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.
Background: Vertical jump performance depends on the take-off velocity of the body's center of mass. This velocity results from vertical acceleration provided by applied force to the ground from the feet. Therefore, forces generated in the muscles and the way these forces transfer to the feet affect vertical jump performance. Objectives: This study aimed to assess the correlation of vertical jump height with ground reaction force and anthropometric parameters of professional male athletes in volleyball, basketball, and wrestling. Methods: In this study, the descriptive method (correlation assessment) was used to investigate the relationship of countermovement vertical jump height with ground reaction force and anthropometric parameters of 18 male professional athletes. Results: This descriptive study indicated that the vertical jump height was significantly correlated with the maximum vertical force (Pearson correlation coefficient = 0.658), maximum rate of vertical force development (Pearson correlation coefficient = 0.399), negative impulse (Pearson correlation coefficient = 0.192), and positive impulse (Pearson correlation coefficient = 0.381). In addition, among 16 anthropometric parameters, only sitting height had a significant correlation with jump height (correlation coefficient = 0.499). However, the four dimensionless anthropometric parameters, including body fat mass to body mass ratio, skeletal muscle mass to body mass ratio, upper limb mass to body mass ratio, and lower limb mass to body mass ratio, were significantly correlated with vertical jump height. Conclusions: The normalized body composition and ground reaction force parameters were significantly related to vertical jump performance. Therefore, designing a training program to enhance these parameters would improve vertical jump performance. According to this study, enhancing GRF characteristics could be considered valuable in such training programs.
Background: Risk analysis file will never be closed in the technical documentation of the dental implants for the marketing purpose. In this paper the most common risk factors categorized as implant-related risks, surgeon-related risks, patient-related risks, and maintenance-related risks in the manufacturing process, application, the long term usage and the so-called survival rate of dental implants are studied. Methods: The importance of any of the potential risk factors directly related to the product or the processes which are indirectly related to the product quality are assessed based on their severity and probability of occurrence. Proper measurement called as mitigations are considered to standardize the risks to the acceptable criteria.Results: The equivalent risk assessment factors are compared in pre-mitigation and post-mitigation stages. The aim was to see whether the factor reduces to the acceptable or conditionally acceptable state for each risk or not.Conclusion: Through this comprehensive study, the risk analysis file is completed however it can be even more complete, in the future, at this industry. In the further studies, discretizing the steps of severity or probability to finer steps, and ultimately converting them to a continuous form would be aimed.
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