1. Introduction

The soccer is the most practiced sport in the world, as well as the most popular, since it was introduced in the Brazilian culture, great proportions in all of the national territory [1].

The performance in this modality depends of several factors, including: technical, tactical, psychological and physical abilities [2]. From the physical point view, the modality is characterized how an intermittent exercise (frequent changes in the intensity of effort) [3].

In this way, it is possible to say that the ability to produce varied actions during the 90-minute game is associated with high aerobic capacity while the ability to perform explosive movements in a short period of time is associated with high anaerobic capacity [1]. Time and motion analyzes have shown that high intensity interval sprints (forward, backward, and lateral movements) are determinants in field sports performance [4].

According to Bloomfield [5] soccer requires players to perform numerous actions involving high levels of strength, power, speed, agility, balance, stability, flexibility and endurance [6].

During a soccer game, players reach a total distance of approximately 10 kilometers, including a sprint each 90 seconds. Each action lasts an average of 2 to 4 seconds and it can reach a distance of 15 meters [1] (smaller distances). In the longer distances (approximately 40 meters) are present about 4 to 8 changes of directions [7-9]. Davids [10] demonstrates that a soccer players executes 1,200 to 1,400 changes of direction during official games. Bloomfield [5] evaluated 55 Premier League players in official matches, finding that 727 turnovers and detours are made during the match.

Agility may be considered an essential component of contemporary soccer [11, 12]. According to Sheppard e Ackland [4, 13], agility is the ability of the rapid body movement involving change of speed and direction in response to a stimulus and it can maintaining the motor control. In this way Benvenuti [14] complement that this capacity is composed by accelerations, decelerations and reacceleration, characterized as essential for the soccer specific skills [15].

Thus, Lyle [16] pointed out that the identification of factors that influence motor skills can be useful for the development of training programs with the aim of sports performance. On the other hand, in younger age groups, differences in maturation, development, learning, as well as rapid physiological and anthropometric changes during the growth are observed and then feature direct influence on the performance [17].

According to Pinder's [18] study, the development of young players may be non-linear, with periods of abrupt performance transitions and anticipations, stable levels with little progression, or even periods of regression.

It is well known that climate changes that permeates soccer matches can induce loss of stability, increasing the chance of some injuries [19]. However, it was not found studies in the scientific literature that have evaluated the behavior of physical capacities, especially agility, in different climatic conditions, including rainfall.

Therefore, the purpose of the present study was to identify the agility of 10 years old soccer athletes category in two different conditions: dry and wet field.

2. Methodological Procedures

Assessed Individuals

Were evaluated sixteen male soccer athletes of the professional soccer team of São Paulo, Brazil. The athletes signed and agreed to the criteria of the Free and Informed Consent and the Term of Assent. The study was approved by the Ethics Committee of São Judas Tadeu University, São Paulo, SP, Brazil, according to protocol (11/2010). The exclusion criteria were: a) absence in more than 25% of training sessions and / or official matches of the team; b) present any osteo-myo-articular pathology.

Procedures

The athletes were evaluated in four different situations with a minimum interval of 72 hours between the tests. On the first day of evaluations, the anthropometric measurements were perform for characterization of the sample, including height, total body mass, body mass index (BMI). On the second day, the evaluation of sexual maturation was realized by the parents / person responsible of the children, using the Tanner Instrument. [20].

On the third and fourth day of evaluation it was applied the Shuttle Run Agility Test in a rainy day (wet field) and in a normal day (dry field), respectively

The two days of evaluations were classified according to the environment and climate conditions (wind speed, ultraviolet rays, possibility of rain, temperature and relative humidity). All athletes were wearing the official soccer equipment, including Dri Fit® T-shirt, shorts and soccer-specific socks, shin guard and soccer boot with rubber studs.

Tanner Scale

It is an evaluation scale of the sexual maturation of the individuals represented by the sequence of the pubertal events in both sexes. In the boys were evaluated: development of external genitalia and pubic hair, while in the girls are evaluated the breast development and pubic hair too [20].

Shuttle Run Agility Test

The Shuttle Run Agility Test (SRAT) involve 20m run with three changes of direction in 180° [21]. Two parallel lines are demarcate with 9.14m between them, measured from her outer edge, in unobstructed space. One of the lines was take as the starting point of the test and the individuals positioned themselves behind this one, prepared to begin the test in the command "Prepare! Go! ". The athletes should make two back and forth in the space marked [22]. When they exceed the line in the last race, the stopwatch was stop and the time recorded.

3. Results

As shown in Table 1, the mean values of height (m), body mass (kg) and body mass index (kg/m²) of subjects in the study were 1.14 ± 0.07m, 33.87 ± 5.14kg and 17.2 ± 1.25Kg/m² respectively.

Table 1. Anthropometric Variables

The value obtained in the Shuttle Run tests in dry and wet conditions was 11.31 ± 0.34sec and 11.42 ± 0.55sec respectively (Chart 1.). No significant difference was found between the tests execution. However, it is possible to observe a trend of minor performance for the wet field.

Chart 1. Shuttle Run Test Values in different environment conditions

4. Discussion

The statistical analysis showed that there were not significant differences between field conditions (wet and dry). The evaluation of certain variables is restricted in the literature, especially because field tests in real climatic conditions may disadvantage the scientific control of the variables, which makes it simultaneously more applicable. In this way, Smeets [23] report that each type of soccer lawn has their own characteristics and, therefore, the performance of the soccer athlete can be influenced by the type of sole of the footwear used (boot).

Smeets [23] still determine the friction force between the sole of the players' shoes and the ground, concluding that in dry conditions, the simulations for determination of the torque culminated in relatively higher values. This fact can justify a greater adhesion to the ground in dry conditions and consequently more safety to the athlete to realize sprints and changes of direction with speed and effectiveness.

According to study by Mirkov [24], the great performance indicator of a soccer player is agility. However, the literature is outdated and it can be explained by the absence of a gold agility test standard, which could contribute methodologically by unifying and standardizing agility tests with specific purposes. There are several agility tests found in recent studies in the literature, and there is no standardization in the application of these tests. Kutlu [2], in a study with 113 individuals (including amateur, professional soccer players and college volunteer students) compared a new Agility and Shooting Skill Test for Soccer with other agility tests, concluded that while the Illinois Test had a high score for the agility test, the Zigzag Test showed a low value. Moreover, the authors showed that according to the analysis of the variables 5 different agility tests and sprint, there was significant difference between them.

Another study that used as sample 52 members of both sexes of the course of Sports and Physical Activity, aimed to analyze the correlation between three agility tests (Illinois Agility Test, 5-0-5 Agility Test and Pro-Agility Shuttle Test). Contrary to the findings of the aforementioned studies, the results showed that all the tests have a positive correlation, do not showing statiscal differences into the different field tests [25]. This does not determine a complete divergence between the tests, but also does not justify a trend, because there was a significant sample difference between the studies. However, many studies have used the Shuttle Run Agility Test to evaluate futsal athletes of 13 years old, such as the studies of Polito [26], Kutlu [2] and Gatterer [27] that used the test as part of the methodological procedures.

In the first study, the Shuttle Run Agility Test was used to characterize the sample. The 13 years old children athletes showed the follow results by position game: Goalkeepers (12,4 ± 0,7); Full-backs (10,4 ± 1,0); wing backs (11,6 ± 0,9); Centre forwards (11,6 ± 0,4) and General results (11,5 ± 0,9). There were not found statistical difference into the positions Polito [26].

Kutlu [2] compared a New Test For Agility and Skill in Soccer with others test of agility. The results showed that were not found statiscal differences between the agility tests protocol (Illinois, Zig-Zag, 30m, Bosco, T-drill agility and Wingate peak power test) and the New Test for Agility and Skill, this way concluding that protocol test proposed by Kutlu 2012 can be acceptable and reliable.

The study of Gatterer [27] suggest identify the hypoxia by the Shuttle Run Sprint Training and if it can improves the repeated sprint ability and the Yo-Yo intermittent recovery test outcome in young elite soccer players. This way, the study conclude that in youth soccer players this type of hypoxia training should induce great progress in repeated sprint ability.

This study is a pioneer in the analysis of the interference of non-simulated climatic environments in the performance of physical and motor skills of children and adolescents soccer practicing of high performance.

After the statistical analysis, it was verified that there were no significant differences in the performance executed in both situations, despite the remarkable tendency of more time spent to perform the test in rainy conditions.

According to Brughelli [28], performance of agility can be improved as a result of the development of muscular strength and power, only in very short sprints, because the accelerations and re-accelerations are characteristics of the rapid changes of direction and are considered power actions [22]. In this sense, Weineck [29] suggests that agility, during the fast and fast duration of the first few passes, represents a greater significance of the motor skill of a soccer player and is considered a fundamental physical quality for the ideal performance of the players. Together with that the ability to anticipate and ball time [4].

According to Mathisen [30] in a study of 132 subjects with 10 to 16 years old, sprint and agility performance improved in relation to chronological age. In this context, the superiority appeared not only of the age differences, but also maturational and according to the level of physical aptitude [22].

5. Conclusions

For this study, it was understood that no significant difference was found between the Shuttle Run Agility Test performed in different environmental conditions. For these results should be considered the type of soles of the boots and the literature said about this subject that this factor can influence in the players’ performance. For this, future specific studies are necessary to understand the behavior of the athletes in different situations within the game environment.

ACKNOWLEDGMENTS

The authors Yago de Moura, Henrique Nunes, Helton Dias, Simone Inácio and Luciane Moscaleski were responsible for the field research, as well as, for the production of the writing of the work, respectively:

Yago de Moura - Subjects and Methods

Helton - Discussion

Henrique Nunes - Introduction

Simone Inácio - Conclusion

Luciane Moscaleski - Abstract

The authors Luis Felipe Tubagi Polito, Aylton José Figueira Júnior, Marcelo Callegari Zanetti and Carla de Sá Pinto were responsible for the improvements in the text and the statistical treatment of the data.