Use of RPE-Based Training Load in Soccer

A Review of the Validity and Reliability of Accelerometer-Based Metrics From Upper Back-Mounted GNSS Player Tracking Systems for Athlete Training Load Monitoring

ABSTRACT

Dawson, L, Beato, M, Devereux, G, and McErlain-Naylor, SA. A review of the validity and reliability of accelerometer-based metrics from upper back-mounted GNSS player tracking systems for athlete training load monitoring. J Strength Cond Res 38(8): e460-e475, 2024-Athlete load monitoring using upper back-mounted global navigation satellite system (GNSS) player tracking is common within many team sports. However, accelerometer-based load monitoring may provide information that cannot be achieved with GNSS alone. This review focuses on the accelerometer-based metrics quantifying the accumulation of accelerations as an estimation of athlete training load, appraising the validity and reliability of accelerometer use in upper back-mounted GNSS player tracking systems, the accelerometer-based metrics, and their potential for application within athlete monitoring. Reliability of GNSS-housed accelerometers and accelerometer-based metrics are dependent on the equipment model, signal processing methods, and the activity being monitored. Furthermore, GNSS unit placement on the upper back may be suboptimal for accelerometer-based estimation of mechanical load. Because there are currently no feasible gold standard comparisons for field-based whole-body biomechanical load, the validity of accelerometer-based load metrics has largely been considered in relation to other measures of training load and exercise intensity. In terms of convergent validity, accelerometer-based metrics (e.g., PlayerLoad, Dynamic Stress Load, Body Load) have correlated, albeit with varying magnitudes and certainty, with measures of internal physiological load, exercise intensity, total distance, collisions and impacts, fatigue, and injury risk and incidence. Currently, comparisons of these metrics should not be made between athletes because of mass or technique differences or between manufacturers because of processing variations. Notable areas for further study include the associations between accelerometer-based metrics and other parts of biomechanical load-adaptation pathways of interest, such as internal biomechanical loads or methods of manipulating these metrics through effective training design.

Relationship Between External Training Load and Session Rating of Perceived Exertion Training Impulse in Elite Sprinters

PURPOSE

To quantify the change in session rating of perceived exertion training impulse (RPE-TRIMP) that may occur in response to increased running distance at 3 running velocity ranges in elite sprinters.

METHODS

We monitored training load in elite sprinters (women: n = 7; men: n = 11) using wearable Global Positioning System technology and RPE-TRIMP for a total of 681 individual training sessions during a 22-week competition-preparation period. Internal training load was operationalized by RPE-TRIMP, and external training load was operationalized by distance covered in 3 velocity ranges. A linear mixed-effects model with athlete as a random effect was fit to RPE-TRIMP with total distance covered at ≤69.99% (low-velocity running [LVR]), 70% to 84.99% (high-velocity running [HVR]), and 85% to 100% (very-high-velocity running [VHVR]) of individual maximum velocity.

RESULTS

Increased running distance in all 3 velocity ranges (LVR, HVR, and VHVR) resulted in a significant (P < .001) increase in RPE-TRIMP. Coefficients (95% CIs) were .10 (.08-.11) for LVR, .23 (.18-.28) for HVR, and .44 (.35-.53) for VHVR. A 50-m increase in running distance covered in the LVR, HVR, and VHVR velocity ranges was associated with increases in RPE-TRIMP of 5, 11.5, and 22 arbitrary units, respectively.

CONCLUSIONS

Internal training load, calculated as RPE-TRIMP, increased with increases in total distance covered in the LVR, HVR, and VHVR velocity ranges (P < .001). RPE-TRIMP can be a practical solution for monitoring global training-session load in elite sprinters.

Quantifying Hitting Load in Racket Sports: A Scoping Review of Key Technologies

PURPOSE

This scoping review aims to identify the primary racket and arm-mounted technologies based on inertial measurement units that enable the quantification of hitting load in racket sports.

METHODS

A comprehensive search of several databases (PubMed, SPORTDiscus, Web of Science, and IEEE Xplore) and Google search engines was conducted following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) extension for scoping reviews guidelines. Included records primarily focused on monitoring hitting load in racket sports using commercialized racket or arm-mounted inertial sensors through noncompetitive and competitive racket-sports players.

RESULTS

A total of 484 records were identified, and 19 finally met the inclusion criteria. The largest number of systems found were compatible with tennis (n = 11), followed by badminton (n = 4), table tennis (n = 2), padel (n = 1), and squash (n = 1). Four sensor locations were identified: grip-attached (n = 8), grip-embedded (n = 6), wrist (n = 3), and dampener sensors (n = 2). Among the tennis sensors, only 4 out of the 11 (36.4%) demonstrated excellent reliability (>.85) in monitoring the number of shots hit either during analytic drills or during simulated matches. None of the other racket-sports sensors have undergone successful, reliable validation for hitting-volume quantification.

CONCLUSIONS

Despite recent advancements in this field, the quantification of hitting volume in racket sports remains a challenge, with only a limited number of tennis devices demonstrating reliable results. Thus, further progress in technology and research is essential to develop comprehensive solutions that adequately address these specific requirements.

A large-scale multivariate soccer athlete health, performance, and position monitoring dataset

Data analysis for athletic performance optimization and injury prevention is of tremendous interest to sports teams and the scientific community. However, sports data are often sparse and hard to obtain due to legal restrictions, unwillingness to share, and lack of personnel resources to be assigned to the tedious process of data curation. These constraints make it difficult to develop automated systems for analysis, which require large datasets for learning. We therefore present SoccerMon, the largest soccer athlete dataset available today containing both subjective and objective metrics, collected from two different elite women's soccer teams over two years. Our dataset contains 33,849 subjective reports and 10,075 objective reports, the latter including over six billion GPS position measurements. SoccerMon can not only play a valuable role in developing better analysis and prediction systems for soccer, but also inspire similar data collection activities in other domains which can benefit from subjective athlete reports, GPS position information, and/or time-series data in general.

Research application of session-RPE in monitoring the training load of elite endurance athletes

Purpose

TRIMP and sRPE are both representative indicators of training load(TL), and the correlation between two has been widely demonstrated across various sports. The aim of this study was to investigate the reliability of sRPE-TRIMP correlation across different intensities/duration of training in cross-country skiing, and whether sRPE can serve as an validity supplement to TRIMP data in cases of lost heart rate data.

Method

10 athletes were used as the experimental objects. The intensity, duration and RPE of 273 different types of training sessions were collected, and statistical methods were used for data analysis.

Results

1. There was a significant correlation between sRPE and TRIMP (r = 0.68, p < 0.05), but the correlation differs among the LIT, MIT and HIT groups (r = 0.70, 0.46, r = 0.31, p < 0.05) 2. sRPE-TRIMP correlation among three different time duration in the LIT group (0-60 min, 60-120 min and 120-180 min), are all highly significant (r = 0.70, 0.67, 0.69, p < 0.05) and the LRsRPE-TRIMP of 3 duration have no significant differences (chow test, p > 0.05). 3. The difference in actual training duration between samples was the main reason for the difference in the application effect of sRPE, because the actual training duration ratio of LIT was 89.7 ± 16.4%; MIT, 98.5 ± 6.2%; and HIT, 94.4 ± 13.5%.

Conclusion

1. The linear relationship between sRPE and TRIMP (LRsRPE-TRIMP) is more significant in LIT compared to that in MIT and HIT. 2. Variations in the duration of LIT sessions do not affect the consistency of the relationship between sRPE and TRIMP. 3. Discrepancies between actual and planned training durations directly impact the significance of the LRsRPE-TRIMP.

Mind the Gap: Comparison of External Load and Load Variation Between a Reserve Team in a 1-Game Week Microcycle and Its First Team in a 2-Game Week Microcycle Within an Elite Professional Soccer Club

ABSTRACT

Carpels, T, Scobie, N, Macfarlane, NG, and Kemi, OJ. Mind the gap: comparison of external load and load variation between a reserve team in a 1-game week microcycle and its first team in a 2-game week microcycle within an elite professional soccer club. J Strength Cond Res 38(5): e235-e242, 2024-The aim of this study was to quantify and compare weekly external load and within-week load variation of reserve team players (RES) in a 1-game week microcycle to first team players (FT) in a 2-game week microcycle within the same professional soccer club. External load data were collected between 2017 and 2020 for the following parameters: duration, total distance (TD), total high-speed distance (THSD; >19.8 km·h -1 ), high-speed distance (HSD; 19.8-25.2 km·h -1 ), sprint distance (SD; >25.2 km·h -1 ), number of sprints (number of efforts >25.2 km·h -1 ), number of high-speed efforts (number of HS efforts >19.8 km·h -1 ), meters per minute (m·min -1 ), and high-speed meters per minute (HS m·min -1 ). First team players were subcategorized into starters (ST) and nonstarters (NST). Intergroup differences in cumulative weekly load and weekly load patterns were statistically analyzed, whereas training monotony (TM) was quantified to assess intragroup, within-week, load variation. Reserve team players showed similar weekly loads to ST, apart from significant differences ( p < 0.005) in duration (8%), TD (21%), and HS efforts (16%). Similar to ST, RES showed greater values than NST ( p < 0.0005) for duration (10%), TD (9%), THSD (30%), HSD (26%), SD (45%), sprints (40%), and HS efforts (22%). Weekly patterns in RES were different from ST and NST ( p < 0.05). Training monotony was highest for NST for all parameters, apart from the number of sprints. Reserve team players need to be prepared to cope with cumulative weekly loads and the lack of recovery between games that ST face. However, when RES become NST, effective loading strategies need to be designed within the limits of 2-game week microcycles to ensure continuous development.

Relationships among Physical Fitness, External Loads, and Heart Rate Recovery: A Study on Futsal Players during an Overseas Congested-Weeks Training Camp

This study examined relationships among players' physical characteristics, match external loads, and heart rate recovery (HRR) during match substitutions in a congested fixture of an overseas futsal training camp. Eleven under-20 national futsal players' anthropometric characteristics (age, body height, body mass, % fat, and % muscle) and physical fitness [HRmax, VO2max, maximal aerobic speed (MAS) during the 30-15 intermittent fitness test (IFT)] were determined. Additionally, locomotion profiles during field play and HRR sitting on the bench were recorded during five matches. A repeated-measures analysis of variance and Pearson's correlation coefficient were used for statistical analysis. The results revealed that the overall observed correlations among anthropometry, body composition, physical fitness, and HRR were inconsistent across all the matches and substitutions. However, the numbers of moderate (1.00-1.99 m/s2), moderate-to-high (2.00-2.99 m/s2), and high (3.00-50.00 m/s2) intensities of acceleration presented negative correlations in the last match (r < -0.76; p < 0.05). HRR during match substitutions may have been influenced by uncontrolled factors across all the match play and recovery. HRR measures may be affected mainly by fatigue caused by the accumulation of accelerations throughout a congested fixture during a congested-schedule of a futsal training camp.

Building Individual Player Performance Profiles According to Pre-Game Expectations and Goal Difference in Soccer

Soccer player performance is influenced by multiple unpredictable factors. During a game, score changes and pre-game expectations affect the effort exerted by players. This study used GPS wearable sensors to track players' energy expenditure in 5-min intervals, alongside recording the goal timings and the win and lose probabilities from betting sites. A mathematical model was developed that considers pre-game expectations (e.g., favorite, non-favorite), endurance, and goal difference (GD) dynamics on player effort. Particle Swarm and Nelder-Mead optimization methods were used to construct these models, both consistently converging to similar cost function values. The model outperformed baselines relying solely on mean and median power per GD. This improvement is underscored by the mean absolute error (MAE) of 396.87±61.42 and root mean squared error (RMSE) of 520.69±88.66 achieved by our model, as opposed to the B1 MAE of 429.04±84.87 and RMSE of 581.34±185.84, and B2 MAE of 421.57±95.96 and RMSE of 613.47±300.11 observed across all players in the dataset. This research offers an enhancement to the current approaches for assessing players' responses to contextual factors, particularly GD. By utilizing wearable data and contextual factors, the proposed methods have the potential to improve decision-making and deepen the understanding of individual player characteristics.

E-Textiles for Sports and Fitness Sensing: Current State, Challenges, and Future Opportunities

E-textiles have emerged as a fast-growing area in wearable technology for sports and fitness due to the soft and comfortable nature of textile materials and the capability for smart functionality to be integrated into familiar sports clothing. This review paper presents the roles of wearable technologies in sport and fitness in monitoring movement and biosignals used to assess performance, reduce injury risk, and motivate training/exercise. The drivers of research in e-textiles are discussed after reviewing existing non-textile and textile-based commercial wearable products. Different sensing components/materials (e.g., inertial measurement units, electrodes for biosignals, piezoresistive sensors), manufacturing processes, and their applications in sports and fitness published in the literature were reviewed and discussed. Finally, the paper presents the current challenges of e-textiles to achieve practical applications at scale and future perspectives in e-textiles research and development.

Menstrual Cycle and Situational Match Variables: Effects on Well-Being in Professional Female Soccer Players

Purpose: We examined whether the situational match factors (location, result, and opposition quality), as well as playing position and menstrual cycle phase, influenced self-reported well-being in female soccer players. Methods: Twenty-two professional players (25 ± 5 years) from a squad in the Women's Super League in England self-reported their menstrual cycle phase via an online survey, and their soreness, sleep, stress, mood, and fatigue on a 1 (positive) to 5 (negative) scale on the morning of match day (MD) and for the next 3 days (referred to as MD + 1, MD + 2, MD + 3, respectively). Data was collected for 26 matches across the 2021-2022 season. Session rate of perceived exertion (sRPE) and total distance covered (measured with GPS) were measured on match and training days. Results: Menstrual cycle phase and the situational match factors had no influence on distance covered during matches and sRPE (p > .05). Sleep was worse on MD + 1 (p < .001; g = 1.59) and MD + 2 (p = .005; g = 0.98) after away matches. Stress and mood were > 28% worse after playing top vs. mid and bottom table opposition at MD + 1, and significantly worse when losing compared to winning and drawing (p > .05). Playing position and menstrual cycle phase has no influence on self-reported well-being (p > .05). Conclusion: Sleep quality was worse after away matches and losing matches negatively affects stress and mood for 2 days post-match, but menstrual cycle phase does not influence post-match well-being.

Relative Match Load in Young Professional Soccer Players during Soccer-7 and Soccer-11

The aim of this study was to analyze the differences in internal and external load during Soccer-7 and Soccer-11, comparing positional requirements and neuromuscular fatigue in both modalities. Twenty-four young soccer players were monitored in Soccer-7 and Soccer-11 matches using global positioning systems. Total distance covered (TD), distance covered at high speed (HSR), distance covered at very high speed (VHSR), peak speed, accelerations (Acc) and decelerations (Dec) and rate of perceived exertion (RPE) were recorded differentiating between central backs (CB), midfielders (MF), external players (EX) and forwards (FW). Neuromuscular fatigue were assessed using a jump test. During Soccer-11, players showed significantly higher TD, HSR and VHSR, with low Acc and greater RPE compared with Soccer-7. During Soccer-11, all positions recorded significantly greater TD, distance at HSR and at VHSR than Soccer-7. In terms of playing position, CB, MF and FW achieved significantly higher Peak Speed during Soccer-1, but there was no difference for EX. During Soccer-7 all positions performed significantly higher numbers of Acc. Although the Soccer-7 modality is considered an optimal format for the development of young soccer players, there is a significant difference in match running activity for all playing positions with respect to the Soccer-11 format.

Training stress, neuromuscular fatigue and well-being in volleyball: a systematic review

BACKGROUND

Volleyball, with its unique calendar structure, presents distinct challenges in training and competition scheduling. Like many team sports, volleyball features an unconventional schedule with brief off-season and pre-season phases, juxtaposed against an extensive in-season phase characterized by a high density of matches and training. This compact calendar necessitates careful management of training loads and recovery periods. The effectiveness of this management is a critical factor, influencing the overall performance and success of volleyball teams. In this review, we explore the associations between training stress measures, fatigue, and well-being assessments within this context, to better inform future research and practice.

METHODS

A systematic literature search was conducted in databases including PsycINFO, MEDLINE/PubMed, SPORTDiscus, Web of Science, and Scopus. Inclusion criteria were original research papers published in peer-reviewed journals involving volleyball athletes.

RESULTS

Of the 2535 studies identified, 31 were thoroughly analysed. From these 31 articles, 22 included professional athletes, seven included collegiate-level volleyball athletes, and two included young athletes. Nine studies had female volleyball players, while the remaining 22 had male volleyball athletes.

CONCLUSIONS

Internal training load should be collected daily after training sessions and matches with the session rating of perceived exertion method. External training load should also be measured daily according to the methods based on jump height, jump count, and kinetic energy. If force platforms are available, neuromuscular fatigue can be assessed weekly using the FT:CT ratio of a countermovement jump or, in cases where force platforms are not available, the average jump height can also be used. Finally, the Hooper Index has been shown to be a measure of overall wellness, fatigue, stress, muscle soreness, mood, and sleep quality in volleyball when used daily.

Impact of the Menstrual Cycle on Physical Performance and Subjective Ratings in Elite Academy Women Soccer Players

Our study aimed to combine psychological and physical factors to explore the impact of the menstrual cycle on performance in elite academy women soccer players through weekly monitoring. Eighteen elite academy women soccer players were monitored. Players reported daily through an online anonymous survey if they were in menstruation. Players answered the Hooper Questionnaire daily, performed an Illinois Agility Test (IAT) twice a week, and rated their perceived exertion (RPE) after every training session. Tests were associated with a complete menstrual cycle reported through the online anonymous survey to determine the two weeks of the follicular phase and the two weeks of the luteal phase. Of the 18 players, 10 completed all requirements and were retained for analyses. IAT did not show significant differences throughout the menstrual cycle (p = 0.633). Fatigue (p = 0.444), Stress (p = 0.868), Sleep (p = 0.398), DOMS (delayed onset muscle soreness; p = 0.725), and Hooper Index (p = 0.403) did not show significant differences either. RPE was also comparable across the cycle (p = 0.846). Our results failed to demonstrate that hormonal variation during the menstrual cycle influenced psychological and physical markers of performance.

Influence of a football match on landing biomechanics and jump performance in female football players

This study aimed to assess the acute effect of a competitive football match on jump performance and kinematic parameters during jump landing in semiprofessional female football players. Twenty-two semiprofessional players (20 ± 3 years) underwent a drop jump task for a posterior video analysis of the landing phase. These measurements were obtained at (1) baseline, (2) after, and (3) 48 h after a competitive football match. A one-way ANOVA with repeated measures was employed to detect differences over the time. There was a main effect of time for maximal knee flexion angle during drop landing (p = 0.001). In comparison with baseline, maximal knee flexion angle was reduced immediately post-match and was still reduced 48 h after the match (63.4 ± 8.6 vs 57.0 ± 11.7 vs 48.9 ± 19.1, p ≤ 0.038). There was also a main effect of time for drop jump height (p < 0.001). Drop jump height was reduced immediately post-match and remained low 48 h after the match in comparison with baseline (27.3 ± 3.6 vs 24.5 ± 2.8 ~ 25.5 ± 3.0 cm, p ≤ 0.002). There was a main effect of time on hip flexion angle during landing (p = 0.001), but the pairwise comparison revealed that this variable was not affected immediately post-match but was lower 48 h after the match than at baseline (50.1 ± 10.1 ~ 50.8 ± 13.2 vs 38.1 ± 17.8 °, p ≤ 0.005). A competitive football match worsened jump performance and several landing biomechanical parameters in female football players, which were still decreased in comparison with baseline even 48 h after the match.

Training Load and Current Soreness Predict Future Delayed Onset Muscle Soreness in Collegiate Female Soccer Athletes

Background

Delayed onset muscles soreness (DOMS) is an indication of muscle stress and trauma that develops from excessive musculoskeletal loads. Musculoskeletal loads can be measured with wearable devices, but there is limited research on specific training load metrics that most correlate with DOMS after activity.

Purpose

To determine the predictive capabilities of training load variables on the development of lower extremity DOMS in female collegiate soccer athletes throughout an entire season.

Study Design

Prospective Cohort.

Methods

Twenty-seven collegiate female soccer athletes reported their lower extremity DOMS each day prior to all soccer activity. Participants wore Polar heart rate and global positioning monitors to capture training load measures. Pearson correlation coefficients were used to assess the relationships between the training load variables and change in DOMS when collapsed across dates. Separate linear mixed models were performed with the following day's DOMS as the outcome variable, training load and the current day's DOMS as predictor variables, and participants serving as random intercepts.

Results

All training load variables significantly predicted change in DOMS, with number of decelerations (ρ=0.72, p <0.001), minutes spent at greater than 80% of maximum heart rate (HRmax) (ρ=0.71 , p <0.001), and distance (ρ=0.70 , p <0.001) best correlating with change in DOMS. Linear mixed models revealed a significant interaction of all training load and current day's DOMS on the following day's DOMS (p<0.001), but number of decelerations, HRmax, and total number of accelerations demonstrated the highest coefficient of determination (R2 marginal=33.2% - 29.2% , R2 conditional= 46.9% - 44.8%).

Conclusions

Training load variables paired with the current day's DOMS significantly predict lower extremity DOMS in the future, with number of decelerations, accelerations, and HRmax best predicting future DOMS. Although this demonstrates that training load variables predict lower extremity DOMS, future research should incorporate objective measures of strength or jump kinetics to identify if similar relationships exist.

Level of Evidence

Level 3.

Be Aware of the Benefits of Drafting in Sports and Take Your Advantage: A Meta-Analysis

Purpose

In competitive sports, optimizing performance is the key. An interesting venue to explore is to consider drafting as a pacing strategy. The purpose of this study is to identify the magnitude of drafting benefits for biomechanical, physiological, and psychobiological parameters in and between athletes in cycling, kayaking, running, skating, skiing, and swimming.

Design

A systematic review and meta-analysis.

Methods

Systematic searches were performed in PubMed, Web of Science, and Embase databases.

Results

In total, 205 studies were found, from which 22 were relevant (including 232 participants and 548 observations). Methodological quality was high for all the included articles. The meta-analyses for all parameters indicated strong evidence for a benefit of drafting, with moderate effects between leading and drafting athletes found for the heart rate (3.9%), VO2 (8.9%), power output (11.3%), and rating of perceived exertion (10.4%). Large effect sizes were found for blood lactate (24.2%), VE (16.2%), and EMG (56.4%). A moderator analysis showed differences between sports on the effect of drafting with most benefits in cycling. Discussion. Based on the observed effects of drafting in the biomechanical, physiological, and psychobiological parameters, it can be considered as an element of pacing, a strategy to conserve energy and optimize performance.

Conclusion

There is strong evidence that drafting benefits athletes, with varying levels of effect for athletes in different sports. Knowledge about the magnitude of benefits can be used to improve training sessions, race strategies, and performance in competition.

Children can rate perceived effort but do not follow intensity instructions during soccer training

The perception of effort is elementary for the self-regulation of exercise intensity in sports. The competence for rating perceived effort (RPE) seems to be related to physical and cognitive development. Children accurately rate perceived effort during incremental exercise tests when loads progressively increase, but it remains unclear how children perform when they participate in sports games, which are characterized by complex tasks with varying intensity profiles. The present study investigates children's competencies for rating perceived effort and producing predetermined intensities during soccer training. Twenty-five children aged 11-13 years performed two similar training sessions. In the first session, the children trained without intensity instructions and continuously rated their effort. In the second session, the children were instructed to produce predefined intensities. Before the first training session, executive functions were assessed by cognitive performance tests and a self-report measure. RPE correlated significantly with heart rate measures (R2 = 0.27, p < 0.001). As confirmed by factor analysis, individual differences in these correlations were related to the outcomes of the cognitive tests and the self-report measure. RPE in training session 2 differed from RPE in training session 1 (d = 1.22, p < 0.001), although the heart rate data did not differ significantly between training sessions (d = -0.19, p = 0.780). Thirteen-year-old children performed significantly better than eleven-year-old children (d = 1.69, p = 0.027). The results suggest that children are able to rate perceived effort during soccer training and that this ability is related to executive functions. Conversely, children may not be able to alter their intensities in response to instructions, although their ratings suggest that they have largely succeeded in doing so.

Assessing the Use of Heart-Rate Monitoring for Competitive Swimmers

PURPOSE

Quantifying training intensity provides a comprehensive understanding of the training stimulus. Recent technological advances may have improved the feasibility of using heart-rate (HR) monitoring in swimming. However, the implementation of HR monitoring is yet to be assessed longitudinally in the daily training environment of swimmers. This study aimed to assess the implementation of HR by comparing the training-intensity distribution from an external measure, planned volume at set intensities (PVSI), with the internal training-intensity distribution measured using time in HR zones.

METHODS

Using a longitudinal observational design, 10 competitive swimmers (8 male and 2 female, age: 22.0 [2.3] y, Fédération Internationale de Natation point score: 842.9 [58.5], mean [SD]) were monitored daily for 6 months. Each session, HR data, and coached-planned and athlete-reported session rating of perceived exertion (Modified Category Ratio 10 scale) were recorded. Based on previously determined training zones from an incremental step test, PVSI was calculated using the planned distance and planned intensity of each swim bout. Training-intensity distributions were analyzed using a linear mixed model (lme4).

RESULTS

The model revealed a small to moderate relationship between PVSI and time in HR zone, based on the Nakagawa R-squared value (range .14-.42).

CONCLUSIONS

Training-intensity distribution differed between the internal measure (ie, HR) and the external measure of intensity (ie, PVSI). This demonstrates that internal and planned external measures of intensity cannot be used interchangeably to monitor training. Further research should explore how to best integrate these measures to better understand training in swimming.

Monitoring Training Load and Wellness of Female Footballers Transitioning Between Club and National Teams

ABSTRACT

Brown, GA, Massard, T, Wignell, T, McCall, A, and Duffield, R. Monitoring training load and wellness of female footballers transitioning between club and national teams. J Strength Cond Res 37(11): 2235-2240, 2023-This study described the change in training and match internal loads, plus perceptual wellness during the transition between club and national teams (NTs) for female international footballers (soccer). Session count, session rating of perceived exertion (s-RPE), and perceptual wellness data were collected from 42 players from 1 NT between 2019 and 2021 for 7 NT tournaments. Data were collated into 7-day (1 week) microcycles to compare the 2 weeks before the first week of NT (transition in: NT-2, NT-1, NT1); and separately from the final NT week to the next 2 weeks in clubs (transition out: NTFinal, NT+1, NT+2). Data were analyzed using linear mixed-models, with session count, s-RPE or wellness as the outcome variable, week as the fixed effect, player name, and tournament as random effects. Tukey's adjusted post-hoc comparisons and Cohen's d effect sizes (ES) were compared between weeks. Significance level was set at p < 0.05. During the transition into NT, training and total session counts increased (p < 0.0001, ES > 0.67), training s-RPE increased (p = 0.012, ES = 0.35), whereas match count and s-RPE decreased (p < 0.05, ES < -0.34). During the transition out of NT, there were decreases in training session count (p < 0.05, ES < -0.37), match count, and total session count (p < 0.0001, ES < -0.86), and match and total s-RPE (p < 0.0001, ES < -0.63). Perceived wellness was not significantly different throughout (p > 0.05, ES = -0.34 to 0.35). Thus, training and match exposures differ between club and NTs, demonstrating these unique transitional periods require simple and effective load monitoring to inform training and recovery prescription when changing between club and NTs.

Short-Term Effects of Lower-Extremity Heavy Resistance versus High-Impact Plyometric Training on Neuromuscular Functional Performance of Professional Soccer Players

BACKGROUND

To compare the effects of short-term 8 week heavy-resistance or plyometric training protocols (HRT or PLY) incorporated into regular soccer practice on measures of neuromuscular functional performance in professional soccer players, a single-blind randomized controlled trial was conducted.

METHODS

Forty-seven participants aged 22.3 ± 3.52 years were assigned to three groups: HRT (n = 15), PLY (n = 15), and control (CON; n = 17). The HRT group performed 3 sets and 10 repetitions twice a week using 80% of their baseline 1-RM (weeks 1-3), followed by 8 repetitions at 85% 1-RM (weeks 4-6), and 6 repetitions at 90% 1-RM (weeks 7-8) of 6 lower-body strength exercises with a 1 min rest period between sets. The PLY protocol involved a preparatory phase (weeks 1-2), followed by two 3-week progressive periods (weeks 3-5 and weeks 6-8). The plyometric sessions consisted of four jump exercises/drills with progressively increasing number of sets and total number of foot contacts. The rest intervals between repetitions and sets were 15 and 90 s, respectively. Outcome measures included tests assessing 10 and 30 m speed (t10m and t30m), one-repetition maximum half-back squat (1-RM squat), isokinetic peak torques for the quadriceps and hamstring muscles (Qcon and Hcon), countermovement jump (CMJ), and squat jump (SJ).

RESULTS

Two-way ANOVA detected main effects of time and group×time interactions for all examined variables, except t30m, 1-RM, and relative 1-RM. Post hoc analyses revealed significant increases in the HRT group (t10m: 6.3%, t30m: 7.1%; absolute 1-RM: 29.6%; relative 1-RM: 30.3%, Qcon: 24.5%; Hcon: 14.4%; CMJ: 5.9%; SJ: 7.2%, all p < 0.001) and the PLY group (t10m: 3.1%; t30m: 4.1%; absolute 1-RM:19.1%; relative 1-RM: 20.3%; Qcon: 12.6%; Hcon: 8.7%; CMJ: 3.3%; SJ: 3.5%, all p < 0.001). HRT was superior compared to PLY in relative 1-RM, Qcon and Hcon (all p < 0.001). In addition, we found knee muscular strength imbalance in 70.5% of participants from the total sample (H/Q ratio < 60%). The HRT and PLY protocols resulted in improved neuromuscular functional performance compared to the regular soccer regime.

CONCLUSIONS

This study showed that during the pre-competitive season, additional HRT and PLY drills/exercises as a substitute for standard soccer training as part of a regular 90 min practice twice a week for 8 weeks, can produce acute physical performance-enhancing effects in professional soccer players.

Fatigue-induced Landing Alterations in ACL Reconstructed Athletes after Return-to-Sport

At the time of return-to-sport, anterior cruciate ligament reconstructed athletes still show altered neuromechanics in their injured leg during single leg hopping tasks. Part of these alterations can be magnified when these athletes are fatigued. So far, little is known whether fatigue-induced landing alterations persist after return-to-sport. Therefore, the aim of this study was to evaluate whether these alterations persist in the six months following return-to-sport. Sixteen anterior cruciate ligament reconstructed athletes performed five unilateral hop tasks before and after a fatigue protocol. The hop tasks were executed at three different time points (return-to-sport, 3 and 6 months post-return-to-sport). A 2-by-3 repeated measures ANOVA was performed to evaluate whether fatigue-induced landing alterations persisted 3 and 6 months following return-to-sport. At 6 months following return-to-sport, fatigue still induces a reduction in hamstring medialis activation and an increase in the knee abduction moment during a vertical hop with 90-degree inward rotation. Most fatigue-induced landing alterations present at the time of return-to-sport normalize after resumption of sports activities. However, a larger knee abduction moment in the injured leg after resumption of sports activities can still be observed.

Contemporary practices of physical trainers in professional soccer: A qualitative study

Introduction

Physical trainers (PTs) are integral for managing load, reducing injury and optimizing performance in professional soccer. However, little is known about how this practitioners operate in the applied setting and how some of the nuances experienced influence practice.

Methods

This study explored the contemporary practices of PTs in professional soccer. Semi-structured interviews were undertaken with eight PTs from different professional teams in European and South American leagues. Interview questions were designed to extract information on the evaluation of physical abilities, monitoring and control of training and injury prevention. Subsequently, the interviews were video-recorded, transcribed, translated and analyzed using a content analysis approach.

Results

The results suggest that the evaluation of physical capacities is carried out by PTs at the beginning of the preseason. It also appears that it is attempted that this process of regular testing is applied during the competitive period, with most participants conducting partial physiological and physical evaluations at different stages throughout the competitive season. In relation to the monitoring and control of training, subjective feedback scales are used to estimate the internal load, and the use of GPS devices is common to quantify external loads. Injury prevention programmes were implemented by all participants and were generally in a multi-component format focused on preventing or optimizing physical capabilities.

Discussion

These insights can be used as a scientific reference point to inform applied practice in professional soccer, especially for practitioners that are inexperienced and aspiring to enhance how they operate in the field. Future investigations should explore the practices of PTs in detail and across a wider network in order to gain deeper and comprehensive insights into the applied soccer environment.

Monitoring Muscle Oxygen Asymmetry as a Strategy to Prevent Injuries in Footballers

Purpose: It has been hypothesized that sports injury risk is explained by muscle metabolism. The objective was to evaluate the muscle oxygen saturation slopes (ΔSmO2 slopes) and muscle oxygenation asymmetry (MO2Asy) at rest and to study their associations with injuries during the pre-season. Methods: A total of 16 male and 10 female footballers participated in this study. Injuries were diagnosed and classified by level of severity during the pre-season. The workload was also evaluated using the rate of perceived exertion × training time, from which the accumulated loads. The SmO2 was measured at rest in the gastrocnemius muscle using the arterial occlusion method in the dominant and non-dominant legs. The repeated measures ANOVA, relative risk, and binary logistic regression were applied to assess the probability of injury with SmO2 and workload. Results: Higher MO2Asy and ΔSmO2 Slope 2 were found among footballer who suffered high-severity injuries and those who presented no injuries. In addition, an MO2Asy greater than 15% and an increase in accumulated load were variables that explained a greater probability of injury. Conclusion: This study presents the new concept of muscle oxygenation asymmetry in sports science and its possible application in injury prevention through the measurement of SmO2 at rest.

Relationships Between Internal and External Load Measures and Fitness Level Changes in Professional Soccer Players

Purpose: Understanding the dose-response relationship between internal and external training load with changes in aerobic fitness and intermittent running capacity, during different periods of the season, may help in optimizing training process. The aim of the present study was to investigate the dose-response relationships between load measures and changes in aerobic fitness and intermittent running capacity among a large cohort of professional soccer players. Methods: Training load, aerobic fitness and intermittent running capacity of 52 male adult professional players from 3 elite teams were monitored across an entire season and analyzed employing linear mixed models, with a significance level set at p≤0.05. Results: Relationships between load measures (training and match duration, sRPE-TL, total distance, high and very high-speed running distances) and changes in physical qualities were stronger during the preparation period (PREP) for both aerobic fitness (d= 0.48 to 0.76, p<0.031) and intermittent running capacity (d= 0.46 to 1.89, p<0.046). The magnitude of the relationships reduced during the first competitive period (d= 0.43 to 0.56) and the relationships became trivial in the second competitive period (d= 0.06 to 0.41, p= 0.063 to 0.846). Conclusion: The moderate to large relationships found between all measures of load and changes in physical capacities suggest that training prescription during the PREP was effective in improving players' fitness. During the competitive phase small changes in aerobic and intermittent running capacities were found, highlighting that coaching staff pursue different aims during the competitive period, such as technical and tactical training and recovery.       .

Toward a New Conceptual Approach to "Intensity" in Soccer Player's Monitoring: A Narrative Review

ABSTRACT

Pillitteri, G, Clemente, FM, Petrucci, M, Rossi, A, Bellafiore, M, Bianco, A, Palma, A, and Battaglia, G. Toward a new conceptual approach to "intensity" in soccer player's monitoring: A narrative review. J Strength Cond Res 37(9): 1896-1911, 2023-In the last decade, monitoring physiological and match-related demands in soccer has become an increasingly common practice in sports sciences. One of the great challenges during monitoring process is the identification of key indicators that permit to generalize evidence and sustain decision-making process during training prescription. Actually, one of the major debates in the scientific community and among practitioners is the identification of the "intensity" concept. Defining a given training session or exercise based on "intensity" is difficult due to the fact that a huge amount of indicators are available (related both to the performed activities and to the athletes' psychophysiological responses). These indicators can lead to specific outcomes with different interpretations. The current narrative review aims to discuss the different measures approaches used in soccer to describe the intensity for both internal and external demands. In addition, a second purpose of this review is to propose general recommendations for combining intensity indicators with the aim of defining an overall intensity score of a training session or drill.

Association between physical demands, skin temperature and wellbeing status in elite football players

The demanding nature of elite football requires players to be closely monitored to ensure optimal performance and minimize injury risk. This study aimed to evaluate the relationship between physical demands, skin temperature, and well-being status in 30 elite football players over a 12-week competitive period. Thermography assessments, weekly Well-being questionnaires, and daily training and match load recordings were used to gather data. Results indicated that along the microcycles there was a decrease in high-intensity accelerations and decelerations distance completed, while maintaining other high-intensity actions. Furthermore, it was found that high-intensity movements contribute to the generation of thermal asymmetries in the thighs; the adductor thermal asymmetry showed a positive relationship with stress and muscle soreness, the knee thermal asymmetry had a positive relationship with fatigue and a negative relationship with rest and quality of rest, and finally the hamstrings muscles exhibited significant differences between the thermal asymmetry groups, with the high asymmetry completing less high intensity actions than the low asymmetry group. In conclusion, this study highlights the interconnections between physical demands, skin temperature, and well-being in elite football players and provides valuable insights for coaches and trainers in their efforts to optimize performance and health.

A meta-analysis of the criterion-related validity of Session-RPE scales in adolescent athletes

BACKGROUND

The objective of this study was to establish the criterion-related validity of the session-rating of perceived exertion (s-RPE) method in adolescent athletes.

METHODS

According to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA 2020) guidelines, a meta-analysis (PROSPERO ID: CRD42022373126) was performed using Stata 15.1 software. Eight databases using the following terms: ('s-RPE' OR 'Rating Perceived Exertion session' OR 'RPE session' OR 'RPE' OR 'Rate of Perceived Exertion' OR 'Rated of Perceived Exertion') AND ('Adolescen*' OR 'Youth*' OR 'Teen*') AND ('validity' OR 'correlation' OR 'concurrent validity') were searched up to 2022. Articles meeting the inclusion criteria were screened and adopted the "Methodological Index for Non-Randomized Studies (MINORS)" to evaluate the risk of bias.

RESULTS

An initial 1798 studies using the s-RPE method were identified and finally, a total of 16 studies were included for further analysis. The relationship between assessment instruments CR-10 or CR-100 modified methods of s-RPE and the heart rate measures of these selected studies were calculated using correlation coefficient (r values) and Fisher's z-score. A strong to very strong correlation between s-RPE and HR was observed (overall: r = 0.74; CR-10: r = 0.69; CR-100: r = 0.80). CR-100 scale (Fisher's z = 1.09) was shown to have a higher criterion validity than that of the CR-10 scale (Fisher's z = 0.85).

CONCLUSION

Preliminary findings showed that s-RPE using either CR-10 or CR-100 scales can be used "stand-alone" for monitoring internal training load for children and adolescent athletes. Future studies should focus on whether CR-100 could better perform than CR-10 for junior and children athletes in different age groups and sports as well as the causes leading to potential scoring biases.

The relationship between wellness and training and match load in professional male soccer players

The aims of this study were to: (i) analyse the within-microcycle variations in professional soccer players; (ii) analyse the relationships between wellness and training and match load demands; (iii) analyse the relationships between match-day (MD) demands and wellness during the following day (MD+1); and (iv) analyse the relationships between MD and wellness during the day before match-play (MD-1). Thirteen professional soccer players (age: 24.85±3.13 years) were monitored daily over 16-weeks for wellness and training and match-play intensity. The daily wellness measures included fatigue, quality of sleep, muscle soreness, mood and stress using a 1-5 scale. Internal intensity was subjectively measured daily using the rating of perceived exertion (RPE) and the multiplication of RPE by session duration (s-RPE). While external intensity was quantified utilising high-speed running, sprinting, and acceleration and deceleration metrics. Data was analysed from each training session before (i.e., MD-5) or after the match (i.e., MD+1). Repeated measures ANOVA or Friedman ANOVA was used to analyse the aims (i) where Spearman correlation was applied to analyse the relationships between the aims (ii) and (iii) between sleep quality and training intensity. The main results for aim (i) showed that MD+1 presented the lowest values for wellness variables (p < 0.05). While MD-1 presented the lowest internal and external load values (for all variables), with MD presenting the highest values (p < 0.05). Regarding aim (ii), the main result showed significant large negative correlations between fatigue and s-RPE (r = -0.593; p = 0.033). Considering aim (iii), significant small to very large negative correlations were found for sleep quality, fatigue and muscle soreness with all internal and external variables (p < 0.05). Lastly, the main results for aim (iv) showed large negative correlations for fatigue and session duration; fatigue and s-RPE; muscle soreness and session duration; muscle soreness and s-RPE; and muscle soreness and decelerations (p < 0.05, for all). The main conclusions were that MD had an influence on wellness and internal and external training intensity, notably MD-1 and MD+1 were most affected. In this regard, a tendency of higher internal and external intensity on MD was associated with lower wellness measures of sleep quality, muscle soreness and fatigue on MD+1.

Noncontact Injury Distribution and Relationship With Preseason Training Load and Nonmodifiable Risk Factors in Rugby Union Players Across Multiple Seasons

ABSTRACT

Evans, SL, Whittaker, G, Elphinstone Davis, E, Jones, ES, Hardy, J, and Owen, JA. Noncontact injury distribution and relationship with preseason training load and non-modifiable risk factors in Rugby Union players across multiple seasons. J Strength Cond Res 37(7): 1456-1462, 2023-This study examined the distribution of noncontact injury during phases of the competitive season and the association between preseason training load (TL) and nonmodifiable risk factors on injury risk during these phases. Injury data were recorded from 1 senior academy team over 3 seasons (2017-2020) and analyzed across early-season, midseason, and late-season phases. A generalized estimating equation was used to model risk factors with noncontact injury for selected phases. The highest noncontact injury incidence occurred in the late-season phase (22.2 per 1,000 hours) compared with early (13.7 per 1,000 hours, p < 0.001) and midseason phases (15.5 per 1,000 hours, p = 0.001). Low preseason TL (8,949-12,589 arbitrary units; odds ratio [OR], 95% confidence interval [CI] = 4.7, 1.0-21.6; p = 0.04) and low preseason TL combined with high early-season TL and injury in the early-season phase (OR, 95% CI = 6.5, 1.1-35.5; p = 0.03) were associated with greater midseason noncontact injury risk. In addition, low preseason TL combined with previous injury was associated with increased risk of noncontact injury risk in the late season (OR, 95% CI = 12.2, 0.9-15.6, p = 0.05). Our results suggest players are at a greater injury risk during the late-season phase, with low preseason cumulative loads combined with a history of previous injury associated with increased in-season injury risk. Strength and conditioning coaches should therefore monitor cumulative preseason TL alongside screening for previous injury history to identify athletes at greater risk of noncontact injury risk during the competitive season.

Regional phase angle, not whole-body, is augmented in response to pre-season in professional soccer players

The objective of this article was to assess the effects of six-week pre-season training on whole-body and regional bioelectrical impedance analysis (BIA)-derived parameters, body composition, power, and aerobic performance in professional soccer players. Ten professional soccer athletes participated in the present study. Whole-body and regional hamstrings BIA-derived parameters [resistance, reactance, impedance, phase angle (PhA)], body composition, total body water (TBW), intracellular (ICW), and extracellular (ECW) were measured before, at mid-point, and after sixth week of the pre-season. Power (countermovement jump and squat jump) and aerobic capacity (Yo-Yo test) were measured before and after pre-season. There was a significant increase in the regional PhA (+13.9%) but not in the whole-body. There was a reduction in fat mass (-4.1%), an increase in fat-free mass (+1.7%), TBW (+8.3%), ICW (+8.8%), and ECW (+7.6%), as well as an increase in jump height (+11.0%) and distance covered in the Yo-Yo test (+34.7%). From our results, it is possible to suggest that pre-season training can induce an increase in hamstring PhA as well as body recomposition and improvement of physical fitness in professional soccer players.

The effects of different small-sided games configurations on heart rate, rating of perceived exertion, and running demands in professional soccer players

We examined the effects of different small-sided games (SSG) configurations on heart rate (HR), rating of perceived exertion (RPE), and running demands in soccer players. Twelve male soccer players (U18) participated in this randomized cross-over study. Players performed three SSG in different "fixed" and "dynamic" pitch sizes (3v3 in large (SSGL) and small (SSGS) fixed area; or 3v3 in dynamic dimensions [SSGD]), with 4x4 minutes interspersed by 2 minutes of rest. HR measures (maximum [HRmax], average [HRavg], and percentage of maximum [%HRmax]), RPE, and running demands were collected across the SGG sessions. The following running activities were recorded: total distance covered (TD), distance covered (DC) at 6-12 km·h-1, ≥ 12-18 km·h-1, and >18 km·h-1, peak running speed, acceleration (ACC) and deceleration (DEC) at 1-2 m·s-2 and 2-3 m·s-2, player load, and high metabolic load distance (HMLD). SSGL displayed higher HRavg, %HRmax, and RPE values than SSGS (p < 0.05). SSGL resulted in higher TD, DC at 6-12 km·h-1, ≥ 12-18 km·h-1, > 18 km·h-1, and higher peak speed than SSGS and SSGD (p < 0.05). Moreover, SSGD presented higher TD and DC at 6-12 km·h-1 and ≥ 12-18 km·h-1 than SSGS (p < 0.05). In contrast, SSGD and SSGS showed higher number of ACC and DEC at 1-2 m·s-2 than SSGL (p < 0.05). In conclusion, the pitch size and playing area of the SSG can be manipulated to promote desired physiological and physical demands in young soccer players.HighlightsWe examined how fixed (small and large) or variable (dynamic) pitch sizes affected the psychophysiological and running demands of young soccer players during small-sided games.Small-sided games with larger pitch sizes and areas per player elicited greater psychophysiological and running demands than small areas.The pitch size designed in the current study does not appear to affect the number of acceleration and deceleration (> 2 m·s-2).Varying the pitch size during the small-sided games (i.e. dynamic condition) could be an interesting constraint to be considered by soccer coaches in order to enhance task variability.

Time Course of Performance Indexes, Oxidative Stress, Inflammation, and Muscle Damage Markers after a Female Futsal Match

BACKGROUND

Our aims were to investigate the time-course effects of a futsal match on performance, oxidative stress, and muscle damage markers, as well as inflammatory and antioxidant responses during a 6-day post-match period.

METHODS

Thirty-four female high-level futsal players were assessed on several oxidative stress, inflammation, subjective muscle soreness, subjective rate perceived exertion, and performance tests before a futsal match, immediately after, and 24 h to 144 h after.

RESULTS

Counter movement jump, 20 m, and 10 m sprints performance significantly decreased immediately after the match (p < 0.05) and returned to baseline 72 h post-match (p > 0.05). Delayed onset muscle soreness peaked 24 h post-match and rate perceived exertion peaked post-match (p < 0.05) and returned to baseline 96 h post-match (p > 0.05). Inflammatory biomarkers peaked at 24 h (p < 0.05) and remained significantly elevated for 72 h after the match (p < 0.05). Muscle damage biomarkers peaked at 24 h (p < 0.05) and remained significantly (p < 0.05) elevated for at least 72 h after the match. Oxidative stress markers peaked at 24 h-48 h (p < 0.05) and returned to baseline 120 h post-match (p > 0.05). In respect to antioxidant responses, these peaked at 24 h-48 h post-match (p < 0.05) and returned to baseline 120 h after the match (p > 0.05).

CONCLUSIONS

A single futsal match induces short/mid-term changes in performance, inflammation, oxidative stress, and muscle damage markers for about 72 h-96 h post-match.

Match running performance profiles of amputee football players at the national level

Even though running performance and positional profiles in football are well described, amputee football (AF) has different characteristics of the movement, pitch dimensions, and time played. There is a gap in the scientific literature about positional profiles based on running performance in AF. This study aimed to investigate the differences between positions, the influence of the amputation level or defect of the lower limb (LD), the differences in running performance between halves, and the relationship with the final match result. Thirteen AF National Team players were monitored by Global Navigation Satellite System (GNSS), tracking 24 official international matches for 17 months. Values of top speed, peak acceleration, peak deceleration, average distance per minute, sprint mean speed, GPS load per minute, inertial load per minute (Gs load/min), number of sprints per minute, and a number of impacts per minute were analyzed for defenders (DEF), midfielders (MID) and forwards (FOR). Additional factors analyzed were amputation level (below the knee, low amputation-LA or over the knee, high amputation-HA or defect of the lower limb-LD) and the match's final result. Midfielders had significantly higher running performance parameters compared to other positions (greater top speed than DEF (+ 0.3 m/s; p < 0.001) and FOR (+ 0.2 m/s; p = 0.045), greater peak acceleration and deceleration than DEF (+ 0.5 m/s² for both measures; p < 0.001) and FOR (+ 0.4 and + 0.3 m/s²; p < 0.001 and p = 0.036, respectively), greater GPS load/minute than DEF (+ 0.2 load/min; p = 0.001) and FOR (+ 0.3 load/min; p < 0.001), greater Gs load per minute than DEF (+ 2.7 load/min; p < 0.001) and FOR (+ 1.8 load/min; p < 0.001), greater number of impacts per minute than DEF (+ 0.2 n/min; p < 0.001) and FOR (+ 0.2 n/min; p < 0.001). Players with LD had significantly higher running performance than those with LA or HA. In the match's second half, a decrease in running performance was registered. The trend of running more when losing could be observed-AF players had higher running parameters in lost matches, but the differences were not statistically significant. Further research complied with contextual game analysis is needed to assess the running performance of AF players deeply.

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.

Blood Flow Restriction Is Not Useful as Soccer Competition Recovery in Youth Male National-Level Soccer Players: A Crossover Randomised Controlled Trial

In soccer, blood flow restriction (BFR) is used to optimise between-match recovery. However, the benefits are unclear. This study evaluated the effects of BFR as a recovery strategy after a competition on countermovement jump (CMJ) height, rating of perceived exertion (RPE) and the wellness of soccer players. Forty national-level soccer players were allocated into two conditions: BFR (an active recovery session wearing a BFR device, 24 h after a competition) or NoBFR (the same recovery without BFR). CMJ, RPE and wellness were evaluated the day (CMJ and RPE) or the morning (wellness) before the competition; just after the competition (CMJ and RPE); and 24, 48 (wellness) and 72 h later. After 4 weeks, the players changed conditions. All players showed impaired CMJ (p = 0.013), RPE (p < 0.001) and wellness (p < 0.001) after the match compared with the baseline. The CMJ returned to the baseline 24 h later and wellness returned 48 h later. Only in the BFR condition did the RPE remain impaired 24 h after the match, which was also the moment after finishing the BFR recovery session (p < 0.001). BFR during active recovery does not provide any additional benefits compared with traditional exercise modalities to recover CMJ, RPE and wellness in youth national-level soccer players. BFR could even induce an immediate higher RPE.

Training Load Quantification in Women's Elite Football: A Season-Long Prospective Cohort Study

The aim of this study was to investigate (1) if there are differences in training load and intensity between the different training days within a microcycle and (2) if training load and intensity within the different training days are stable over the course of a season. Data were collected over a full season from a team in the women's premier division in Norway. External load (total distance, high-speed-running distance, sprint distance, and the combined number of accelerations and decelerations [ACCDEC]) was assessed using a 10-Hz GPS system with a built-in accelerometer. Internal load was assessed through session rating of perceived exertion, which was multiplied with session duration (session rating of perceived exertion-load). Training days were classified in relation to their proximity to the upcoming match day (MD): MD - 4, MD - 3, MD - 2, and MD - 1. Contents on these days were standardized according to a weekly periodization model followed by the coaching staff. Differences between training days were analyzed using a linear mixed-effects model. All training days were significantly different from each other across multiple variables. ACCDEC values were highest on MD - 4 (147.5 [13.0] ACCDEC count), and all distance variables were highest on MD - 3. All measures of training load were significantly reduced from MD - 3 to MD - 2 (effect size [ES] = 1.0-4.1) and from MD - 2 to MD - 1 (ES = 1.6-4.3). A significant negative effect across the season was observed for session rating of perceived exertion-load and ACCDEC (ES = 0.8-2.1). These results provide evidence that elite female football teams can be successful in differentiating training load between training days when implementing a weekly periodization approach.

External and internal training load comparison between sided-game drills in professional soccer

This study aims to quantify and compare the external and internal training load demands of sided-game drills in professional team players during the competitive season. Twenty-four male professional soccer players of the same club were enrolled in this study. Drills were categorized as large-sided games (LSG): 10vs10 (84 × 60 m or 72 × 60 m), Hexagon possession 9vs9 + 3 (36 × 48 m), Possession gate 8vs8 + 2 (36 × 44 m), Possession 7vs7 + 3 (30 × 32 m) or as Small-sided games (SSG): 6vs6 (48 × 42 m), and Possession 6vs4 (30 × 60 m). A total of 7 drills and 279 individual data points were included in this analysis. Distance covered, high-speed running (HSR), and sprinting distance were all calculated in meters per minute (m.min−1) while total accelerations (&gt;3 m.s−2) and total decelerations (− &lt; 3 m.s−2) were calculated in number of actions per minute (n.min−1). All external load was measured with global navigation satellite systems (GNSS) STATSports Apex units. Players’ internal load was quantified using their rating of perceived exertion (RPE). We found that distance covered (p &lt; 0.01, large), HSR (p &lt; 0.01, large), and sprinting distance (p &lt; 0.01, large) changed between drills (e.g., greater in LSG formats), acceleration (p &lt; 0.01, large) and deceleration (p &lt; 0.01, large) demands were greater in smaller formats (e.g., SSG 6vs6, and Possession 6vs4), while RPE was lower in the Possession gate 8vs8 + 2 format (p &lt; 0.01, large). This study found that sided-games can replicate and sometimes exceed some match-specific intensity parameters, however, HSR and sprinting were consistently lower compared to official matches.

New Zealand Youth Rugby Sevens: A Comparative Match Demands Study

Rugby sevens has established itself on the world stage since its inclusion in the 2016 Olympics. Participation among New Zealand (NZ) youth has surged. Sevens games have specific high demands, but little is known about these competitive demands in regards to youth. Two NZ male youth squads (U15, n = 13; U19, n = 14) were monitored during a national sevens tournament. Microsensor technology captured heart rate (HR) and kinematic performance. The rating of perceived exertion (RPE) was collected for U15 matches only. U19 and U15 players ran 108 ± 11 and 116 ± 13 m·min^-1 at an average speed (V_AVG) of 6.5 ± 0.6 and 6.9 ± 0.8 km·h^-1. Peak speeds (V_PEAK) reached 33.7 km·h^-1, and high-intensity running distance (HIRD) averaged 252 ± 102 m. U15 (44.3 ± 9.2 game^-1) and U19 (39.4 ± 6.1 game^-1) showed different sprint rates. U15 covered more moderate-velocity distance (20-80% V_MAX) and less low-velocity distance (<20% V_MAX). RPE was 13 ± 1 (U15). An average HR of 90.0 ± 3.9% HR_MAX was recorded. Upwards of 57% of game time was played at >95% HR_MAX. Youth sevens competition is specifically demanding. U15 can experience greater loads than older peers in rugby. Coaches can use this information to optimize players' physical development.

Subjective Measures of Workload and Sleep in Australian Army Recruits; Potential Utility as Monitoring Tools

INTRODUCTION

Subjective measures may offer practitioners a relatively simple method to monitor recruit responses to basic military training (BMT). Yet, a lack of agreement between subjective and objective measures may presents a problem to practitioners wishing to implement subjective monitoring strategies. This study therefore aims to examine associations between subjective and objective measures of workload and sleep in Australian Army recruits.

MATERIALS AND METHODS

Thirty recruits provided daily rating of perceived exertion (RPE) and differential RPE (d-RPE) for breathlessness and leg muscle exertion each evening. Daily internal workloads determined via heart rate monitors were expressed as Edwards training impulse (TRIMP) and average heart rate. External workloads were determined via global positioning system (PlayerLoadTM) and activity monitors (step count). Subjective sleep quality and duration was monitored in 29 different recruits via a customized questionnaire. Activity monitors assessed objective sleep measures. Linear mixed-models assessed associations between objective and subjective measures. Akaike Information Criterion assessed if the inclusion of d-RPE measures resulted in a more parsimonious model. Mean bias, typical error of the estimate (TEE) and within-subject repeated measures correlations examined agreement between subjective and objective sleep duration.

RESULTS

Conditional R2 for associations between objective and subjective workloads ranged from 0.18 to 0.78, P < 0.01, with strong associations between subjective measures of workload and TRIMP (0.65-0.78), average heart rate (0.57-0.73), and PlayerLoadTM (0.54-0.68). Including d-RPE lowered Akaike Information Criterion. The slope estimate between objective and subjective measures of sleep quality was not significant. A trivial relationship (r = 0.12; CI -0.03, 0.27) was observed between objective and subjective sleep duration with subjective measures overestimating (mean bias 25 min) sleep duration (TEE 41 min).

CONCLUSIONS

Daily RPE offers a proxy measure of internal workload in Australian Army recruits; however, the current subjective sleep questionnaire should not be considered a proxy measure of objective sleep measures.

Does External Load Reflect Acute Neuromuscular Fatigue and Rating of Perceived Exertion in Elite Young Soccer Players?

ABSTRACT

Martínez-Serrano, A, Freitas, TT, Franquesa, X, Enrich, E, Mallol, M, and Alcaraz, PE. Does external load reflect acute neuromuscular fatigue and rating of perceived exertion in elite young soccer players? J Strength Cond Res 37(3): e1-e7, 2023-This study aimed to analyze the acute and residual effects of increased high-speed running (HSR) demands during an in-season training microcycle in young elite soccer players on localized neuromuscular fatigue (NMF) of the knee extensors (KE), posterior chain muscles, and rating of perceived exertion (RPE). Thirty-four elite young soccer players (age = 17.1 ± 0.8 years) were assessed in 2 consecutive days at different time points (baseline, POST-activation gym-based session, POST-small-sided game [SSG], POST-training 1 [TR1], POST-6H, POST-24H, POST-preventive gym-based session, and POST-training 2 [TR2]). Neuromuscular fatigue of the KE and posterior chain muscles was measured with a maximum voluntary isometric contraction (MVIC). External (total distance, number of accelerations or decelerations, and HSR distance) and internal (RPE) load was assessed during the SSG, TR1, and TR2 sessions. Players were divided through a median split, into "HIGH" or "LOW" group according to the training demands. The alpha level was set at p ≤ 0.05. A 2-way mixed effects model ANOVA showed a significant decreased in 90:20 MVIC after TR1 in the "HIGH" HSR group ( p = 0.037; effect size [ES] = 0.45). No significant differences in RPE were found after TR1 ( p = 0.637; ES = 0.58) and TR2 ( p = 0.109; ES = 0.62) when comparing the "HIGH" HSR group with the "LOW" HSR group. Assessing player's force production capabilities can be an effective strategy to detect NMF when HSR demands are acutely increased. Special caution should be taken when prescribing the training load of the training session based solely on RPE, as NMF might be present.

Scheduling Concurrent Training 48 versus 72 h after Simulated Match Play: Effects on Neuromuscular Function and Fatigue

INTRODUCTION

Scheduling concurrent training (CT) during the in-season microcycle in field-based team sport is driven by prematch and postmatch recovery. This study examined the neuromuscular function, fatigue, and soreness responses to CT administered 48 h (match day (MD) + 2) versus 72 h (MD + 3) after match.

METHODS

Ten male recreational-level team sport athletes were monitored daily during two 5-d microcycles, which began with a simulated match (Soccer-specific Aerobic Field Test (SAFT90)) and CT performed either 48 or 72 h after match. Maximal voluntary force, quadriceps maximum EMG, voluntary activation, muscle contractile function (evoked twitch responses), muscle soreness, and fatigue were assessed immediately before and after the SAFT90, and every 24 up to 96 h after match. Outcome measures were also assessed immediately after CT. The CT consisted of an intermittent sprint protocol and a lower limb resistance training session separated by 1 h.

RESULTS

Immediately after the SAFT90 in both conditions, maximal voluntary force was below baseline (mean change (Δ), -14.6% ± 10.0%; P = 0.03), recovering 48 h post. Quadriceps contractile function (Δ, -31.5% ± 11.4%; P = 0.003) and voluntary activation (Δ, -8.9 ± 6.2%; P = 0.003) were also hampered after the SAFT90, recovering 24 h post in both conditions. In addition, the SAFT90 elicited elevated levels of fatigue and muscle soreness that recovered 24 h after the SAFT90 before increasing at 72 and 96 h post in the MD + 2 and MD + 3 conditions, respectively.

CONCLUSIONS

Recovery of fatigue was only observed at the end of the microcycle when CT was prescribed on MD + 2. Therefore, CT scheduled early (MD + 2) in the microcycle might avoid compromising forthcoming match preparation.

Pharmacological Blockade of Muscle Afferents and Perception of Effort: A Systematic Review with Meta-analysis

BACKGROUND

The perception of effort provides information on task difficulty and influences physical exercise regulation and human behavior. This perception differs from other-exercise related perceptions such as pain. There is no consensus on the role of group III/IV muscle afferents as a signal processed by the brain to generate the perception of effort.

OBJECTIVE

The aim of this meta-analysis was to investigate the effect of pharmacologically blocking muscle afferents on the perception of effort.

METHODS

Six databases were searched to identify studies measuring the ratings of perceived effort during physical exercise, with and without pharmacological blockade of muscle afferents. Articles were coded based on the operational measurement used to distinguish studies in which perception of effort was assessed specifically (effort dissociated) or as a composite experience including other exercise-related perceptions (effort not dissociated). Articles that did not provide enough information for coding were assigned to the unclear group.

RESULTS

The effort dissociated group (n = 6) demonstrated a slight increase in ratings of perceived effort with reduced muscle afferent feedback (standard mean change raw, 0.39; 95% confidence interval 0.13-0.64). The group effort not dissociated (n = 2) did not reveal conclusive results (standard mean change raw, - 0.29; 95% confidence interval - 2.39 to 1.8). The group unclear (n = 8) revealed a slight ratings of perceived effort decrease with reduced muscle afferent feedback (standard mean change raw, - 0.27; 95% confidence interval - 0.50 to - 0.04).

CONCLUSIONS

The heterogeneity in results between groups reveals that the inclusion of perceptions other than effort in its rating influences the ratings of perceived effort reported by the participants. The absence of decreased ratings of perceived effort in the effort dissociated group suggests that muscle afferent feedback is not a sensory signal for the perception of effort.

Evaluation of Athlete Monitoring Tools across 10 Weeks of Elite Youth Basketball Training: An Explorative Study

The growth of sport science technology is enabling more sporting teams to implement athlete monitoring practices related to performance testing and load monitoring. Despite the increased emphasis on youth athlete development, the lack of longitudinal athlete monitoring literature in youth athletes is concerning, especially for indoor sports such as basketball. The aim of this study was to evaluate the effectiveness of six different athlete monitoring methods over 10 weeks of youth basketball training. Fourteen state-level youth basketball players (5 males and 9 females; 15.1 ± 1.0 years) completed this study during their pre-competition phase prior to their national basketball tournament. Daily wellness and activity surveys were completed using the OwnUrGoal mobile application, along with heart rate (HR) and inertial measurement unit (IMU) recordings at each state training session, and weekly performance testing (3x countermovement jumps [CMJs], and 3x isometric mid-thigh pulls [IMTPs]). All of the athlete monitoring methods demonstrated the coaching staff's training intent to maintain performance and avoid spikes in workload. Monitoring IMU data combined with PlayerLoad™ data analysis demonstrated more effectiveness for monitoring accumulated load (AL) compared to HR analysis. All six methods of athlete monitoring detected similar trends for all sessions despite small-trivial correlations between each method (Pearson's correlation: -0.24 < r < 0.28). The use of subjective monitoring questionnaire applications, such as OwnUrGoal, is recommended for youth sporting clubs, given its practicability and low-cost. Regular athlete education from coaches and support staff regarding the use of these questionnaires is required to gain the best data.

Perception of effort and the allocation of physical resources: A generalization to upper-limb motor tasks

Purpose

The perception of effort (PE) is widely used to prescribe and monitor exercise during locomotor and resistance tasks. The present study examines the validity of PE to prescribe and monitor exercise during upper-limb motor tasks under various loads and speed requirements.

Methods

Forty participants volunteered in two experiments. In experiment 1, we used four PE intensities to prescribe exercise on a modified version of the box and block test (BBT) and a pointing task. We investigated the possibility of monitoring the exercise intensity by tracking changes in PE rating in response to three different tempos or additional weights. Experiment 2 replicated the possibility of prescribing the exercise with the PE intensity during the BBT and explored the impact of additional weights on performance and PE during the standardized version of the BBT. Muscle activation, heart rate, and respiratory frequencies were recorded.

Results

In experiment 1, increasing the PE intensity to prescribe exercise induced an increased performance between each intensity. Increasing task difficulty with faster movement tempo and adding weight on the forearm increased the rating of PE. Experiment 2 replicated the possibility to use PE intensity for exercise prescription during the BBT. When completing the BBT with an additional weight on the forearm, participants maintained performance at the cost of a higher PE. In both experiments, changes in PE were associated with changes in muscle activation.

Conclusion

Our results suggest that PE is a valid tool to prescribe and monitor exercise during upper-limb motor tasks.

Influence of Scoring Systems on Mental Fatigue, Physical Demands, and Tactical Behavior during Soccer Large-Sided Games

Constraints are common in soccer training to develop physical, technical-tactical, and mental training concurrently. This study examined how different scoring systems influence physical, tactical, and mental demands during large-sided games in soccer. Eighteen youth-elite male (17.39 ± 1.04 y) soccer players completed three 8 vs. 8 large-sided games where the different score systems were i) official score system (OSS; i.e., 1 goal = 1 goal), ii) double the value of the goal-4 min (DVx4; i.e., 1 goal = 1 goal from 0.00 to 7.59 min, and 1 goal = 2 goals from 8.00 to 12.00 min), and iii) double the value of the goal-8 min (DVx8; i.e., 1 goal = 1 goal from 0.00 to 3.59 min, and 1 goal = 2 goals from 4.00 to 12.00 min). Physical demands and tactical behaviors were recorded during tasks using a global positioning system and video camera. Mental fatigue was recorded pre- and post-task using a visual analogue scale. Also, the ratio of perceived exertion and mental load were recorded after tasks were finished. Results reported the highest values of mental and physical demands in DVx4. Mental fatigue increased during all three large-sided games, although this increase was significantly higher in DVx4 compared with OSS (p = 0.006) and DVx8 (p = 0.027). Tactical behavior showed a trend towards more direct play during DVx4, which was less observed during DVx8, and not at all during OSS. In conclusion, changing the scoring system affects physical, tactical, and mental demands.

Effects of Playing Position and Contextual Factors on Internal Match Loads, Post-Match Recovery and Well-Being Responses of Elite Male Water Polo Players

This study aimed to investigate the effects of playing position and contextual factors (match outcome, final score difference, match location, travel duration, number of scored and conceded goals) on the internal match load, players' perceived recovery and players' well-being. The session-RPE (s-RPE), Perceived Recovery Scale (PRS) and Hooper Index (HI) of 17 male elite water polo players were monitored during all matches (regular season and play-out) of the 2021/22 Italian Serie A1 championship. Three separate, mixed linear models for repeated measures showed significant main effects: drawn compared to won matches led to higher s-RPE values (mean ± SE = 277 ± 17.6 vs. 237.3 ± 20.6), while longer travel duration (estimate = -0.148) and goals scored (estimate = -3.598) led to lower s-RPE values; balanced compared to unbalanced matches led to higher PRS values (mean ± SE = 6.8 ± 0.3 vs. 5.1 ± 0.4), while playing time (estimate = -0.041) and goals scored (estimate = -0.180) led to lower PRS values; higher scores of the HI were registered for regular season compared to the play-out (mean ± SE = 15.6 ± 0.9 vs. 13.5 ± 0.8). This study marks the importance of ecological and non-invasive monitoring tools to assess internal match load, recovery and the well-being of elite water polo players.

Video-based technical feedback and instruction improves tackling technique of community rugby union players

The aims of this study were to test the change and retention of player's overall tackling technique and technical components following a player-specific video-based technical feedback and instruction intervention on both their dominant and non-dominant shoulders. Twenty-four (n = 24) rugby union players participated in a non-randomized control-intervention, which consisted of a video-based technical feedback and instruction group (video-based technical feedback) and a no video-based technical feedback and instruction group (control). During 3 sessions (baseline, intervention, retention) separated by one week, participants in each group performed six tackles (3 tackles on each shoulder) on a tackle simulator. In total, 432 tackles (video-based technical feedback = 216, control = 216) were analysed. Each tackle was analysed using a standardized list of technical criteria (arbitrary units, AU). For the dominant shoulder, tackling technique scores significantly improved from baseline to intervention for both groups. For the non-dominant shoulder, only the video-based technical feedback group improved their tackling technique from baseline to intervention (baseline 6.89 [6.33-7.45] AU vs. intervention 7.72 [7.35-8.10] AU p = .001, ES = 0.60 moderate). For the retention session, the video-based technical feedback group scored significantly higher than the control group, for dominant (video-based technical feedback 8.00 [7.60-8.40] AU vs. control 7.22 [6.83-7.62] AU p = .014, ES = 0.66 moderate) and non-dominant (video-based technical feedback 8.11 [7.81-8.41] AU vs. control 7.22 [6.90-7.55] p = .004, ES = 0.96 moderate) tackles. This study demonstrates the efficacy of video-based technical feedback as a method to optimize tackle training for player safety and performance. HIGHLIGHTSVideo-based technical feedback can improve tackling technique in both dominant and non-dominant shoulders.Video-based technical feedback group continued to improve following a retention interval of one week.The video-based technical feedback group showed a significant (with a moderate effect size) improvement from baseline for two techniques - namely, "body position - upright to low" and "drive through contact with legs and shoulders".Video-based technical feedback can be used as a method to optimize tackle training for injury prevention and performance.