Superior short-term results with eccentric calf muscle training compared to concentric training in a randomized prospective multicenter study on patients with chronic Achilles tendinosis

In a previous uncontrolled pilot study we demonstrated very good clinical results with eccentric calf muscle training on patients with painful chronic Achilles tendinosis located at the 2-6 cm level in the tendon. In the present prospective multicenter study (Sundsvall and Umea) patients with painful chronic Achilles tendinosis at the 2-6 cm level in the tendon were randomized to treatment with either an eccentric or a concentric training regimen for the calf muscles. The study included 44 patients, with 22 patients (12 men, 10 women; mean age 48 years) in each treatment group. The amount of pain during activity (jogging or walking) was recorded by the patients on a visual analogue scale, and patient satisfaction was assessed before and after treatment. The patients were instructed to perform their eccentric or concentric training regimen on a daily basis for 12 weeks. In both types of treatment regimen the patients were told to do their exercises despite experiencing pain or discomfort in the tendon during exercise. The results showed that after the eccentric training regimen 82% of the patients (18/22) were satisfied and had resumed their previous activity level (before injury), compared to 36% of the patients (8/22) who were treated with the concentric training regimen. The results after treatment with eccentric training was significantly better (P<0.002) than after concentric training. The good clinical results previously demonstrated in the pilot study with eccentric calf muscle training on patients with chronic Achilles tendinosis, were thus reproduced in this multicenter, showing superior results to treatment with concentric training.