Analysis of the small-sided games in volleyball: an ecological approach

– The aim of the present study was to compare the tactical and technical behavior of beginner players in volleyball side-out between four distinct situations of reduced games with different area/player ratios: 4.5 m 2 (3.0 m x 3.0 m), 8.0 m 2 (4.0 m x 4.0 m), 10.58 m 2 (4.6 m x 4.6 m), and 13.52 m 2 (5.2 m x 5.2 m). We analyzed 76 games played by 16 players with a mean age of 12.2 ± 0.5 years and experience of 1.2 ± 0.8 years of practice. Tactical and technical behavior was analyzed using an adaptation of the Game Performance Analysis Instrument (GPAI). The analysis was conducted for passing, setting and attacking according to the components related to technical adjustment, technical efficiency and decision-making. The results showed that players presented higher technical and tactical indexes in the passing and setting skills in 4.6 m x 4.6 m and 5.2 m x 5.2 m situations. Also, in the 3.0 m x 3.0 m situation higher technical indexes were found for the attacking. No differences were found in the tactical behavior of attacking for tested situations. We conclude that the environmental constraints imposed by the small-sided games imply distinct technical and technical behaviors. Thus, the pedagogical strategy of using small-sided games for the teaching of volleyball for beginner players must be associated with the intended objectives for each basic volleyball skills.


INTRODUCTION
Small-sided games (SSGs) are considered effective strategies for sports teaching, as they reduce the number of players 1 and increase the number of tactical and technical actions taken by players 2 . Thereby, SSGs require players to adapt to new game scenarios and enhance additional tactical experience in distinct situational contexts 3,4 . In volleyball, players relate to the environment through their senses. The information that comes from the environment to provide a solution (mental and motor) for the game problem relates to their tactical knowledge and accord to the player's experience 5 .
In this sense, such teaching and training strategy provides an increase in physical, technical and tactical performance, with a high motivational level, since it promotes the integration of decision-making processes and other intervening factors to performance 6 . In addition, differences in tactical and technical behavior have been observed according to the sport (i.e. soccer 7,8 , basketball 9 , handball 10 , hockey 11 ), as their specificities demand different solutions within the rules of action.
The SSGs enable the identification of the skill level of the players 12 , as well as proposing effective interventions in the teaching and learning process in a contextualized manner 13 . Thus, it seems that this kind of pedagogical approach is effective in teaching children in physical education classes 14 , as well as in high performance training 6 . This fact is due to the SSGs to increase the knowledge of the game, as it allows the active participation in conditioned formats of practice, besides reinforcing the specificity of tactical-technical behavior 15 . In this context, changes regarding the number of participants, court size, rule adaptation, action possibilities, decision-making, among others, should be analyzed and considered according to the proposed objective for the activity and the player's performance level 6,15 .
However, although SSGs are effective in different sports contexts, it is not clear how reduced games influence tactical-technical behaviors and how these are altered by task-specific 16 . Moreover, it is not fully understood in the literature how environmental restrictions, specifically game space, affect the tactical-technical behavior of volleyball players in SSGs. Thus, the aim of the present study was to compare the tactical-technical behavior on side-out, i.e. passing, setting and attacking, between four distinct situations of reduced volleyball games with novice players. We chose to analyze the side-out, as this game complex shows greater effectiveness in volleyball games 17,18 .

Sample
The sample consisted of 979 side-out actions resulting from the analysis of 76 small-sided games played by 16 players with an average age of 12.2 ± 0.5 years and an average of 1.2 ± 0.8 years of practical experience. Players participated in a school volleyball team and trained at a frequency of 3 times a week lasting 90 minutes each training session. The study was approved by the University's Research Ethics Committee under number 2.394.440.

Experimental Design
Players were split into pairs using ranking as a criterion for their constitution. The highest ranked player paired the worst ranked player, and so on. The ranking was performed by three experienced volleyball coaches (more 10 years of experience in deliberate practice with coach and with experience in national and international tournaments) and the players technical-tactical levels were considered, adopting the definition proposed by Erickson et al. 19 .
Each pair played between two and three games on each intervention day with a minimum interval of 10 minutes between each game. The intervention took place for 3 days for each pair respecting a minimum interval of

Technical-tactical behavior assessment
The technical-tactical behavior of the players during the games was evaluated through the instrument validated by Collet et al. 20 . The analysis was conducted for the passing, setting and attacking, considering the components related to technical adjustment, technical efficiency and decisionmaking. According to Porath et al. 21 , the performance analysis observation criteria can be understood as follows: adjustment as movements and postures performed before, during and after contact with the ball; efficiency characterized as technical execution; and choices and decisions that are made in the game defined as decision-making.

Data Collection Procedure
The games were filmed from the top perspective with a camera positioned behind the court approximately 4 m above the ground and 4 m from the bottom line. A Sony camera with 1080p HD definition and a frequency rate of 60 Hz was used.

Data analysis
Descriptive data analysis used frequencies, percentages, means and standard deviations. The comparison of the game situations by means of the one-way variance test (Anova) and Bonferroni's post hoc test was used in adjustment and efficiency, as well as the chi-square test ( 2) and the power of the phi effect (ɸ) for the analysis of categorical variables (decision-making) and significance value in both cases was p <0.05. To calculate the reliability 20% of the actions were reanalyzed, exceeding the reference value of 10% 22 . The intra-observer values were between 0.93 and 0.98 and the inter-observer values between 0.89 and 0.98. Data were analyzed in the Statistical Package Social Science (SPSS) 23.0.

RESULTS
Results are presented for each volleyball skill according to the parameters of adjustment, efficiency and decision-making. In analyzing passing (Table 1) Post hoc test showed that in item 1, the 4.0m x 4.0m condition differed from the others, and the 3.0m x 3.0m condition differed from 4.6m x 4.6m; in item 2, the condition 3.0m x 3.0m differed from the other conditions; and in item 3, the condition 3.0m x 3.0m differed from 4.6m x 4.6m. The chi-square test showed that there was an association between decision-making at passing and the game condition ( 2=94,625; p<0,001; ɸ=0,31). There was a positive association between "sending the ball directly to the opposing court" and the 3.0m x 3.0m playing condition (Adjusted Residuals [AR]: 2.7); between "keeping the ball in play in the team itself, but without direction (puts the ball up) and the condition 4.0m x 4.0m (AR: 5,3); and between "anticipating and directing the ball into the lifting zone" and condition 4.6m x 4.6m (AR: 5,6) and 5.2m x 5.2m (AR: 5,8). On the other hand, there was a negative association between "keeping the ball in play in the team itself, but without direction (puts the ball up) and the playing conditions 4.6m x 4.6m (AR: -2.5) and 5.2m x 5.2m (AR: -3.2); and between "anticipating and directing the ball to the setting zone" and the 4.0m x 4.0m condition (AR: -7.0).
Considering the setting, the one-way Anova identified difference in the following adjustment items (    The chi-square test showed that there was an association between decision-making at setting and the game condition ( 2 = 15.229; p <0.002; ɸ = 0.15). A positive association was observed between "Keep the ball in play in the team itself, but without direction (put the ball up)" and the condition 3.0m x 3.0m (AR: 3.0) and between "imposing strength and proper direction for the ball to reach the attacking player." and the 4.0m x 4.0m condition (AR: 3.7). On the other hand, there was a negative association between "Keep the ball in play in the team itself, but without direction (put the ball up)" and the 4.0m x 4.0m condition (AR: -3.7) and between "impose adequate force and direction so that the ball reaches the attacking player " and condition 3.0m x 3.0m (AR: -3.0).
Considering the attacking, the one-way Anova identified difference in the following adjustment items (Table 3) Regarding the attacking efficiency differences were found only in item 1 [F(3,839)= 18,659; p<0,001]. Post hoc test showed that the 3,0m x 3,0m condition differed from the other conditions and 4,6m x 4,6m condition differed from the 5,2m x 5,2m.
The chi-square test showed that there was no association ( 2 = 10,251; p = 0.114; ɸ = 0.11) between attacking decision-making and game condition.

DISCUSSION
The aim of the present study was to compare the tactical-technical side-out behavior between four distinct reduced volleyball game conditions with novice players. The passing results showed that the best adjustment index occurred in the condition of 3.0m x 3.0m while the best efficiency indexes were in the situations where the courts presented larger sizes than this one. In addition, it was observed that the 4.6m x 4.6m and 5.2m x 5.2m conditions were positively associated with the highest decision-making score. These results highlight the importance of increasing the size of the court in SSGs, and consequently, the area/player ratio, since it seems that technical gesture is conditioned by situational constraints and momentary tactics 20 . Thus, possibly the results related to the adjustment of reception are due to the size of the court, since smaller dimensions require less displacement and facilitate high scores in this dimension, when considering this noninvasion sport. However, the literature shows that the increase in density, represented by the smaller space per player, results in a worse technical index in invasion sports games 11 , making it necessary to investigate this behavior in volleyball. In this context, our findings suggest that performing SSGs in sizes that approximate the actual area game (square footage per player) is important to maintain characteristics that emerge from the competition environment 23 , a fact observed in the indexes of technical and tactical analysis of passing.
Regarding the setting, we found that the 4.6m x 4.6m and 5.2m x 5.2m conditions presented the best adjustment indexes, except when it was necessary to adjust the body position according to the ball's trajectory. Moreover, considering the efficiency, it was observed that the players presented better indexes of coordination of flexion and extension of the upper and lower limbs, as well as orienting the body position to the finishing zone of attacking at the moment of contact with the ball during the 4.6m x 4.6m and 5.2m x 5.2m conditions compared to 3.0m x 3.0m. Decision-making analysis showed that the lowest scores were positively associated with the 3.0m x 3.0m and 4.0m x 4.0m conditions, while the highest score was negatively associated with the 3.0m x 3.0m condition. These results corroborate the literature, showing that actions are interconnected in volleyball, that is, passing interferes in setting 17,18 , suggesting that the worst technical and tactical scores found in the 3.0m x 3.0m situation influenced the setting. On the other hand, situational constraints imposed by different court dimensions and technical-tactical demands specific to the game scenario affect player behavior 11,23 .
The attacking analysis showed that the players presented better technical indexes in the 3.0m x 3.0m condition, although the decision-making did not differ between the spatial restrictions of the game. The results suggest that the limited space may have favored the execution of technical elements of spike, considering the smaller displacement to perform the technical action. In this sense, based on ecological theory and considering the relationship between organisms and environment, differences in the technical aspects observed emerge from environmental constraints 24,25 . Technical behavior showed to be dependent on the environmental constraints imposed by changes in the playing space, thus suggesting that court size and different rules promote different behaviors, given the need to solve problems inherent to the game context and to consider tactical-technical indivisibility in volleyball performance 26,27 .
In summary, our findings indicate that environmental constraints and the interrelationship between game procedures promoted distinct tacticaltechnical behaviors, suggesting that the pedagogical strategy of using small-sided games for volleyball teaching should be rethought according to the objectives of teacher/coach 3,8,9 . Thus, the situational constraints inherent in the type of practice 7-16 modify the tactical-technical behavior 11 and the size of the court must be considered in the teaching and learning processes. In addition, from the ecological approach point of view, players must train and adapt to the enormous variability of actions that the context can provide in order to have more effective evolutions when experiencing these training problems 28 , as behaviors tactical tactics emerge from the context, the ecology of the game and possibilities for action 29 .

CONCLUSION
The results of this study contribute to understanding of tactical and technical behavior in novice volleyball players in different playing conditions. In this context, our findings reveal that the small games played with dimensions similar to the size of the official court are those that promote higher technical and tactical indices in the passing and setting skills. On the other hand, reduced playing area (4.5m2 per player) results in better technical indices on the attacking skill. These findings allow us to conclude that environmental restrictions modify the tactical-technical behavior of novice volleyball players, suggesting that different ecological contexts enable actions inherent to the specific context of the game.

Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. This study was funded by the authors.

Ethical approval
Ethical approval was obtained from the local Human Research Ethics Committee -Universidade Federal de Goiás and the protocol (no. 2.394.440) was written in accordance with the standards set by the Declaration of Helsinki.