DIFFERENCES IN EXPLOSIVE POWER BETWEEN BASKETBALL PLAYERS OF DIFFERENT AGE

The aim of this research is to determine the differences in explosive power between basketball players of different age. This research was conducted on the sample of 34 basketball players, 17 of them wereat the age of 11 and 17 of them were at the age of 14 (±0.5 years). They are all members of basketball club „Ras”, Novi Pazar. Six different kinds of test were used to estimate their explosive power: long jump, triple jump, medicine balls throw while lying, medicine ball sit‐up throw, sprinting in 20 m from the low start position, sprinting in 30 m from the high start position. For identifying the significant differences in main values of two groups of players was used t-test. The statistics significance in differences was analyzed at the level (p<0.05). The results show that there are statistically significant differences between basketball players of different age in all observed variables and that they go in favor of players aged 14.


INTRODUCTION
Basketball is anaerobic-aerobic sport with interchangeable phases of high load, where for being successful is necessarily technical, tactical and physical preparation.The explosive power in basketball is manifested through different jumps, starting acceleration, sudden changes in the direction of movement, slowing down (deceleration), sudden stopping and in passing the ball to each other (Khlifa, et al., 2010).Knowing the explosive power of players of different age is the direct relationship with the effects of training and it makes easier the coach to choose the methods, the process of planning and program for the players.Mostly, the explosive power depends on the number of motor units, the genetic conditionality is 80%.It is defined as the ability of sportsman, in the shortest period of time the highest possible force is produced (Zatsiorsky & Kraemer, 2009).
The researches of this type are numerous in the world and at our place (Maffiuletti, Simović, 2012).Even though the inborn coefficient plays an important role, the development of explosive power can be done through good and organized trainings which should be conducted as well planned, rational and organized.Many authors show that the explosive power is the characteristic of professional basketball players (Latin, Berg, & Baechle, 1994; Hoffman, Tenenbaum, Maresh, & Kraemer, 1996; Ziv & Lidor, 2009).This belief was shown to be shared by the National Basketball Association strength and conditioning coaches who reported an extensive to improve explosive-power performance in elite-level professional basketball players (Hoffman et al., 1996;Simenz, Dugan, & Ebben, 2005).Furthermore, the published papers only addressed young basketball players selectively using drop jumps as training exercises (Meyer, Brown, Krilowicz, & Kushmerick, 1986; Matavulj, Kukolj, Ugarkovic, Tihanyi, & Jaric, 2001).Also, application plyometric training with young athletes has been recommended for explosive strength development (Kolb, 2003;Chu, Faigenbaum, & Falkel, 2006).Only one basket game consists of 46±12 jumps per player (МcInnes, Carlson, & McKenna, 1995), and this shows us the importance of explosive power in jumps.Due to the fact that today's basketball demands durable players with developed motor skills, the explosive power is one of the most important factors for achieving the best sports results in sport such as basketball results (McBride, Triplett-McBride, Davie, & Newton, 2002;Carlock, et al., 2004).The researches also show the positive correlation of jumps and throws at basketball players of different age (Santos & Janeira, 2011).In the past, the basketball coaches were convinced that the speed of sprinting is conditioned with genetics and it could not be improved with training, but in the last few years, the basketball coaches recognized the importance of explosive power such as sprinting (Moreno, 1994).Today, genetics is considered as one of the factors which help to determine the maximal speed of potential sportsman.
The assumption of research is that there will be differences in explosive power between basketball players of different age.So, it is expected that there will be differences in the explosive power, in favor of basketball players aged 14 years, and the key factors that contribute to the confirmation of hypotheses are biological maturity, anthropometric dimension, the level participants preparedness and age players.Therefore, the aim of this study is to determine the differences in explosive power between basketball players of different age.

METHOD Participans
The sample of players for this research is 34, and all of them are members of basketball club "Ras'' from Novi Pazar.They were divided into two groups.In the first group, there were 17 of players, (age 14 ± 0.5 years, body height 172.7 ± 8.78 cm, body weight 60.7 ± 11.3 kg, BMI 20.57± 2.15 kg/m 2 ), and the second group consisted also of 17 players (age 11 ± 0.5 years, body height 153.2 ± 5.83 cm, body weight 46.9 ± 8.3 kg, BMI 20.04 ± 2.09 kg/m 2 ).All of the exami-nees accepted to take part in this research.They were all healthy, without any chronic diseases or injuries which could influence the results of testing.

Samples of variables
In order to estimate the explosive power of players different tests were used (

Data Analysis
All the data were processed in Statistical Package for Social Sciences SPSS (v19.0,SPSS Inc., Chicago, IL, USA).Data processing was used basic descriptive parameters: minimum value (Min.), maximum value (Max.), arithmetic mean (Mean), Standard deviation (St.Dev.),rate asymmetry (Skewness and Kurtosis).To determine a statistically significant differences between the groups for each variable, t-test was used.Because of the small sample of participants, Cohen's d effect size (ES) was used to compare the explosive power between basketball players age 14 and 11 years.ES magnitudes were classified according to the scale (≥0.2 = small; 0.2< ES < 0.8 = moderate; ≤0.8 = large) described by Cohen (1998).Probability level for statistical significance was set at p<0.05.

RESULTS
In tables 1 and 2 are showed new descriptive parameters for basketball players at the age of 14 and 11.By examining the tables and comparing the results of Standard Deviation (St.Dev.), with maximal range (Max.) and minimal (Min.), one can conclude the normal sensibility of chosen tests In table 3 are shown the results of the t-test, which shows the explosive power of basketball players, age 14 and 11.The given results show the significant differences between the players of different age in all kind of tests which were used for evaluating the explosive power, and that were long jump (MSDM .000),triple jump (MTRS .002),medicine balls throw while lying (MBML .000),medicine ball sit-up throw (MBMS .000),sprinting in 20 m from low start position (M20N .000),sprinting in 30 m from high start position (M30V .000).

DISCUSSION
The primary purpose of the current study study was to determine the differences in explosive power between the basketball players aged 14 and 11 years.After the data evaluation, it is concluded that there are significant differences between the players of different age in all observed variables, and all of them are in favor of older players, age 14.The given results are expected, and the reason for that can be the age, their anthropometric dimension (body height, body weight), genetic predisposition, the level parcitipans preparedness, and playing position in team.Köklü, Alemdaroğlu, Ünver Koçak, & Findikoğlu (2011) discovered the differences in the explosive power of the lower limbs in basketball players of the First and the Second Turkish League, and discovered significant differences in the performance, as well as in the playing position.
Perhaps the most sensitive factor of given results is age, since the training of children and young basketball players mustn't be based on the principles that training for adults is based on.It has to be in compliance with their biological, chronological, psychological and physical growth.The researches show that the basketball players, who belong to the group of young pioneers (10-12 years old), develop their explosive power through different ways of moving, the body's weight itself makes resistance through the game and the explosive power such as sprint is improved through short sprints.At basketball pioneers (13-14 years) the one can influence the most on the development of explosive power, and can be used minimal external loads (Pavlović, 2007).
It should also be noted that in the implementation of training to develop explosive power players, we should bear in mind the anthropometric dimensions (body height and body weight) for anthropometric dimensions of his influence exercised in applying the most exercises with reversible contraction.Athletes with specific morphological constitution should not apply high-intensity exercise and scale (Čoh, 2004).
When it is about the explosive power of upper extremities, the next tests were used throwing a medicine ball, and the results showed differences in favor of basketball players aged 14 years, as it is expected.Research suggests that the use of medicinal balls can affect the development of explosive power of upper extremities (Gambetta, 1986) because the three most common types of inclusion that can be seen in basketball are passing from the chest, above his head and baseball defense.It is also known that the growth and maturation have a positive effect on the improvement of explosive power at men.The explosive power during this period is positively associated with chronological age, constitution and the variation in body weight (Bosco, 1994).From this point of view, after analyzing the groups, it can be said that differences were confirmed in all tests for the evaluation of explosive power where the importance of growth, development and maturation factors of men are confirmed.
Explosive power is manifested in basketball through various types of jumps, starting acceleration and quick changes of direction, deceleration, passing the ball, and is therefore the very topical field of research ( Besides that it was established a positive correlation between explosive power and running in short distances (Berthoin, Dupont, Mary, & Gerbeaux, 2001), which is considered to be a significant predictor of success in basketball (Latin et al., 1994).Zhang (2013) in addition to investigating explosive power, also investigated the speed of running over short distances, endurance in strength, and noted the positive influence of the explosive force in individual leg strength and endurance in general.It is necessary to know that type of short endurance training was specially designed for young basketball players, causing an increase in explosive strength, which is very important for the results of the game without any extra burden on the development of skeletal muscles (Ademović et al., 2015).As such, it is a common routine training which needs devotion of certain period of time in the development of explosive power, especially during the preparatory period (Pauletto, 1994).

CONCLUSION
This research was conducted on a sample of 34 basketball players, at the age of 11 and 14 (± 0.5 years) with the aim to determine the differences in explosive power between the basketball players of different age.By applying t-test, we have got the results which show us that there is a significant difference between the basketball players of different age in all observed variables, and all of them are in favor of older players, age 14.The given results provide the important information for coaches, which helps in players selection and it helps in making a proper plan and program of work for players of different age and points out to the further researches in the field of explosive power between players of different age.(Santos & Janeira, 2011).Последњих година кошаркашки тренери су препознали значај експлозивне снаге типа спринта, јер су у прошлости били убеђени да је брзина трчања условљена генетиком, и да се не може побољшати тренингом (Moreno, 1994).Данас се генетика сматра једним од фактора за утврђивање максималног брзинског потенцијала спортисте.
Casartelli, Müller, & Maffiuletti, 2010; Castagna, Ganzetti, Ditroilo, Giovannelli, Rocchetti, & Manzi, 2013; Battaglia, Paoli, Bellafiore, Bianco, & Palma, 2014).Several studies show a significant difference in the jumps between players with different levels of performance (Hoare, 2000; Delextrat & Cohen, 2008; Ostojić, Stojanović, & Ahmetović, 2010) indicating that the best players in the team tend to jump more than others.The research suggests that a player (if he plays the entire game) runs 6000-7000 meters carries out up to 40 different jumps, makes about 280 changes of direction, catching 120 balls, passing 80. Researchers say that for each player for the game half plays 16-17 jumps, which would through recalculating of the whole game turned out to be about 35 (Narazaki, Berg, Stergiou, & Chen, 2009).For this reason (Stojanovic, Ostojic, Calleja-González, Milosevic, & Mikic, 2012) suggest that coaches should spend more time on developing the explosive power to elite basketball players because it has a big impact on the competitive success in basketball.The conclusion has been made that it is necessary to use more strength training in sports practice, and that this type of training is an effective tool for basketball coaches, very innovative in terms of strength development, contributing to the efficiency of training time (Ademović, Kocić, Berić, & Daskaloski, 2015).

Table 1 .
The basic statistic parameters of basketball players, age 14

Table 2 .
The basic statistic parameters of basketball players, age 11

Table 3 .
The differences in explosive power between the players of age 14 and 11