 Musculoskeletal disorders MSD are among the main causes of pain and disability in adults. Tendon disorders are an important part of MSD. Among them, the rupture of the Achilles tendon is the most common, with a prevalence of about 18 to 100000. The disorder mostly affects men between 30 and 50 years. Up today, the mechanical and elastic properties of the Achilles tendon are still unknown, and that both in healthy subjects in pathology. The viscoelastic properties or dynamic mechanical properties are directly related to the tendon of the health status and its elongation capacity. Additional tests that we have to explore the Achilles tendon are ultrasound and MRI. They bring mainly morphological information but can not demonstrate the mechanical properties of the tendon. 