Publications by Year: 2021

2021
Sotiropoulos, K., Drikos, S., & Barzouka, K. (2021). Variations in attack patterns between female and male opposite players in top-level volleyball. International Journal of Sports Science and Coaching.Abstract
In volleyball, the opposite player is the most requested hitter since she/he is the player with a higher probability of successfully carrying out attacks. The main objective of this study was to analyze variables that predicted attack effectiveness, in top-level teams depending on gender. Inferential analysis and multinomial logistic regression were applied to analyze 1512 attacks of men and women opposite players from 79 sets of the six top-ranked teams in the Men and Women 2018 World Championships. The analysis revealed that in female volleyball to increase the odds for a winning attack from the opposite player, teams have to pass the ball more accurately, setters have to set in a faster tempo and opposites avoid off-speed attack and spike in a diagonal direction from position 2. On the contrary, in male volleyball the odds for a winning attack from the opposite player are increased when male setters set accurate to the pre-agreement point on the net independent of the quality of the previous pass, opposite players hit in parallel and volleyball coaches select proper line-up and process tactical substitutions to increase the number of rotations with an opposite player in the offensive zone.
Gkreka, S., Barzouka, K., Drikos, S., & Sotiropoulos, K. (2021). Performance of Male and Female Top-level Outside Hitters Regarding the Spatiotemporal Characteristics of the Volleyball Spike. Inquiries in Sport & Physical Education, 19, 30-45.Abstract
The present study aimed to analyze the attack effectiveness of top-level outside hitters regarding spatiotem- poral parameters, such as the volleyball complex, the position of the setter, the type of opponent block, the tempo and the zone of attack. A three-member team of experienced coaches recorded and assessed 1968 attacks of male (N=800) and female (N=1168) outside hitters from 20 volleyball matches (M=10; W=10) of the six top-ranked teams in Men and Women 2018 World Championships. The assessment was based on a five-level ordinal tactical scale. The test of independence for categorical variables was carried out using χ2 test and Fisher’s exact test. A follow- up correspondence analysis was applied to visualize the entries in the table of relative frequencies. The analysis revealed that male outside hitters were more effective than female in a) the complexes I and II, b) the offensive actions from zones 4 and 6, c) the 2nd fast attack tempo, d) either the setter was in the offensive or defensive line, e) when facing single or double block. Nevertheless, female outside hitters performed fewer unforced errors than male in a) the complex I, b) spikes from zone 4, c) 3rd attack tempo, d) when the setter was on the defensive line and d) the offensive actions facing double block. Finally, the male outside hitters who played according to line-up positions either near the setter (OH1), neither the away from the setter (OH2) were more effective than the female outside hitters but OH1 performed more frequent unforced errors. These findings can lead volleyball coaches to develop specified training plans to improve the performance of outside hitters of both genders.
Drikos, S., Barzouka, K., Balasas, D. G., & Sotiropoulos, K. (2021). Effect of quality of opposition on game performance indicators in elite male volleyball. International Journal of Sports Science & Coaching. presented at the 5, SAGE PublicationsSage UK: London, England.Abstract
Performance in a volleyball match is the result of a dynamic and interactive process between two teams. The current study aimed to investigate the influence of the quality of opposition on skill performance indicators. A total of 550 teams’ performances (N¼550) from 275 sets of men’s European Championship 2019 was recorded and the effectiveness of 12 parameters from 5 basic volleyball skills was analyzed. A two-step cluster analysis was performed to divide 24 teams into three quality groups (upper, middle, lower) and 6 types of match status were created according to the quality of the opponents. Binomial logistic regression showed that for each type of match, the key performance factors that discrim- inate win and loss are differentiated, while the efficacy of attack win is associated with the success almost with all contexts studied. Other significant parameters were serve aces for matches between upper-quality teams, opponent’s errors for matches between teams of different quality and avoidance of blocked attacks for balanced matches. The findings emphasize the need for coaches to plan strategies that allow players with special serving abilities to risk for an ace, to enhance the side-out skills of their team and to work detailed on attack coverage systems
Ntzoufras, I., Palaskas, V., & Drikos, S. (2021). Bayesian models for prediction of the set-difference in volleyball. IMA Journal Of Management Mathematics, 2.Abstract
We study and develop Bayesian models for the analysis of volleyball match outcomes as recorded by the set-difference. Due to the peculiarity of the outcome variable (set-difference) which takes discrete values from −3 to 3, we cannot consider standard models based on the usual Poisson or binomial assumptions used for other sports such as football/soccer. Hence, the first and foremost challenge was to build models appropriate for the set-difference of each volleyball match. Here we consider two major approaches: (a) an ordered multinomial logistic regression model and (b) a model based on a truncated version of the Skellam distribution. For the first model, we consider the set-difference as an ordinal response variable within the framework ofmultinomial logistic regression models. Concerning the second model, we adjust the Skellam distribution to account for the volleyball rules. We fit and compare both models with the same covariate structure as in Karlis & Ntzoufras (2003). Both models are fitted, illustrated and compared within Bayesian framework using data from both the regular season and the play-offs of the season 2016/17 of the Greek national men’s volleyball league A1.
Tsakiri, M., Drikos, S., Sotiropoulos, K., & Barzouka, K. (2021). Active and non-active time during elite men and women sitting volleyball matches. Journal of Physical Education and Sport, 21, 1715-1721. presented at the 6, Editura Universitatii din Pitesti.Abstract
This paper aims to determine and sort the rally and break-time duration (including the rest time) in elite men’s and women’s Sitting Volleyball matches. The sample of study comprises 9195 rallies were retrieved from 68 (34 men and 34 women) Sitting Volleyball matches (corresponding to 224 sets) of the 2019 European Sitting Volleyball championship which monitored and recorded. Inter-rater and intra-rater reliability coefficients were estimated using Cohen’s kappa coefficient. The results of the study showed that the total average attempts in the block of serve, setting, attack, block and defence are higher in men compared to women (p≤.001). Also, the duration of the rally was longer in men, 5.98s, compared to 4.98s of women (p≤.001). The non-parametric Kruskal-Wallis test demonstrated that in both genders the highest average rally length was recorded in the 5th set (7.42s for men and 5.4s for women, respectively) and in the 3rd period of that set for men (6.22s) and the 1st period for women (5.06s). For both genders, the highest average break-times were recorded in the 5th set (28.23s for men and 27.73s for women) and, in particular, the 3rd period of that set (23.75s for men and 25.14s for women). According to the study result, one of the reasons contributing to the higher rally length in men’s matches is the higher number of attempts for all Sitting Volleyball skills that men performed comparing to women. The results of this study can be used by players, coaching staff, teams and federations for the organization, design, planning and managing of workouts and matches.
Sotiropoulos, K., Drikos, S., Papadopoulou, S. D., & Barzouka, K. (2021). Characterizing adaptations of serve indicators in top-level male volleyball among seasons. International Journal of Sports Science and Coaching, 16, 784-792.Abstract
{The purpose of this study was to analyse selected serve characteristics in top-level male volleyball, with a special focus on detecting adaptations of the serve skill among seasons. The indicators examined were type, position, direction and quality of serve. The sample consisted of 5482 serves from three final phases of different top-level tournaments (Olympic Games 2012
Drikos, S., Nikolaidou, M. E., Sotiropoulos, K., & Barzouka, K. (2021). Inquiry of discriminant variables to predict success in balanced sets and performance level in elite men's volleyball. In 29th International Conference of Physical Eduaction and Sports (pp. 429-432). WebsiteAbstract
{Effectiveness in the volleyball players' ability to control their postural sway during the game's actions involving contact with the floor (i.e. passing, digging) contributes to the final score. The purpose of this study was to investigate the postural stability performance of female veteran volleyball players (VVP). Sixty nine top-level female VVP were assigned to an active (N=29) and a non-active group (N=40). Due to the age range (43.7-66.7 years) of participants, they were further assigned to a younger (<51 years) and older (≥51 years) age group (Active: Younger=14
M.E., N., Schroll, A., Sotiropoulos, K., Drikos, S., Barzouka, K., & Arampatzis, A. (2021). Postural stability performance in female veteran volleyball players. In 29th International Conference of Physical Education and Sports (pp. 87-91). WebsiteAbstract
{Effectiveness in the volleyball players' ability to control their postural sway during the game's actions involving contact with the floor (i.e. passing, digging) contributes to the final score. The purpose of this study was to investigate the postural stability performance of female veteran volleyball players (VVP). Sixty nine top-level female VVP were assigned to an active (N=29) and a non-active group (N=40). Due to the age range (43.7-66.7 years) of participants, they were further assigned to a younger (<51 years) and older (≥51 years) age group (Active: Younger=14