The effect of eccentric and concentric calf muscle training on Achilles tendon stiffness.
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.
Morrissey
Dylan
D
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
Roskilly
Anna
A
Twycross-Lewis
Richard
R
Isinkaye
Tomide
T
Screen
Hazel
H
Woledge
Roger
R
Bader
Dan
D
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