Effect of a 12-week eccentric and isometric training in achilles tendinopathy on the gastrocnemius muscle: An ultrasound shear wave elastography study

Background. Eccentric exercises (EE) and isometric exercises (ISO) are standard treatment options for Achilles tendinopathy, but still their exact effect remains uncertain. Shear Wave Elas-tography (SWE) was used to examine the influence of these exercises on the elastic properties of Mm. gastrocnemii medialis and lateralis in a 12-week training program. Methods. Prospective study with patients suffering from Achilles tendinopathy, which were randomised into 2 groups and conducted exercises for 12 weeks on the symptomatic limb: EE (n=15, 9 male, 55a ± 6.5) and EE+ISO (n=15, 10 male, 47a ± 16.1). Shear Wave Elastography of the gastrocnemius medialis (MG) and lateralis (ML) was made before exercises (T0), after 4 (T1) and 12 weeks (T2) using an established protocol. Results. Muscles of asymptomatic and symptomatic legs did not differ at baseline neither for EE (p=0.139) nor for EE+ISO (p=0.778). SWE values of MG and ML of symptomatic limbs showed no significant alterations neither for EE and EE+ISO nor for the whole population (p=0.567-0.746) without any difference between EE vs. EE+ISO for the whole study period (T0: p=0.247, T1: p=0.990, T2: p=0.516). Contrary, MG and ML of the asymptomatic untrained limb showed increased SWE values over the course for the EE-group (p=0.041) and the whole population (p=0.003) with a significant difference of the symptomatic and asymptomatic limb at T2 for the EE group (p=0.01) and the whole population (p=0.03). MG and ML of asymptomatic limbs differed significantly between EE vs. EE+ISO at T2 (p=0.03), showing higher SWE values for EE. Conclusions. Using Shear Wave Elastography there was no measurable effect neither for EE nor for EE+ISO on MG and ML of symptomatic limbs over a 12-week intervention period. Contrary, in the asymptomatic untrained limb elastic properties increased in the EE group which might be based on the cross-education effect.