Recovery in Soccer

Elite Soccer Players' Weekly Workload Assessment Through a New Training Load and Performance Score

Purpose: Monitoring players' training load allows practitioners to enhance physical performance while reducing injury risk. The aim of this study was to identify the key external load indicators in professional U19 soccer. Methods: Twenty-four-professional Italian young (U19) soccer players were monitored by using the rating of perceived exertion (CR-10 RPE scale) and a wearable inertial sensor during the competitive season. Three main components were detected by a Principal Component Analysis (PCA): i) volume metabolic related component, ii) intensity mechanical stimuli component, and iii) intensity metabolic/mechanical component. We hence computed two scores (i.e. Performance [PERF] and total workload [WORK]) permitting to investigate the weekly microcycle. Results: Correlation analysis showed that scores (i.e. PERF and WORK) are low correlated (r = -0.20) suggesting that they were independent. Autocorrelation analysis showed that a weekly microcycle is detectable in all the scores. Two-way ANOVA RM showed a statistical difference between match day (MD) and playing position for the three PCA components and PERF score. Conclusion: We proposed an innovative approach to assess both the players' physical performance and training load by using a machine learning approach allowing reducing a large dataset in an objective way. This approach may help practitioners to prescribe the training in the microcycle based on the two scores.

Impact of temperature on physical and cognitive performance in elite female football players during intermittent exercise

There is limited research on female football players, especially related to their physical and cognitive performance under different climactic conditions. We analyzed the impact of a hot environmental temperature on physical performance and anticipation in elite female football players during a fatigue-inducing intermittent protocol. Elite female players (n = 21) performed the countermovement jump (CMJ) and responded to filmed sequences of offensive play under two distinct environmental temperatures (i.e., mild environment temperature- 20°C and 30% rh versus hot environment temperature- 38°C and 80% rh), interspersed by 1-week interval. Linear mixed models were used. CMJ performance declined following the intermittent protocol on both temperature conditions (p < 0.05). Moreover, there were significant main effects for protocol on CMJ speed (m/s) (p = 0.001; ηp 2 = 0.12), CMJ power (p = 0.002; ηp 2 = 0.11), and CMJ Heightmax (p = 0.002; ηp 2 = 0.12). After performing the intermittent protocol, exposure to a hot temperature caused a greater decline in anticipation accuracy (mild temperature = 64.41% vs. hot temperature = 53.44%; p < 0.001). Our study shows impaired performance in elite female football players following an intermittent protocol under hot compared with mild environmental conditions. We report decreased performance in both CMJ and anticipation performance under hotter conditions. The results reveal that exposure to hot temperatures had a negative effect on the accuracy of their anticipatory behaviors. We consider the implication of the work for research and training interventions.

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.

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.

The Impact of 120 Minutes of Soccer-Specific Exercise on Recovery

Purpose: The extra-time (ET) period of soccer is competed during fixture congested schedules with often limited recovery time between matches. The aim of this study was to assess muscle damage recovery following 90- and 120-min (i.e., incorporation of ET) of simulated soccer match-play. Methods: Twelve semiprofessional soccer players completed 90 and 120-min treadmill-based soccer-specific exercise in a counterbalanced order. Creatine kinase (CK), creatinine, urea, aspartate aminotransferase, perceived muscle soreness, pain pressure threshold, reactive strength index, countermovement jump height, and isokinetic strength assessments of eccentric knee flexors at 60, 180 and 270 deg‧s^-1 were taken at baseline and immediately-, 24, 48 and 72-hr post-exercise to assess recovery. Results: No significant between-trial interactions except for CK were found. Pairwise comparisons detected a 53% increase in CK at 24-hr (455 ± 29 μ∙L^-1) following 120-min of simulated match-play vs. the corresponding post 90-min time-point (299 ± 29 μ∙L^-1; p < .01). The 120-min trial caused a 58% higher CK response at 72-hr (244 ± 25 μ∙L^-1) vs. post 90-min comparisons (154 ± 29 μ∙L^-1; p = .02). No interaction effects were detected for any other recovery variables. Creatine kinase and perceived muscle soreness remained elevated up to 72-hr in both trials (p < .01). Conclusions: These data indicate that 120 min of simulated soccer match-play delays the time-course of CK recovery up to 72-hr post-match. However, 120 min of simulated soccer has no additional impact on functional recovery and perceived muscle soreness vs. 90 min. Recovery should be investigated following 90- and 120-min of actual match-play.Trial registration The study was pre-registered on the Open Science Framework (DOI: 10.17605/OSF.IO/VGU6T Date: 10/06/2019).

Mental fatigue changes from regular season to play-offs in semiprofessional soccer: A comparison by training days

The main purpose was to compare by each training the mental load and fatigue reported by semiprofessional soccer players comparing between regular season phase and the play-offs. Fifty-three players (M_age  = 24.59 years) for two teams participated during the 2020/21 season. Mental load was measured with a Likert questionnaire. Mental fatigue was quantified with a Visual Analogue Scale. Four trainings were recorded each week (Monday = MD+1, Wednesday = MD-4, Thursday = MD-3 and Saturday = MD-1), with a competitive match on Sunday across 10 weeks (five dates of regular season - five dates of play-offs). A Linear Mixed Model was performed with R-studio, using the training days and the competitive phase as independent variables. The influence of time played as co-variable was also checked. Results showed MD+1 as the more mentally fatiguing day in both phases, although MD-4 were the training with higher mental load reported (p = 0.001). Comparing phases, mental fatigue was significantly higher during the play-offs (p = 0.037). With regard time played, players that did not usually play showed a decrease in mental load during the play-offs. Then, we recommend coaches to use recovery strategies for mental fatigue, avoid mentally fatiguing tasks close to competition and considerer the time played as a factor which may contribute to individual differences in player mental fatigue.

Perspectives on Postmatch Fatigue From 300 Elite European Soccer Players

PURPOSE

To examine the general perspectives of elite soccer players on the time course of perceived postmatch fatigue and the influence of away matches on subjective perceptions.

METHODS

Adopting a cross-sectional study design, we invited 371 subjects from 14 top-division European clubs competing in the Belgian First Division A, English Premier League, French Ligue 1, Italian Serie A, Portuguese Primeira Liga, Russian Premier League, and Swiss Premier League to take part in a short survey on general issues relating to postmatch fatigue measurement and tracking in professional soccer.

RESULTS

Three hundred male professional soccer players completed the short questionnaire. For perceptions relevant to the time course of postmatch fatigue, two-thirds of respondents (67%) indicated higher postmatch fatigue perceived 2 days (48 h) after an official competition. Among these respondents, a higher proportion of answers was observed in wide midfielders (74%), attackers (74%), and central midfielders (68%). Approximately two-thirds of respondents (63%) indicated more than usual and much more than usual perceived postmatch fatigue following away matches.

CONCLUSIONS

For the first time, our investigation addressed practical aspects that remained unexplored and fundamental to the definition of an optimal player management process following a competition. From a practical standpoint, perspectives of individual elite soccer players substantiated the notion of implementing processes with dedicated recovery protocols within 48 hours postmatch and highlighted the need for differential strategies addressing the additional burden of away matches and travel.

Kick proficiency and skill adaptability increase from an Australian football small-sided game intervention

This investigation is the first to explore the effect of a 4 week small-sided game (SSG) and traditional training intervention on player kick proficiency and player adaptability in Australian football. Twenty-two amateur Australian football players (mean ± SD; age 22.3 ± 2.46; height 182.4 ± 5.25; weight 82.1 ± 6.10; years playing senior amateur football 3.86 ± 3.09) were randomly selected into either a traditional training group (n = 11) or a SSG group (n = 11). Traditional training involved activities where skills were generally executed in isolation and with minimal contact (e.g., kicking lane drill or possession football). The SSG training group participated in 5v6 competitive games on varied shaped areas (approximately 272 m² per player) and changing constraints (e.g., game tempo, game rules). All players participated in the team training sessions; however, the SSG group participated in a 4 × 3min training protocol, with 60 seconds recovery, in the last 20-min of the session. The SSG group participated in these alternative sessions twice a week for 4 weeks. Results indicated only the SSG enhanced their kick proficiency (17%) and were found to be more adaptable. The intervention group executed more kicks over longer distances (i.e., 20-40 m), made quicker decisions (e.g., executing more kicks in < 1s), applied more pressure to the opposition when they were executing a skill and were more likely to "take the game on" by decreasing the amount of times a skill was executed from a stationary position. The results of this study can be used by coaches when designing and implementing training programs as different training strategies will elicit different player behavioral adaptations.

Physical match performance and creatine kinase levels in elite football players

Many studies have shown that creatine kinase (CK) concentration increases following an elite-level football competition. However, the relationship between match performance and CK levels at 72 hours after the match is still unclear. The aim of this study was to determine the relationship between physical match performance data and blood CK levels 72 hours post-match in elite football players. The study included 11 male elite football players (age=26.36±3.29 years, height=181.60±6.1 cm, weight=75.41±5.96 kg). Capillary blood samples were collected from the participants approximately 72 hours post-match and examined by reflectance photometry. Physical match performance data from 2 consecutive matches of a Turkish Super League team (while competing in the UEFA Europa League) were collected by a computerized video tracking system. There was no significant correlation between the players’ CK level and their total distance (p=0.6012), high-intensity (20-24 km/h) running distance (p=0.8837), or sprinting distance (p=0.235). CK level was also not correlated with the percentage of total distance covered in high-intensity running (r=-0.62, p=0.052). However, moderate to strong negative correlations were observed between CK level and percentage of total distance covered in sprinting (r=-0.67, p=0.032) and percentage of total distance covered in high-intensity running and sprinting (r=-0.70, p=0.022). The current study suggests the benefit of evaluating distances covered in the game and CK concentrations 72 hours post-match while planning recovery interventions.

Muscular heat shock protein response and muscle damage after semi-professional football match

PURPOSE

A typical football match leads to neuromuscular fatigue and physical performance impairments up to 72-96 h post-match. While muscle damage is thought to be a major factor, damage on the ultrastructural level has never been documented. The purpose of this study was to investigate post-match cellular muscle damage by quantifying the heat shock protein (HSP) response as a proxy for protein damage.

METHODS

Muscle biopsies, blood samples, countermovement jumps, and perception of muscle soreness were obtained from twelve semi-professional football players 1, 24, 48, and 72 h after a 90-min football match. Muscle biopsies were analyzed for αB-crystallin and HSP70 in the cytosolic and cytoskeletal sub-cellular fractions by Western blotting. Fiber type-specific αB-crystallin and HSP70 staining intensity, and tenascin-C immunoreactivity were analyzed with immunohistochemistry. Blood samples were analyzed for creatine kinase and myoglobin.

RESULTS

Within 24 h post-match, a 2.7- and 9.9-fold increase in creatine kinase and myoglobin were observed, countermovement jump performance decreased by -9.7% and muscle soreness increased by 0.68 units. αB-crystallin and HSP70 accumulated in cytoskeletal structures evident by a 3.6- and 1.8-fold increase in the cytoskeletal fraction and a parallel decrease in the cytosolic fraction. In type I and II fibers, αB-crystallin staining intensity increased by 15%-41% and remained elevated at 72 h post-match. Lastly, the percentage of fibers with granular staining of αB-crystallin increased 2.2-fold.

CONCLUSIONS

Football match play induced a muscular HSP stress response 1-72 h post-match. Specifically, the accumulation of HSPs in cytoskeletal structures and the granular staining of αB-crystallin suggests occurrence of ultrastructural damage. The damage, indicated by the HSP response, might be one reason for the typically 72 h decrease in force-generating capacity after football matches.

Re-assessing the Psychometric Properties of Stress Appraisal Measure in Ghana Using Multidimensional Graded Response Model

Despite the widespread use of the stress appraisal measure questionnaire in sport psychology literature, information on the psychometric properties of this survey instrument across different cultures and samples is still lacking. This study sought to validate the stress appraisal measure among male football players in the Ghana’s Premier League using the multidimensional item response theory. The descriptive cross-sectional survey design was adopted to recruit 424 footballers from the 2020/2021 Ghana Premier League season using the census approach. The 28-item Stress Appraisal Measure was used to assess six (6) appraisal mechanisms under primary and secondary cognitive appraisals. The ordered polytomous item response theory was used for analyzing the data. The study found that although some items were problematic, the majority of them were found to have good item parameters, effective scale option functioning, and provided adequate empirical information in the measurement of stress appraisal. This research concluded that the stress appraisal measure has promising applicability among male footballers who participated in the premier league in Ghana. Future researchers are encouraged to re-validate the stress appraisal measure with a different sample to contribute to the understanding of the applicability of the instrument in non-western populations.

Antioxidants Markers of Professional Soccer Players During the Season and their Relationship with Competitive Performance

The aim of this study was to assess antioxidant markers before and after a mid-season of professional soccer players from the 3^rd Spanish Division, and to correlate antioxidant markers with competitive performance. Sixty-five male players (age = 25.3 ± 4.2 yr, body mass = 73.2 ± 6.7 kg, body height = 177.8 ± 5.7 cm) from three soccer clubs from Cádiz (Spain) participated in the study. Body composition, maximal aerobic capacity (VO_2max), and baseline antioxidant blood markers (Total Antioxidant Status (TAS) and Reduced glutathione/Oxidized glutathione ratio) were assessed in the first week of the championship season (pre-test) and after 18 weeks in the mid-season (post-test). Soccer performance was registered according to the official classification ranking at both the mid-season and at the end of the season; ranking positions for Team A were 2^nd and 1^st, for Team B were 5^th and 5^th, while for Team C were 12^th and 14^th, respectively. Regression analyses showed that TAS and VO_2max were able to independently predict (p < 0.05) performance in our participants. Moreover, antioxidant levels showed significant main effects on performance (p < 0.001); where a higher antioxidant capacity was observed in the best performance soccer team, both before and after the mid-season. Notwithstanding, the competitive period compromised the antioxidant status since TAS levels significantly decreased after the 18-week training program and competition compared with baseline values in all soccer teams (p < 0.001). These results suggest the need of monitoring antioxidants in soccer players to prevent excessive oxidative stress and cellular damage which could compromise success in competition, by adjusting the training loads, diet or ergogenic aids, if needed.

Quantifying Fatigue in the Rugby Codes: The Interplay Between Collision Characteristics and Neuromuscular Performance, Biochemical Measures, and Self-Reported Assessments of Fatigue

Locomotor and collision actions that rugby players complete during match-play often lead to substantial fatigue, and in turn, delays in recovery. The methods used to quantify post-match fatigue and recovery can be categorised as subjective and objective, with match-related collision characteristics thought to have a primary role in modulating these recovery measures. The aim of this review was to (1) evaluate how post-match recovery has been quantified in the rugby football codes (i.e., rugby league, rugby union, and rugby sevens), (2) to explore the time-course of commonly used measures of fatigue post-match, and (3) to investigate the relationships between game-related collisions and fatigue metrics. The available evidence suggests that upper-, and lower-body neuromuscular performance are negatively affected, and biomarkers of muscular damage and inflammation increase in the hours and days following match-play, with the largest differences being at 12–36 h post-match. The magnitude of such responses varies within and between neuromuscular performance (Δ ≤ 36%, n = 13 studies) and tissue biomarker (Δ ≤ 585%, n = 18 studies) measures, but nevertheless appears strongly related to collision frequency and intensity. Likewise, the increase in perceived soreness in the hours and days post-match strongly correlate to collision characteristics across the rugby football codes. Within these findings, there are specific differences in positional groups and recovery trajectories between the codes which relate to athlete characteristics, and/or locomotor and collision characteristics. Finally, based on these findings, we offer a conceptual model of fatigue which details the multidimensional latent structure of the load to fatigue relationship contextualised to rugby. Research to date has been limited to univariate associations to explore relationships between collision characteristics and recovery, and multivariate methods are necessary and recommended to account for the latent structures of match-play external load and post-match fatigue constructs. Practitioners should be aware of the typical time windows of fatigue recovery and utilise both subjective and objective metrics to holistically quantify post-match recovery in rugby.

The Effects of Successive Soccer Matches on the Internal Match Load, Stress Tolerance, Salivary Cortisol and Jumping Performance in Youth Soccer Players

The study aim was to analyze the effects of successive matches on the internal match load, stress tolerance, salivary cortisol concentration and countermovement vertical jump height in twelve youth soccer players (16.6 ± 0.5 yr; 175 ± 8 cm; 65 ± 8 kg) who performed four official matches within a four day-period with a 24-h recovery interval between the matches. The internal match load, monotony index and competitive strain, as well as stress tolerance were examined. Saliva samples were collected and countermovement vertical jump height was assessed 60 min pre and 30 min post each match; delta of salivary cortisol and countermovement vertical jump height for each match were analyzed. Salivary cortisol was analyzed using an enzyme-linked immunosorbent assay. The results of ANOVA with repeated measures showed no differences between matches for the internal match load (p > 0.05). The scores of the monotony index and competitive strain were 4.3 (±2.3) and 8104 (±6795) arbitrary units, respectively. There was no difference for stress tolerance between matches (p > 0.05). Delta values of salivary cortisol were not different among the assessed matches (F_(3,33) = 1.397, p = 0.351, η²: 0.09); however, delta of countermovement vertical jump height decreased from match 1 to match 4 (F_(3,33) = 8.64, p < 0.001, η²: 0.44). The current findings suggest that participating in four successive matches, with 24-h of recovery in between, may not lead to changes in stress tolerance and salivary cortisol of youth players, but it may induce a decrease in players' jumping performance after the fourth match.

Weekly Variations of Short-Duration Maximal Jumping Performance in Soccer Players: Exploring Relationships With Accumulated Training Load and Match Demands

Purpose: The aim of this study was 2-fold: (1) to analyze variations of short-duration maximal jumping performance in players exposed to a match and those who were not and (2) to analyze the relationships between changes in the short-duration maximal jumping performance and different accumulated training load and match demands measures.

Methods: Twenty-four professional soccer players (age: 20.3 ± 1.7 years) were monitored daily for their training load and match demands over 6 weeks. In addition, they performed a weekly short-duration maximal jumping performance test (72 h after the last match).

Results: Negative moderate correlations were found between percentage of change of countermovement jump (CMJ) height and Acummulated training load (ATL) of total distance (TD), high metabolic load (HML), accelerations (ACC), and decelerations (DEC) (r = −0.38, p = 0.004; r = −0.33, p = 0.013; r = −0.39, p = 0.003; and r = −0.30, p = 0.026). No correlations were found for match load (ML). TD, HML, ACC, and DCC (r = 0.27, r = 0.25, r = 0.31, and r = 0.22, respectively) were used to predict the percentage of change of CMJ height.

Conclusion: Match participation has negative effects on CMJ performance. The ATL of HML, ACC, DCC, and TD have a significant influence on both CMJ measures changes. Also, the ATL values of those metrics are the best predictors of the percentage changes of CMJ performance.

The use of recovery strategies by Spanish first division soccer teams: a cross-sectional survey

OBJECTIVES

different active and passive post-exercise recovery techniques such as massage, foam rolling, stretching or ice baths among others, are used by elite athletes to promote effective physiological, physical, and mental restoration. However, limited research is available investigating the use of recovery strategies in professional soccer. As such, we aimed to explore and describe the use of strategies by professional teams throughout the season, describing competitive and preparatory phases.

METHODS

the present study collected data from all professional Spanish soccer teams who played in 'LaLiga' (The Spanish first division), during the season 2018-2019 (n = 20) and the ones promoted for the season 2019-2020 (n = 3). A six-section online survey was responded once.

RESULTS

teams used different recovery protocols and combinations, although natural and physical strategies such as sleep/nap, food/fluid replacement, cold/ice bath/shower/immersion, and massage were always present. However, there is no agreement in the protocols and timings employed. Three physical strategies showed a higher presence in the recovery protocols after competition: cold/ice bath/shower/immersion, massage and foam rolling; always used by seventeen teams (74%), sixteen (70%) and thirteen (57%) respectively. The design and supervision of recovery are multidisciplinary tasks in 87% of the teams. Our findings also demonstrate that although there is a body of scientific evidence on recovery, a gap between theory and practice exists with 13% of the teams acknowledging that insufficient logistics and economic resources limit the use of some strategies, and two teams (9%) not periodizing or individualizing recovery.

CONCLUSION

the investigation provided insight into the current use of recovery strategies by 'LaLiga' teams, highlighting that all clubs used them to one extent or another, but also that significant variability responding to individualized perceptions exists. Moreover, this study provides relevant contextual information that may be useful for professional soccer staff concerning the use of recovery strategies.

Exploring Shank Circumference by Stretching after Training among Volleyball Players

This preliminary study examined the effects of a stretching intervention after training and its duration (15 vs. 30 min) on participants’ shank circumference (SC) reduction and subjective discomfort score. Ten male volleyball players underwent a routine 3 h training. A two-way analysis of variance revealed that the stretching intervention had significant effects on SC reduction (p < 0.01) and subjective discomfort scores (p < 0.001). Stretching after training could help eliminate shank strain, and a slighter discomfort in shanks when stretching was also seen (score, 20.1/100). An independent-samples t test revealed a significantly higher SC reduction (p < 0.01) with 30 min of stretching (5.6 mm) than with 15 min of stretching (2.7 mm); both stretching durations reduced SC significantly more than the no-stretching condition did. The findings of this study can serve as a reference for volleyball players to alleviate shank strain after daily routine training.

Post-match Recovery Practices in Professional Football: Design, Validity, and Reliability of a New Questionnaire

Introduction: Although several approaches have been proposed to mitigate post-match fatigue, few studies have been conducted in team sports to understand the types of recovery methods and the underlying reasons for the choices of medical and technical staff. This study aimed to develop a valid and reliable online questionnaire to assess the recovery practices implemented by football clubs within 72 h post-match.

Methods: Two research members developed the original questionnaire proposal, and two experts in sports science and sports medicine confirmed the content and face validities. Then, 20 football coaches (age: 39.4 ± 6.8 years) with a minimum of 5 years of experience in professional football (9.1 ± 4.9 years) and with an academic background participated in determining the ecological validity and reliability of the questionnaire. The acceptability and relevance of the questionnaire were determined using descriptive statistics.

Results: After confirming the content and face validities, one questionnaire section with two questions was excluded due to lack of relevance, seven open-ended questions were removed due to the adherence of small participants (i.e., 45.4%), and one section was divided into three to facilitate clearness in reading. The remaining sections were considered acceptable and relevant (>94.1%). About 91.8% of nominal and ordinal items derived from the questionnaire questions showed good to very good reliability outcomes (average k classification: 0.73 ± 0.13; min–max: 0.22–1.00, p < 0.05; average wk classification: 0.82 ± 0.15; min–max: 0.22–1.00, p < 0.05).

Conclusions: This study provided a novel, valid, reliable, and easy-to-use tool to examine the post-match recovery practices in professional football contexts.

Technical match actions and plasma stress markers in elite female football players during an official FIFA Tournament

This study analyzed the impact of performing four consecutive football matches separated by 48-72 hours during a FIFA tournament on physical load, technical performance and plasma markers of redox state, muscle damage and inflammation in elite female players. Forty-eight players from three national teams were evaluated at seven time points: before (baseline) and throughout the tournament (after each match and before two training sessions). Only data from players who played all matches were included in the analyses (N = 13). The players were divided into high-rank (N = 6) and low-rank (N = 7) team players according to FIFA standards. Plasma creatine kinase (CK), C-reactive protein (CRP), total antioxidant status (TAS), and uric acid (UA) were analyzed at the selected time points. Technical performance and physical load were also quantified according to team rank. Players from low-rank teams played significantly more time than high-rank players (85 ± 10 vs 67 ± 15 minutes; P = .02; d = 1.51). Low-rank team players presented higher values in technical performance actions than the high-rank team players, but most of the differences were explained by the longer match time played. UA content differed across the matches, increasing from baseline (F_(4,40)  = 3.90; P = .01) and more in the high-rank team players (F_(1,10)  = 20.46; P = .001), while CRP only differed across the matches (F_(4,36)  = 2.66; P = .05), also increasing from baseline. A large time effect was shown for UA only in the high-rank players (η² _p  = 0.50; P = .02). Four consecutive matches did not result in considerable alterations in plasma stress markers, physical load, and technical performance in elite female football players from distinct rank levels.

Large Reductions in Match Play Physical Performance Variables Across a Professional Football Season With Control for Situational and Contextual Variables

This investigation examined match play physical performance across a professional football season using a multicamera computerized tracking system. A linear mixed-effects model, controlling for situational and contextual variables, identified decreases in team average total distance (TD): season quarter 1 (Q1) (11,047 m) > season quarter 2 (Q2) (10,473 m) (P = 0.002; ES = Small), season quarter 3 (Q3) (10,449 m) (P < 0.001; ES = Moderate), and season quarter 4 (Q4) (10,385 m) (P < 0.001; ES = Moderate); work rate (WR): Q1 (115 m/min) > Q3 (108 m/min) (P < 0.001; ES = Moderate), Q4 (107 m/min) (P < 0.001; ES = Moderate); Q2 (109 m/min) > Q4 (107 m/min) (P = 0.003; ES = Small); high-speed running distance (HSR): Q1 (1,051 m) > Q2 (813 m) (P = 0.006; ES = Small); number of high-speed runs (NHSR): Q1 (87) > Q2 (65) (P < 0.001; ES = Small), Q3 (64) (P = 0.002; ES = Small); sprint distance (SD): Q1 (202 m) > Q4 (130 m) (P < 0.001; ES = Moderate), Q2 (179 m) > Q3 (165 m) (P = 0.035; ES = Small), Q4 (130 m) (P < 0.001; ES = Moderate) and number of sprints (NS): Q1 (20.4) > Q3 (10.2) (P < 0.001; ES = Moderate), Q4 (8.3) (P < 0.001; ES = Large); Q2 (14.9) > Q3 (10.2) (P < 0.001; ES = Moderate), Q4 (8.3) (P < 0.001; ES = Large). Within-position changes were observed for WR: Q1 (122 m/min) > Q4 (113 m/min) (P = 0.002; ES = Large) in central midfielders and for NS: Q1 > Q3 in wide defenders (21.7 vs. 10.8) (P = 0.044; ES = Large) and central midfielders (18.1 vs. 8.3) (P = 0.002; ES = Large); Q1 > Q4 in central defenders (13.1 vs. 5.3) (P = 0.014; ES = Large), wide defenders (21.6 vs. 7.1) (P < 0.001; ES = Very Large), central midfielders (18.1 vs. 8.5) (P = 0.005; ES = Large), and wide midfielders (20.8 vs. 12.2) (P = 0.012; ES = Large); Q2 > Q3 in central midfielders (16.9 vs. 8.3) (P = 0.002; ES = Large) and Q2 > Q4 in wide defenders (16.3 vs. 7.1) (P = 0.005; ES = Very Large), central midfielders (16.9 vs. 8.5) (P = 0.004; ES = Large), and wide midfielders (20.8 vs. 12.2) (P = 0.007; ES = Large). The match-play physical performance was reduced across the competitive season. The most notable reductions were observed in wide defenders, central midfielders, and wide midfielders in sprint performance indices.

Intra-Individual and Seasonal Variation of Selected Biomarkers for Internal Load Monitoring in U-19 Soccer Players

The aim of this study was to investigate inter-day and -week as well as intra- and inter-individual variation of selected biomarkers in high-performance youth soccer players to assist practitioners interpreting player's internal load to counteract underperformance and unwanted health risks. Eleven male youth soccer players were tested multiple times during two 3-week periods at midpoint (3-wk_mid) and at the end (3-wk_end) of the first half of a German under-19 1. Bundesliga season. The levels of creatine kinase (CK), urea, and C-reactive protein (CRP) were measured during 3-wk_mid and 3-wk_end each Monday, Wednesday, and Friday. In 3-wk_mid the CK median was 14% higher (241 vs. 212 U/L) compared to 3-wk_end (P = 0.26, ES = 0.16). Overall, the medians of CK, urea (P = 0.59, ES = 0.08), and CRP (P = 0.56, ES = 0.10) during 3-wk_mid did not differ to the values of 3-wk_end. Daily coefficient of variations (CVs) ranged from 22 to 71% (CK), 17 to 37% (urea), and 9 to 164% (CRP). Individual medians ranged from 101 to 350 U/L (CK), 23 to 50 mg/dL (urea), and 0.6 to 1.1 mg/L (CRP). High intra-individual variability was demonstrated by large intra-individual CVs (medians: CK 50%, urea 18%, and CRP 45%). Our data show (i) large inter-day and inter-week variability of all biomarkers, depending on the external load and (ii) considerable inter- and intra-individual parameter variations. Creatine kinase concentrations could sensitively reflect soccer-specific loads during the season.

The Interplay Between Plasma Hormonal Concentrations, Physical Fitness, Workload and Mood State Changes to Periods of Congested Match Play in Professional Soccer Players

Background

The regular assessment of hormonal and mood state parameters in professional soccer are proposed as good indicators during periods of intense training and/or competition to avoid overtraining.

Objective

The aim of this study was to analyze hormonal, psychological, workload and physical fitness parameters in elite soccer players in relation to changes in training and match exposure during a congested period of match play.

Methods

Sixteen elite soccer players from a team playing in the first Tunisian soccer league were evaluated three times (T1, T2, and T3) over 12 weeks. The non-congested period of match play was from T1 to T2, when the players played 6 games over 6 weeks. The congested period was from T2 to T3, when the players played 10 games over 6 weeks. From T1 to T3, players performed the Yo-Yo intermittent recovery test level 1 (YYIR1), the repeated shuttle sprint ability test (RSSA), the countermovement jump test (CMJ), and the squat jump test (SJ). Plasma Cortisol (C), Testosterone (T), and the T/C ratio were analyzed at T1, T2, and T3. Players had their mood dimensions (tension, depression, anger, vigor, fatigue, confusion, and a Total Mood Disturbance) assessed through the Profile of Mood State questionnaire (POMS). Training session rating of perceived exertion (sRPE) was also recorded on a daily basis in order to quantify internal training load and elements of monotony and strain.

Results

Significant performance declines (T1 < T2 < T3) were found for SJ performance (p = 0.04, effect size [ES] ES_1–2 = 0.15−0.06, ES_2–3 = 0.24) from T1 to T3. YYIR1 performance improved significantly from T1 to T2 and declined significantly from T2 to T3 (p = 0.001, ES_1–2 = 0.24, ES_2–3 = −2.54). Mean RSSA performance was significantly higher (p = 0.019, ES_1–2 = −0.47, ES_2–3 = 1.15) in T3 compared with T2 and T1. Best RSSA performance was significantly higher in T3 when compared with T2 and T1 (p = 0.006, ES_2–3 = 0.47, ES_1–2 = −0.56), but significantly lower in T2 when compared with to T1. T and T/C were significantly lower in T3 when compared with T2 and T1 (T: p = 0.03, ES_3–2 = −0.51, ES_3–1 = −0.51, T/C: p = 0.017, ES_3–2 = −1.1, ES_3–1 = −1.07). Significant decreases were found for the vigor scores in T3 when compared to T2 and T1 (p = 0.002, ES_1–2 = 0.31, ES_3–2 = −1.25). A significant increase was found in fatigue scores in T3 as compared to T1 and T2 (p = 0.002, ES_1–2 = 0.43, ES_2–3 = 0.81). A significant increase was found from T1 < T2 < T3 intension score (p = 0.002, ES_1–2 = 1.1, ES_2–3 = 0.2) and anger score (p = 0.03, ES_1–2 = 0.47, ES_2–3 = 0.33) over the study period. Total mood disturbance increased significantly (p = 0.02, ES_1–2 = 0.91, ES_2–3 = 1.1) from T1 to T3. Between T1-T2, significant relationships were observed between workload and changes in T (r = 0.66, p = 0.003), and T/C ratio (r = 0.62, p = 0.01). There were significant relationships between performance in RSSA_best and training load parameters (workload: r = 0.52, p = 0.03; monotony: r = 0.62, p = 0.01; strain: r = 0.62, p = 0.009). Between T2-T3, there was a significant relationship between Δ% of total mood disturbance and Δ% of YYIR1 (r = −0.54; p = 0.04), RSSA_best (r = 0.58, p = 0.01), SJ (r = −0,55, p = 0.01), T (r = 0.53; p = 0.03), and T/C (r = 0.5; p = 0.04).

Conclusion

An intensive period of congested match play significantly compromised elite soccer players’ physical and mental fitness. These changes were related to psychological but not hormonal parameters; even though significant alterations were detected for selected measures. Mood monitoring could be a simple and useful tool to determine the degree of preparedness for match play during a congested period in professional soccer.

External Responsiveness of the SuperOpTM Device to Assess Recovery After Exercise: A Pilot Study

Post-exercise recovery is a complex process involving a return of performance and a physiological or perceptual feeling close to pre-exercise status. The hypothesis of this study is that the device investigated here is effective in evaluating the recovery state of professional cyclists in order to plan effective training. Ten professional male cyclists belonging to the same team were enrolled in this study. Participants performed a 7-day exercise program [D1, D4, and D7: low-intensity training; D2 and D5: passive recovery; D3: maximum oxygen consumption (VO2Max) test (for maximum mechanical power assessment only); and D6: constant load test]. During the week of monitoring, each morning before getting up, the device assessed each participant's so-called Organic Readiness {OR [arbitrary unit (a.u.)]}, based on blood pressure (BP), heart rate (HR), features of past exercise session, and following self-perceived condition. Based on its readings and algorithm, the device graphically displayed four different colors/values, indicating general exercise recommendations: green/3 = "you can train hard," yellow/2 = "you can train averagely," orange/1 = "you can train lightly," or red/0 = "you should recover passively." During the week of research, morning OR values and Bonferroni post-hoc comparisons showed significant differences between days and, namely, values (1) D2 (after low intensity training) was higher than D4 (after VO2Max test; P = 0.033 and d = 1.296) and (2) D3 and D6 (after passive recovery) were higher than D4 (after VO2Max test; P = 0.006 and d = 2.519) and D5 (after low intensity training; P = 0.033 and d = 1.341). The receiver operating characteristic analysis area under curve (AUC) recorded a result of 0.727 and could differentiate between D3 and D4 with a sensitivity and a specificity of 80%. Preliminarily, the device investigated is a sufficiently effective and sensitive/specific device to assess the recovery state of athletes in order to plan effective training.

Acute effects of recreational soccer on inflammatory response and cardiac and skeletal muscle damage indicators

Introduction: Previous studies have indicated that acute bouts of strenuous, long duration exercise induce significant increases in the inflammatory profile and cardiovascular risk markers. Although recreational soccer (RS) is a widespread activity, there are no data on this topic. Thus, the aim of this study was to examine RS-induced changes in inflammatory, cardiac, and skeletal muscle damage indicators in young and middle-aged males.

Methods: Twelve young and 11 middle-aged males participated in the study. The participants played 6v6 1 h RS, where heart rate (HR) responses and external loads (distance covered, number of accelerations/decelerations) were determined. Blood samples were taken immediately prior to and following the matches, and 2 h, 4 h, 24 h, 48 h, and 72 h later.

Results: Absolute HR responses and the number of accelerations and decelerations were higher in young participants than the middle-aged participants (p < 0.05). RS increased high sensitivity cardiac troponin I (hs-cTnI) in almost all participants. A total of 83.3% of the young participants exceeded the upper reference limit (URL), whereas none of the middle-aged participants exceeded the URL. Hs-cTnI levels returned to baseline after 24 and 48 h in the middle-aged and young participants, respectively. High sensitivity C-reactive protein (hs-CRP) and creatine kinase (CK) increased in the middle-aged participants (p < 0.05), and in the young participants, though not significantly (p > 0.05). RS also led to significant increases in lactate dehydrogenase (LDH) in both groups (p < 0.05). Hs-CRP, CK, and LDH values returned to baseline levels within 48 to 72 h, except for the LDH values of the young participants.

Conclusion: RS induced short-term increases in cardiac and skeletal muscle damage markers and the inflammatory profile in young and middle-aged RS participants.

Evidence-based post-exercise recovery strategies in rugby: a narrative review

In the sport of rugby, athletes need a multitude of sport-specific skills along with endurance, power, and speed to optimize performance. Further, it is not unusual for athletes to play several competitive matches with insufficient recovery time. Rugby requires repeated bouts of high-intensity actions intermixed with brief periods of low-to-moderate active recovery or passive rest. Specifically, a match is characterized by repeated explosive activities, such as jumps, shuffles, and rapid changes of direction. To facilitate adequate recovery, it is necessary to understand the type of fatigue induced and, if possible, its underlying mechanisms. Common approaches to recovery may include nutritional strategies as well as active (active recovery) and passive recovery (water immersions, stretching, and massage) methods. However, limited research exists to support the effectiveness of each strategy as it related to recovery from the sport of rugby. Therefore, the main aim of the current brief review is to present the relevant literature that pertains to recovery strategies in rugby.

Etiology and Recovery of Neuromuscular Fatigue following Competitive Soccer Match-Play

Aim: Previous research into the etiology of neuromuscular fatigue following competitive soccer match-play has primarily focused on peripheral perturbations, with limited research assessing central nervous system function in the days post-match. The aim of the present study was to examine the contribution and time-course of recovery of central and peripheral factors toward neuromuscular fatigue following competitive soccer match-play.

Methods: Sixteen male semi-professional soccer players completed a 90-min soccer match. Pre-, post- and at 24, 48, and 72 h participants completed a battery of neuromuscular, physical, and perceptual tests. Maximal voluntary contraction force (MVC) and twitch responses to electrical (femoral nerve) and transcranial magnetic stimulation (TMS) of the motor cortex during isometric knee-extension and at rest were measured to assess central nervous system (voluntary activation, VA) and muscle contractile (potentiated twitch force, Q_{tw, pot}) function. Electromyography responses of the rectus femoris to single- and paired-pulse TMS were used to assess corticospinal excitability and short-interval intracortical inhibition (SICI), respectively. Fatigue and perceptions of muscle soreness were assessed via visual analog scales, and physical function was assessed through measures of jump (countermovement jump height and reactive strength index) and sprint performance.

Results: Competitive match-play elicited significant post-match declines in MVC force (−14%, P < 0.001) that persisted for 48 h (−4%, P = 0.01), before recovering by 72 h post-exercise. VA (motor point stimulation) was reduced immediately post-match (−8%, P < 0.001), and remained depressed at 24 h (−5%, P = 0.01) before recovering by 48 h post-exercise. Q_tw,pot was reduced post-match (−14%, P < 0.001), remained depressed at 24 h (−6%, P = 0.01), before recovering by 48 h post-exercise. No changes were evident in corticospinal excitability or SICI. Jump performance took 48 h to recover, while perceptions of fatigue persisted at 72 h.

Conclusion: Competitive soccer match-play elicits substantial impairments in central nervous system and muscle function, requiring up to 48 h to resolve. The results of the study could have important implications for fixture scheduling, the optimal management of the training process, squad rotation during congested competitive schedules, and the implementation of appropriate recovery interventions.

Mental fatigue impairs soccer-specific decision-making skill

This study aimed to investigate the impact of mental fatigue on soccer-specific decision-making. Twelve well-trained male soccer players performed a soccer-specific decision-making task on two occasions, separated by at least 72 h. The decision-making task was preceded in a randomised order by 30 min of the Stroop task (mental fatigue) or 30 min of reading from magazines (control). Subjective ratings of mental fatigue were measured before and after treatment, and mental effort (referring to treatment) and motivation (referring to the decision-making task) were measured after treatment. Performance on the soccer-specific decision-making task was assessed using response accuracy and time. Visual search behaviour was also assessed throughout the decision-making task. Subjective ratings of mental fatigue and effort were almost certainly higher following the Stroop task compared to the magazines. Motivation for the upcoming decision-making task was possibly higher following the Stroop task. Decision-making accuracy was very likely lower and response time likely higher in the mental fatigue condition. Mental fatigue had unclear effects on most visual search behaviour variables. The results suggest that mental fatigue impairs accuracy and speed of soccer-specific decision-making. These impairments are not likely related to changes in visual search behaviour.

What is the extent of exposure to periods of match congestion in professional soccer players?

This study investigated exposure to periods of match congestion in regular starter players in a professional soccer team across 4 competitive seasons (2009-2013). Players were divided into 2 groups: club players (club match exposure only, n = 41) and national team players (club and national team exposure, n = 22). The frequency of congested periods that players were potentially exposed to per season was initially determined: 2-match cycles - potential exposure to 2 successive matches separated by a ≤ 3-day interval calculated immediately from the end of play in match 1 to the start of play in match 2 occurred on 12.5 ± 5.1 and 16.0 ± 4.7 occasions for club and national team players, respectively. Multiple-match cycles: potential exposure to 3-, 4-, 5- or 6-matches played successively within a ≤ 4-day period commencing from the day after each match occurred on 8.5 ± 2.1, 4.3 ± 1.7, 3.0 ± 0.8 and 1.8 ± 0.5 occasions for club and 11.5 ± 2.4, 6.5 ± 0.6, 4.5 ± 1.9 and 3.0 ± 1.4 occasions for national team players, respectively. With regard to actual exposure in club and national team players, respectively, participation in both matches in 2-match cycles attained 61.2% and 59.3% while 90-min play in both matches was only completed on 38.2% and 40.5% of occasions and ≥75-min play on 47.6% and 50.0% of occasions, despite availability to play in both groups being >86%. While availability to play in all players was frequently >70% for multiple-match cycles, a trend was observed for a sharp decline in participation as the number of matches in the cycles increased. Therefore, the present players were not extensively exposed to periods of fixture congestion.

Recovery-stress balance and injury risk in professional football players: a prospective study

Professional football is a contact sport with a high risk of injury. This study was designed to examine the contribution of stress and recovery variables as assessed with the Recovery-Stress Questionnaire for Athletes (RESTQ-Sport) to the risk of injury in professional football players. In a prospective, non-experimental cohort design, 22 professional football players in the highest German football league were observed over the course of 16 months. From January 2010 until April 2011, the players completed the RESTQ-Sport a total of 222 times in monthly intervals. In addition, injury data were assessed by the medical staff of the club. Overall, 34 traumatic injuries and 10 overuse injuries occurred. Most of the injuries were located in the lower limb (79.5%), and muscle and tendon injuries (43.2%) were the most frequently occurring injury type. In a generalised linear model, the stress-related scales Fatigue (OR 1.70, P = 0.007), Disturbed Breaks (OR 1.84, P = 0.047) and Injury (OR 1.77, P < 0.001) and the recovery-related scale Sleep Quality (OR 0.53, P = 0.010) significantly predicted injuries in the month after the assessment. These results support the importance of frequent monitoring of recovery and stress parameters to lower the risk of injuries in professional football.

The effects of congested fixtures period on tactical and physical performance in elite football

The aim of this study was to examine the physical and tactical performances of a professional football team under congested and non-congested fixture periods. Six home matches of an English professional football team were analysed during competitive season (3 matches distancing three days from the previous fixture and 3 matches distancing six or more days from the previous fixture). Players' physical performances were measured by the total distance covered and distance covered at different speed categories. Tactical performances were measured by the percentage of time of players' movement synchronisation of lateral and longitudinal displacements. This variable was calculated considering all the possible pairs of outfield players, for the overall match and at different speed categories. Results showed no differences in the physical performance, although players' spent more time synchronised during the non-congested fixtures compared to congested fixtures, both for lateral (41.26% to 38.51%, ES: -0.3, P < 0.001) and longitudinal displacements (77.22% to 74.48%, ES: -0.5, P < 0.001). These coordination differences were particularly evident at the lower speed categories and in dyads composed by positions that tend to be further apart during the match, typically central and wing positioned players. Tactical performance seems to be affected by fixtures distribution, with players' spending more time synchronised during the non-congested fixtures. As players' cover the same amount of distance at similar intensities in both fixtures distribution, this reduction of synchronisation may be associated with an increased perception of fatigue and consequent adaptation strategies.