title: The effect of eccentric and concentric calf muscle training on Achilles tendon stiffness.
abstract: OBJECTIVE
  To compare in vivo effects of eccentric and concentric calf muscle training on Achilles tendon stiffness, in subjects without tendinopathy.
  
  
  METHODS
  Thirty-eight recreational athletes completed 6 weeks eccentric (6 males, 13 females, 21.6  ±  2.2 years) or concentric training (8 males, 11 females, 21.1  ±  2.0 years). Achilles tendon stiffness, tendon modulus and single-leg jump height were measured before and after intervention. Exercise adherence was recorded using a diary.
  
  
  RESULTS
  All data are reported as mean  ±  SD. Groups were matched for height and weight but the eccentric training group were more active at baseline (P < 0.05). Tendon stiffness was higher in the eccentrically trained group at baseline compared to the concentrically trained group (20.9  ±  7.3 N/mm v 13.38  ±  4.66 N/mm; P = 0.001) and decreased significantly after eccentric training (to 17.2 ( ±  5.9) N/mm (P = 0.035)). There was no stiffness change in the concentric group (P = 0.405). Stiffness modulus showed similar changes to stiffness. An inverse correlation was found between initial, and subsequent, reduction in stiffness (r = -0.66). Jump height did not change and no correlation between stiffness change and adherence was observed in either group (r = 0.01).
  
  
  CONCLUSIONS
  Six weeks of eccentric training can alter Achilles tendon stiffness while a matched concentric programme shows no similar effects. Studies in patients with Achilles tendinopathy are warranted.
authors.affiliation: Queen Mary University of London, Barts and the London School of Medicine and Dentistry, Centre for Sports and Exercise Medicine, London, UK. dylan.morrissey@thpct.nhs.uk
authors.forename: Dylan
authors.initials: D
authors.lastname: Morrissey
authors.forename: Anna
authors.initials: A
authors.lastname: Roskilly
authors.forename: Richard
authors.initials: R
authors.lastname: Twycross-Lewis
authors.forename: Tomide
authors.initials: T
authors.lastname: Isinkaye
authors.forename: Hazel
authors.initials: H
authors.lastname: Screen
authors.forename: Roger
authors.initials: R
authors.lastname: Woledge
authors.forename: Dan
authors.initials: D
authors.lastname: Bader
mesh_terms: D000125:Achilles Tendon / Q000503:physiopathology*; D056352:Athletes; D016001:Confidence Intervals; D005081:Exercise Therapy / Q000379:methods*; D005260:Female; D006801:Humans; D007866:Leg; D008297:Male; D018482:Muscle, Skeletal / Q000503:physiopathology*; D010147:Pain Measurement; D018570:Risk Assessment; D012494:Sampling Studies; D052256:Tendinopathy / Q000534:rehabilitation*; D016896:Treatment Outcome; D055815:Young Adult