In modern soccer, coaches are continuously looking for drills and modified games, which may concurrently improve the physical, technical, and tactical capacities of players. Although soccer match play is played with 10 field players per team, small-sided games (SSGs) often include <4 players per team (with or without a goalkeeper) on reduced pitch areas (8). In this context, SSGs are often being used in the belief that they concurrently develop the key qualities of the soccer athlete (8,18,20), irrespective of status (amateur vs. professional) or age (adult vs. youth) (8,15,16,29).
More precisely, SSGs are believed to enhance the endurance (16,25), aerobic capacity, and maximal oxygen uptake of the player (4,10). This type of exercise allows the attainment of maximal heart rate (HRmax) in an equivalent proportion to that observed during a match play, that is, ranging from 80 to 90% of HRmax (34). Dellal et al. (8) have also shown that the intensity of effort during short intermittent runs was similar to those of some SSGs, with the key difference being the homogeneity of responses between players. Moreover, a number of prescriptive variables influence the intensity, time-motion characteristics and technical load of SSGs. These include rules, pitch size (36), the presence of goalkeepers (25), the presence and the size of the goal (24), the number of players (15), the duration of the exercise (20), the availability of replacement soccer balls (29), and the balance of opponents (8,15). The physical activity of players during various SSGs has been thoroughly investigated, especially with respect to the analysis of the high-intensity running (HIR) and sprint activities (15). Nevertheless, although modern elite soccer is characterized by an increase in playing intensity (with coaches often asking for fewer ball touches per possession) (34), to the authors' knowledge the physical impact of modifying the number of ball touches authorized by possession has not been studied. The majority of published studies have used free play (no limit on number of touches on the ball per player), despite the fact that it has been reported that high-level players average between 1.74 and 2.24 ball contacts per individual possession (9). Mallo and Navarro (25) have shown that the 3 vs. 3 without goalkeepers facilitates more ball contacts and more short passes per player than a 3 vs. 3 played in the presence of goalkeepers. In the same context, the pitch dimensions altered the technical activity, with especially the number of tackles and shots (22). Therefore, technical load is influenced by rule changes. The study of Owen et al. (27) also showed that the number of players per team and the pitch size altered both the physiological responses and the technical load. However, Rostgaard et al. (33) have revealed that the physical activity influences technical performance (load) in soccer.
Consequently, a logical extension of these previous studies is an analysis of a player's physiological response during various SSGs, combined with both the time-motion characteristics and the technical load, and analyzed with respect to the number of ball contact authorized per individual ball possession. The latter point is a key characteristic of elite soccer and differentiates between different playing levels during match play. For example, amateur players typically require a greater number of ball contacts per individual possession as compared to professional players (9,10). Thus, it could be interesting to examine if this difference of the level of play also exists during SSGs and, therefore, if the modification of this rule induces the same physiological responses, physical and technical load between amateurs and professionals during SSGs.
In this context, the purpose of this study was to compare the physiological responses, and the technical and physical activities of amateur and professional players during various SSGs to investigate if there exists a difference of workload according to the playing level. It was hypothesized that the HR response, rating of perceived exertion (RPE), blood lactate concentration, and total distance covered in sprinting and in HIR during SSGs will be different in amateurs when compared to professionals. A secondary hypothesis was that the technical load in amateur players would be lower because of a lower percentage of successful passes and a greater amount of lost balls per possession. Finally, the last hypothesis of this study examines if professional players tolerate this method of exercise better than amateur players do.
Experimental Approach to the Problem
The physical activities of soccer players during various SSGs are well known. However, the influence of playing level or expertise within various SSG formats has not been investigated. Therefore, both the player number and rules were manipulated to investigate if physiological responses, technical load, and physical activities differed between elite and amateur players within various SSG formats. In this context, elite and amateur players played in 3 different SSG formats (2 vs. 2, 3 vs. 3, 4 vs. 4) in which the number of ball touches was varied (1 touch [1T], 2 touches [2T], or free play [FP]). The physiological responses, time-motion characteristics, and technical activities were analyzed across the 3 different SSG formats. The pitch size and the duration of the SSGs were strictly controlled (Table 1). The SSGs were performed with 4 support players positioned outside the playing area, with the instruction to maintain collective possession of the ball. All SSG sessions were performed at the same time of the day to avoid any effect of circadian rhythms on the measured variables (11) with at least 2 days separating each session. An appropriate standardized warm-up was performed before each SSG session. Consistent verbal encouragement was provided by the coaches for all the SSGs to ensure the maintenance of a consistently high work rate.
Twenty international soccer players (27.4 ± 1.5 years old, 79.2 ± 4.2 kg, 180.6 ± 2.3 cm, 12.7 ± 1.2% of body fat, vV̇o2max of 17.4 ± 0.8 km·h−1) and 20 amateur soccer players (26.3 ± 2.2 years old, 77.1 ± 5.3 kg, 178.2 ± 2.8 cm, 13.4 ± 2.0% of body fat, vV̇o2max of 17.0 ± 1.2 km·h−1) of the fourth French division participated in the study. All players had performed the Vameval field test (3) to determine the lowest velocity associated with their maximal oxygen uptake (vV̇o2max). Amateur players participated in 3-4 training sessions per week plus 1 match. In contrast, the professional players completed 5-7 training sessions per week plus 1-2 matches. Goalkeepers were excluded from the study because they did not participate in the same physical training program as the remainder of the squad. The study was conducted according to the ethical standards in sport and exercise science research (14). The local university ethics committee approved the protocol. All subjects received a detailed explanation about the aims of the study and were free to withdraw from the study at any time.
The SSGs were implemented in random order over the duration of the study (6 weeks) (Table 1). The number of players (2 vs. 2, 3 vs. 3, 4 vs. 4) and ball touches (1, 2, and FP) were the dependent variables with the natural grass playing area a constant (Table 1). The aim for each team was to keep possession of the ball for the longest time possible. A similar standardized warm-up preceded each training session for both professional and amateur players. None of the SSGs included goalkeepers. To avoid excessively long game stoppages, soccer balls were disposed around the game areas for immediate availability. Both total and effective playing times were recorded. The SSG formats used in this study formed part of the players' normal training sessions and have been implemented in various other scientific research studies (15,29). The following variables were analyzed during all SSGs: physiological measurements (HR, blood lactate), subjective perception of effort (RPE), physical, and technical performances.
Heart Rate Measurements
During the SSGs, each player's HR was continuously recorded every 5 seconds using HR monitors (Polar RS400, Polar-Electro, Kempele, Finland), and the percentage of the reserve HR (%HRreserve) was calculated according to Dellal et al. (8).
Blood lactate samples were appropriately collected from the fingertip at the third minute postexercise (35) with reliable portable lactate analyzers (Lactate Pro, Arkray, Kyoto, Japan) (28).
Rating of Perceived Exertion
The RPE scale proposed by Foster et al. (12) was used to assess the global internal load of each SSG (6,19) and had been used for 2 weeks before the experiment to ensure subjects' familiarization. The RPE of each player was recorded immediately on completion of each SSG using a standardized question, with no information provided to the players with respect to any of the previous measurements.
Technical Performance (Load)
The SSGs were analyzed using 4 fixed digital video cameras placed on each corner (positioned 3 m from the corner) of the game area. Duels, percentage of successful passes, the amount of lost balls per possession, and the total number of possessions were monitored by video recording, which was played back several times until analysis was complete.
Physical Performance during Each Small-Sided Game
The players' physical activity during each SSG was monitored using portable global positioning satellite system (GPS) technology (GPSports SPI Elite System, Canberra, Australia). The GPS units have previously been validated for monitoring high-intensity and sprint activity during soccer (1). This method of analysis of soccer activity presents a coefficient of variation of 3.6% for total distance and 5.8% for sprint (5). The position of each player was recorded with a frequency of 5 Hz and then translated into distances covered and speed of movement. For analysis purposes, the distances covered both in sprinting and during HIR were selected. According to previous time-motion analysis (9,10,15), 2 thresholds were used to evaluate the distances covered at selected running speeds: 13-17 km·h−1 for HIR and >18 km·h−1 for sprinting.
Lower Body Power Performance after the Small-Sided Games
Players performed 3 squat jumps (SJs) and 3 countermovement jumps (CMJs) immediately after each SSG (after having recorded their RPE). The jumps were evaluated by means of the Optojump system (Polifemo, Microgate©, Bolzano-Bozen, Italy), measuring both flight and ground-contact times. The jumps were interspersed with 30 seconds of rests, and the highest jump of each type was selected for statistical analysis (37).
Data are presented as mean ± SD. The normality distribution of the data was first checked using the Kolmogorov-Smirnov test and the Mauchly test. This was followed by a 1-way analysis of variance that was used to test for differences in performance measures between the 2 different playing levels of soccer players (amateur vs. professional) in each SSG (2 vs. 2, 3 vs. 3, or 4 vs. 4). Follow-up univariate analyses using Bonferroni-corrected pairwise comparisons were used where appropriate. The level of significance was set at p ≤ 0.05. Cohen's effect sizes were also calculated to describe any trends apparent in the data. An effect size of ≤0.3 was considered small, 0.3-07 moderate, and ≥0.7 large. The interclass correlation (ICC) values ranged from 0.87 to 0.93.
The comparison of professional and amateur soccer players demonstrated that the level of play influenced the physiological responses and physical and technical activities during each SSG. Across all SSGs, amateurs completed a lower percent of successful passes (p < 0.01), recorded higher values for RPE and [La], lost a greater number of possessions (p < 0.001), and covered less total distance in sprinting and HIR. Furthermore, both SJs and CMJs after each SSG was greater for professionals (p < 0.001) compared with amateurs.
Two vs. 2 Small-Sided Games
Both RPE and [La] were higher in amateurs (p < 0.001), whereas HR responses were similar when expressed in terms of %HRmax and %HRreserve (Table 2). The [La] values recorded by amateurs in FP, 2T, and 1T were greater than those recorded by professionals (18.0, 33.0, and 30.3%, respectively). The time-motion results showed a lower total distance covered by amateurs. In contrast, total distance covered in HIR, expressed as a percentage of total distance covered, was similar for amateurs and professionals (respectively, 22.6 ± 4.0 vs. 22.8 ± 3.3) despite amateurs covering a lower absolute total distance in HIR (p < 0.01) (Figure 1).
The technical activity analysis revealed that amateur players, despite achieving a greater amount of ball possession, executed a greater number of unsuccessful passes (p < 0.01), lost a greater amount of balls per possession (p < 0.001), and were involved in fewer duels (p < 0.01) compared to their professional counterparts. Although the absolute number of duels increased for both amateurs and professionals during the 2 vs. 2 SSGs, amateurs were involved in a lower number of duels compared with professionals during both 2T (12.4% lower than professionals, p < 0.001) and 1T SSGs (11.1% lower than professionals, p < 0.001). Moreover, amateurs lost a greater amount of balls per possession particularly during the 2T and the 1T SSGs (49.3 and 30.4%, respectively).
Three vs. 3 Small-Sided Games
The time-motion activities for amateurs were significantly lower for all the analyzed parameters in comparison with professionals (Table 3). The greatest difference between amateurs and professionals related to the total distance covered during sprinting in the FP condition (p < 0.01).
Differences in [La] and RPE values for both amateurs and professionals were less marked across the various 3 vs. 3 SSGs compared to 2 vs. 2 SSGs (Table 3).
The analysis of the technical activities illustrated that the amateur players attained less ball possession during 3 vs. 3 SSGs, which is in contrast to more possession attained during 2 vs. 2 SSGs. This difference was greatest for the 3 vs. 3 in FP (p < 0.01 vs. p < 0.05 for the 1T and the 2T, respectively). Moreover, the total number of duels was 20.9% (FP) and 17.6% (2T) lower in amateurs, but the differences between the 2 groups were less marked when the 3 vs. 3 was played in 1T.
Four vs. 4 Small-Sided Games
The physiological responses for amateurs during various 4 vs. 4 SSGs were similar to those recorded for the various 3 vs. 3 SSGs. More specifically, there was no significant difference in the HR response between amateur and professional players during the various 4 vs. 4 SSGs (Table 4), whereas a significant difference existed between the 2 groups across the various 2 vs. 2 SSGs (Table 2).
In the same context, differences in the time-motion activities were similar to the 3 vs. 3 SSGs, with the exception of the distance covered in HIR (Figure 1). Indeed, amateurs presented an equivalent percent of the total distance covered in HIR and sprinting (20.4 vs. 19.8% of the total distance, respectively) when the 4 vs. 4 was played in FP.
The technical analysis showed no significant differences in the number of duels and percentage of successful passes, whereas the difference in the number of ball lost was less important (p < 0.05) than those observed during the 2 vs. 2 and the 3 vs. 3 (p < 0.001). No difference existed concerning the total number of ball possessions (35.9 vs. 35.6 for professionals and amateurs, respectively) for each 4 vs. 4 tested.
The main objective of this study was to examine the differences in physiological responses, technical and time-motion activities between amateur and professional players during various SSG formats (2 vs. 2, 3 vs. 3, and 4 vs. 4) when 3 different playing rules concerning the number of ball contacts authorized by individual possession were applied (1T, 2T, and FP). The main finding was that the technical activities, time-motion characteristics, physiological, and perceptual responses differed between amateurs and professionals for all SSGs played. Furthermore, changes in playing rules (1T, 2T, or FP) appeared to have a heterogeneous influence on the various studied parameters, whereas the HR responses were similar for both groups across all SSGs.
The results of this study demonstrated a significant difference between amateur and professional players in selected time-motion variables during SSGs, particularly for the total distance covered in sprinting and HIR. This is in agreement with the findings of a previous study that measured the time-motion responses in various SSGs (7). Indeed, amateurs performed significantly less total distance in sprinting across all the different SSGs. The ability to complete repeated sprints, with limited rest, is a major physical determinant of success in modern soccer, and it may represent the best physical factor differentiating the playing level (31). During these specific SSGs, the relative proportion of sprinting as a percentage of total distance was greater than that reported during matches. Commonly, sprint activities range from 1.8 to 2.6% of the total distance covered during a match (9), whereas during these SSGs, the sprint efforts ranged from 14.5 to 17.8% for the professionals and from 13.6 to 16.3% for the amateurs. Consequently, the higher proportion of sprint activities may partially explain the differences in the [La] observed. Moreover, SSGs, by their nature, also require players to perform more directional changes which, when combined with increased sprinting, may have contributed to the greater [La] values and perceptual responses for the amateur players.
With respect to the HIR activities, the results of this study were less homogeneous. Similarly to the sprint activities, amateurs performed less absolute total distance in HIR during both the 2 vs. 2 and the 3 vs. 3 SSGs (p < 0.01). However, these differences were not apparent when distance covered in HIR was expressed as a percentage of the total distance covered. More specifically, for 3 vs. 3 SSGs in elite youth soccer players, Hill-Haas et al. (15) showed similar results compared to amateur players of this study when played using a 2T rule. In addition, this particular study has demonstrated a significant difference between amateurs and professionals in sprinting and HIR, when the 1T and FP rules were applied to 3 vs. 3 SSGs. It is has been established that soccer at the elite level requires players to perform a substantial amount of HIR as reported by Bradley et al. (2) and Dellal et al. (9). Consequently, these factors could also be key factors for differentiating the playing level and at the same time may explain the difference in [La] and perceptual responses. Therefore, SSGs appear to provide a variety of training stimuli that would be of key importance to a coach including sprinting, changes of direction, technical load, and tactical activities.
The analysis of the total distance covered in all the SSGs also differentiated amateurs from professionals (p < 0.05), which is not always the case in match play (9). The HR responses, expressed as either %HRmax or %HRreserve, were similar between amateurs and professionals. Stolen et al. (34) reported that HR responses during match play ranged between 80 and 90% of the HRmax. In this study, HR response values ranged from 85 to 92%. According to Dellal et al. (8), although SSGs do tax the aerobic system quite heavily, but this study showed that this was not dependent on the playing level. However, this study suggests that the modification of ball possession rules may influence the HR responses quite strongly both in amateurs and professionals. Indeed, the 3 vs. 3 SSG played in FP form with the objective of keeping ball possession elicited higher HR responses than the 3 vs. 3 played with special instructions like the presence of a floater or neutral zone (15).
Therefore, the main physical differences between amateurs and professionals during these SSGs related to the HIR and sprinting activities with attendant physiological responses, including [La] values and perceptual responses, being higher for amateurs perhaps because of their lower fitness level. These results confirm previous studies on match play, which describe that the key difference between amateurs and professionals relates to the high-intensity efforts (21). The [La] values in this study were generally higher compared to the values reported by Hill-Haas et al. (15) for elite youth soccer players, and this fact is logical because lower [La] responses are reported in young subjects (38). The level of play may be differentiated by the [La] response, although similar responses have been reported when the number of players was modified. Indeed, [La] increases as the number of players is reduced as shown by former studies (29).
The results of this study also demonstrated a significant difference in lower limbs power, as evidenced by the difference in SJs and CMJs performance immediately after each SSG. The professionals demonstrated a significantly higher jump height compared with amateurs (p < 0.001). In general, all players generated lower jump values after the 2 vs. 2 SSGs and higher jump values after the 4 vs. 4 SSGs. This may be explained by the 2 vs. 2 SSGs inducing greater fatigue compared to the 4 vs. 4, especially because of the relative increase in HIR and sprinting as a proportion of the total distance covered. The lower limb power of the players may be altered by the 2 vs. 2 SSG independently of the level of play. Therefore, analysis of this parameter reveals the differing level of fatigue accumulated during various SSGs in this study. Indeed, during the 4 vs. 4 SSGs, the modification of the number of ball touches induced a similar performance in jump height for both amateurs and professionals, whereas the 2 vs. 2 and the 3 vs. 3 SSGs employing the 1T rule revealed a greater lower body fatigue for amateurs.
The technical pattern is also considered as one of the key factors that differentiate amateur and professional playing levels. Hughes and Franks (17) and Dellal et al. (10) have reported that elite level soccer requires a good technical ability. This study revealed that amateurs seemed to be less technically proficient than their professional counterparts as evidenced by a greater amount of lost balls per possession (p < 0.001) and a greater number of skill errors including missed passes. Grehaigne (13) reported that approximately 80% of goals resulted from a sequence of ≤3 passes. Consequently, the ability to execute high-quality passes is a key requirement in the modern high-level soccer, which bears a direct relationship with goal scoring (26). Indeed, professional players have been reported to demonstrate a pass completion rate of between 73.5 and 77.0% in the Spanish Liga, English Premier League, and French first League (9,10). This study revealed that this technical performance parameter was significantly lower for the amateurs in each SSG performed, with the greatest difference being most apparent in the 2 vs. 2 and 3 vs. 3 SSGs. These differences were amplified when the SSG was played using the 1T rule. Moreover, Hughes and Franks (17) suggested specifying the analysis of passes according to the type of pass. These factors appear to be important in soccer as Rampinini et al. (30) indicated that a decrease in the percentage of successful passes during a match would be correlated to the score of the game; in this case, a defeat. Therefore, because of the reduced pitch dimensions of SSGs, the majority of passes were short and the physical requirement increase the high-intensity actions as compared to a match play. In this context, it would be interesting to analyze if the score of the game during SSGs is also linked to the successful passes as in a match play.
The difference in the technical ability in amateurs was also shown by the greater amount of lost balls per possession across all the SSGs and particularly when the SSG was played according to the 2T and 1T rules. This finding is very important because it reflects the inability of the amateurs to maintain their skill performance when rules dictated a reduction in the number of ball touches. In arguably the 2 best premier soccer leagues in the world, the Spanish Liga and English Premier League, Dellal et al. (9) reported that the players performed between 1.74 and 2.24 ball touches per possession. This ability is one of the most important characteristics of modern elite soccer, and this study confirmed that it was a parameter, which could differentiate between amateurs and professionals also during training SSGs.
The analysis of the duels also differentiated between the 2 playing levels. Indeed, significantly different values were found between amateurs and professionals during the 2 vs. 2 and the 3 vs. 3 SSGs, whereas contrasting findings were observed for the 4 vs. 4. The lower number of duels per minute of play in amateurs may be explained by the fact that professional players have a higher running speed (21) and a better sense of anticipation (32). Consequently, the professionals are able to ‘shadow’ their opponents more closely, thus creating more duels, especially when the number of players decreases (such as in 2 vs. 2 and 3 vs. 3 SSGs).
Concerning the total number of ball possessions, contrasting results were found, which correspond with the findings of Lago and Martin (23). In this study, this particular parameter did not appear to differentiate between amateur and professional players. Lago and Martin (23), for example, reported that a number of variables might influence ball possession including quality of the opponent and the current score.
The major findings of this study are that the SSGs elicit different physical and technical activities in amateur and professional soccer players. More specifically, the total distances covered in HIR and in sprinting were greater for professionals independently of the number of ball touches authorized. At elite level, players need to be able to complete several repeated sprints bouts with incomplete recovery, and perform many high-intensity actions (including duels) and directional changes throughout the match. These have to be executed with a minimal reduction in physical and technical performance. Similarly, the difference between amateurs and professional was more apparent when the requirement for high-intensity physical activities was increased by reducing the number of ball touches authorized (1T and 2T). These parameters appear to constitute the key physical requirement factors at professional level. Consequently, for amateurs, the coach should aim to reduce these differences by including specific training of high-intensity intermittent exercises (38), repetition of sprints and SSGs played using the 2T rule.
All of these differences in the physical activities have to be combined with the fact that the blood lactate concentration and the perceptual response were always higher in amateurs. Professionals appear to better tolerate the training load of SSGs. However, an interesting question is, “What is the impact of the physical load on the technical performance during SSGs?” Indeed, this study revealed that amateurs both missed a greater number of passes and lost the ball with a higher proportion. This difference in the technical activities is probably because of a lower technical ability and thus, for amateurs, the coach should focus a part of their training on the capacity to not only execute passes of good quality and with a quick gestural execution but also to lose the smallest quantity of ball per possession.
For these reasons, SSGs appear to have the potential for improving both the physical and technical abilities of amateurs. The present differences between amateurs and professionals could guide youth and amateur soccer players' coaches to orientating their training toward the studied parameters. In this context, amateur soccer coaches should favor the use of SSGs with at least 2 touches authorized per ball possession because of their lower technical abilities as compared to professional players, whereas in elite soccer, coaches should be encouraged to use only 1 or 2 touches authorized per ball possession to recreate the nature of elite match play. Moreover, it should be investigated by longitudinal studies whether focusing youth players' training on high-intensity SSGs with a minimum of ball lost may help a greater proportion of young players to reach professional level. Finally, this method of training closely replicates the physical and technical match-play conditions for professionals and constitutes a useful training tool for the elite soccer coaches.
We would like to thank all the players of the Ivory Coast national soccer team for their participation. The authors have no conflicts of interest that are directly relevant to the content of this article. This study was not supported by any financial aid. Results of this study do not constitute endorsement of the product by the authors or the National Strength and Conditioning Association. Competing interests: None declared.
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