seyed amirhossein emamian shirazi

 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.

 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.

 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.

 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.

 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.

 Countermovement vertical jump is a crucial skill in many sports. Plyometric training is a prevalent method to improve athletes' jumping ability.

 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.

 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.

 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).

 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.

T Abstract To improve motor function, movement pattern and changes in joint kinematic parameters are investigated in different conditions. Using a treadmill in human gait analysis, makes it possible to record several steps of gait in a limited space and also controlled conditions. The purpose of this study was to investigate the consistency of the kinematic parameters of lower limb joints during walking on the ground and treadmill. Intraclass correlation coefficients (ICC) for kinematic parameters of lower limb joints of 15 healthy young male participants were calculated during walking on the ground and treadmill. The angles of pelvic, hip, and ankle were often in the range of excellent reliability (ICC>0.9) when walking on the ground, while the results were in the range of average reliability (ICC<0.7) when walking on a treadmill. Therefore, in treatment activities or research studies, considering the decrease in consistency of walking trials on the treadmill is important.

The use of electromyography (EMG) parameters depends on their reliability. The purpose of this study was to determine the reliability of common EMG parameters recorded from muscles of lower extremity during walking on the stairs and an inclined surface.
Subjects and Fourteen healthy young males went up the stairs and an inclined surface with normal speed and after 30s rest went down. This was repeated 5 times with 1 min intervals. At the same time, surface EMG of rectus femoris, vastus medialis, vastus lateralis, and tibialis anterior muscles were recorded. In time domain, integrated EMG (IEMG) and root mean square of EMG (RMS), and in frequency domain, median frequency (MF) and mean power frequency (MPF) were calculated. Intra-class correlation coefficients and standard error of measurement for each parameter were calculated.
The average relative and normalized absolute reliability of iEMG and RMS were higher than MF and MPF. The average relative and normalized absolute reliability in going up were better than going down. In overall, there was no difference between the reliability of RMS and IEMG and also between MF and MPF.
Differed reliability of EMG parameters in various movement conditions emphasizes the need to have reliability measures for all parameters of each muscle in conducting researches.