ویژگی های حرکت پرش اسپک والیبال در زنان
Abstract
1- Introduction
2- Methods
3- Results
4- Discussion
5- Conclusion
References
Abstract
Objectives: Performance factors in the volleyball spike jump are well known for male players; however, technical-coordinative differences for female players are known only marginally. The objective of this study was to investigate the relationship between movement characteristics and female’ spike jump performance and to identify the most relevant aspects of jump height and ball velocity. Design: Single group correlation and regression.
Methods: Fifteen elite female volleyball players performed spike jumps by striking a stationary ball at maximal jump height. Data were collected via twelve MX13 Vicon cameras (250 Hz), two AMTI force plates (2000 Hz), and controlled via Visual3D software.
Results: Ten out of 42 characteristics correlated with jump height and none of 22 correlated with ball velocity. A stepwise regression model (adjusted R2 = 0.82, p < 0.001) predicted jump height based on orientation step length and maximal angular velocity of dominant knee extension. For ball velocity, stepwise regression analysis was not feasible; however, an alternative model yielded adjusted R2 = 0.55, p < 0.01.
Conclusions: Key aspects for jump height were (1) optimised approach and energy conversion, (2) wide dynamic arm swing allowing for a forceful countermovement and, thus, increased range of motion in lower limbs, and (3) large angular velocities in ankles and knees, especially on the dominant side. These aspects strongly determined jump height in females and should be included in technical and strengthrelated training. For ball velocity, upper body anthropometrics and angular joint velocities emerged as the mostimportant criteria. The importance of specific joints may depend on variations in striking technique.
Introduction
Volleyball is an Olympic sport wherein athletes perform multiple technically complex movements. In offensive play, a spike is the most effective attack play associated with success in matches. Players attempt to reach a great jump height when spiking (1) to increase possibilities for various differenttypes of actions and (2)to maximise the effective court size, allowing for a steepballtrajectory at great ball velocity. Two of the main performance determinants for the spike are jump height and ball velocity; previous studies found correlations between these factors and overall competition level in volleyball. Therefore, jump height and spike velocity are major factors in volleyball training and competition. Due to the specificity and complexity of the volleyball spike, it is imperative to possess not only strength and power but also technical and coordinative aspects that contribute to performance. According to theoretical descriptions the volleyball spike jump should be introduced with a horizontal approach that assists in transferring the body into vertical acceleration. Swinging the arm with maximal range of motion promotes increased momentum and ground reaction forces.Acountermovementis performed via upper body lean and the decrease of lower limb angles. This pre-activates lower limb muscles, initiates a stretch-shortening-cycle, and optimises the distance of acceleration. Subsequently, a dynamic arm swing, elevation of upper body, and extension in the hips, knees, and ankles establish an explosive push-off. During the end of pushoff, pelvis rotation generates momentum that is transferred during the flight phase via trunk rotation and flexion into fast shoulder and elbow movements to spike the ball at maximal speed.