The Effect of 4 Weeks of Plyometric Training on Coactivation of Antagonist and Agonist Muscles in Lower Limb of Active Girls during Different Phases of Drop Jump

Female athletes are more likely to have knee ligament injuries than men due to less coactivation. The aim of this study was to determine the effect of 4 weeks of plyometric training on the coactivation level of the lower limb muscles of active girls in different phases of drop jump. 20 female physical education students (mean age: 21.8±0.63 years, height: 1.64± 0.05 m, weight: 56.98± 9.26 kg) were randomly divided into two groups: experimental plyometrics (n=10) and control (n=10). The experimental group performed plyometric training twice a week for four consecutive weeks. In pretest and posttest, surface electromyography was performed on tibialis anterior, medial gastrocnemius, biceps femoris and rectus femoris. The coactivation level of dominant thigh and shin muscles was calculated during 3 phases of drop jump from 20 cm height. Analysis of covariance was used to investigate the effect of training at the significance level of P≤0.05. The results of univariate analysis of covariance with controlling the pretest effect showed no significant differences between experimental and control groups in posttest coactivation of thigh and shin muscles in phase 2 (pre-activity, P=0.14 and P=0.07), phase 3 (contact, P=0.41 and P=0.11) and phase 4 (fly, P=0.65 and P=0.12). In the plyometric group, the coactivation level of thigh and shin muscles showed increasing and decreasing trends respectively. Backward plyometric movements increase the activity level of leg dorsal muscles and help the ACL stability.