The influence of the field orientation on physical demands in soccer small-sided games

Introduction

High-standard soccer players typically travel about 9 to 12 km and achieve approximately 85% maximum heart rate (HRmax) and 70–75% of maximal oxygen uptake (VO2max) during the normal 90 min game time.^1–5 The intermittent nature of soccer means that total distance covered comprises approximately 1000–1400 individual runs, of which up to 220 are high intensity in nature.^6,7 The demands of this physically challenging sport have resulted in trainers and coaches developing a variety of methods for improving the physical fitness of players. A particularly common physical fitness training method is the use of small-sided games (SSG). ⁸ Depending on the purpose of the physical training session, the configuration of SSG can be manipulated to expose players to different stimuli.^8–12 The most common SSG manipulations include changes in the number of players, ¹² game rules, ¹³ and/or field dimensions.^8–10 SSG provide a highly specific method for enhancing players’ physical capacity, ¹⁰ while also developing technical and tactical skills in an environment similar to an official game. ¹⁴

A common area of investigation in this domain is to analyze how changes in the SSG playing field orientation, width and/or length impact on playing style and workload.^8–10,15 Folgado et al. ¹⁵ reported that changing the pitch orientation affects the physical demands of the 4-a-side SSG, since a more elongated pitch elicited a higher distance covered at high intensities. Research by Coutinho et al. ⁸ indicates that a rotated pitch with greater width than length results in a larger effective playing space during 5 versus 5 (75 m² per player) SSG. However, the regular condition (greater length) results in a higher game pace, total distance covered and distance in high speed. In a similar study, Casamichana et al. ⁹ report that increasing the length rather than the width of the playing field during SSG (100–330 m² per player) results in the greatest increases in the rating of perceived exertion, peak speed, number of accelerations and decelerations. Accordingly, it would appear that the manipulation of a variable as simple as the dimensions of the SSG playing field can have quite marked effects on the associated training responses (technical, tactical and physiological) experienced by the players.

An important consideration when developing soccer-based SSG must always relate to their specificity to actual normal match play. In terms of field dimensions, an official soccer field has lateral lines longer than the back lines, but the dynamics and rules of the game induces an approximation of its players to each other and the ball. This means that players rarely adopt a playing shape that conforms to the exact dimensions of the field. ¹⁴ For example, the offside rule effective establishes a dynamic decrease in the pitch area, which constrains the players’ ability to explore the field space along the lateral lines. Researchers in this domain often expand on this and consider the relative playing area of an official soccer field to be wider than it is long. ¹⁴ In order to investigate this concept further Caro et al. ¹⁶ analyzed the width and length dimensions of the relative playing area in all 4v4 situations during normal official games. In this novel project, the researchers report that the effective playing area size during these events is wider than it is long in all zones of the playing field. Based on these data Caro et al. ¹⁶ suggest that to recreate match-play conditions, the playing area in soccer-specific 4v4-SSG should also be wider than they are long.

While it would appear relatively obvious that SSG such as these provide soccer skills training in sport-specific contexts, the question remains as to whether the physical demands of soccer-based SSG are comparable to conventional soccer match play. This assumption appears integral with their use, but at the time of submission of this manuscript no studies were found in the scientific literature that compared the physical demands of SSG with different pitch orientations (length and width) with the physical demands of official soccer matches. Therefore, the aim of the present study was to compare the physical demands of SSG with either greater length (SSG_length) or width (SSG_width) with the physical demands of official 11 per side matches. We hypothesized that physical demands during SSG_width would be more representative to those from conventional match play.

Methods

Design

Official matches and SSG were played during the competitive season and official playing rules were applied in both situations (Figure 1). The official match durations (45 min) were different to SSG (26 min). For this reason, some variables were expressed relative to the time of each activity, resulting in a measurement unit per minute.

OPEN IN VIEWER

Figure 1.

Timeline of data collection.

Methodology

Sample characterization tests

Body mass and height were measured using the weight-scale balance with a stadiometer (Filizola; São Paulo, Brazil, precision of 0.01 m and 0.1 kg). The Yoyo Intermittent Endurance Test Level 2 (YIET2) was carried out during two weeks before the competitive period (Figure 1), as a measure of the ability to perform repeated intense exercise. The YIET2 was carried out on the soccer field and consisted of 2 × 20 m shuttle runs at increasing speeds, controlled by audio signals, interspersed with a 10-s period of active recovery. ¹⁷

Small-Sided games<TE/CE: please check heading levels>

The SSG sessions were held during the competitive period. All sessions were carried out on the same field in the club's training center after a minimum of a 72 h interval from the official game (Figure 1). In each session, soccer players competed in four SSGs of 5 min each with 2 min of passive recovery between them. ¹⁸ The players were distributed in four teams, with player's team allocation based on their playing position and performance during the YIET2 using a matched-pair research design. ¹⁹ Each team (A – 55.2 ± 2.5 mL.kg⁻¹.mL⁻¹, B – 56.2 ± 3.4 mL.kg⁻¹.mL⁻¹, C – 57.6 ± 1.8 mL.kg⁻¹.mL⁻¹, D – 56.2 ± 1.9 mL.kg⁻¹.mL⁻¹) consisted of four players: a goalkeeper, two defenders, a midfielder, and a forward. We assumed that the homogeneity of the sample would not require an intentional team composition based on technical skills since all players were part of an elite under-20 team. Traditional soccer playing rules, including ball and goal sizes, were used for all SSG and the players were instructed to try and score goals while also preventing the opposition from scoring. No verbal encouragement was given. This structure allows teams and players to explore the physical and technical-tactical specificities of each playing position during the different SSG. ¹⁴ In the first session Team A competed against Team B in SSG_length, while Team C competed against Team D in SSG_width (Figure 2). In the following sessions, the opponents were kept and only the field orientation was changed. Before each SSG training session, a standard warm-up (12 min) was performed consisting of dynamic stretching exercises and soccer-specific movements.

OPEN IN VIEWER

Figure 2.

SSG sessions configuration.

Official matches

Official games were monitored from the under-20 Brazilian Football League (organized by Confederação Brasileira de Futebol – CBF, the Brazilian national confederation) and from the first division of the State under-20 Championship (organized by the Minas Gerais Football Federation – FMF). There was an average of 12.8 ± 8.9 games per athlete. Only the first 45 min of each official game was analyzed. Official matches were played during the competitive season, and official playing rules were applied.

External load data

The time-motion variables were collected with 16 GPS units with a sampling frequency of 10 Hz, and 200 Hz 3D accelerometer, gyroscope and magnetometer (Polar Team® Pro System; Polar Electro Oy, Kempele, Finland). This system has showed good accuracy and reliability during low-speed running (0.00–13.99 km/h; intraclass correlation coefficient (ICC) = 0.99, typical error of measurement (TEM) = 5.05%), high speed running (14.00–19.99 km/h; ICC = 0.99, TEM = 1.06%) and very high-speed running (≥20.0 km/h; ICC = 0.99, TEM = 2.89%). ²⁰ To facilitate the acquisition of satellite signals, all devices were activated 20 min before the data collection. External load variables collected were total distance covered (km), maximum speed (km/h), high-speed distance covered (≥19.8 km/h), sprint distance covered (≥25.0 km/h), number of high-speed actions, number of sprints, number of accelerations (≥2.8 m/s²) and number of decelerations (≤-2.8 m/s²). With the exception of the maximum speed, all external load variables were standardized to the time.

Internal load

Heart rate (HR) responses were monitored during the SSG and official matches. These data were reported as relative average heart rate (average HR as a percentage of HRmax), as this is more indicative of what occurs over the entire training session compared to HRmax. ⁴ The internal load was also quantified through the HR from the training impulse (TRIMP) method, which evaluates the session volume and intensity through specific scores in each training zone. The time in which the athlete remained in each zone during each session was multiplied by factors as proposed by Edwards ²¹ (Zone 1–50.1 to 60% HRmax, factor 1/; Zone 2–60.1 to 70% HRmax, factor 2/; Zone 3–70.1 to 80% HRmax, factor 3/; Zone 4–80.1 to 90% HRmax, factor 4/; Zone 5–90.1 to 100% HRmax, factor 5). The highest HR value during the YIET2 was considered as the HRmax. According to Bangsbo et al., ¹⁷ the YIET2 is a reliable tool to determine the maximal heart rate of an individual. The HRmax value was replaced if during the official matches a higher HR value was registered.

Results

Differences were found between external load data from official match play and SSG_length and/or SSG_width for all but the number of decelerations (Figure 3). Total distance covered was the only external load variable that differed between SSG_length and SSG_width (p = 0.05; ES = 0.83 – moderate ES). The highest values were registered in the officials’ matches than SSG_length and SSG_width respectively for high-speed distance (p < 0.01; ES = −1.69– large ES) (p < 0.01; ES = −2.20– very large ES), sprint distance (p < 0.01; ES = −1.32–large ES) (p < 0.01; ES = −1.47– large ES), maximal speed (p < 0.01; ES = −3.15 – large ES) (p < 0.01; ES = −3.53– very large ES) and number of sprints (p < 0.01; ES = −1.66 – large ES) (p < 0.01; ES = −2.22– very large ES). In opposite, the number of accelerations was lower during official matches than SSG_width (p < 0.01; ES = 1.59- large ES) and SSG_length (p < 0.01; ES = 2.29- very large ES). The number of high-speed actions was higher in official games when compared to SSG_width (p < 0.01; ES = −1.80- large ES). No differences were found between official games and SSG_length (p = 0.06; ES = −0.93- moderate ES). No differences were found between SSG_length and SSG_width for high-speed distance (p = 0.14; ES = 0.90- large ES), sprint distance (p = 0.21; ES = 0.75- moderate ES), maximal speed (p = 0.58; ES = 0.28- small ES), number of high-speed actions (p = 0.09; ES = 0.69 – moderate ES) and number of sprints (p = 0.20; ES = 0.38- small ES).

OPEN IN VIEWER

Figure 3.

External and internal load from official games, SSG_width, and SSG_length.

Relative average heart rate differed between official match play and SSG_length and/or SSG_width (p < 0.01; ES = −2.10- very large ES). There were no significant differences in any of the internal load data between SSG_length and SSG_width (p = 0,99; ES = 0.02- trivial ES). The relative magnitudes of these differences showed that relative average heart rate was lower during SSG compared to traditional match play, while there were trivial differences in TRIMP between match play and both SSG types (Figure 4).

OPEN IN VIEWER

Figure 4.

Effect size and confidence intervals of SSG_width and SSG_length, when compared to official games. Positive and negative values mean positive and negative effects from the SSG, respectively.

Discussion

The aim of this study was to compare the physical demands of SSG involving greater length (SSG_length) and greater width (SSG_width), with the physical demands of official games. Internal and external load variables were used in the comparison. The results of this study showed that official game relative loads were significantly different than both SSG field configurations. In addition, the use of a field with a greater width rather than length does not appear to influence the physical demands of the SSG.

Our results for the total distance covered are in conflict with research reporting that this variable is greater during traditional match play than during SSG. ²³ Research on SSG indicates that total distance increases during SSG as a function of increases in both the total playing area and area per player. ²⁴ It would appear that this relationship does not translate when comparing SSG with traditional match play, as the SSG total field area in our study was 1040 m² and field area per player was 104 m². Conversely the minimum dimensions required for a International Federation of Association Football (FIFA) registered playing field result in a total playing area of 4050 m² and field area per player of 184 m². The small, non-significant differences for total distance covered between the official matches and SSG_width may be due to the players reducing their in-length spatial exploration as a function of the offside rule. ¹³ This is also reflected in match play research which shows the relative 4v4 playing area size is wider than longer in all zones of the official playing area. ¹⁶ The significantly greater total distance covered during SSG_length compared to SSG_width is consistent with research by Casamichana et al. ⁹ and Folgado et al. ¹⁵ One possible explanation for these results is the fact that during the SSG_width the goals are closer than the SSG_length. This situation might increase the opportunities to shoot, decreasing the necessity to move to create goal-scoring opportunities.

High-intensity running actions such as maximal running speed have a particular importance in soccer, as they often correspond to the most crucial moments in the game ²⁵ and represent a key determinant of the final game result. ⁵ In addition to our result for maximum speed, the number of sprints, high-speed running distance and sprint distance covered were all significantly higher during official games than both SSG field orientations. These findings are consistent with research reporting that the magnitude and/or frequencies of these variables all increase when the area per player increases. ²⁴ Conversely, our results on the frequency of accelerations (≥2.8 m/s²) show these occur more frequently during SSG than during traditional match play. This is consistent with research indicating acceleration patterns in SSGs are relatively greater than those observed during professional matches. ²⁶ We argue that during SSGs, players engage more frequently in actual match-play activities since there are fewer players than in the regular match (hence, there are few “passive moments” within the game) and the game is less frequently paralyzed by fouls, throw-ins, corner kicks, and goal kicks, which are fastly performed by the players. Besides that, having a higher pitch area creates more space to cover without the need to change direction, allowing the players to achieve higher speed intensities (e.g. long pass into the back of defensive line, counter-attack situations). On the other hand, the smaller area in the SSG could decrease the distance between the player in possession and the immediate defender, as well as the remaining players, increasing the number of accelerations and decelerations. Therefore, the previously reported increase in acceleration demands when the pitch is increased ²⁷ might apply only to SSGs, not when comparing them with official matches. Further research in larger formats of SSGs is recommended to confirm such an assumption.

Our results for the number of decelerations (≤-2.8 m/s²) appears contrary to our acceleration (≥2.8 m/s²) data, but it is likely that the former are influenced by the slower maximum running speeds achieved during the SSG. This is consistent with research by Gaudino et al., ²⁴ who report slower maximum running speeds when playing field dimensions and area per player decrease. These researchers also indicate that the number of moderate (2–3 m/s²), but not high intensity (>3 m/s²), accelerations and decelerations increase as the pitch dimensions during SSG decrease. Similarly, Hodgson et al. ²⁷ report that medium playing field sizes impose a greater total deceleration than smaller playing fields. Unlike our findings (small, non-significant differences between SSG_length and SSG_width), Casamichana et al. ⁹ suggest that longer SSG playing fields result in significantly greater maximum speeds. Increasing the pitch length has also a greater effect, if compared to increasing the pitch width, on number of accelerations, decelerations, and changes of direction. ⁹ Similar results were found by Folgado et al. ¹⁵ and Coutinho et al.8. These authors reported a higher distance covered at high intensities during the length rather than the width scenario. Possible explanations for our different results could be the differences in players’ age, game rules, number of players, and area per player. It would appear that the smaller field sizes typical in SSG limit players’ ability to achieve high running speeds regardless of field orientation. Our results also suggest minimal differences in all these high-intensity running actions between SSG_width and SSG_length. It seems that irrespective of playing field orientation, the smaller pitches used in our SSG result in different overall external workload profiles than associated with traditional match play. Folgado et al. ¹⁵ reported that changing the pitch orientation affects the physical demands of the 4-a-side SSG, since a more elongated pitch elicited more distance covered at high intensities. Research by Coutinho et al. ⁸ indicates that a rotated pitch with a greater width than length results in a larger playing space during 5 versus 5 SSG (75 m² per player). However, the regular condition (greater length) resulted in a higher game pace, total distance covered and distance at high speed. In a similar study, Casamichana et al. ⁹ report that increasing the length rather than the width of the playing field during SSG (100–330 m² per player) results in the greatest increases in the rate of perceived exertion, peak speed, number of accelerations and decelerations.

HR values during the official games (87.8%), SSG_width (80.8%) and SSG_length (80.9%) were all similar to the 80–90% of the maximal heart rate described in other studies during competitive matches.^4,5 However, our %HRmax values during the official games were significantly greater than in both SSG formats, with no significant differences in these data between SSG_width and SSG_length. These results are in contrast to earlier research reporting significantly higher HR responses during SSG than traditional match play.^18,26 However, differences in the SSG formats ²⁶ and the use of friendly games ¹⁸ may explain the differences in these data. Dellal et al. ¹⁸ suggest that HR responses to SSG appear to be more position-specific than relating to the nature of the SSG. Importantly these researchers also conclude that HR responses during SSG appear similar to official games when 1 and 2 touch rules are applied.

In the present study, trivial non-significant differences were observed for TRIMP between official games and SSG. These data are in direct contrast to research comparing TRIMP of friendly matches to different types of standard training sessions usually performed by professional soccer players (tactical, pre-match activation, fitness-reserves, and fitness sessions). ²⁸ Campos-Vásquez et al. ²⁸ indicate that friendly matches produce a higher training load when compared to all other training sessions. In a recent study, Riboli et al. ²⁹ determined the area-per-player during SSG that replicates the official match demands. These authors report that the area per player needed to replicate the official match demands in SSG for total distance (187 ± 53 m²) and metabolic power (177 ± 42 m²) were smaller than the area per player necessary for high-intensity running variables such as high-intensity running distance (262 ± 72 m²) and sprint distance (316 ± 75 m²). It appears that the area per athlete in the SSG used in our study was more similar to the area needed for total distance and metabolic power rather than to the area needed for high-intensity running and sprint distance. Perhaps because of this, no differences were found between the TRIMP of SSG and official games. Accordingly, despite players presenting with different external load and average HR data during our SSG and official games, the intensity fluctuations produced resulted in similar TRIMP values among SSG and match play. These results highlight the need for coaches and trainers to be mindful of the challenges associated with incorporating SSG into their soccer training.

SSG are one of the most popular soccer training methodologies, ¹⁶ but the significant differences between official games and both SSG formats in this study for nearly all external and internal workload variables assessed suggests extreme care should be taken if relying solely on the latter for player conditioning. In their research, Gimenez et al. ¹¹ emphasize that the training routines of professional soccer players rarely replicate the main set of high-intensity efforts experienced during official matches. According to Campos-Vásques, ²⁸ the demands of competition should be used as a reference to assess the volume, intensity, and workload of training sessions. These authors conclude that for soccer training to be effective, it should be specifically related to the demands required by competitive matches. ²⁸ Gabbett & Mulvey ³⁰ compared the movement patterns of SSG with these movement patterns in domestic, national, and international elite women soccer games. These authors concluded that SSG offer an insufficient training stimulus to simulate the high-intensity, repeated-sprint demands of international competition and suggested that SSG should be supplemented with game-specific training that simulates the competitive demands.

To conclude, the physical demands of the 4v4 SSG adopted in this study were shown to differ markedly from the competitive physical demands of official match play. Our results indicate that the use of 4v4 SSG as a physical preparation for official match play, particularly in the population tested, be reconsidered. Coaches and trainers who use 4v4 SSG in training need to understand how variables such as playing field size and area per player impact on the nature of physical loads experienced by players. In the case of our data, relying on SSG as the principal conditioning tool for official match play would result in players being underprepared in many of the key high-speed running actions that determine match performance. Despite the apparent specificity of the 4v4 SSG to the official game, our research highlights the relative poor specificity in nearly all external and internal workload data. In addition, changing the orientation of the playing field had minimal impact on these workload data. The use of a field with a greater width rather than length does not appear to make the physical demands of the SSG more similar to the official games. Nevertheless, the results of the present study can help coaches and trainers to design training sessions and microcycles. Depending on the moment of the microcycle or the goals of each session (e.g. increasing or decreasing physical demands, promoting acceleration and deceleration, developing endurance, or replicating match play), using a wider or longer pitch would be useful for a specific day, or could be less appropriate for other days due to the low representativeness to match play.

It has been shown that the relative pitch area per player during SSG is an important variable to be considered to replicate the official match demands. ²⁹ Therefore, a major limitation of this study was that we tested the effect of the pitch orientation using only one relative area per player. Besides that, since our sample comprised of U20 players of a national level, they may not be at a level of coordination yet (team collective patterns) that would allow them to play more effectively during the SSG. We suggest that future studies should verify the effects of the pitch orientation during SSG performed without the offside rule, only using the pitch length as the in-length constraint. We also recommend that future investigations should explore the effects of the field orientation regarding different age categories.