The mechanism for efficacy of eccentric loading in Achilles tendon injury; an in vivo study in humans

▸ Rees JD, Lichtwark GA, Wolman RL, Wilson AM. Rheumatology 2008;47:1493–7.

Background:

Eccentric (as opposed to concentric) exercise training has been advocated in the treatment of Achilles tendon injury — however, the mechanism for this is not well documented

Research question/s:

What is the possible mechanism for the beneficial effect of eccentric exercise in Achilles tendinopathy?

Methodology:

Subjects: Seven healthy subjects (19–41 years)(male = 4, female = 3)

Experimental procedure: All the subjects were assessed and then tested in a laboratory where changes in tendon force and length changes were determined (utilising a combination of motion analysis, force plate data, electromyographic data and real-time ultrasound data) during eccentric (ECC) and concentric (CONC) loading exercises of the Achilles tendon.

Measures of outcome: Peak tendon force (N), tendon length (change), frequency of oscillations in tendon force (inflections per cycle)

Main finding/s:

Peak tendon force and tendon length: No significant differences in peak tendon force or tendon length change were observed between ECC and CONC conditions

High-frequency oscillations in tendon force occurred in all subjects during eccentric exercises, but less in concentric exercises (p<0.001)

Conclusion/s:

In a laboratory-based study, the therapeutic benefit of eccentric loading in Achilles tendinopathy is shown to be possibly related to increased tendon force oscillations during loading — this is supported …