Agility and COD ability are considered as relevant motor performances in soccer despite no universally shared gold standard (9,26,28). In this study, agility was assumed as time needed to cover a set sprint course after reaction to an unpredicted visual stimuli provided by a performer simulating a possible opponent. According to Sheppard and Young (26), COD ability was considered as time to cover proposed COD test protocols.
Thirty-six male elite-level field soccer players who were members of a first division Tunisian soccer club (age: 14.2 ± 0.9 years; height: 167.2 ± 5.7 cm; body mass: 54.1 ± 6.3 kg; body fat; 12.5 ± 2.2%) volunteered to this study. Maturation stage was assessed using the Tanner's pubic hair technique (19). Prestudy assessment showed a 3–4 maturation stage with no significant difference between the considered groups (p > 0.05). Players were randomly allocated into CONG (n = 12, only soccer training), SSGG (n = 12), and CODG (n = 12). Written informed consent was obtained from all the players and their guardian/parents after receiving verbal and written information about the nature and the associated risk and benefit involved in this study and successively to procedure familiarization by players. The Ethics Committee of the Tunisian National Centre of Medicine and Science in Sports approved all the procedures involved in this study before the commencement of data collection. All players trained 3 times a week (i.e., 90 minutes per session) with a match played during the weekend over the entire training period (6 weeks). All the procedures were carried out during the competitive season (14).
All players after familiarization were pre- and post-training tested for sprinting ability for more than 15 and 30 m (with split times at 10 and 20 m, respectively). Players' COD abilities were assessed with the 15-m run with and without the ball (COD: 15 m and ball: 15 m, respectively) according to Mujika et al. (20), the 10-8-8-10 test (7), and a zig-zag test over 20 m (Z-20 m) (4). Agility was assessed in all players with a Reactive Agility Test protocol either with (RAT-B) or without ball dribbling (RAT) (27,32). During RATs, the tester had 4 options for each condition: preplanned and randomly ordered (i.e., 8 trials). All these conditions were provided to each player in 2 series (5–8 minutes between-sets rest) in a random order. Players were instructed to recognize the cues as soon as possible (essentially while moving forward). To increase consistency, the mean of all trials (i.e., 8) was considered as RATs performance.
All the tests were timed with photocell gates (Brower Timing Systems, Salt Lake City, UT, USA) placed 0.4 m above the ground and with players standing at the start of 0.5 m behind the first timing gate. Players performed 2 trials of each test (2 minutes between-trial passive recovery) with the best measure used for calculations. Explosive power was assessed using the 5-jump test for distance and an arm-aided vertical countermovement jump (arm swing, ACMJ) (8). The ACMJ performance was assessed using a force platform (Kistler 9281 C; Kistler, Winterthur, Switzerland) (3,8). Flight height was calculated using the force-time method, and attention was paid that players jumped and landed in the same biomechanical conditions (18). The testing procedures were performed for more than 3 consecutive days at least 24 hours apart. To avoid possible circadian influence over test performances, the procedures were carried out at the same time of the day in each testing session. Ad libitum water drinking was promoted to avoid dehydration status effect over the testing procedures. Internal training load of all players was monitored using the session rate of perceived exertion (Session-RPE) method according to the procedures proposed by Impellizzeri et al. (15) and expressed in arbitrary units (AU).
Data are presented as mean ± SD with the normality verified using the Shapiro-Wilk W-test. Baseline between-group differences suggested analysis of covariance with repeated measures (groups × time). Post hoc analyses were performed using a least significant difference test. Association between variables was assessed using Pearson's correlation coefficient. The internal consistency of the variables of interest was assessed using the intraclass correlation coefficient (ICC) and the SEM (i.e., SEM, SD × [1 − ICC]0.5). Significance was set at p ≤ 0.05.
No significant pre- to post-training variation in anthropometric and maturation variables was found in the groups of interest. The ICC and the SEM of the timed variables of interest ranged from 0.86 to 0.97 and from 0.006 to 0.162 seconds, respectively. The SEM for the ACMJ and 5JT were 0.53 cm and 0.08 m, respectively. Weekly session-RPE was not significantly different between SSGG and CODG across the training period (from 1,367 ± 80 to 1,732 ± 60 and from 1,379 ± 63 to 1,767 ± 98 AU). However, the CONG experienced weekly session-RPEs (from 1,148 ± 73 to 1,288 ± 56 AU) significantly lower than SSGG and CODG. A significant main effect for time (i.e., training application) and groups (i.e., protocol prescription) was detected for the considered variables (Table 3). The CONG showed significant improvement on linear sprinting over a distance longer than 10 m and in all the agility and COD tests used in this study. The SSGG group showed improvements in linear sprinting (+1.5%) and COD (+5.1%) that resulted significantly lower than those in the CODG (4 and 6.7%, respectively). Significantly higher improvements in agility tests were found in the SSGG (+6.2%) compared with CODG (+4.2%) and CONG (+3.7%). The CODG achieved significantly higher improvements in jumping tests (3.5%) than in SSGG and CONG groups (1.9 and 1.5%, respectively).
This is the first study that examined the effects of a multidirectional sprint and SSG training on agility, COD ability, soccer-specific sprinting, and jumping performance in elite-level young male soccer players. The main finding of this study was the significant superior effect of SSG practice on agility performance considered as the ability to provide a proper COD according to an unpredicted external stimulus (26).
Additionally, the use of SSG as training intervention was effective in improving sprinting, preplanned COD, and leg power. These results provide further supporting evidence to the interest of SSG in soccer training even at youth level (13). Interestingly, the use of selected COD training drills was effective in providing greater improvements in line sprinting over distances ≥10 m compared with SSGG. The CODG also was successful in promoting shorter sprint times in tests proposed to evaluate COD in soccer.
In soccer, the use of SSGs was suggested for the reported effectiveness in promoting aerobic fitness in populations of players of different ages and competitive levels (13). In adult soccer, for health, the use of various forms of SSG was effective in promoting a wide range of fitness improvements in the aerobic and anaerobic performance spectrum (16,17). In this study, the use of selected SSG (i.e., 1 vs. 1, 2 vs. 2, and 3 vs. 3) showed to foster the individual's ability to provide a sudden and effective motor response to an external stimuli and to concurrently improve a wide range of short-term anaerobic performances relevant to soccer (20,28). These novel results are of great interest in youth soccer, as longitudinal studies showed that physical performance and skill development were age related, with anaerobic fitness more susceptible to training-induced changes in the early stage of soccer players' development (23–25). It could be speculated that the reported effects were the result of the reiterated acceleration and deceleration that took place in the considered SSGs that were performed at high intensity and over playing areas of small dimensions (22). Indeed, in this study, the proposed SSG involved no more than 3 players a side and small playing areas that were modified for dimensions accordingly to players' number to allow 100 m2 per player. This players' density was remarkably lower than those reported (i.e., 145–210 m2) by other authors in descriptive and training studies that examined the effects or potential of SSG on aerobic fitness (5). However, they were in line with the 3 vs. 3 paradigms proposed by Hill-Haas et al. (13) and Rampinini et al. (22) (i.e., 90–100 m2). This players' density is remarkably lower than the usual encountered by players in the 11-a-side soccer (i.e., 300 m2).
In light of this study results, a reduced player density is suggested when improvements in agility and in the short-term anaerobic power domain are expected. In this study, SSG were devised to provide similar volume of CODs in the experimental groups through a preliminary pilot study. Despite no direct control on the nature and the frequency per drill of CODs in this study, players were encouraged to provide maximal effort throughout the SSG drills to match CODG training intensity. Further studies examining the external load experienced by players during SSG similar to this study are warranted. This with the aim to establish possible cause-effect and dose-response relationships between the occurring unpredicted COD during SSG and the expected improvements in agility and in the short-term anaerobic fitness domain.
Training studies addressing COD ability development showed course-specific improvements (31). However, the proposed training interventions only used single COD paradigms consequently driving training outcomes (31). Differently from Young et al. (31) in this study, the multidirectional training in CODG considered several drills that although limiting the possible understanding of a selective effect on performance, aimed to stress a wide range of adaptations in the COD domain (26,31). The results of this study showed that the drills used were successful in promoting significant improvements not only in the COD domain. Indeed, the multidirectional training protocol considered in the CODG provided superior improvements in line sprinting from 10 to 30 m also.
These findings provide further evidence to the adaptive responses to COD training suggesting the potential of a multidirectional training program to warrant a wide effect on COD abilities in young soccer players (9).
Because of the provided relevance of line sprinting in soccer, the improvements over soccer-relevant sprinting distances (i.e., 10–30 m) achieved only the results of great practical interest using SSGs (12,28). This contrasts to the supposed speed development specificity of ball-game forms suggested by Casamichana et al. (6).
However, the reported significant improvements over sprint distances exceeding 10 m in CONG may suggest a possible effect of soccer training on short-term anaerobic fitness. Again, future studies considering the assessment of the external load (i.e., speed and accelerations) imposed to players during training may be useful to detect possible cause-effect relationships.
In this study, either the intervention or the control groups reported significant pre-to-post improvements in RAT with or without the ball. Despite the remarkable superiority in improvement magnitude found in SSGG, the parallel improvement in agility performance across groups may probably be the result of soccer practice due to the significant improvement in the CONG. However, it could be speculated that the concurrent improvement in agility was the result of a lack in specificity of the used tests warrant future studies considering more complex patterns in response to a soccer-relevant external visual stimuli.
Youth soccer studies examined the effect of in-season and pre-season strength training protocols on sprint, vertical jump, and COD test performances (10,30). Christou et al. (10) examining the effect of a weight training protocol (i.e., 50–80% 1 repetition maximum) in 12–15 years male soccer players reported improvement in 30 m (2.5%) but not in 10-m sprinting. The COD (i.e., 10- × 5-m shuttle running) improvements were of 5.4% after 15 weeks of training. With a strength and power training intervention, Wong et al. (30) found significant improvements in 10, 30 m, and vertical jump performance (4.9, 2.3, and 6%, respectively).
The CODG improvements were similar to that reported in the study of Wong et al. (30) for sprint performance but higher than in the research of Christou et al. (10). Interestingly, weight training in young soccer players resulted in COD ability improvements similar to this study (10). These findings showed that with the functional training (i.e., SSG and COD drills), it was possible to obtain improvements that were in line and of the same magnitude of when using strength training protocols in young soccer players. Further studies promoting the comparison of strength and functional anaerobic training are warranted.
To foster the internal validity of this study, the considered research design involved training protocols that were chosen for proven applicability in the usual youth soccer training set-up (i.e., ecologic validity). The results showed that to train the whole range of short-term anaerobic performance, the use of specifically designed SSG may be a viable option in young male soccer players. Furthermore, these agility-oriented SSG drills may help coaches in concurrently improving the individual and team skills in association with anaerobic fitness (13).
Interestingly, the generic training involving preplanned COD drills over a wide range of angles may provide significant although lower improvement over agility as well. Given that, agility in young soccer players can be improved either using specific or generic training but for maximum gains, it is recommended to include appropriate exercises (i.e., SSG). Because of the unpredicted nature of SSG, quantification of match COD occurrence would be of interest to set dose-response paradigms. The use of accelerometers could be a viable strategy to achieve an objective measure of the produced external training load, and future studies are warranted.
Small-sided games may be a successful strategy to improve agility, COD, and sprinting in young male soccer players at elite level. To improve agility, 1 vs. 1 to 3 vs. 3 SSG drills should be implemented (100 m2 per players) as specific drills. Multidirectional sprint training should consider a wide range of COD drills to provide greater results in young male soccer players.
The relevance of agility, COD, and sprinting performance in soccer, promote the practical interest of future studies addressing the possible cumulative-additive effect of combining COD and SSG training.
The authors have conflict of interest with the procedures used in this research design. No financial support was provided for the completion of any part of this study.
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Keywords:Copyright © 2014 by the National Strength & Conditioning Association.
sprinting; association football; randomized design; functional strength