Statistics in volleyball: the Italian Professionals Leagues

A 3D Biomechanical Analysis of Volleyball Block R. LOBIETTI, F. MERNI, S. CIACCI Faculty of Exercise and Sport Science, University of Bologna, Italy INTRODUCTION: Blocking is an indispensable feature of winning teams in volleyball. Key points for the effectiveness of the block are anticipation, decision-making, movement speed and jumping ability. Players should use a technique that guarantees the shortest time, the longest movement and a vertical jump close to the net. Coaches regard also very important the “frontality” of the body to the net: pelvis and shoulders have to be parallel to the net as much as possible. Hands have to form an efficient surface over the net and control the rebound of the ball to score direct point or to touch the ball, deflect the hard shot and help the floor defence. Biomechanical studies are important to help coaches to teach players the best techniques. Researchers have generally two aims: the description of different footwork techniques and jumps, and the description of the move of the arms at the net. This study focuses on the differences in the lower limbs movement sequences in various step techniques and their modifications. We used four types of techniques as described by Lobietti (4). The movements to the right side we analyzed are: -Slide (SS): the right foot moves laterally and the left foot follows close to the lead foot, than the feet push up for the jump -Cross (CS): the left foot crosses over the right passing closer to the net and the right foot closes the move crossing back, than the feet push up for the jump Slide steps and Cross steps and combinations of these steps like Double Slide (DSS) and Slide-Cross (SCS) are basic frameworks of footwork in blocking. There are few published studies to determine the best footwork technique for the lateral movement sequence in volleyball blocking. Cox et al. (2) demonstrated that the cross-over (CS) and jab cross-over (SCS) techniques were the better in terms of getting the blocker off the ground and into the proper blocking position quickly. Buekers (1) stated that the optimal step technique should vary as a function of the lateral distance that must be travelled by the blocker. Lehnert et al. (3) stated that dropping hands during lateral displacement positively affects kinematics characteristics of movement and block jump height and that it is necessary to investigate further modifications of the middle blockers footwork used in top level volleyball. AIM OF THE STUDY To build and test a system for a quantitative description to establish different footwork techniques and to indicate to coaches tendencies to follow in training. METHODS A system for three-dimensional analysis of motion, VICON (Vicon Motion Systems, Oxford, UK), has been used filming six (4 hitters, 1 middle blocker, 1 setter) male volleyball players (age 25.1 y, height 188.8 m, weight 83.5 Kg) of B1 Italian League. Six infra-red video cameras (max resolution 300.000 pixel, frequency 100 Hertz) filmed passive markers fixed in different repere points of joints during blocking exercises. The system uses the stereophotogrammetry procedures to create a 3-D image. The procedures started with the cameras placement in relation with movement, very wide in space development, either in length (4m) than height (> 3m). Second step is the static and dynamic calibrations of the workspace. According with Tokuyama (6) we used 16 markers (diameter 14 mm) in pelvis and legs and instead of the centre of mass (COM) we analysed the kinematics data of the centre of the Pelvis (MEDH). Two additional markers where fixed to the net to calculate the angle between pelvis and net in the different phases of the move, to have data about the “frontality at the net”. Then the subject is calibrated using the Helen Hayes marker-set (5). Each player executed 4 trials for each type of movement in both directions. The players were required to reach the best speed, the longest distance...