 1.6 y of training experience in minimalist shoes.
  
  
  METHODS
  The authors used diagnostic ultrasound and isokinetic dynamometry to generate a force-elongation curve and its derivatives.
  
  
  RESULTS
  Minimalist runners had a greater CSA: mean difference (MD) = 9.2 mm2, stiffness (MD = 268.1 N/mm), and modulus (MD = 202.9 MPa). ATs of minimalist runners experienced greater stress (MD 8.6 N/mm2) during maximal voluntary isometric contraction of the plantar-flexor muscles due to greater force of contraction (MD 798.9 N).
  
  
  CONCLUSIONS
  The AT in minimalist runners adapts by increasing size, stiffness, and modulus, which is consistent with our understanding of mechanical adaptation of tendon to increased loading. Increased stress to the AT likely requires a slow transition to minimalist running to allow the AT to adapt without evidence of injury.
authors.forename: Katherine
authors.initials: K
authors.lastname: Histen
authors.forename: Julia
authors.initials: J
authors.lastname: Arntsen
authors.forename: Lauren
authors.initials: L
authors.lastname: L'Hereux
authors.forename: James
authors.initials: J
authors.lastname: Heeren
authors.forename: Benjamin
authors.initials: B
authors.lastname: Wicki
authors.forename: Sterling
authors.initials: S
authors.lastname: Saint
authors.forename: Giselle
authors.initials: G
authors.lastname: Aerni
authors.forename: Craig R
authors.initials: CR
authors.lastname: Denegar
authors.forename: Michael F
authors.initials: MF
authors.lastname: Joseph
mesh_terms: D000125:Achilles Tendon / Q000502:physiology*; D000328:Adult; D001696:Biomechanical Phenomena / Q000502:physiology; D003430:Cross-Sectional Studies; D005260:Female; D005528:Foot / Q000502:physiology*; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D012420:Running / Q000502:physiology*; D012775:Shoes / Q000145:classification*
keywords: adaptation; material properties; running; tendon