THE EFFECT OF THE STARTING LINE-UP OF THE PLAYERS ON THE OUTCOME OF THE SET IN VOLLEYBALL.Laios. A.,  Kountouris. P.,  Laios. Y., Drikos. S.Faculty of Physical Education and Sport Science, University of AthensOne of the peculiarities of the game of Volleyball is its rotation system. Before the beginning of every set the team coach must give to the referees in written form the starting positions of the six players of his team. During the set, every time the team wins a rally served by the opponent all its players shift their positions in a clockwise manner 1→6→5→4→3→2→1. During position shifts the relative positions of the players do not change. A complete rotation of the team is achieved after six position shifts, whence the players are again in the same positions as the starting line-up. After the application of the rally point system the number of rallies played per set (except the fifth one) was significantly reduced. The aim of the present study was to examine the distribution of the number of position shifts per set in various situations, with the intention to infer whether this information may prove to have practical importance. The primary data were collected from the Greek Men’s Volleyball Championship of 2005-2006 with the participation of twelve teams in a two round system. This gives a total of 132 matches, in which 491 sets were played. The primary dependent variable was the number of position shifts of the winning team. Its distribution was examined in different kinds of sets (first four or fifth) and in different outcomes of the set, measured as point differences between the winning and the losing team. For the first four sets the mean value of position shifts was 14.8±2.8 with only 6.8% of the sets having position shifts equal to or greater than 18. Even in the sets with a minimum difference between the two teams (25-23) and therefore a maximum number of points, the mean value of position shifts was 16.4±1.7 with only 9.1% of the sets having position shifts equal to or greater than 18. For the fifth set the mean value of position shifts was 9.0±2.3 with only 3.1% of the sets having position shifts equal to or greater than 12. Therefore the number of complete rotations for the first four sets was around two-and-a-half and the number of complete rotations for the fifth set was around one-and-a-half. In a previous research it was found that there seem to be favourable situations during position shifts, when the serving team has increased chances of winning the point. Since most probably during a set a team will not complete a whole number of complete rotations, the coach should start the set with the most favoured positions coming up first, or at least in the middle, but certainly not last. This will guarantee that the favoured positions will appear more frequently and most probably at crucial points at the end of the set. This is especially important in view of the fact that the winning team must win at least two more points than its opponent when serving, with the odds of winning against losing the rally when serving being only one to two.

EXPRESSIONS OF SKILL EFFECTIVENESS THAT ARE MORE CONGRUENT WITH TEAM PERFORMANCE IN VOLLEYBALL.Kountouris. P., Laios. Y., Drikos. S., Laios. A. Faculty of Physical Education and Sport Science, University of Athens The identification and quantification of the most consequential factors in reflecting the overall team’s performance is of primary importance in every team sport. In Volleyball it is obvious that these factors should be sought within those skills that lead to either winning or losing the specific rally. The aim of the present study was to determine whether latent derivative parameters, computed from relative proportions of decisive actions that lead immediately to winning or losing the rally, can be better predictors of team’s performance in Volleyball. Data were collected over eight seasons (2000-2008) of the Greek Men’s Volleyball Championships. For each season the overall statistics for each of the twelve teams were calculated. The original independent variables were proportions of actions that immediately led to winning or losing the rally to the total number of these actions: serve aces, serve errors, kill attacks and attack errors. From these two new variables were derived: the serve efficiency ratio (SER), which is the ratio of serve errors to serve aces, and the attack efficiency ratio (AER) which is the difference between the proportion of kill attacks and attack errors. The primary dependent variable is the set ratio (SR), which is the number of sets won divided by the total number of set played by the team. Pearson’s correlation coefficients were calculated between the dependent and the independent variables. The teams were also divided into two groups: teams with SR≤0.5 and teams with SR>0.5 and the derived variables were tested with Student’s t-test. SR does not correlate with the proportion of lost serves (r=0.037), but correlates well with the proportion of serve aces (r=0.589) and even better with SER (r=-0.661). Also the correlation coefficient between the proportions of serves errors and serve aces is quite high (r=0.530). The mean value of SER for teams with SR>0.5 is 2.3±0.5, while for teams with SR≤0.5 it is 3.0±0.6 (t-test, p<0.01). SR has a significant negative correlation with the proportion of lost attacks (r=-0.694) and an even higher positive correlation coefficient with the proportion of attack kills (r=0.819). Again SR correlates best with AER (r=0.851). The mean value of AER for teams with SR≤0.5 is 29.4%±3.7%, while for teams with SR>0.5 it is 36.1%±4.6 (t-test, p<0.01). The fact that the proportion of serve errors correlates highly with the proportion of serve aces can be founded on the nearly universal trend in modern Volleyball towards jump serves. These serves certainly have higher prospects to win a serve ace, or at least to encumber the opposing team’s reception. At the same time they undoubtedly entail a higher risk of execution. Teams that did not perform well managed on the average only one serve ace per three serve errors and their AER was less than 30%, while the for the teams that performed better the SER was nearer to two and the AER was more than 35%. Therefore the overall team’s performance in Volleyball can be better predicted by quantifiable combinations of its actions with both positive and negative outcome.