Background: Countermovement vertical jump is a crucial skill in many sports. Plyometric training is a prevalent method to improve athletes' jumping ability. Objectives: The present study aimed to investigate the effect of a 6-week plyometric training on the kinematics of take-off and countermovement vertical jump height. Methods: Fifteen young, healthy male subjects performed plyometric exercises in three sessions per week for six weeks. Digital videos of pre-training and post-training jumps were captured. The Kinovea software was used to measure the kinematic parameters of take-off in the sagittal plane. Pre and post-training values were compared by paired sample t-test with the statistical significance level of P < 0.05. Results: Post-training results showed a higher jump height (P < 0.05), more flexed shoulder, and more extensive hip and knee at take-off (P < 0.05). Also, while hip extension velocity was decreased, shoulder flexion and knee extension velocities were significantly increased (P < 0.05). Conclusions: The 6-week plyometric training, including 720 jumps, improved shoulder flexion, and hip and knee extensions at take-off, resulting in high CMJ height. We employed plyometric training to improve the shoulder flexion and hip and knee extension velocities and increase CMJ height.

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In previous studies, the acute effects of movement constraints on the countermovement jump performance are investigated; however, the longitudinal effects of implementing the constraint in a training regimen are not well studied. The purpose of this study was to examine the phenomenon of motor learning development due to application of task constraint in a training regimen following 6 weeks of training. Forty-five healthy adult males were randomly assigned to a control or one of two experimental constraint training groups (i.e., no arm swing or restricted knee flexion). Pre- and posttraining jump height and kinematic variables of six maximum effort countermovement jumps were compared longitudinally within the groups, and also compared between the groups. The findings of this study indicated that jump height significantly increased in all the groups while in the unrestricted control group it was increased greater than the experimental conditions (21% compared with 12% and 5.5%). However, the applied task constraints significantly improved some of the contributors to jump performance, establishing specific adaptation of kinematic variables to the constraint training. Therefore, constraint training approach could be suggested in case of demanding specific adaptation of kinematic variables of countermovement jump in a training regimen.