Ohberg et al examined the effect of a 12 week eccentric training regime in twenty five patients with Achilles tendinopathy. An eccentric muscle contraction occurs when a muscle lengthens as it contracts. Treatment by heavy load eccentric calf muscle training has been shown to have a positive effect in most patients with tendinopathies, with decreased pain levels reported and many patients able to return to their previous activity level. The physiology of the positive treatment effects achieved with this method is not fully understood.
In Ohberg et al's study all patients were classified as having ‘chronic' Achilles tendinopathy (where the duration of symptoms ranged from 6 months to 12 years). In all twenty five patients there was thickening of the Achilles tendon to various extents, which was painful during palpation and activity, with the pain located at the 2–6 cm level from the insertion in the heel.
The patients were examined with grey scale ultrasonography (ultrasound scans) before and (on average) 3.8 years after the 12 week eccentric training regimen. At follow up, a questionnaire was used to assess present activity level and satisfaction with treatment. Before treatment, there was an abnormal structure (hypoechoic areas and irregular structure visible on the ultrasound scan) in all tendons from patients with painful chronic Achilles tendinopathy. After treatment, the structure was normal in 19 of the 26 tendons. Two patients with remaining structural tendon abnormalities after treatment were not satisfied with the result of treatment because of residual pain in the Achilles tendon during heavy tendon loading activities
Although larger studies are required, this prospective investigation shows that after treatment of painful mid-portion chronic Achilles tendinopathy with eccentric calf muscle training , in most successfully treated tendons there was decreased tendon thickness and a normalised tendon structure in the area that had exhibited symptoms.