Laurent, C, Baudry, S, and Duchateau, J. Comparison of plyometric training with two different jumping techniques on Achilles tendon properties and jump performances. J Strength Cond Res 34(6): 1503-1510, 2020-This study compared the influence of 10 weeks of plyometric training with 2 different jumping techniques on Achilles tendon properties and the height achieved in drop jumps (from 20, 40, and 60 cm) and countermovement jumps (CMJ). Subjects were allocated to 2 training groups (n = 11 in each group) and 1 control group (CON, n = 10). One training group kept the knees extended (KE) during ground contact, whereas the other training group flexed the knees to ∼80-90° (KF). Achilles tendon stiffness was assessed with ultrasonography, and jump performance was derived from force platform recording. Training increased jump height (p < 0.01) in both groups. The increase for the 20-cm drop jump was greater (p < 0.05) for the KE group (11.3%) thanfor the KF group (6.3%), with no statistical difference between groups for the 40- and 60-cm drop jumps. Contact time during the 20-cm drop jump decreased (∼8%; p < 0.01) after training, with no difference between the training groups. The increase in CMJ height was greater (p = 0.05) for the KF group (17.5%) than for the KE group (11.8%). Achilles tendon stiffness increased (32%; p < 0.001) for the KE group but not for the KF group (11%; p = 0.28). There was a positive association (p < 0.001) between the changes in tendon stiffness and jump height for 20-cm drop jump in both KE group (r = 0.49) and KF group (r = 0.62). None of these parameters changed in CON group. In conclusion, the extent of increase in jump height (20-cm drop jump and CMJ) and in Achilles tendon stiffness after training differed between the 2 jumping techniques.