title: Eccentric calf muscle exercise produces a greater acute reduction in Achilles tendon thickness than concentric exercise.
abstract: OBJECTIVE
  To investigate the acute effects of isolated eccentric and concentric calf muscle exercise on Achilles tendon sagittal thickness.
  
  
  METHODS
  Within-subject, counterbalanced, mixed design.
  
  
  METHODS
  Institutional.
  
  
  METHODS
  11 healthy, recreationally active male adults.
  
  
  METHODS
  Participants performed an exercise protocol, which involved isolated eccentric loading of the Achilles tendon of a single limb and isolated concentric loading of the contralateral, both with the addition of 20% bodyweight.
  
  
  METHODS
  Sagittal sonograms were acquired prior to, immediately following and 3, 6, 12 and 24 h after exercise. Tendon thickness was measured 2 cm proximal to the superior aspect of the calcaneus.
  
  
  RESULTS
  Both loading conditions resulted in an immediate decrease in normalised Achilles tendon thickness. Eccentric loading induced a significantly greater decrease than concentric loading despite a similar impulse (-0.21 vs -0.05, p<0.05). Post-exercise, eccentrically loaded tendons recovered exponentially, with a recovery time constant of 2.5 h. The same exponential function did not adequately model changes in tendon thickness resulting from concentric loading. Even so, recovery pathways subsequent to the 3 h time point were comparable. Regardless of the exercise protocol, full tendon thickness recovery was not observed until 24 h.
  
  
  CONCLUSIONS
  Eccentric loading invokes a greater reduction in Achilles tendon thickness immediately after exercise but appears to recover fully in a similar time frame to concentric loading.
authors.affiliation: Institute of Health and Biomedical Innovation,Queensland University of Technology, Brisbane, Australia. nicole.grigg@qut.edu.au
authors.forename: N L
authors.initials: NL
authors.lastname: Grigg
authors.forename: S C
authors.initials: SC
authors.lastname: Wearing
authors.forename: J E
authors.initials: JE
authors.lastname: Smeathers
mesh_terms: D000125:Achilles Tendon / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D000328:Adult; D015444:Exercise / Q000502:physiology*; D005081:Exercise Therapy / Q000379:methods*; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D052256:Tendinopathy / Q000000981:diagnostic imaging / Q000473:pathology* / Q000534:rehabilitation; D014463:Ultrasonography; D055815:Young Adult