Submitted by José Manuel Palao¹ and David Valadés²

1 Department of Physical Activity and Sport, Faculty of Sport Science at the University of Murcia, Spain.
2 Department of Biological Sciences, Faculty of Medicine and Health Sciences, Alcalá University, Alcalá de Henares. Madrid, Spain.

ABSTRACT

The objectives of the present study were: a) to assess normative profiles for the serve speed of peak-performance volleyball players in order to guide practice sessions for men´s teams (study 1) and women´s teams (study 2), and b) to establish the possibilities and the ranges of speed that a volleyball throwing machine can offer for working on reception in volleyball (study 3). In studies 1 and 2, the serve techniques and the maximal speeds were analysed in men´s (2097 serves) and women´s (2056 serves) volleyball. Study 3 consisted of analysing the release speeds of the ball that are generated from the various speed settings that can be programmed with the throwing machine. The results provide normative profiles for the ranges of speed of the different types of serve for both men´s and women´s volleyball. Additionally, they indicate the speeds that a volleyball throwing machine provides for reception training in volleyball.

INTRODUCTION

Athletic success is largely influenced by how athletes train and prepare for competition. This means that it is necessary to follow a plan and for there to be ways to monitor all the details that affect training. Peak-performance volleyball is characterised by teams´ search for equilibrium between the different actions, complexes, or game phases (i.e. serve-reception balance, attack-block balance, attack-defence balance, balance between each rotation, etc.) (10).

The modification of volleyball´s scoring system, from side-out to rally point scoring, has affected the way teams earn points in volleyball (17). Due to this change in regulation, the phase of complex 1 (K1), or serve reception, has gone from trying to prevent the other team from scoring to being the phase in which 40-45% of the team´s points are scored. This modification of the scoring system, in addition to the rule that allows the ball to touch the net during the serve, have together affected the execution and the risk that is taken in the serve (6, 12), given that each serve error gives the opponent a point. However, this aspect is not empirically clear (12).

Serve performance affects serve-reception balance. In peak-performance volleyball, this balance tips toward reception. Thus, 62.0% – 72.6% of receptions are perfect in men´s volleyball (allowing the setter to set up all attack options), and 53.0% – 70.5% are perfect in women´s volleyball (11, 13). These values are higher than those found for the success of the serve in men´s volleyball (4.4% – 6.8%) as well as women´s volleyball (3.3% – 5.0%) (11, 12). This imbalance of reception efficacy over serve efficacy is, in part, the foundation for the success of complex 1 (10). For women´s volleyball, the serve´s efficacy is greater due, among other things, to: 1) a lower net height, and 2) a lower capacity for strength and displacement of the players (3, 4, 13).

In recent years, as demonstrated in the European and World Championships, there has been an increase in the use of the power jump serve both in men´s and women´s volleyball (1, 11). This increase is due to the fact that the use of this serve seeks an improvement in performance through the power and speed that this type of serve involves. The increase of this type of serve in competition has created the need to increase the volume of training of its specific reception. Due to the physical requirements of this type of serve, the use of volleyball throwing machines in practices is common. Their use makes it possible to specifically work on the reception of this type of serve without the need to physically overload the players. There are two types of throwing machines used in volleyball: a) machines with two wheels that throw the ball and b) hitting or striking machines.

However, although the use of throwing machines is common in peak-performance volleyball teams´ training sessions, it has been observed that when they are used, objective criteria are not used in the establishment of the teams´ speeds of work (trial and error and the coach´s criteria are used). This is primarily due to the absence of normative profiles for the speeds obtained by the players in competition. The studies found in a bibliography search have been carried out with a wide variety of levels and with small samples (regarding players and numbers of serves). In the bibliography, average reference values that were found include jump serves of 85.3 km/h (2), 91.4km/h (5), and 82.9 km/h (7) and float serves of 41-43 km/h for men (7) and 47.52km/h for women (16). Information was not found in the bibliography or from the manufacturer regarding the ball´s release speed that their machines have at the different settings.

The objectives of the present study were: a) to assess normative profiles for the serve speed of peak-performance volleyball players in order to guide practices for men´s teams (study 1) and women´s teams (study 2), and b) to establish the possibilities and the ranges of speed that a throwing machine can offer for working on reception in volleyball (study 3).

 METHODS

Study 1. Establishing normative profiles for serve speed in men´s volleyball

 Objective and methodology: The objective of study 1 was to establish the ranges of speed for the various types of serve in men´s volleyball. A descriptive study was carried out. The variables studied were the type of serve (standing, jump float, or power jump (14)) and the peak speed reached by the ball in the serve. Also, the zones of the serve´s origin and destination were recorded to correct the measurement errors of the serve (the court was divided into seven lanes). A total of 2767 serves were analysed, corresponding to 16 matches (61 sets) from the 2006 men´s World League organised by the FIVB. The serves were carried out by 85 players from eight teams. Only valid in-bounds serves were used in this study (2097 serves). The authorisation and informed consent of the event´s organising committee was sought to record the data about the speed of the serves and to record the matches. A radar gun was placed in one of the ends of the court at six meters from the serving line on a platform at a height of three meters. The measurement protocol was described by Palao and Valades (9). As radar correctly records only the rectilinear trajectories that get closer or farther from it, for the serves that involved curvilinear trajectories, a correction of the measure that was registered was made in accordance with the recommendations by the manufacturer, utilising the lane of origin and the lane of destination of the serve (15). The observation of the type of serve technique was carried out by an expert observer (with a doctorate in sport science, the highest certification for a Spanish volleyball coach, and more than 10 years of scouting experience). Before beginning and at the end of the data collection, the inter-observer correlation index was calculated with one of the researchers, and it was calculated at >0.96. The intra-observer correlation index was 0.990 (Cohen´s Kappa). The instruments used in this study were a digital video camera and a Stalker Radar Pro (Stalker Radar; Plano, TX). The descriptive and inferential analysis of the data was carried out with the SPSS v15.0 software (means, standard deviation, 10th and 90th percentiles, and Mann-Whitney U Test) to test differences between serve types.

Results Study 1

In Table 1, the ranges of speed from the different types of serve are presented. The results demonstrate differences between the various types of serve with regards to means, maximum speeds, and ranges of speed. The different types of serve demonstrate different levels of use: standing (7.1%), jump float (40.7%), and power jump (52.2%).

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Discussion Study 1

The results demonstrate the degree of occurrence and the differences in speed ranges from the various types of serve. Indirectly, we can assess the time that the receivers have to read the ball´s trajectory and intercept it: standing serve (approximately 0.98-1.29 s), jump float serve (approximately 0.72-1.35 s), and power jump serve (approximately 0.52-0.74 s). The standing serve is the serve that allows the receiver the most time, and it is effective if it requires the receiver to move or if its trajectory is not foreseeable for the receiver. This serve´s degree of use at this level of competition seems to indicate that it is not achieving this intent. The float serve seeks a certain direction as well as to be unpredictable. The possible reasons for its use, when compared to the standing serve, in spite of the theoretical benefit of executing it without displacement, are the higher contact height (angle of incidence in the opponent court) and greater initial speed of the server that can be transmitted to the ball when executing the serve. The power jump serve seeks to make it more difficult for the receiver to act by reducing the time that he or she has to respond as well as by the speed with which the ball reaches the receiver. The mean values found in this study are higher than those found in the bibliography (7). The results confirm the need to work on each type of serve and its reception in a different manner.

Study 2. Establishing normative profiles for serve speeds in women´s volleyball

 Objective and methodology: The objective of study 2 was to establish the speed ranges of the various types of serves taken in women´s volleyball. A descriptive study was done. The study variables were the type of serve (standing, jump float, or power jump (14)) and the peak speed reached by the ball in the serve. Further, the zones of serve origin and destination were recorded to correct the measurement errors of the serve (the court was divided into seven lanes). A total of 2247 serves were analysed, from 14 matches (51 sets) corresponding to two competitions of the Spanish Queen´s Cup (the 2006-2007 and 2008-2009 seasons). The serves were taken by 151 players from 16 teams. Only valid in-bounds serves were used in this study (2056 serves). To collect the data about serve speed and to record the matches, the authorisation and informed consent of the Spanish Volleyball Federation was sought. A radar gun was placed at one end of the court, nine meters behind the serving line and on a platform at a height of three meters. Since radar only correctly registers the rectilinear trajectories that get closer or farther from it, for the serves that involved curvilinear trajectories, a correction of the measure that was registered was made in accordance with the recommendations by the manufacturer, utilising the lane of origin and the lane of destination of the serve (15). The observation of the type of serve technique was carried out by an expert observer (with a doctorate in sport science, the highest certification for a Spanish volleyball coach, and more than 10 years of scouting experience). Before beginning and at the end of the data collection, the inter-observer correlation index was calculated with one of the researchers, and it was calculated at >0.97. The intra-observer correlation index was 0.990 (Cohen´s Kappa). The instruments used in this study were a digital video camera and a Stalker Radar Pro (Stalker Radar; Plano, TX). The descriptive and inferential analysis of the data was carried out with the SPSS v15.0 software (means, standard deviation, 10th and 90th percentiles, and U-Mann-Whitney Test).

 Results Study 2

In Table 2, the ranges of speed from the various types of serve are presented. The results demonstrate similar values between the standing serve and the float serve with regard to means, to maximal speeds, and to ranges of speed. The power serve presented higher speeds regarding mean, maximal speed, and range of speed. The different types of serve were not equally utilised. The standing serve was used 45.9% of the time, the float jump serve was used 37.5% of the time, and the power jump serve was used 16.6% of the time.

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Discussion Study 2

The results demonstrate that the standing serve and float serve present similar speeds. This means that with the exception of the contact height, which affects the angle of incidence of the serve in the opponent court, these serves could be worked on similarly in practices with regard to their speed, since they allow the receiver similar execution times (approximately 0.89-1.26 s vs. 0.87-1.35 s). The power jump serve has important differences regarding speed (>25km/h of difference) and execution time (approximately 0.61-0.82 s) when compared to the standing serve and the jump float serve. The differences regarding occurrence between the different types of serve seem to demonstrate that the standing float serve achieves its goal to a higher degree than the power jump serve. The results confirm the need to work on each type of serve in a different way.

Study 3. Calculating the speeds obtained by a volleyball throwing machine at the different settings that it offers

 Objective and methodology:The objective of study 3 was to establish the speed ranges of a throwing machine (with wheels) to facilitate specific training of reception. A descriptive study was carried out. The variables were the throwing machine´s wheels´ turning speed settings and the peak velocity reached by the ball. Twenty valid attempts with each combination of the throwing machine´s wheels´ turning speed settings were carried out, both for a net height corresponding to the women´s game (2.10 m) as well as that of the men´s game (2.43 m). A radar gun was placed in front of the throwing machine at three meters from the serving line of the opponent court. The height of the middle point between the wheels of the throwing machine was placed at 2.90 metres for the women and 3.25 metres for the men. A volleyball coach with more than three years of experience in the use of a throwing machine was in charge of running it. Those speed combinations of the machine´s wheels in which the percentage of error was greater than 30% (e.g. balls into the net or out-of-bounds) and those in which the spin on the ball was counterclockwise (the spin should be clockwise, as in real serves) were not taken into consideration for this study. Further, the speeds of the serves that went out-of-bounds or into the net were not taken into consideration in the calculation of the ranges of speed. In this study, only the speed settings from the machine that involved speeds greater than 60-65 km were considered. The instruments used in this study were a Sports Attack Volleyball machine, Molten IV5XC balls (official game balls), and a Stalker Radar Pro. A descriptive analysis of the data utilising the SPSS v15.0 software (mean, standard deviation, 10th percentile, and 90th percentile) was done. The official competition balls were used with the regulation pressure (1.6b).

 Results Study 3

In Table 3, the combinations of the throwing machine´s settings and the speed ranges that are involved are presented. The results demonstrate stable ranges of speeds in the combinations of speed presented. The degree of variability is 2-3 km.

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 Discussion Study 3

The results demonstrate that the wheel system does not allow you to precisely adjust a uniform range of take-off speeds for the ball. The fact that the ball´s take-off speed depends on the combined effect of the two turning wheels means that to achieve the desired intensity, a specific combination must be found. It should be kept in mind that as a starting point, it was established that the ball trajectories had to land inside the opponent´s court for at least 70% of the attempts. Despite not being able to obtain the serve you are looking for regarding speed, in the present study, uniform ranges of speed were found. None of the machine´s combinations of intensity allowed speeds higher than 105 km/h with low levels of error (>70% efficacy).

GENERAL DISCUSSION

 The objective of the present study was to provide normative profiles about how the serve is carried out with regard to the technique used and the speed settings that a throwing machine provides. The level of use of the different types of serve and the differences with regard to mean speed and speed ranges demonstrate that the serve and the reception should be practiced while keeping in mind the technique employed when players execute the serve. The results demonstrate that men´s volleyball presents different tendencies than women´s volleyball and that this should be kept in mind when planning practices. The results confirm the predominance of the jump serve in men´s volleyball (1, 11). The values that were found can serve as a reference for designing training tasks in regard to both proportions and conditions (e.g. speed of ball arrival, time needed to execute the action). Specifically, in men´s volleyball, the three types of serve presented different realities. Two values among the results stand out: the fact that nine of every ten receptions are jump serves (power or float) and five of every ten serves are power serves. On the other hand, in women´s volleyball, two of every ten serves are power jump serves, and the most common serve is the standing serve. The similarities between the standing serves and the jump float serve regarding speed, and indirectly the timing for the receiver, suggest the possibility that the training of the two serves can be carried out together.

The values presented can serve to get the work on reception that is done in practice sessions to be done with the speeds and variability of serves that are specific to competition. Therefore, it is necessary to keep in mind the type of serve, the way it is executed, and its tactical intention. The present study looks only at the first of these aspects and its relationship with the serve speeds. The differences that were found demonstrate that in the work on reception that is done in practices for the power jump serve, it is necessary to control the speed of the ball to assure the efficacy of the work that is done. A range of speeds from 20-30 km/h cannot simply be left to the subjective evaluation of the coach. For the rest of the serves (50% for the men´s game and 80% for the women´s game), the importance of the serve speed is not as great; instead, the way it is executed and the tactical intention acquire more importance. For these types of serves (standing and jump float), controlling the speed is not a priority.

One of the problems that working on the reception of a jump serve entails is the physical demand that the servers have after carrying out a high number of repetitions (8). Additionally, it involves the availability of a lineup of players that master this technique in such a way that they are able to direct the serve with high precision and power to the receivers. For this type of training, the use of volleyball throwing machines may be useful. One of the problems that its use involves is the absence of reference values regarding the speeds that the machines´ different settings generate. This makes the possibility of getting the work to be specific and objective more difficult. The results obtained in study 3 provide information to objectively establish what speed (release speed of the ball) the receivers are going to work at when they practice with this type of machine. From the results obtained, specifically related to the 10% of players that are able to serve at higher speeds in men´s volleyball (>105 Km/h), the results demonstrate that the model of machine that was analysed in the present study (Sports Attack Volleyball) is not able to obtain those speeds in trajectories similar to those of competition. In order to carry out this type of work (reception of serves >105 km/h), it is necessary to work with players who execute this type of serve. The use of the machine is only possible if the height from where the ball is tossed is raised.

The use of throwing machines has several positive aspects such as that these machines have a high range of reliability and repetitiveness regarding the speed of work, and they allow for a high number of repetitions. However, their use also involves several drawbacks, such as the fact that there is wear to the balls due to the high rotation of the wheels that throw the ball (equipment deterioration) and that they do not provide receivers with spatial or temporal cues.

CONCLUSIONS

 Knowledge regarding the way the serve is carried out in competition and being able to simulate it in practices is key for adequately practicing the reception. The serve in men´s and women´s volleyball is different with regard to the technique that is used and their speeds. The present study provides normative profiles to guide the training process for reception. On the one hand, it provides information about valid serves, and on the other hand, it provides information about the possibilities that volleyball throwing machines offer for working on reception. The serve´s characteristics in men´s volleyball are: the standing serve (7.1% of serves) is carried out with a range of 42.0 – 55.0 km/h, the jump float serve (40.7% of serves) is carried out with a range of 40.0 – 75.0 km/h, and the power jump serve (52.2% of serves) is carried out with a range of 73.0 – 104.0 km/h. The characteristics of the serves in women´s volleyball are: the standing serve (45.9% of serves) is carried out with a range of 43.0 – 61.0 km/h, the float jump serve (37.5% of serves) is carried out with a range of 40.0 – 61.0 km/h, and the power jump serve (16.6% of serves) is carried out with a range of 66.0 – 89.0 km/h. Regarding the second aim of this study, throwing machines allow for release speeds that are similar to the ranges generated by the power jump serve. The model of the machines analysed in the present study does not allow for the simulation of the highest speed power jump serves that are carried out in the men´s game (10%).

IMPLICATIONS FOR COACHING

 The values provided in this study may serve as a reference for the process of designing training tasks for reception. The study provides values about the proportion of each of the different types of serve and the ranges of speed at which they should be executed. It should be understood that the values are only a reference. These values should be considered along with the reference levels of the competition and the level of the team´s players (regarding serve and reception) when training tasks are designed. The results demonstrate that each serve has its own tactical aim that should be respected when designing tasks. Monitoring speed, for example through the use of radar, allows coaches to achieve jump serve training that is specific (speed and temporal aspects that are in line with competition).

ACKNOWLEDGMENTS

To the Spanish Volleyball Federation for allowing access to the matches (study 1 & 2).

REFERENCES

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