The Influence of Playing Position and Contextual Factors on Soccer Players' Match Differential Ratings of Perceived Exertion: A Preliminary Investigation

A multimodal approach integrating cognitive and motor demands into physical activity for optimal mental health: Methodological issues and future directions

Physical activity is known for its positive effects on cognition and affect, with existing literature suggesting that these mental health benefits may be optimally experienced by incorporating cognitive and motor demands during physical activity (PA). However, the existing body of literature lacks a comprehensive guideline for designing the qualitative characteristics of a PA program. Accordingly, this narrative review aimed to (1) provide a working two-dimension model that operationally defines the cognitive and motor demands involved in PA and the rationale for systematically studying these qualitative aspects of PA, (2) identify methods to assess the cognitive and motor demands of PA and address associated methodological issues, and (3) offer potential future directions for research on the cognitive and motor aspects of PA in support of the development of PA programs designed to maximize PA-induced cognitive and affective benefits. We anticipate this article to inform the need for future research and development on this topic, aiming to create clear, evidence-based guidelines for designing innovative and effective PA interventions.

Internal workload in elite female football players during the whole in-season: starters vs non-starters

The aim of this study was to quantify weekly internal workload across the in-season and compare the workload variables between starter and non-starter Spanish female first league (Liga Iberdrola) football players. Twenty-six participants belonging to the same team (age, height, and mass: 25.4 ± 6.1 years, 167.4 ± 4.8 cm and 57.96 ± 6.28 kg, respectively) participated in this study. Training loads (TL) and match loads (ML) were assessed through breath-cardiovascular (RPEbreath), leg-musculature (RPEleg) and cognitive (RPEcog) rating of perceived exertion (RPE0-10) for each training session and match during the in-season phase (35 weeks). Session-RPE (sRPE) was calculated by multiplying each RPE value by session duration (minutes). From these, total weekly TL (weekly TL+ML), weekly TL, weekly ML, chronic workload, acute:chronic workload ratio, training monotony, and training strain were calculated. Linear mixed models were used to assess differences for each dependent variable, with playing time (starter vs non-starter players) used as a fixed factor, and athlete, week, and team as random factors. The results showed that total weekly TL (d = 1.23-2.04), weekly ML (d = 4.65-5.31), training monotony (d = 0.48-1.66) and training strain (d = 0.24-1.82) for RPEbreath, RPEleg and RPEcog were higher for starters in comparison with non-starters (p = 0.01). Coaches involved in elite female football should consider implementing differential sRPE monitoring strategies to optimize the weekly load distribution for starters and non-starters and to introduce compensatory strategies to equalise players' total weekly load.

Differences in Situational Patterns During Change of Direction Movements Greater than 90° in Youth Male and Female Soccer Players

Change of direction (COD) maneuvers in soccer create tactical advantages, but also expose the player to an increased risk of injury. COD ability is commonly tested with pre-planned drills including cuts greater than 90°. These tests do not take into consideration positional differences players encounter during games. This case-series study used principal component analysis (PCA) to examine situational differences during COD movements between playing positions in youth soccer games. For each of the four teams included (26 females, 27 males), one game was analyzed using video-analysis. Two independent reviewers identified situational patterns and a PCA was used to examine differences between playing positions. Three principal components explained 89% of the variation in the data and were categorized as the total quantity of CODs, attacking/goal-scoring and defensive reacting types of CODs. One-way ANOVA on the individual principal component (PC) scores showed significant differences (p < 0.05) between centre midfielders, goalkeepers, and centrebacks in the quantity of CODs (PC1), and between wingers and fullbacks and centre backs in attacking/goal-scoring CODs (PC2), whereas PC3 was not different between playing positions. Differences between playing positions suggest that training and testing protocols in soccer could be enhanced to better match the individual and playing position-based needs.

Comparison of external load measures per minute based on match seasonal periods and playing positions of a soccer Turkish super league team

BACKGROUND

Turkish Super League teams need more information about the external load. Considering the specific country and the coaches' philosophies, the purpose of this study was to compare the external match load of a Turkish Super League team considering the different playing positions and in-season periods.

METHODOLOGY

A longitudinal study design was employed by observing 29 official matches of the same team. A total of fifteen players, consisting of five defenders, five midfielders, and five forwards, were analyzed using the Sentio Sports Optical Tracking System. The following outcomes were extracted in each match: total distance (TD), walking [from 0 to 7.2 km/h], jogging [from 7.2 to 14.4 km/h], running [from 14.4 to 20 km/h], high speed running (HSR) [> 20 km/h], metabolic power (MP), maximum deceleration (Decmax) [Dec < -3 m/s2], total deceleration distance (Dectotal), maximum acceleration (Accmax) [Acc > 3 m/s2], and total acceleration distance (Acctotal). Statistical analysis consisted of ANOVA and Bonferroni correction post hoc tests.

RESULTS

The main results showed that all variables were similar between periods of the season (p > 0.05) except for walking (p = 0.021 witha large effect size), which revealed lower values in the mid-season period. When analyzing periods of the season considering playing positions, there were several significant results for TD, walking, jogging, running, HSR, Dectotal and Acctotal (p < 0.05, with small to large effects). A tendency for higher values was noted in the mid and end-season. Considering the playing positions comparisons, midfielders showed higher values than defenders for TD, MP, Dectotal and Acctotal (p < 0.05 with large effect for all). Midfielders also showed higher values than forwards for TD, jogging, Dectotal and Acctotal (p < 0.05 with a large effect for all).

CONCLUSIONS

The present study emphasizes the significance of analyzing data based on minute, playing position, and season period. Findings reveal that defenders consistently displayed the lowest values in all external load measures during matches compared to other positions throughout the season. Furthermore, midfielders demonstrated a higher activity profile during the initial and middle stages of the season compared to other positions, with a slight tendency to decrease load towards the end of the season.

A random forest approach to explore how situational variables affect perceived exertion of elite youth soccer players

The aim of this study was to explore how situational variables affect youth soccer players' perceived exertion (RPE) after official matches. Thirty-five elite youth male players (14.33 ± 0.86 years; 173.49 ± 6.16 cm; 63.44 ± 5.98 kg) who belonged to two different teams of a professional club participated in this study. Data collection was conducted during two seasons (2016-2017, 2017-2018) and included 60 official matches (30 official matches per team). Ten minutes after each match players rated their RPE and using a modified Borg CR-10 scale. A Random Forest Regression was used to quantify the importance of match-related situational variables in RPE. Afterwards, a linear mixed model analysis was applied to identify the variability in RPE among the situational variables. The game-playing time, the player status (starter or substitute) and the player identity were the strongest predictors of RPE. Moreover, the match outcome and the final scoreline showed significant effects on both starter and substitute players but the main effect of the quality of the opponent was only identified in starter players (p < 0.05). These results allow practitioners to know how situational variables interact and modulate RPE after official matches and help them to prescribe and adapt the players' training content and load before and after matches.

Elite North American soccer performance in thermally challenging environments: An explorative approach to tracking outcomes

AIMS

The physiologic challenges related to performances in hot conditions calls for dedicated consideration when planning athlete training, although complete amelioration of the effects of heat may not be possible. We aimed to quantify within-subject correlations between different measures of environmental temperature and performance changes over multiple elite soccer competitions.

METHODS

Thirty-seven elite male soccer players (age: 26 ± 3.4 years, height: 171 ± 2 cm, body mass: 78 ± 7.1 kg) competed in North America over four seasons (range: 3 to 98 matches). Players wore global positioning system devices during games and reported differential-RPE immediately post game. Temperatures at kick-off, week average temperature, the difference between game-day and week average (DiffTemp), and heat index at kick-off were obtained. Within-player correlations were calculated using general linear models to quantify associations between fluctuations in temperature measures and physical and perceived outputs.

RESULTS

Correlations between total distance and the various temperature measures were trivial to small (range: -0.08 to 0.13, p=<0.001-0.02). Small negative correlations were found between all temperature measures except DiffTemp and high-speed running (HSR) (range: -0.17 to -0.14, p=<0.001). Most correlations between differential-RPE and temperature measures were trivial to small and not significant (r = 0.06 to 0.18 p = 0.03-0.92) although breathlessness-RPE and heat index showed a small significant association (P = 0.018).

CONCLUSION

Decrements in HSR appear to be associated with increased environmental temperature, however, these associations are small in magnitude.

Acute effects of mental recovery strategies in simulated air rifle competitions

Objectives

The present study aimed to assess the perception and change of mental and physical fatigue and to examine acute effects of mental recovery strategies in air rifle athletes across simulated competition days with two consecutive competition bouts.

Design

We conducted a randomized counterbalanced crossover study.

Method

22 development air rifle athletes (M_age = 17.77 ± 4.0) of a regional squad participate in the study. The Short Recovery and Stress Scale (SRSS), perception of mental fatigue, physical fatigue, concentration and motivation as well as differential Ratings of Perceived Exertion (RPE) were used to assess recovery-stress states and fatigue states. During a recovery break, participants underwent two mental recovery strategies (powernap, systematic breathing) or a control condition. Total shooting scores were recorded for both competition bouts.

Results

Study results revealed a significant increase of post ratings for mental (p < .001) and physical fatigue (p < .001) for both competition bouts. The correlation coefficient between change in mental and physical fatigue for both competitions revealed a shared variance of 7.9% and 18.6%, respectively. No significant group-based acute effects of the use of mental recovery strategies on shooting performance, and psychological and perceptual measures were found. On an individual level, results illustrated statistical relevant improvements of shooting performance after powernapping or systematic breathing.

Conclusion

Mental and physical fatigue increased and accumulated across a simulated air rifle competition and mental fatigue emerged as a separate construct from physical fatigue. The use of strategies to accelerate mental recovery on an individual level (e.g., powernap, systematic breathing) may be a first step to manage a state of mental fatigue, but further studies on mental recovery strategies in an applied setting are needed.

Predictive modeling of the ratings of perceived exertion during training and competition in professional soccer players

OBJECTIVES

Evaluate the ability of predicting the ratings of perceived exertion from the external load variables in professional soccer players through a chronological perspective (i.e., past features values are considered additional features) through machine learning models by considering the playing position.

DESIGN

Prospective cohort study.

METHODS

Thirty-eight elite soccer players aged 19-27 years were observed during 151 training sessions, 44 matches across a full season. External load variables (58 derived from Global Positioning System and 30 from accelerometers) and the internal load derived from ratings of perceived exertion were collected for each player and each session and match. Machine learning models (linear regression, K-NN, decision trees, random forest, elastic net regression, XGBoost) were compared and interpreted in order to deepen the relationship between external load variables and ratings of perceived exertion according to the player position in a predictive perspective.

RESULTS

Application of the machine learning models on the dataset provided enough predictive power to reduce the Root Mean Squared Error of 60 % from dummy predictions. The most accurate models (Root Mean Squared Error ≈ 1.1 for random forest and = 1 for XGBoost) highlighted a memory effect in subsequent ratings of perceived exertion values. Past ratings of perceived exertion values over one month were the strongest predicting factors of ratings of perceived exertion as compared to various external load indicators.

CONCLUSIONS

The tree-based machine learning models showed statistically significant predictive ability, indicating valuable information for understanding the training load responses based on ratings of perceived exertion changes.

Seasonal variations of the relationships between measures of training monotony and strain in professional soccer players

The purposes of this study were (a) to determine the variations in internal and external measures of training monotony (TM) and strain (TS) in professional soccer players according to periods of the season and playing positions, and (b) to analyze the relationships between internal and external measures of TM and TS. Twenty male professional players (age = 29.4 ± 4.4 years) were followed for 20 weeks through session rating of perceived exertion (s-RPE), total distance (TD), high-speed running distance (HSRD) and sprint distance (SpD). Regardless of measure, highest mean TM and TS scores were observed in mid-season and end-season. In general, wingers and strikers tended to have greater values in TM. Midfielders exhibited greater TS of TD and SpD. Correlation results for TM revealed that s-RPE was positively associated with SpD in early-season (r = 0.608) and negatively associated in mid-season (r = − 0.506). Regarding the TS, result demonstrated that s-RPE is negatively associated with HSRD in early-season (r = − 0.464) and positively associated in mid-season (r = 0.476). In general, there different meanings in correlations between internal and external measures across the season. On the one hand, our findings highlighted that TM and TS of professional soccer players is sensitive to period of the season and player’s position, but on other hand, correlation analyses proved that changes in one external/internal measure does not cause changes in another external/internal measure which support the constant monitoring of these values across the season.

Neuromuscular Fatigue in Cerebral Palsy Football Players after a Competitive Match According to Sport Classification and Playing Position

This study aimed to determine the rated perceived exertion (RPE) and match load (RPE-ML) to compare pre-post-match vertical jump (VJ) capacity according to cerebral palsy (CP) players’ sport classes (i.e., FT1−FT3) and playing positions and to explore whether the neuromuscular performance variation is associated with the internal load of para-footballers with CP. Fifty-six male para-footballers performed two VJ tests before and immediately after a competitive CP football match, followed by measurements of the players’ RPE and RPE-ML. There were no significant differences (p > 0.05) in the pairwise comparisons for RPE and RPE-ML according to sport classes and playing position. A significant reduction in the VJ performance was found for each player sport class and playing position in squat jump (SJ) (p < 0.01; 0.24 < dg < 0.58) and countermovement jump (CMJ) (p < 0.05; 0.22 < dg < 0.45). Regarding the pairwise comparisons, players with the minimal impairment criteria (FT3) obtained higher deficit scores during SJ than those belonging to the FT1 and FT2 (p = 0.003; 1.00 < dg < 1.56). Defenders experienced the lowest performance compared to midfielders and attackers in SJ performance (p = 0.027; 0.94 < dg < 1.28). Significant correlations were obtained between ΔSJ or ΔCMJ and RPE or RPE-ML (r = −0.58 to −0.75; p < 0.001). These findings provide novel information supporting the notion that fatigue induced after a competitive match causes notable impairments in VJ performance differentiated according to sport class and playing position in para-footballers with CP.

Training Monitoring in Sports: It Is Time to Embrace Cognitive Demand

Appropriate training burden monitoring is still a challenge for the support staff, athletes, and coaches. Extensive research has been done in recent years that proposes several external and internal indicators. Among all measurements, the importance of cognitive factors has been indicated but has never been really considered in the training monitoring process. While there is strong evidence supporting the use of cognitive demand indicators in cognitive neuroscience, their importance in training monitoring for multiple sports settings must be better emphasized. The aims of this scoping review are to (1) provide an overview of the cognitive demand concept beside the physical demand in training; (2) highlight the current methods for assessing cognitive demand in an applied setting to sports in part through a neuroergonomics approach; (3) show how cognitive demand metrics can be exploited and applied to our better understanding of fatigue, sport injury, overtraining and individual performance capabilities. This review highlights also the potential new ways of brain imaging approaches for monitoring in situ. While assessment of cognitive demand is still in its infancy in sport, it may represent a very fruitful approach if applied with rigorous protocols and deep knowledge of both the neurobehavioral and cognitive aspects. It is time now to consider the cognitive demand to avoid underestimating the total training burden and its management.

External Match Load in Amateur Soccer: The Influence of Match Location and Championship Phase

Assessment of the physical dimension implicit in the soccer match is crucial for the improvement and individualization of training load management. This study aims to: (a) describe the external match load at the amateur level, (b) analyze the differences between playing positions, (c) verify whether the home/away matches and if (d) the phase (first or second) of the championship influence the external load. Twenty amateur soccer players (21.5 ± 1.9 years) were monitored using the global positioning system. The external load was assessed in 23 matches, where 13 were part of the first phase of the competition (seven home and six away matches) and the other 10 matches belonged to the second (and final) phase of the championship (five home and five away matches). A total of 173 individual match observations were analyzed. The results showed significant differences between playing positions for all the external load measures (p < 0.001). There were higher values observed in the total distance covered for central defenders (p = 0.037; ES = 0.70) and in high-intensity decelerations for forwards (p = 0.022; ES = 1.77) in home matches than in away matches. There were higher values observed in the total distance (p = 0.026; ES = 0.76), relative distance (p = 0.016; ES = 0.85), and moderate-intensity accelerations (p = 0.008; ES = 0.93) for central defenders, in very high-speed running distance for forwards (p = 0.011; ES = 1.97), and in high-intensity accelerations (p = 0.036; ES = 0.89) and moderate-intensity decelerations (p = 0.006; ES = 1.11) for wide midfielders in the first phase than in the second phase of the championship. Match location and championship phase do not appear to be major contributing factors to influence the external load while the playing position should be used as the major reference for planning the external training load.

In-Season Quantification and Relationship of External and Internal Intensity, Sleep Quality, and Psychological or Physical Stressors of Semi-Professional Soccer Players

The purpose of this study was two-fold: (a) to describe and analyse the relationship of the in-season variations of external and internal intensity metrics as well as well-being measures across different periods of a semi-professional soccer season (early-, mid- and end-season); and (b) to describe training monotony (TM) and training strain (TS) for 20 weeks in a semi-professional soccer season. Eighteen semi-professional players (age: 29 ± 4.1) from the Asian First League team participated in this study. The players were monitored for 20 consecutive weeks during in-season for external training intensity, internal training intensity and well-being parameters. The in-season was organized into three periods: early-season (weeks 1−7); mid-season (weeks 8−13); and end-season (weeks 14−20). Total distance (TD), high-speed running distance (HSRD), sprint distance, rate of perceived exertion (RPE), session-RPE (s-RPE), TM, TS, heart rate average and maximum, as well as sleep quality, stress and muscle soreness were collected. Results revealed that TD, HSRD and sprint distance (total values) were meaningfully greater during end-season than in the early-season. RPE showed a significantly highest value during the end-season (4.27 AU) than in early- (3.68 AU) and mid-season (3.65 AU), p < 0.01. TS showed significant differences between early-season with mid-season (p = 0.011) and end-season (p < 0.01), and the highest value occurred in week 17 during end-season (6656.51 AU), while the lowest value occurred in week 4 during early-season (797.17 AU). The average TD periods showed a moderate to large correlation with RPE, sleep and s-RPE at early-, mid- and end-season. Increasing the training intensity without considering the well-being of the players affects the performance of the team. Examining processes of the relationship between training intensity and other psychological indicators among players will probably be effective in training planning. Sports coaches and fitness professionals should be wary of changes in TM and TS that affect players performance. Therefore, to better control the training, more consideration should be given by the coaches.

Wearable Inertial Measurement Unit to Measure External Load: A Full-Season Study in Professional Soccer Players

The aim of this study was to describe weekly acute workload (wAW), chronic workload (wCW), acute: chronic workload ratio (wACWR), training monotony (wTM), and training strain (wTS) variations over a full season across playing positions. Twenty-one professional soccer players were daily monitored during 48 consecutive weeks. Total distance, sprint total distance (STD), high-speed running distance (HSRd), maximum speed, number of the repeated sprints, and body load (BL) were obtained during training and matches using a Wearable Inertial Measurement Unit. The wAW was determined for each external load measure. The wCW, wACWR, and wTM were calculated based on BL metric. Higher values of weekly STD were observed in lateral defenders/wingers (LDW) compared to central defenders/forwards (CDF) (p = 0.009; ES = Large) and midfielders (MDF) (p = 0.034; ES = Large). Additionally, weekly HSRd was higher in LDW vs. CDF (p = 0.016; ES = Large) and MDF (p = 0.011; ES = Large). The CDF presented a lower weekly number of repeated sprints than LDW (p = 0.021; ES = Large). In conclusion, weekly external load metrics were position-dependent over the season. Moreover, LDW a presented greater weekly STD, HSRd, and number of repeated sprints compared to other positions.

Training Management of the Elite Adolescent Soccer Player throughout Maturation

Professional soccer clubs invest significantly into the development of their academy prospects with the hopes of producing elite players. Talented youngsters in elite development systems are exposed to high amounts of sports-specific practise with the aims of developing the foundational skills underpinning the capabilities needed to excel in the game. Yet large disparities in maturation status, growth-related issues, and highly-specialised sport practise predisposes these elite youth soccer players to an increased injury risk. However, practitioners may scaffold a performance monitoring and injury surveillance framework over an academy to facilitate data-informed training decisions that may not only mitigate this inherent injury risk, but also enhance athletic performance. Constant communication between members of the multi-disciplinary team enables context to build around an individual's training status and risk profile, and ensures that a progressive, varied, and bespoke training programme is provided at all stages of development to maximise athletic potential.

The Effect of Isolated and Combined Application of Menthol and Carbohydrate Mouth Rinses on 40 km Time Trial Performance, Physiological and Perceptual Measures in the Heat

The current study compared mouth swills containing carbohydrate (CHO), menthol (MEN) or a combination (BOTH) on 40 km cycling time trial (TT) performance in the heat (32 °C, 40% humidity, 1000 W radiant load) and investigates associated physiological (rectal temperature (Trec), heart rate (HR)) and subjective measures (thermal comfort (TC), thermal sensation (TS), thirst, oral cooling (OC) and RPE (legs and lungs)). Eight recreationally trained male cyclists (32 ± 9 y; height: 180.9 ± 7.0 cm; weight: 76.3 ± 10.4 kg) completed familiarisation and three experimental trials, swilling either MEN, CHO or BOTH at 10 km intervals (5, 15, 25, 35 km). The 40 km TT performance did not differ significantly between conditions (F2,14 = 0.343; p = 0.715; η2 = 0.047), yet post-hoc testing indicated small differences between MEN and CHO (d = 0.225) and MEN and BOTH (d = 0.275). Subjective measures (TC, TS, RPE) were significantly affected by distance but showed no significant differences between solutions. Within-subject analysis found significant interactions between solution and location upon OC intensity (F28,196 = 2.577; p < 0.001; η2 = 0.269). While solutions containing MEN resulted in a greater sensation of OC, solutions containing CHO experienced small improvements in TT performance. Stimulation of central CHO pathways during self-paced cycling TT in the heat may be of more importance to performance than perceptual cooling interventions. However, no detrimental effects are seen when interventions are combined.

Evaluation of cognitive load in team sports: literature review

In team sports, load management has become one of the most common areas of investigation, given that effective control over load is the key to being able to optimize performance and avoid injuries. Despite the constant evolution and innovation in the latest theories, we can see a clear tendency in load management that focuses on physiological and mechanical aspects and neglects its cognitive character, which generates the variability inherent in the performance of athletes in a changing environment. Indicators of response that inform methods of control over cognitive load can include cognitive, physiological and behavioral indicators. However, limited investigations exist to support the reliability of each indicator regarding cognitive load. For this reason, the objective of this literature review is to present strategies used to manage cognitive load in team sports, as well as the indicators utilized for such a proposition and their relationships in specific contexts.

Will Next Match Location Influence External and Internal Training Load of a Top-Class Elite Professional European Soccer Team?

Background: The purpose of this study is to compare training load (TL) preceding a home versus away match in a top-class elite European team during the 2015–2016 season. Methods: Twenty elite outfield soccer players with a mean ± SD age, height and body mass of 25.9 ± 4.6 years, 183.1 ± 6.6 cm and 78.6 ± 6.6 kg, respectively, participated in this study. Total distance covered, high-speed running distance (HSRD), average speed (AvS), rating of perceived exertion (RPE) multiplied by training duration (s-RPE) and Hooper index (HI) were collected. Data from 24 weeks were analyzed through match-day minus/plus approach (MD-5, -4, -3, -2, -1, MD + 1). Results: All external TL variables indicated a decrease from MD-5 until MD-1 and then an increase to MD + 1 (p < 0.01). HI decreased from MD-5 to MD-1, but s-RPE increased until MD-3 and then decreased until MD + 1. When comparing TL data that preceded home matches versus away matches, for MD-5, HSRD and muscle soreness exhibited higher values when away match neared (p < 0.05). For MD-4 and MD-3, total distance, HSRD and AvS exhibited higher values closer to an away match than a home match (p < 0.05). For MD-1, total distances covered were higher closer to a home match than an away match (p < 0.01). For MD + 1, all HI items and AvS were higher when an away match was played (p < 0.05). Conclusions: This study confirms and provides evidence regarding the influence on internal and external TL data preceding home and away matches from a team that played in European competitions.

Load Measures in Training/Match Monitoring in Soccer: A Systematic Review

In soccer, the assessment of the load imposed by training and a match is recognized as a fundamental task at any competitive level. The objective of this study is to carry out a systematic review on internal and external load monitoring during training and/or a match, identifying the measures used. In addition, we wish to make recommendations that make it possible to standardize the classification and use of the different measures. The systematic review was carried out according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The search was conducted through the electronic database Web of Science, using the keywords "soccer" and "football", each one with the terms "internal load", "external load", and "workload". Of the 1223 studies initially identified, 82 were thoroughly analyzed and are part of this systematic review. Of these, 25 articles only report internal load data, 20 report only external load data, and 37 studies report both internal and external load measures. There is a huge number of load measures, which requires that soccer coaches select and focus their attention on the most useful and specific measures. Standardizing the classification of the different measures is vital in the organization of this task, as well as when it is intended to compare the results obtained in different investigations.

Upper-Body Resistance Training Following Soccer Match Play: Compatible, Complementary, or Contraindicated?

PURPOSE

During heavily congested schedules, professional soccer players can experience exacerbated fatigue responses, which are thought to contribute to an increased risk of injury. Given that match-induced residual fatigue can last up to 72 hours, many coaches naturally prioritize recovery in the days immediately following match day. While it is intuitive for coaches and training staff to decrease the amount of auxiliary training practices to focus on recovery, prescribing upper-body resistance training on the day after match play has recently emerged as a specific training modality in this context. While these sessions may be implemented to increase training stimulus, there are limited data available regarding the efficacy of such a practice to improve recovery kinetics.

METHODS

In this narrative review, the authors look at the theoretical implications of performing upper-body resistance training on the day after match play on the status of various physiological and psychological systems, including neuromuscular, metabolic, hormonal, perceptual, and immunological recovery.

RESULTS

The available evidence suggests that in most cases this practice, as currently implemented (ie, low volume, low intensity), is unlikely to be complementary (ie, does not accelerate recovery) but is potentially compatible (ie, does not impair recovery).

CONCLUSION

Overall, because the perception of such sessions may be player dependent, their programming requires an individualized approach and should take into account match dynamics (eg, fixture scheduling, playing time, travel).

Biomechanical and Physiological Responses to 120 Min. of Soccer-Specific Exercise

Purpose: The purpose of the study is to investigate biomechanical and physiological responses to soccer-specific exercise incorporating an extra-time period (ET) and assess the test-retest reliability of these responses. Methods: Twelve soccer players performed 120 min of soccer-specific exercise. Tri-axial (PL_Total) and uni-axial PlayerLoad™ in the vertical (PL_V), anterior-posterior (PL_A-P), and medial-lateral (PL_M-L) planes were monitored using a portable accelerometer. Likewise, respiratory exchange ratio (RER) was recorded throughout exercise. At the end of each 15-min period, players provided differential ratings of perceived exertion for legs (RPE-L), breathlessness (RPE-B) and overall (RPE-O), and capillary samples were taken to measure blood lactate (BLa) concentrations. The soccer-specific exercise was completed twice within 7 days to assess reliability. Results: A main effect for time was identified for PL_Total (p = 0.045), PL_V (p = 0.002), PL_A-P (p = 0.011), RER (p = 0.001), RPE-L (p = 0.001), RPE-O (p = 0.003), and CMJ (p = 0.020). A significant increase in PL_Total (234 ± 34 au) and decrease in RER (0.87 ± 0.03) was evident during 105-120 versus 0-15 min (215 ± 25 au; p = 0.002 and 0.92 ± 0.02; p = 0.001). Coefficients of variations were <10% and Pearson's correlation coefficient demonstrated moderate-to-very strong (0.33-0.99) reliability for all PL variables, RPE-B, BLa, and RER. Conclusions: These results suggest that mechanical efficiency is compromised and an increased rate of lipolysis is observed as a function of exercise duration, particularly during ET. These data have implications for practitioners interested in fatigue-induced changes during ET.

Use of Numerically Blinded Ratings of Perceived Exertion in Soccer: Assessing Concurrent and Construct Validity

PURPOSE

To examine the concurrent and construct validity of numerically blinded ratings of perceived exertion (RPEs).

METHODS

A total of 30 elite male youth soccer players (age 16.7 [0.5] y) were monitored during training and matches over a 17-wk in-season period. The players' external loads were determined via raw 10-Hz global positioning system. Heart rate (HR) was collected continuously and expressed as Bannister and Edwards training impulses, and minutes >80% of the players predetermined the maximum HR by the Yo-Yo Intermittent Recovery Test Level 1. RPE was collected confidentially 10 to 15 min after training/matches using 2 methods: (1) a traditional verbal response to the 0 to 100 category-ratio "centiMax" scale (RPE) and (2) numerically blinded RPE centiMax scale (RPEblind) with the response selected manually via a 5 × 7-in tablet "slider." The RPE and RPEblind were divided by 10 and multiplied by the duration to derive the sessional RPE. Linear mixed models compared ratings, and within-subject repeated-measures correlations assessed the sessional RPE versus HR and external load associations.

RESULTS

There were no differences between the RPE and RPEblind (0.19; 95% confidence intervals, -0.59 to 0.20 au, P = .326) or their session values (13.5; 95% confidence intervals, -17.0 to 44.0 au, P = .386), and the ratings were nearly perfectly correlated (r = .96). The associations between the sessional RPE versus HR and external load metrics were large to very large (r = .65-.81), with no differences between the RPE methods (P ≥ .50). The RPEblind also reduced verbal anchor clustering and integer bias by 11% and 50%, respectively.

CONCLUSIONS

RPEblind demonstrated concurrent and construct validity versus the traditional method, and may be used in situations where practitioners have concerns regarding the authenticity of athlete ratings.

Does the distribution of the weekly training load account for the match results of elite professional soccer players?

PURPOSE

The aim of the study was to compare training load (TL) of the days preceding a win, draw or defeat in a sample of elite professional soccer players across the in-season 2015/16.

METHODS

Twenty elite soccer players participated in this study. Total distance covered, high-speed running distance (HSRD), average speed, session rate of perceived exertion (s-RPE) and Hooper index scores (HI) were collected. Data from 24 weeks with one match were analysed through the match-day (MD-5, 4, 3, 2, 1) and MD+1.

RESULTS

The main finding emerges in MD-1, where a longer training duration preceding draws (95.1 ± 1.5 min) > defeats (91.5 ± 1.6 min) > wins (84.7 ± 0.5 min) was found, while total distance and average speed were higher in wins (3628.6 ± 57.2 m) > draws (3391.3 ± 153.3 m) > defeats (3236.1 ± 113.7 m) and draws (130.7 ± 17.6 m/min) > wins (86.0 ± 6.9 m/min) > defeats (54.8 ± 7.1 m/min), respectively. HSRD was higher in draws (42.8 ± 0.6 m) > wins (36.1 ± 1.7 m) > defeats (35.8 ± 1.7 m). In MD+1, there were differences in HI between wins vs draws (p<0.01).

CONCLUSIONS

The results are drawn from one team that participated in UEFA Champions League. It was observed that different TL applied in training sessions can influence match result. Our findings can be considered in future soccer planning and periodization to win matches. This study emphasizes the use of HI especially in the day following the match.

Systematic review of the use of "magnitude-based inference" in sports science and medicine

Magnitude-based inference (MBI) is a controversial statistical method that has been used in hundreds of papers in sports science despite criticism from statisticians. To better understand how this method has been applied in practice, we systematically reviewed 232 papers that used MBI. We extracted data on study design, sample size, and choice of MBI settings and parameters. Median sample size was 10 per group (interquartile range, IQR: 8-15) for multi-group studies and 14 (IQR: 10-24) for single-group studies; few studies reported a priori sample size calculations (15%). Authors predominantly applied MBI's default settings and chose "mechanistic/non-clinical" rather than "clinical" MBI even when testing clinical interventions (only 16 studies out of 232 used clinical MBI). Using these data, we can estimate the Type I error rates for the typical MBI study. Authors frequently made dichotomous claims about effects based on the MBI criterion of a "likely" effect and sometimes based on the MBI criterion of a "possible" effect. When the sample size is n = 8 to 15 per group, these inferences have Type I error rates of 12%-22% and 22%-45%, respectively. High Type I error rates were compounded by multiple testing: Authors reported results from a median of 30 tests related to outcomes; and few studies specified a primary outcome (14%). We conclude that MBI has promoted small studies, promulgated a "black box" approach to statistics, and led to numerous papers where the conclusions are not supported by the data. Amidst debates over the role of p-values and significance testing in science, MBI also provides an important natural experiment: we find no evidence that moving researchers away from p-values or null hypothesis significance testing makes them less prone to dichotomization or over-interpretation of findings.

Changes in subjective mental and physical fatigue during netball games in elite development athletes

OBJECTIVES

To assess the magnitude of changes in, and relationships between, physical and mental fatigue pre-to-post match in elite development netballers.

DESIGN

Observational.

METHODS

Twelve female netballers (21.3±2.9 years) competing in the Australian Netball League reported perceptual measures of mental and physical fatigue pre- and post-match on 12 separate competition occasions. Minutes played, to allow for calculation of weighted changes (ratings proportional to playing time), positional groups and performance analysis variables were also assessed.

RESULTS

Post-match ratings were higher (p<0.01) than pre-match for both mental (pre: 31.02±19.28; post: 44.73±24.47) and physical fatigue (pre: 28.86±15.37; post: 47.21±24.67). The correlation coefficient between change in mental and physical fatigue (r=0.37, p<0.01) revealed a shared variance of 13.9%. Acute changes in mental fatigue were related to minutes played (r=0.32, p<0.01) as was change in physical fatigue (r=0.59, p<0.01). No differences in change in mental fatigue were found between positional groups (p=0.07) though change in physical fatigue was higher for shooters compared to defenders (p<0.05). Performance variables revealed no relationships with mental or physical fatigue, with the exception of turnover number with both post-match weighted physical (r= -0.23, p<0.01) and weighted-change in physical fatigue (r=-0.16, p<0.05).

CONCLUSIONS

Mental and physical fatigue were found to increase across netball matches in elite development athletes. Mental fatigue emerged as a largely separate construct to physical fatigue.

Using the Rating of Perceived Exertion and Heart Rate to Quantify Training Intensity in Female Soccer Players: Validity and Utility

Costa, JA, Brito, J, Nakamura, FY, Figueiredo, P, and Rebelo, A. Using the rating of perceived exertion and heart rate to quantify training intensity in female soccer players: validity and utility. J Strength Cond Res XX(X): 000-000, 2019-The aims of this study were as follows: (a) to analyze associations between session rating of perceived exertion (sRPE) and training impulse (TRIMP); (b) to verify whether significantly different ranges of percentage of heart rate peak (%HRpeak) would be reached in each discrete RPE category; and (c) to investigate the amount of time spent >90% of HRpeak and associated intraplayer and interplayer variability during soccer technical training sessions with similar contents and duration. This was a single-group observational study that measured the internal training load during 6 weeks of the competitive period in 17 high-level female soccer players. All training sessions started around 9 PM. and lasted on average 94 ± 5 minutes. During each training session, RPE, sRPE, TRIMP, HRex (%HRpeak), and time spent at >90% of HRpeak were assessed. A very large correlation was found between sRPE and TRIMP (r = 0.78; 95% confidence interval: [0.74-0.82]). Significant differences were observed between %HRpeak associated with each RPE value (i.e., RPE = 2 arbitrary unit [68%; 65-69% of %HRpeak]; RPE 3 [72%; 69-75%]; RPE 4 [79%; 76-82%]; RPE 5 [84; 81-87%]; χ = 73.34; df = 3; P < 0.001). Intraplayer and interplayer coefficients of variation for the time spent >90% of HRpeak (∼8% of training time, ∼7 minutes per session) during training sessions were 73 and 92%, respectively. In conclusion, it was confirmed that sRPE and TRIMP displayed good convergent validity, and different %HRpeak were observed for each discrete RPE. However, because of the high variability in the time >90% of HRpeak, careful monitoring of individual exercises should be performed to ensure the desired training stimulus for each player.

Contextual Variables and Training Load Throughout a Competitive Period in a Top-Level Male Soccer Team

Rago, V, Rebelo, A, Krustrup, P, and Mohr, M. Contextual variables and training load throughout a competitive period in a top-level male soccer team. J Strength Cond Res XX(X): 000-000, 2019-The aim of the present study was to investigate and quantify the weekly training load (TL) according to different match-related contextual factors in a professional male soccer team (n = 23). Training load was quantified using a 10-Hz global positioning system with integrated 100-Hz accelerometer and heart rate recordings over a 3-month competitive period. Total distance (TD) covered and high-speed running (HSR, >16 km·h) during training were higher in the week after playing against a bottom-level or top-level opponent compared to a medium-level opponent (p < 0.05; effect size [ES] = 0.30-1.04). TD was also higher when preparing for a match against a bottom-level opponent (p < 0.05; ES = 0.39-0.76). In addition, the percentage of HSR was higher after playing a bottom-level compared to a medium-level opponent (p < 0.001; ES = 0.49 [0.27; 0.71]). TD covered was higher in the week following a draw or a win, and higher before a loss compared to a draw (p < 0.05, ES = 0.32-0.81). Both absolute HSR and HSR expressed as percentage of TD were higher before losing and winning a match compared to a draw (p < 0.05; ES = 0.72-0.98). Weekly TL seems to be slightly affected by match-related contextual variables, with special emphasis on the opponent standard and match outcome. Higher training volume was observed before and after playing against a top-level opponent, and after losing a match, whereas the volume of high-intensity training seems to be higher when preparing for a game against a top-level opponent. Future experimental research should clarify the interaction between match-related contextual variables (e.g., cause) and weekly TL (e.g., effect).

Using differential ratings of perceived exertion to assess agreement between coach and player perceptions of soccer training intensity: An exploratory investigation

We aimed to assess the coach-player agreement of subjective soccer training loads via differential ratings of perceived exertion (dRPE). The coach initially underwent quantifiable familiarisation (blackness test) with the Borg CR100 scale. Data were collected from 16 semi-professional soccer players across seven consecutive training sessions. For the measurement of subjective training load, the coach and players provided dRPE (CR100) for legs (RPE-L), breathlessness (RPE-B) and technical exertion (RPE-T). Coach-prescribed dRPE were recorded prior to training, with coach observed and player reported dRPE collected post training. Statistical equivalence bounds for agreement between coach (prescribed and observed) and player reported dRPE scores were 4 arbitrary units on the CR100 and we used a probability outcome of likely (≥75%) to infer realistic equivalence. Following three familiarisation sessions, the coach improved their blackness test score from 39% to 83%. Coach observed and player reported RPE-T scores were likely equivalent, with all other comparisons not realistically equivalent. Since training prescription is coach-led, our data highlight the importance of accurate internal load measurement and feedback in soccer. The improved accuracy and precision of coach intensity estimation after three attempts at the blackness test suggests that this method could be worthwhile to researchers and practitioners employing dRPE.

Editorial: Fatigue and Recovery in Football

The football codes (soccer, American football, Australian rules football, rugby league, and union and Gaelic football) are intermittent team sports with bouts of high-intensity activity interspersed with low-intensity activities or rest [...]

Physical Fitness Characteristics of High-level Youth Football Players: Influence of Playing Position

The aim of this study was to determine whether the speed, agility, aerobic and anaerobic capacities of football players varied by playing positions. Elite youth football players (n = 123, age = 15.7 ± 0.5 years) who played in six different positions, as goalkeepers (GK), full backs (FB), central defenders (CD), wide midfielders (WM), central midfielders (CM), and attackers (AT), were assessed. Multivariate analysis of variances was used to compare the following variables: Linear running sprint for 5 m (S5) and 10 m (S10), flying sprint for 20 m (F20), agility 505 test with turn on the dominant (A505D) and non-dominant leg (A505N), agility K-test, Yo-Yo intermittent recovery (YYIR1) test and repeat sprint ability (RSA) test. The results showed significant influence of playing positions on linear-running sprint performance (F1,123 = 6.19, p < 0.01, ηp² = 0.23). Midfielders reached significantly higher performance levels (CM = 2.44 ± 0.08 s, WM = 2.47 ± 0.13 s) in the A505N test compared to GK (2.61 ± 0.23 s). Outfield players had significantly higher performance in both YYIR1 and RSA tests compared to GK (p < 0.01). The results of this study may provide insightful strategies for coaches and clinical practitioners for developing position-specific conditioning programs.

The Current State of Subjective Training Load Monitoring-a Practical Perspective and Call to Action

This commentary delivers a practical perspective on the current state of subjective training load (TL) monitoring, and in particular sessional ratings of perceived exertion, for performance enhancement and injury prevention. Subjective measures may be able to reflect mental fatigue, effort, stress, and motivation. These factors appear to be important moderators of the relationship TL has with performance and injury, and they also seem to differ between open and closed skill sports. As such, mental factors may affect the interaction between TL, performance, and injury in different sports. Further, modeling these interactions may be limited due to the assumption that an independent signal can adequately account for the performance or injury outcomes. An independent signal model does not accurately reflect training environments where multiple stressors (e.g., mechanical, emotional, nutritional) impact adaptations. Common issues with using subjective TL monitoring, including a lack of differentiation between biomechanical, physiological, and cognitive load, may be overcome by considering psychometric measurement best practices, finer graded scales, and differential ratings of perceived exertion. Methods of calculating TL, including different acute and chronic time periods, may also need to be individualized to different sports and potentially different individuals within the same sport. As TL monitoring is predominately a "chronic" decision-making tool, "acute" decision-making tools, e.g., subjective wellness and autonomic nervous system measures, should be combined in a bespoke multivariate model to aid sports coaches. A call to action is presented for future research on key issues associated with TL monitoring that will have relevance for practitioners in an applied setting.