The Effect of Basic Technical Training on Performance Capabilities of Young Soccer Players

It was suggested that training of players at young ages should focus on the development of basic technical skill since optimal responses to such training can be obtained at these ages. The aim of the present study was to examine the inclusion of basic technical exercises to regular soccer training on performance capabilities in young players. Twenty-eight young (12 - 14 yrs) players were assigned to either a soccer training group that performed specific soccer training (SG), or a group that combined soccer and basic technical training (TG). Both groups completed two similar sets of tests prior to and following nine weeks of training. While SG training led to a significant improvement only in the 20 m shuttle run aerobic test (645 ± 368 vs. 738 ± 308 m, p < 0.05), TG training led to a significant improvement in 10 m (2.05 vs. 2.00 sec) and 30 m (5.13 vs. 5.07 sec) sprint times (p < 0.05 for both). However, a significant reduction in the 4 × 10 m agility test (9.99 vs. 10.20 sec, p < 0.01) was found for the TG. Neither of the training programs had a significant effect on the long-jump power test. The findings demonstrate the complexity and the various requirements of soccer, suggesting that in order to comply with all game requirements technical training program for young players may be more efficient if implemented together with resistance—and endurance-type exercises.


Introduction
Although soccer players perform low-intensity activities such as walking or jogging during the game, it was shown that quickness and speed are qualities that are very often required by the players to perform anaerobic-type activities such as sprinting, turning or changing running direction (Stølen et al., 2005). Although these activities account for only 8% -12% of the total distance covered in a soccer match, it was found that they are essential to a soccer match's outcome (Rampinini et al., 2007).
In adult players, numerous types of training methods are known to improve the performance of anaerobic-type activities. High-intensity intervals, plyometric drills, and weight lifting are examples of such training (Markovic et al., 2007;Meckel et al., 2012). However, due to the high impact of these training methods on the skeletal, neuromuscular, and energy systems, their use among young children is not very common. In addition, since various activities in soccer are complicated and require a high level of motor control, it was suggested that players at young ages (9 -14 yrs) should focus on basic technical skill training rather than on the "common adult-training" methods (Branta, Haubenstricker, & Seefeldt, 1984;Yasumitsu & Nogaw, 2013). It was argued that basic technical training sessions are appropriate for young athletes, as they are important and useful for the development of basic motor skills at these ages. Such a notion relies on the concept that technical exercises should be conducted in the early phases of relies growth and development-during the so-called "sensitive phase" when the optimum responses to basic skill exercises can be obtained from the young trainees (de Villarreal et al., 2015;Naughton et al., 2000). Then afterwards, as the players grow up, soccer-specific skills will be easier to train and acquire. Indeed, Velickovic (2012) found significant correlations between general coordination variables (speed, agility) and specific skills of young soccer players. Similar results were found by Bojić & Palović (2015), showing significant relationships between coordination abilities (sprinting, jumping, sideway steps) and specific motor skills of young (age 12 -14 yrs) female handball players.
Despite these conclusions and suggestions, it is not clear whether the inclusion of basic technical training among players is superior to specific soccer training alone, for improving physical performance such as sprinting, jumping, and change of direction, which have found to be important in soccer (Malina, Ribeiro, & Aroso, 2007). This question is particularly important among the young players, who are expected to develop new skills. The purpose of the present study, therefore, was to investigate the effects of a training program that includes regular soccer training combined with basic technical training, as compared to a training program that includes soccer training alone, on selected performance capabilities of young soccer players. We hypothesized that the inclusion of basic technical training with regular soccer training would result in substantial improvements in performance capabilities (speed, agility, power, and endurance) compared to soccer training alone.

Participants
Thirty-five young male soccer players (age range 12 -14), members of two teams

Design
The study lasted eleven weeks and consisted of one week of pre-testing, nine weeks of training, and one week of post-testing. The study was conducted from November until January-the middle of the competitive season. Using a controlled study design, players were randomly assigned to one of two training groups after matching for sprinting ability according to pre-test results. One between the groups for the total training time. In order to achieve complete matching time in physical activity between groups, participants were asked to avoid any leisure physical activity during the study other than the study training.

Statistical Analysis
A two-way repeated-measure analysis of variance was used to compare fitness differences, with time serving as the within-group factor and training regimen as the between-group factor. A Cohen's d-effect size (ES) was also performed to demonstrate the magnitude of the training effect in each group. Cohen's d < 0.30 was considered a low effect, 0.30 -0.70 a moderate effect, and > 0.70 a strong effect. The Shapiro-Wilk test was used to ensure normal distribution of the results.
Data are presented as the mean ± SD. Significance level was set at p ≤ 0.05.

Results
There were no baseline differences in age (13.5 ± 6.8 and 13.4 ± 8.2 yrs), body mass (41.8 ± 6.9 and 42.3 ± 6.3 kg), or height (151.1 ± 9.8 and 156.6 ± 7.6 cm) prior to the training between the groups. Changes in anaerobic and aerobic performances following the training programs are presented in Table 2. There were no baseline differences in any of the anaerobic or aerobic test scores prior to the training between the groups. SG training led to a significant improvement only in the 20 m shuttle run test (p < 0.05). In addition, the percent change in the 20 m shuttle run test was significantly greater in the SG compared to the TG (p < 0.01) (see Figure 1). TG training led to a significant improvement in the 10 m sprint time (p < 0.05) and the 30 m sprint time (p < 0.05), but to a significant reduction in the 4 × 10 m time (p < 0.01). However, there were no significant between-group differences in the training effects on any of the anaerobic variables measured (Figure 2). Neither of the training programs had a significant effect on the standing long-jump test results. In addition, no significant interaction was found between the training groups in any of the variables that were tested.

Discussion
The findings of the present study revealed inconsistency as to the effectiveness of the two training programs, demonstrating the complexity of the performance requirements in the game. While the TG showed significant improvement in the 10 m and the 30 m sprint runs with no such improvement for the SG, significant improvement was found in the aerobic capacity for the SG with no such change for the TG. Neither of the training programs induced significant effects in the long-jump test. In addition, significant deterioration was found in the 4 × 10 m agility test for the TG, with no change in this variable for the SG.
These results are partially in contrast to our hypothesis and to several previous studies showing that short-term technique training has a consistent positive effect on fitness components such as power, speed, and agility among children (e.g., Branta, Haubenstricker, & Seefeldt, 1984;Venturelli, Bishop, & Pettene, 2008). It was suggested that this improvement resulted mainly from neural adaptations.
Although this adaptation is dependent on the specific training variables (e.g., volume, intensity, and complexity of drills), it generally consists of selective activation of muscles, selective activation of motor units, synchronization, and improved intermuscular coordination (Markovic & Mikulic, 2010).
When evaluating the effectiveness of the technical training program in the present study, certain methodological and physiological elements should be considered. First, some of the testing procedures that were used in the present study required fitness components, such as muscle power and strength (e.g., the standing long jump test) rather than just specific motor skills (Markovic & Mikulic, 2010).
In light of the present results, it is possible that the SG training, involving activities such as acceleration, stopping, pushing, and tackling during the small-sided games and the soccer-specific drills, may have produced greater muscle strength and power than the TG, which performed relatively low intensity activity during  Table 2). In line with this, an improvement of 6.0% was found in standing long-jump scores of 12-to 15-year-old boys following a six-week training program that combined technical exercises with weight-lifting training (Faigenbaum et al., 2007). It may therefore be recommended that for significant improvement in power performances such as horizontal or vertical jumps, specific resistance training should be included in the weekly training schedule.
The significant deterioration in the 4 × 10 m agility test in the TG was a surprise and in contrast to our hypothesis. Previous studies have found significant improvement in agility of children following short-term training programs that involved technical and motor control drills (Altinkök, 2016;Branta, Haubenstricker, & Seefeldt, 1984;Smits-Engelsmana, Jelsmab, & Ferguson, 2017). However, the participants in these studies were sedentary children with no previous involvement in training program. Although the children in the present study did not experienced a systematized technical training program before, they were certainly familiar with activities such as change of direction or with back and forth running that are highly typical to soccer. It, therefore, reasonable to assume that the agility-level starting point of these players was already high at the beginning of the present study leaving only minor room for improvement in the 4 × 10 m agility test performance of both training groups. The significant decrease in the 4 × 10 m test score of the TG may be relates to the fact that the technical drills in this group were performed only in a unidirectional fashion without turning points or change of direction. In that regard, Young, James, & Montgomery (2002) suggested that agility tasks could be more influenced by specific motor control factors than by muscle strength and power activity. Furthermore, in young children, the improvement of muscle power depends on neural factors rather than muscle strength (Thomas, French, & Hayes, 2009). Given the results of the present study, these neural factors should probably be stimulated and practiced in specific drills that relate to the specific sport or testing procedures used. Obviously, the issue of specific technical exercises for improving agility and quickness among children needs to be clarified in future studies.
All-out sprinting represents a complex movement that requires a high level of neuron activation (Markovic et al., 2007;Matavulj et al., 2001;Nicol, Avela, & Komi, 2006;Ross, Leveritt, & Riek, 2001). It was previously shown that increased nerve activation, together with frequency or degree of muscle innervation, was associated with specific technical training, especially in young populations (Markovic & Mikulic, 2010). Differences in running technique and in muscle activation patterns have also been reported among trained sprinters, and included sprint-specific technical drills in their training compared with controls (Ross, Leveritt, & Riek, 2001). In agreement with these and with our hypothesis, the 10 m and the 30 m sprint results in the present study were improved significantly in  Table 2). Although we did not assess neuron adaptation, these results may confirm that a general adaptation phase of basic technical training is essential for young soccer players in order to improve sprint performances. This is consistent with previous studies reporting significant improvement in technique-related performances such as in sprint running following training programs that included technical exercises (Bojić & Pavlović, 2015;Ross, Leveritt, & Riek, 2001).
Moreover, general technical training in 11-year-old soccer players was found to increase specific soccer skills such as sprinting with ball, more than sprint training alone (Venturelli, Bishop, & Pettene, 2008). Similar results were found for 13-year-old male soccer players (Branta, Haubenstricker, & Seefeldt, 1984) and for 12 -14-year-old young female handball players (Bojić & Pavlović, 2015). The investigators in these studies suggested that technical training provides a greater neural stimulus, resulting in better intramuscular and intermuscular coordination for sprint running.
The 20 m shuttle run ("yo-yo") test results-as an indicator of the participants' aerobic capacity in the present study-showed a significant improvement in the SG, with no such improvement in the TG ( Table 2). The improvement in aerobic capacity was significantly different between the groups (see Figure 1). The significant superiority of the SG over the TG in aerobic improvement can probably be attributed to the nature of the training in the two groups. As described earlier, while the TG implemented low-intensity coordination drills into their training sessions, the SG performed relatively high-intensity soccer training, consisting of small-sided games, in all weekly training sessions. Given the differences in training intensity between the two groups, the significant difference in the aerobic capacity changes between the groups may be reasonable.
Furthermore, the use of the 20 m shuttle run test, which replicates soccer-specific activity, as the evaluating procedure for the players' aerobic capacity in the present study, may have had a positive impact on the SG scores compared to the TG scores. The significant aerobic superiority of the SG over the TG following training should be taken into consideration by coaches since it may indicate that the inclusion of low-intensity exercises such as technical drills on the account of high-intensity soccer-specific exercises may interfere with the players' desired aerobic capacity.
One limitation of the present study may be that our groups sample sizes were relatively small. This was the result of a 20% dropout rate of players who missed testing or training sessions. In addition, changes in some of the anaerobic performances that were measured in the present study could have reflected changes in muscle power and strength rather than motor skills. The use of special and specific testing procedures that rely and reflect specific motor skills could have been more appropriate for the purpose of the study. Furthermore, level of intensity and volume of activity was not monitored during training. This prevented an accurate comparison between the two training protocols.

Conclusion
In conclusion, given the complexity and the various requirements of soccer, it can be suggested that in order to comply with all game requirements, technical training programs for young players may be more efficient if implemented together with other fitness agendas. Among these are resistance exercises that may improve soccer-specific actions such as jumping, accelerating, and changing of running direction. In addition, the implementation of aerobic-oriented type drills should be considered, given the low intensity of technical drills and the possible reduction in aerobic capacity. Future studies may examine the effect of technical training programs on players of different age groups. In addition, different technical drills, of different complexity and volume may be applied in future studies in order to examine their impact on young soccer players.