Fig. 3. Ultrasound images of the gastrocnemius medialis (GM) at rest, at 50% of the maximum voluntary contraction (MVC) and at the plateau of the MVC. The elongation of the tendon and aponeurosis was examined at the GM muscle belly at about 50% of its length. The displacement of the analysed cross-point in relation to the skin marker was defined as measured elongation of the tendon and aponeurosis.