Showing 3 results for Ameli
Ali Fatahi, Heydar Sadeghi, Razieh Yousefian Molla, Mitra Ameli,
Volume 9, Issue 3 (Summer 2019)
Abstract
Purpose: The present study examined selected kinematic characteristics analysis of knee and ankle joints during block jump in elite junior volleyball players.
Methods: Thirty male junior elite volleyball players (Mean±SD age: 18.14±1.12 y, height: 197.10±3.16 cm, sports history: 4.39±0.95 y, & weight: 771.20±59.83 N) participated in this study. A time-synchronized 5-camera sampling at 100 Hz was used to determine the Three Dimensional (3D) coordinates of markers. Kolmogorov-Smirnov test, linear regression, and magnitude of coefficient were used in SPSS to analyze the obtained data (P<0.05).
Results: The Mean±SD height of block jump was 45.5±2.06 cm, and the Mean±SD angles of knee and ankle flexion were 93.37±4.75 and 21.25±2.98 cm, respectively. Moreover, there was a negative relationship between knee and ankle flexion angle and block jump height (-0.051, -0.054, respectively) (P<0.05). However, smaller knee flexion angles had more negative effect on block jump height (0.741) (P<0.05).
Conclusion: The study results could be used by coaches as a simple tool in jumping performance among junior volleyball players. The obtained data could also be beneficial in the efficient control of applied training procedures.
Ali Fatahi, Razieh Yousefian Molla, Mitra Ameli,
Volume 11, Issue 3 (Summer 2021)
Abstract
Purpose: Frequent and powerful jumps and landings in volleyball exert significant stresses on lower extremities which can be determinant of injury prevalence. This study aimed to investigate the possible correlation between Maximum Jump (MJ) performance and force-time variables of volleyball block landing.
Methods: Thirty elite junior volleyball players (Mean±SD of age: 18.140±1.125 y, sports background: 4.390±0.957 y, and height: 197.100±3.161 cm) performed three block jumps, and best of trials was considered for further analysis. The study data were collected by the KISTLER force platform (1000 Hz). Force-time, velocity-time, and displacement-time were obtained using the Excel program. The Kolmogorov-Smirnov and Pearson correlation coefficient were used for assessing data normality and possible correlations between variables using SPSS v. 21 (P<0.05).
Results: Peak vertical impact forces were reported in a range of 1.8-3.5 BW (F1, F2) during 27 to 83 ms of peak times (T1, T2). Significant positive correlations were obtained between temporal variables of time of peaks (T1, T2), the time elapsed between peaks (TP), and end of landing time (Tf). A significant negative correlation was found between F2 and T2 and a significant positive correlation between MJ performance with peak vertical forces (F1, F2).
Conclusion: According to the findings, T1 has little impact on shock absorption. Coaches and volleyball players should consider the importance of soft landing through increasing T2, which decreases F2, not only for performance improvement but also for reducing injuries.
Ali Fatahi, Razieh Yousefian Molla, Mitra Ameli,
Volume 11, Issue 4 (Autumn 2021)
Abstract
Purpose: Various kinematics and kinetics methods have been proposed for the assessment of jumping ability as a critical skill in professional volleyball players, but little is known about the accuracy and differences between these methods. Therefore, the objective of the current study was to answer the question “Is there any difference between the results of various kinetic methods in the assessment of block jump height in volleyball players or not?”
Methods: Twenty-one healthy male junior volleyball players of the Iran national team performed the block jump task on a force platform. Three common formulas mostly used in literature based on kinetics output of force platform were selected for the comparison of resultant jump height. Descriptive analysis, Shapiro-Wilk test, and ANOVA were used for statistical calculations (p<0.05).
Results: The results showed no significant difference between the means of block jump heights measured based on different kinetic methods in volleyball players.
Conclusion: Formula calculation methods are very valid for measuring the jump height of the block jump and lead to very similar results for estimating jump height and are also replaceable with each other.
