Analysis of positional training loads (ratings of perceived exertion) during various-sided games in European professional soccer players

Abstract

The primary aim of the study was to perform a comparative analysis of the positional training loads during various game formats among European professional soccer players. Twenty-two male professional soccer players participated in the investigation and were divided into their tactical positional roles for analysis. Ratings of perceived exertion were collected daily and corresponded to specific formatted game types (small-sided games; large-sided games; large-sided games within a smaller area size) implemented as part of the weekly periodised training structure. Across the sample period, only one game per week training scenarios were analysed (9 × small-sided games; 9 × large-sided games; 9 × large-sided games within a smaller area size). Analysis of the mean ratings of perceived exertion between various game formats revealed significant differences between large-sided games within a smaller area size vs. small-sided games (5.53 vs. 7.79; p = 0.007); however, no differences were presented between small-sided games vs. large-sided games format types (7.9 vs. 7.35; p > 0.05). No differences between mean ratings of perceived exertion and small-sided games and large-sided games, respectively, were found. Differences were shown between positional demands during large-sided games within a smaller area size game type formats, with wide forwards reporting higher mean ratings of perceived exertion values when compared against centre forwards (p = 0.02). Therefore, within a periodised microcycle, variance of game formats can be used to manipulate training loads, manage accumulation of fatigue through a tapering method in order to facilitate optimal match preparation. Furthermore, players of certain position types may require additional training stimulus to induce the desired physical adaptations.

Keywords

Association football periodization small-sided games tactical positions

Introduction

Maximising the preparation of elite players whilst also reducing the injury risk is paramount to team development and successful soccer performance.¹ The potential risk of sustaining an injury can be heightened through many variables, which can be categorised as intrinsic (physical condition, muscle tightness, fatigue levels) or extrinsic (weather conditions, playing surface).² In order to effectively reduce the injury risk of players, specific preventive and multimodal programmes have been proposed.^3,4 However, it may be more appropriate to develop periodised approaches to training which better facilitate a progressive training load stimulus whilst concurrently reducing injury risk.⁵ Understanding subjective training assessment data such as ratings of perceived exertion (RPE) is vital due to small marginal errors present whilst overloading players to elicit training adaptations in conjunction with being appreciative of the potential injury risk.^6,7

Over the last few decades, there has been an ever-growing appreciation for the use of tools to quantify and monitor the training and match play load of soccer players.^8–10 Indeed, the use of global positioning system (GPS), heart rate (HR) and RPE, amongst others, is currently more commonplace in many professional clubs. It is widely accepted that a collective use of these specific methods can provide practitioners with a detailed holistic summary of the training load.¹¹

Central measures such as HR are unable to inform aspects of wellness, fatigue and performance, so the collective daily assessments such as training logs, questionnaires and other non-invasive cost-effective performance tests (e.g. jump tests) may offer a complete training status assessment amongst athletes participating in aerobic-oriented sports.¹⁰ GPS tracking technology typically centres around distances covered, accelerations, deceleration and additional speed threshold categories;^9,12 however, this method underestimates the internal demands of exercise due its failure to incorporate the energy cost associated with bodily movements imposed during soccer-specific activities.^13,14

Despite the recent increased levels of research and literature regarding the use of specific technology, the use of internal training loads and subsequent RPE representations at the elite professional level of the game is still sparse. Furthermore, regarded as a comparatively simple method, RPE assessment for the determination of training load is still underrepresented in the literature even though it remains a key facet of the data collection process. Its simplicity, minimal time demand and appreciation of the player’s subjective feelings of the training intensity substantiate RPE as an effective monitoring tool. The use of this method has been validated as a measure of training load and has been commonly applied in many different circumstances.^15,16 Financial constraints within clubs below the elite level may present a barrier to the use of GPS and HR technology. Likewise, the time constraints associated with data analyses may denote that they are not used for all training sessions.

Training games are a fundamental preparation tool for players at many age groups and levels of competition and are gaining attention as a suitable method of simultaneously improving the technical, tactical and physical qualities of players.^8,17 Accordingly, several studies have reported the activity profiles and workloads of different sided games with various instructions and task constraints.^18,12 Furthermore, the demands have shown to significantly differ in accordance with manipulation of technical rules,¹⁹ playing surface area and player numbers.^12,17,18 The objective is often to use small-sided games (SSGs) as a way of preparing players for the demands of actual match play. However, in some instances, they might not deliver the specific stimulus to fully prepare players for competition (e.g. high-speed running and extended periods of high-intensity effort).^12,20 Large-sided games (LSGs), as a training exercise, have been studied far less but research suggests they provide players with an important stimulus when preparing for competitive match-play. Match-play demands of soccer have been extensively studied in the literature,^21,22 whereas limited amounts of evidence are available reporting the demands of large-sided training games. This lack of understanding is surprising given how LSGs are likely to be performed just as frequently amongst various levels of football as a preparation tool focussing on habituating the players with some of the expected match demands.

Based on current literature, we may conclude that the high-intensity demands of soccer training may be underestimated when only using GPS and HR technology, particularly for positions or training sessions involving less high-intensity, high-speed activities.¹² As a result, estimations of metabolic demands from subjective assessments on a daily basis may inform the coach as to the true demands of a training session from the players’ perspective.⁷ Researchers have previously investigated the physical demands on players within SSGs and LSGs revealing significant differences between them.^8,12,17,23 Furthermore, GPS and HR monitoring analyses highlight how different physical activity profiles and physiological responses are elicited from varying the numbers and surface area of training games.^12,24,25 It is yet to be determined whether or not differences in internal training, using the RPE method, occur between different sided games.

Positional differences are commonly cited within the literature when detailing the activity profiles and workloads of soccer players.^13,22 Comparable research, however, is less prevalent when detailing the differences between players RPE. It should not be assumed that simply performing higher or lower exertion exercises or training drills corresponds to changes in RPE. This may correspond to different perceptions of exertion, despite no changes in physical workloads. One such study has shown how players conquering the tactical demands can become habituated and more effective with their positional requirements resulting in a significant effect on physical outputs.²⁶ Therefore, it would appear that greater knowledge is required to understand the load of training for different sided games and the positional demands.

The primary aim of the present study was to perform a comparative analysis of the positional training load (RPE) during SSGs and LSGs in European professional soccer players. Secondly, potential differences in RPE values between small- and large-sided training games within elite European soccer were examined. It is hypothesised that the rate of perceived exertion will differ between game types, with SSGs expected to present a greater perception of fatigue than LSG formats. Coinciding with this, it is hypothesised that the greater position-specific demands presented by LSG formats will better reflect differences in rate of perceived exertion across playing positions.

Method

Procedures

This specific investigation was performed over a 12-week period during the competitive 2014–2015 season. The daily training sessions used for assessment were conducted at the same time of day (i.e. morning sessions) as to reduce the potential effects of circadian variation on the participants. Analysis from sessions situated within a one game per week in this study period has been used to compare across the phases. For the reliability and validity of the study, only data from players who performed the full session duration have been used, withdrawing the data from players whose training load was manipulated during this time.

Participants

Twenty-two male European professional soccer players participated in this investigation (mean ± SD: age: 24.2 ± 3.53 years; height: 182.4 ± 5.43 m; body mass: 78.4 ± 5.75 kg; maximal aerobic capacity: 58.65 ±6.23 mL·kg⁻¹·min⁻¹; body fat: 51.45 ± 10.01 mm), and all had been playing soccer for a minimum of eight years. Written informed consent was received from all players after an explanation about the aims and benefits involved with this investigation. The study was conducted and fully approved by the Servette Football Club Research Group and the collaborating organisations and university before the commencement of the assessments. The players were also instructed to maintain their normal daily food, sleep patterns, water and fluid intake, and no additional dietary interventions were undertaken (Table 1).

Table 1.

Physical profile of the squad.

Variable	Squad profile
Age (in years)	24.2 + 3.53
Height (cm)	182.4 ± 5.43
Body mass (kg)	78.4 5.75
Aerobic capacity: VO₂max (mL·kg^−l·min⁻¹)	58.65 ± 623
Body fat: sum of eight skinfolds (mm)	51.45 + 10.01

Training games (SSGs, LSGs and large-sided games within a smaller area size)

All training games were played on outdoor grass surfaces with an average temperature of 14.6 ± 3.65℃ and followed the rules, formats and playing durations shown in Table 2. The analysis was performed during the mid-phase of the competitive season as to reduce the effects of conditioning variance. All games from 27 training sessions (9 × SSGs; 9 × LSGs; 9 × LSGs-Sm (large-sided games within a smaller area size)) were preceded by a standardised warm-up period of ∼20 minutes inclusive of low-intensity technical drills as part of the warm up and technical aspect of the session.

Table 2.

Specific game variables and format.

Variables		Sided game format
	SSGs	LSGs	LSGs-Sm
Player numbers	4 vs. 4 + Gks	10 vs. 10 + Gks	9 vs. 9 + Gks
Sets × bout duration/ recovery (min)	7 × 3 min/2 min	3 × 8 min/2 min	4 × 5 min/2 min
Total work duration (min)	21 min	24 min	20 min
Pitch size	30 × 25 yds	90 × 68 yds	45 × 38 yds
Playing area	750 m²	6120 m²	1710 m²
Grid ratio	1:1.2	1:1.3	1:1.1
Rules	Free play	Free play, offside	Free play, offside
Coach encouragement	Yes	Yes	Yes
Availability of balls	Yes	Yes	Yes

SSGs: small-sided games; LSGs: large-sided games; LSGs-Sm: large-sided games within a reduced area size.

A passive 3-minute recovery was applied following the last technical aspect of the warm up before the initiation of the game analysis. No added technical conditions (i.e. free play) or tactical restraints were placed upon the players within the sided games. A large number of soccer balls were placed around the perimeter of the playing area to aid in a rapid continuation of play, and there were no stoppages of time for any injury. The playing order in which the game formats were fixed due to the training week was determined by the technical staff in order to prepare for competition as shown in Table 3. Team selections within the training sessions were solely determined by the technical and management staff. Furthermore, each game analysed included teams composed of full backs, central defenders, centre midfielders, wide forward (WF) and centre forward (CF). Team selection in this way ensured objectivity of the study was maintained throughout all game variations and between respective sided game formats implemented.

Table 3.

Weekly training structure.

	Match day	Match day	Match day	Match day
	−4	−3	−2	−1
Game type	SSGs	LSGs	LSGs-Sm	Tactical
Sets × bout duration	7 × 3 min	3 × 8 min	4 × 5 min
Pitch size	30 × 25 yds	90 × 68 yds	45 × 38 yds

SSGs: small-sided games; LSGs: large-sided games; LSGs-Sm: large-sided games within a smaller area size.

Subjective training load assessment

A perceived exertion rating scale (RPE) was completed by each player after a period of ∼15 minutes following the last repetition or bout of sided game play as to ensure the perceived effort referred to the most recent exercise period within the training session.²⁰ The internal RPE value for the game format was generated in line with previous research from Foster et al.²⁷ For the clarity of the investigation, the modified CR10-scale by Foster et al.²⁷ used post-games had been translated into French, German and Italian in order to ensure a better understanding from the players involved (Table 4). It is highly unlikely that the small translations to Borg’s CR10-scale would have affected the reliability and the validity of the data obtained. In that regard, the French translation has been validated by Haddad et al.²⁸ All players were extremely familiar with this particular scale for RPE before the commencement of the study due to the previous use of this method throughout the pre-season training phase. Data were only taken from the weekly periods consisting of one competitive fixture per week in order to compare across the same training build up and preparation phase.

Table 4.

Borg’s CR10-scale modified by Foster et al.²⁷

Rating	Description
0	Rest
1	Very, very easy
2	Easy
3	Moderate
4	Somewhat hard
5	Hard
6
7	Very hard
8
9
10	Maximal

Note: Preparation phase in relation to game format (with one match day per week).

Statistical analysis

Before using parametric tests, the assumption of normality was verified using the Kolmogorov–Smirnov test. One-way analysis of variance for repeated measures was used to examine the differences between mean sessions RPE during various-sided training games. When significant F values were observed within the data (p ≤ 0.05), paired comparisons were used in conjunction with Holm’s Bonferroni method for controlling type 1 error²⁹ to determine significant differences.

The effect size (ES) was calculated for all analysis of variances with the use of a partial eta-squared. Values of 0.01, 0.06 and 0.15 were considered as small, medium and large, respectively.³⁰ The ESs were also calculated for all paired comparisons and evaluated with the method described by Cohen³⁰ (small:<0.50, moderate: 0.50–<0.80 and large: >0.80).

Pearson product-moment correlation coefficients were calculated to determine whether TL RPE were convergent. The magnitude of the correlations was determined using the modified scale of Hopkins:³¹ r < 0.1: trivial; 0.1–<0.3: small; 0.3–<0.5: moderate; 0.5–<0.7: large; 0.7–<0.9: very large; ≥0.9: nearly perfect and 1 perfect. Significance and meaningful acceptance of the correlation were set at 5% (p ≤ 0.05) and 0.5 (large to perfect), respectively.

Results

Comparative analysis of the mean RPE between the various-sided game formats

A significant effect was observed for RPE within the three types of sided game formats used within the study (F = 8.615; ES = 0.71). However, a pairwise comparison revealed only a significant difference between LSGs-Sm vs. SSGs (p = 0.007). As the grid ratio (player per surface area) reduced to 1:1.1 in the LSGs-Sm area so did the mean RPE. There was no significant difference between the SSGs and LSGs (p < 0.05) type formats (Figure 1).

Figure 1.

Sided games RPE values. Significant difference between LSGs-Sm vs. SSGs (p = 0.007). RPE: ratings of perceived exertion; SSGs: small-sided games; LSGs: large-sided games; LSGs-Sm: large-sided games within a reduced area size.

Comparative analysis of the positional differences in mean RPE within various-sided game formats

Results investigating the positional differences in mean RPE derived from the various training game formats revealed no significant differences were observed during SSGs (F = 2.432) and LSGs (F = 0.679). However, a significant difference was shown between positional differences during LSGs + small area format (F = 5.29; ES = 0.35). Pairwise comparison showed how mean RPE values were significantly higher when comparing WFs vs. CFs positions (p = 0.02) (Figure 2). Furthermore, additional analysis of the data revealed no levels of significance between the other positions during the other sided game formats (p < 0.05).

Figure 2.

Positional RPE values for LSGs-Sm. Significant difference between wide forwards vs. centre forwards (p = 0.02). RPE: ratings of perceived exertion.

Discussion

This particular investigation included a comparative analysis of the positional training load (RPE) during SSGs and LSGs in European professional soccer players whilst also examining the difference of RPE between small- and large-sided training games amongst professional European soccer players. The main finding of this investigation highlighted how RPE values within the LSGs-Sm were significantly different from RPE reported from SSGs.

Interestingly, the playing area or grid ratio (Table 2) may be one of the main reasons for the significant less perceived intensity of the LSGs-Sm (1:1.1) vs. SSGs (1:1.2). This is in accordance with previous studies showing that for the same number of players, the larger the playing pitch, the higher the physiological responses and related RPE observed.³² The smaller relative pitch area size per player in the LSGs-Sm may have reduced the player’s capability and need to accelerate or produce high-speed efforts to the levels they can possibly achieve on greater pitch dimensions. Due to this smaller surface area, the distance between players and opponents in possession will be decreased, leading to reduced distances needing to be covered in order to apply pressure on opponents. This is in line with previous research suggesting how changing the dimensions of the training pitch in addition to player numbers can elicit significantly different physiological and movement profiles.^8,12

One such study researching the effects of changing pitch sizes suggested that no significant differences between intensity (HR) were observed when training games were played on three different dimensions using the same number of players,¹⁷ whereas contrasting findings revealed that significant increases in intensity (HR) values have been reported during SSGs when played on larger sized pitches, compared to smaller dimensions.^6,33 However, the contrast among the literature may have been due to the variance of playing level used, in conjunction to the variance of player numbers and area sizes.

Further analysis highlighted that there was no significant difference between SSGs and LSGs (p < 0.05) for RPE. This is an interesting finding as recently, there have been many publications surrounding the demands of SSGs vs. LSGs.^8,12,17,33 Recent research by Owen et al.⁸ examined the differences between HR responses upon elite European level players when exposed to two different sided training games (SSGs vs. LSGs) with results indicating how SSGs induced significantly (p < 0.05, large effect) higher HR responses when compared to the LSGs. Furthermore, SSGs ensure players spend significantly longer time in the > 85% maximal HR zone (p < 0.05, large effect) as compared to LSGs. Based on the findings of the present study showing no significant difference between SSGs and LSGs, practitioners should be careful to solely base their judgement concerning training intensity on session RPE if trying to elicit sufficient adaptations in order to enhance aerobic capacity. Recent literature has shown how LSGs are fundamental in the physical preparation of elite professional soccer players due to them allowing specific positional and technical demands to be met through greater high-speed running bouts, sprint distances, aerial duels, and greater distances to apply pressure to opposition players, relative to competitive match outputs.^12,22,13 Differences shown between SSGs and LSGs-Sm may coincidentally be attributed to a psychological phenomenon known as the social loafing theory,^34,35 as previous research by Latane et al.³⁵ It was reported that as the number of group or team members increase, so does the effect of social loafing, whereby a reduced effort and/or commitment to the task are perceived. The technical and physical demands of SSGs have been previously discussed; however, it may be that as the number of players per sided game increases, participants reduce their own level of effort leading to subsequent decreases in intensity. This may not be a conscious decision to do so but certainly is something that may require further investigations in the future within elite professional soccer.

Positional difference

The only significant differences shown during LSGs-Sm was highlighted between CFs vs. WFs (p = 0.02) with WFs reporting a higher RPE value. According to Casamichana et al.,²⁰ total distance covered has shown a large correlation to session RPE. Furthermore, Suarez-Arrones et al.³⁶ revealed through positional specific analysis that players playing in wide area (wide midfielders, otherwise known as wide forwards) recorded a significantly higher internal and external demand when compared to other positions on the pitch mainly induced through total distance covered and accumulation of high-speed activities. From an applied perspective, technical and physical coaches should note the ‘link’ function wide players serve between defending and attacking transitions and irrespective of the outcome of the session (e.g. technical, tactical), these positional roles are more physically demanding in general. It may be suggested that the lack of involvement in LSGs surrounding the CFs as previously suggested by Owen et al.¹² and the lack of attacking technical actions induced in these games may cause reduced RPE scores. With this possibly being a reason for the lack of perceived intensity or exertion of CFs in LSGs-Sm, practitioners may wish to perform additional position-specific work in order to elicit an additional training load.

The data revealed that no significant difference existed between the other positions during the sided game formats (p < 0.05). This may be as a result of the SSGs being played in a smaller surface area, subsequently ensuring players being in a closer proximity to engage with opposition players eliciting a higher intensity of the session irrespective of the positional role within the team. Small-sided games have been well documented to increase intensity of play and in line with this particular investigation, previous research shows that RPEs from SSGs do not vary in accordance to playing positions.³⁷ However, it should be highlighted that the analysis within the present study as compared to previous research was performed with a greater number of games.

Perspective

The present study in conjunction to other similar research has verified a number of statistically significant differences between playing positions irrespective of quantitative methodologies used (GPS, HR, RPE).^36,37 According to Suarez-Arrones et al.,³⁶ coaches should be focusing on the specific physical and physiological requirements of the playing positions in order to maximise their efficiency of training in professional soccer. The use of session RPE for the monitoring of the internal training is hugely important; however, it should be used as part of a holistic approach when preparing training sessions for players at the elite level. From both a positional specific and global session perspective, respectively, the current investigation demonstrates that the use of LSG-Sm games should be implemented latterly within the training week as to ensure, across all playing positions, fatigue accumulation is managed accordingly and tapered to facilitate optimal preparation for subsequent match performance.

Conclusion

Within elite professional soccer, understanding and managing the fatigue response to both training and match play is paramount in order to facilitate optimal preparation for subsequent performance in addition to reducing the risk of injury. It can be concluded that within the periodised microcycle, whereby different game type formats can be used to manipulate training load, the application of RPE to subjectively assess internal loading is merited. Practitioners should recognise, however, that through the use of different game format types, specific positional demands will invariably demonstrate disparity with respect to the training load imposed. As such, players of certain position types may require additional training stimulus to induce the desired physical adaptations.

There is no doubting studies investigating the preparation of elite players should further examine more than just biochemical, biomechanical and technological factors associated with training load based on the variance of perception from subjective assessment; however, recent advances in elite sport, especially soccer, and the way technology is used to assess training load have left certain unknown factors regarding the internal, subjective appraisal of training. Within soccer, the use of various training games (e.g. large and small sided) is a well-documented and universally recognised training method; however, the need for more high-quality elite level studies investigating various-sided training games as well as the comparisons of positional demands during different training games is apparent in order to see variations of RPEs among professional players.

Footnotes

Acknowledgements

The authors would like to thank the soccer players for their participation and professionalism throughout the duration of the study, and the sport science and medical staff.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship and/or publication of this article.

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