To evaluate the tendon response after acute strength training in chronic Achilles tendinosis using magnetic resonance imaging (MRI).Methods:
Twenty-two patients (44 Achilles tendons, 15 males, 8 patients with bilateral symptoms) with a median age of 45 yr (range 28–57 yr) were included in the study. In all patients, both Achilles tendons were examined with MRI before and immediately after a standardized training program. The most painful side underwent 6 sets and 15 repetitions of heavy-loaded eccentric training. The contralateral tendons underwent only concentric loading during the training program. The tendon volume and the intratendinous signal were evaluated and calculated by MRI using a seed-growing technique.Results:
The immediate response of eccentric loading on the symptomatic tendons resulted in a 12% increase of the tendon volume, evident on T2-WI, from 7.8 ± 2.0 to 8.8 ± 2.7 cm3 (P < 0.001), and a 31% increase of the intratendinous signal evident on PD-WI, from 221 ± 74 to 278 ± 78 signal units (SU) (P < 0.001). The corresponding sequences on the contralateral concentrically loaded tendons showed an increase of 17% of tendon volume, from 6.1 ± 1.5 to 7.0 ± 1.6 cm3 (P < 0.001), and an increase of 27% of the intratendinous signal, from 170 ± 55 to 211 ±57 SU (P < 0.001). There was no significant difference of the mean of the increased tendon volume and the intratendinous signal between the eccentrically heavily loaded symptomatic tendons and the concentrically loaded contralateral tendons.Conclusions:
Both eccentric and concentric loading of the Achilles tendon resulted in increased total tendon volume and intratendinous signal. This increase may be explained by a higher water content and/or hyperemia in the Achilles tendon during and/or immediately after strength training of the gastrocnemius-soleus complex.