The purpose of this study was to evaluate the change of the hardness of the gastrocnemius muscle (GM) and the Achilles tendon (AT) using Real-time Tissue Elastography (RTE) before and after acute exercise. Nine healthy young male without any exercising custom performed a total of 100 reps. of one-leg heel-rise exercise and the hardness of the gastrocnemius muscle and the Achilles tendon before and after the exercise was examined in comparison. The strain ratio (SR) was even measured in comparison to a reference material. The result indicated that the SR of the GM significantly increased immediately, 15min, 30min and 24h after the exercise, whereas the SR of the AT significantly increased just immediately and 15min after the exercise. In summary, the hardness of GM and AT increased after exercise. These findings suggest that RTE is a useful technique for assessing specific hardness of muscles and tendon, More RTE measurements of various parts of the body and the examination of the relationship between injury and RTE are required for the conditioning of muscles and tendons.