Latest research in football - week 24 - 2022

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases. 


Following studies were retrieved for this week:

#1 The ability of energy recovery in professional soccer players is increased by individualized low-intensity exercise

Reference: PLoS One. 2022 Jun 30;17(6):e0270484. doi: 10.1371/journal.pone.0270484. eCollection 2022.

Authors: Jihwan Hwang, Na-Ram Moon, Oliver Heine, Woo-Hwi Yang

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Summary: The aim of this study was to investigate whether individualized low-intensity exercise (ILIE) within the recovery domain before lactate threshold 1 (LT 1) improves energetic recovery and general endurance capacity in professional soccer players. Twenty-four professional soccer players (age: 24.53 ± 4.85 years, height: 180 ± 6.30 cm, body mass: 75.86 ± 8.01 kg, body fat: 12.19 ± 2.69%) participated in the study (n = 24). The 1-h ILIE intervention involved 27 jogging sessions spanning nine weeks and jogging speed corresponding to 72% of LT 1 (7.15 ± 0.95 km∙h-1). Pre-ILIE and post-ILIE LT testing variables measured within 9 weeks included blood lactate concentrations (La-) and heart rate (HR) at specific exercise intensities during ILIE LT test. The jogging/running speeds (S), delta (Δ) S, HR, and ΔHR were measured at 1.5, 2.0, 3.0, and 4.0 mmol∙L-1 La-, respectively. Values of La- and HR at the same exercise intensities (5.4-16.2 km∙h-1) in the post-ILIE LT test compared with pre-ILIE LT test were significantly decreased (P < 0.05 and P < 0.01, respectively). Furthermore, S at all specific La- levels (1.5, 2.0, 3.0, and 4.0) were significantly increased, while HR at 2.0, 3.0, and 4.0 La- decreased significantly (P < 0.05 and P < 0.01, respectively). Low to moderate positive correlations were observed between ΔS and ΔHR at 1.5 and 2.0 La- (r = 0.52 and r = 0.40, respectively). The nine-week ILIE improved energy recovery and general endurance of professional soccer players. This relates to repeated high-intensity intermittent sprints during the 90-min soccer game.



#2 Etiology and Recovery of Neuromuscular Function Following Academy Soccer Training

Reference: Front Physiol. 2022 Jun 13;13:911009. doi: 10.3389/fphys.2022.911009. eCollection 2022.

Authors: Ciaran Deely, Jamie Tallent, Ross Bennett, Alex Woodhead, Stuart Goodall, Kevin Thomas, Glyn Howatson

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Summary: The aim was to profile the etiology and recovery time-course of neuromuscular function in response to a mixed-content, standard training week in professional academy soccer players. We concurrently examined physical performance, cognitive function, and perceptual measures of mood and wellness states to identify a range of simple tests applied practitioners could use in the field as surrogate measures of neuromuscular function. Sixteen professional academy soccer players completed a range of neuromuscular, physical, perceptual, mood, and cognitive function tests at baseline and after a strenuous training day (pitch and gym), with retest at 24, 48, and 72 h, and further pitch and gym sessions after 48 h post-baseline. Maximal voluntary contraction force (MVC) and twitch responses to electrical stimulation (femoral nerve) during isometric knee-extensor contractions and at rest were measured to assess central nervous system (voluntary activation, VA) and muscle contractile (potentiated twitch force, Qtw,pot) function. Strenuous training elicited decrements in MVC force post-session (-11%, p = 0.001) that remained unresolved at 72 h (-6%, p = 0.03). Voluntary activation (motor nerve stimulation) was reduced immediately post-training only (-4%, p = 0.03). No change in muscle contractile function (Qtw,pot) was observed post-training, though was reduced at 24 h (-13%, p = 0.01), and had not fully recovered 72 h after (-9%, p = 0.03). Perceptions of wellness were impaired post-training, and recovered by 24 h (sleepiness, energy) and 48 h (fatigue, muscle soreness, readiness to train). Countermovement jump performance declined at 24 h, while RSI (Reactive Strength Index) decrements persisted at 48 h. No changes were evident in adductor squeeze, mood, or cognitive function. Elite youth soccer training elicits substantial decrements in neuromuscular function, which are still present 72 h post-strenuous exercise. Though central processes contribute to post-exercise neuromuscular alterations, the magnitude and prolonged presence of impairments in contractile function indicates it is the restitution of muscular function (peripheral mechanisms) that explains recovery from strenuous training in academy soccer players.



#3 Effects of COVID-19 Lockdown on Physical Performance, Sleep Quality, and Health-Related Quality of Life in Professional Youth Soccer Players

Reference: Front Sports Act Living. 2022 Jun 13;4:875767. doi: 10.3389/fspor.2022.875767. eCollection 2022.

Authors: Jil Keemss, Johanna Sieland, Florian Pfab, Winfried Banzer

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Summary: In March 2020, the COVID-19 outbreak led to the declaration of a pandemic. The accompanying restrictions on public life caused a change in the training routines of athletes worldwide. The present study aimed to investigate the effects of a 13-week supervised home training program on physical performance, sleep quality, and health-related quality of life in professional youth soccer players during the first COVID-19 lockdown in Germany. Eight professional soccer players (age range 16-19; height: 1.81 ± 0.07 m; body weight: 72.05 ± 6.96 kg) from a Bundesliga team in Germany participated in this study. During the lockdown, they trained 5-6 days per week with home-based training plans and were monitored via tracking apps and video training. To determine the effects of home training, measurements were taken before (March 2020) and after (June 2020) the home training period. Bioelectrical impedance analysis was used to determine body composition, and an isokinetic strength test and a treadmill step test, including lactate measurements, were used to measure physical performance. Two questionnaires were responded to in order to assess health-related quality of life [Short-Form 36 Health Survey (SF-36)] and sleep quality (Pittsburgh Sleep Quality Index). When comparing measurements before and after the home training period, we observed significant increases in the following variables: body weight (72.05 ± 6.96 kg vs. 73.50 ± 6.68 kg, p = 0.034), fat mass (11.99 ± 3.13 % vs. 13.98 ± 3.92 %, p = 0.030), body mass index (22.04 ± 0.85 kg/m2 vs. 22.49 ± 0.92 kg/m2, p = 0.049), and mental health component summary score (MCS) of the questionnaire SF-36 (53.95 ± 3.47 vs. 58.33 ± 4.50, p = 0.044). Scores on the general health (77.88 ± 14.56 vs. 89.75 ± 13.76, p = 0.025) and mental health (81.50 ± 9.30 vs. 90.00 ± 11.71, p = 0.018) subscales of the SF-36 also increased significantly. The COVID-19 lockdown led to an increase in body composition parameters and showed an improvement in the MCS and scores on the general and mental health subscales of the SF-36. Physical performance and sleep quality could be maintained during the home training period. These observations may help trainers for future training planning during longer interruptions in soccer training.



#4 Peripheral muscle function during repeated changes of direction in professional soccer players

Reference: Eur J Appl Physiol. 2022 Jun 29. doi: 10.1007/s00421-022-04988-2. Online ahead of print.

Authors: Ermanno Rampinini, Marco Martin, Ferioli Davide, Andrea Bosio, Matteo Azzolini, Marco Riggio, Nicola A Maffiuletti

Summary: The purpose was to evaluate peripheral muscle function of the knee extensors during repeated changes of direction in professional soccer players by examining differences between competitive levels, periods of the season and playing positions, and to investigate the relationships between peripheral muscle function and physical activities during matches. Knee extensor peripheral muscle function (twitch peak torque, PT) of 593 male soccer players from 13 European professional clubs competing at 3 different levels was evaluated 4 times during the season. The main outcomes were PTmax (maximal PT, muscle contractility), MPmax (maximal metabolic power exercise intensity) and PTdec (PT decline, muscle fatigability) obtained during intermittent runs of increasing intensity with multiple changes of direction interspersed with electrically evoked contractions. Relative total and sprint distances covered during a whole match and during short intervals were quantified from a sub-sample. PTmax and MPmax were higher for first than for second division (p < 0.047; d = 0.15-0.23) and Under-19 players (p < 0.007; d = 0.17-0.25). MPmax was lower (p < 0.016; d = 0.23-0.32) and PTdec was higher (p < 0.004; d = 0.26-0.39) in the pre-season compared to all the other time points. MPmax was higher for fullbacks than attackers and defenders (p < 0.041; d = 0.20-0.22). PTdec was higher for defenders than fullbacks, midfielders and wings (p < 0.029; d = 0.21-0.28). PTmax was associated with whole-match relative total distance (p = 0.004; d = 0.26). PTdec was associated with whole-match relative total distance and relative short-interval sprint distance (p < 0.050; d = 0.18-0.22). The ability to sustain repeated change of direction efforts at high intensities while preserving peripheral muscle function should be considered an important determinant of soccer physical performance.



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

Reference: Sci Rep. 2022 Jun 29;12(1):10930. doi: 10.1038/s41598-022-15278-4.

Authors: Hadi Nobari, Alexandre Duarte Martins, Rafael Oliveira, Luca Paolo Ardigò

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



#6 Effects of small-sided games and running-based high-intensity interval training on body composition and physical fitness in under-19 female soccer players

Reference: BMC Sports Sci Med Rehabil. 2022 Jun 28;14(1):119. doi: 10.1186/s13102-022-00516-z.

Authors: Sinan Nayıroğlu, Ali Kerim Yılmaz, Ana Filipa Silva, Rui Silva, Hadi Nobari, Filipe Manuel Clemente

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Summary: The aim of this study was to compare the effects of small-sided games (SSGs) and running-based high-intensity interval training (HIIT) on the body composition and physical fitness of youth female soccer players. This study followed a randomized parallel study design. Twenty-four female soccer players (age: 18.63 ± 2.36 years) were randomly allocated to two training groups (SSG, n = 12; and HIIT, n = 12). The training intervention had a duration of eight weeks, consisting of three training sessions per week. Players were assessed twice (pre- and post-intervention) for anthropometrics, vertical (countermovement jumps, CMJ; and drop jumps, DJ) and horizontal jumping (single, triple and crossover hop), sprinting (10- and 30-m), change-of-direction (COD), COD deficit and final velocity at 30-15 Intermittent Fitness Test (VIFT). A covariance analysis (ANCOVA) was used to determine differences between the groups in the effect on post-intervention by controlling for covariates (pre-intervention). The within-group analysis (time) was performed using a paired t-test, while the between-group analysis per assessment moment was performed using an independent t-test. The between-group analysis with ANCOVA revealed that there are no significant differences between the SSG and HIIT groups in the post-intervention for any outcome (p > 0.05). The within-group analysis revealed significant improvements in both the SSG and HIIT groups in CMJ (p < 0.05), single, triple and crossover hops (p < 0.05), RSI DJ 30-cm and RSI DJ 40-cm (p < 0.05), VIFT (p < 0.05) and COD (p < 0.05). SSG and HIIT are both effective for improving vertical and horizontal jumping ability, change-of-direction, and aerobic capacity status measured at a progressive and intermittent multistage test in youth soccer players.



#7 Oxidative Stress, Testosterone, Cortisol and Vitamin D: Differences in Professional Soccer Players of African and Caucasian Origin

Reference: Med Princ Pract. 2022 Jun 28. doi: 10.1159/000525728. Online ahead of print.

Authors: Michele Abate, Vincenzo Salini

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Summary: Under conditions of intense athletic exercise free radicals and cortisol production increases, whereas testosterone and vitamin D blood levels decrease. Ethnic differences in the levels of these biological mediators have been reported. Aim of the present study was to evaluate the behavior of these biological parameters, the differences ethnic, and their relationships with clinical symptoms of overtraining. Fifty professional soccer players were studied. Oxidative stress, testosterone, cortisol and vitamin D were evaluated in pre-season and in the mid competitive season. The differences related to the values collected in these two periods were evaluated. Symptoms of possible overtraining were checked. A significant increase of oxidative stress was observed in mid-season in both groups, but more significant in Africans players (386 ± 162.6 vs 277.8 ± 106.9 UCarr, p= 0.005; 2965.4 ± 815.8 vs 2560.6 ± 608.1 BAP, p= 0.035). Testosterone and vitamin D values were higher in August in all participants; however, in both months, testosterone levels were higher in Africans players (11.5 ± 2.4 vs 9.1 ± 2.6, p= 0.004; 10.3 ± 1.6 vs 7.7 ± 2.3, p= 0.000) whereas vitamin D levels were higher in Caucasians (39.4 ± 11.1 vs 33.4 ± 9.7, p= 0.048; 31.8 ± 9.7 vs 27.4 ± 9.4, in August and February, respectively). Insufficient/deficient levels of vitamin D were more frequently observed in Africans players, but the difference was near to significance only in August. Although lower vitamin D and higher cortisol and oxidative stress levels in mid-season in African players could have a negative influence on performance, no symptoms of overtraining were observed in these athletes. This is probably due to the higher levels of testosterone which allow to reach the homeostatic balance.



#8 Cardiocirculatory Stress in Professional Football (Soccer) Coaches

Reference: Clin J Sport Med. 2022 Jul 1;32(4):414-417. doi: 10.1097/JSM.0000000000001013. Epub 2022 Feb 8.

Authors: Tim Meyer, Vera Demond, Jürgen Scharhag

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Summary: It was intended to quantify cardiocirculatory stress and risk of professional football (soccer) coaches during competition. Medical screening examination and measurements during match were used on Seventeen coaches and 11 assistant coaches of the 2 highest German football leagues (male coaches; 46 ± 7 years; 8 ± 7 years in job). Professional football matches with highly competitive character were chosen and monitored for elicited cardiocirculatory stress and possible damage. Indicators of general health status, occurrence of arrhythmias, and course of heart rate and cardiac biomarkers (brain natriuretic peptide [BNP], troponin I) during the match. Besides a few preexisting cardiovascular diseases, medical screening revealed a risk factor profile similar to the general population and above-average maximal/submaximal cycle ergometry performance: Pmax 2.9 ± 0.5 W*kg-1; PWC130 1.9 ± 0.5 W*kg-1. No match-induced changes were detected for BNP (20.5 ± 9.4 to 19.7 ± 10.7 pg/mL; P = 0.48) and troponin I (12.6 ± 16.5 to 10.5 ± 14.1 ng/L; P = 0.31). Maximal heart rate during the first and second half was 127 ± 15 and 132 ± 19 beats per minute, respectively. No match-induced arrhythmias of higher degree were detected. Head and assistant coaches of German professional football teams do not show any match-induced cardiac damage, despite considerable cardiocirculatory stress. Possibly, their above-average fitness level saves them from more detrimental outcomes.



#9 How Coaches Can Improve Their Teams' Match Performance-The Influence of In-Game Changes of Tactical Formation in Professional Soccer

Reference: Front Psychol. 2022 Jun 9;13:914915. doi: 10.3389/fpsyg.2022.914915. eCollection 2022.

Authors: Leon Forcher, Leander Forcher, Darko Jekauc, Hagen Wäsche, Alexander Woll, Timo Gross, Stefan Altmann

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Summary: The tactical formation has been shown to influence the match performance of professional soccer players. This study aimed to examine the effects of in-game changes in tactical formation on match performance and to analyze coach-specific differences. We investigated three consecutive seasons of an elite team in the German Bundesliga which were managed by three different coaches, respectively. For every season, the formation changes that occurred during games were recorded. The match performance was measured on a team level using the variables "goals," "chances," and "scoring zone" entries (≙successful attacking sequence) for the own/opposing team. Non-parametric tests were used to compare the 10 min before with the 10 min after the formation change, as well as games with and without formation change. In the 10 min after the formation change, the team achieved more goals/chances/scoring zone entries than in the 10 min before the formation change (mean ES = 0.52). Similarly, the team conceded fewer opposing goals/chances/scoring zone entries in the 10 min after the formation change (mean ES = 0.35). Furthermore, the results indicate that the success of the respective formation change was dependent on the responsible coach. Depending on the season, the extent of the impacts varied (season 1: mean ES = 0.71; season 2: mean ES = 0.26; and season 3: mean ES = 0.22). Over all three seasons, the formation changes had a positive effect on the match performance of the analyzed team, highlighting their importance in professional soccer. Depending on the season, formation changes had varying impacts on the performance, indicating coach-specific differences. Therefore, the quality of the formation changes of the different coaches varied. The provided information can support coaches in understanding the effects of their in-game decisions.



#10 Injury prevention programs that include balance training exercises reduce ankle injury rates among soccer players: a systematic review

Reference: J Physiother. 2022 Jun 23;S1836-9553(22)00050-9. doi: 10.1016/j.jphys.2022.05.019.

Authors: Wesam Saleh A Al Attar, Ehdaa H Khaledi, Jumana M Bakhsh, Oliver Faude, Hussain Ghulam, Ross H Sanders

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Summary: The research question was: What is the effect of injury prevention programs that include balance training exercises on the incidence of ankle injuries among soccer players? Soccer players of any age, sex or competition level. The experimental intervention was an injury prevention program that included balance training exercises. The control intervention was the soccer team's usual warm-up program. Nine articles met the inclusion criteria. The pooled results of injury prevention programs that included balance training exercises among 4,959 soccer players showed a 36% reduction in ankle injury per 1,000 hours of exposure compared to the control group with an injury risk ratio (IRR) of 0.64 (95% CI 0.54 to 0.77). The pooled results of the Fédération Internationale de Football Association (FIFA) injury prevention programs caused a 37% reduction in ankle injury (IRR 0.63, 95% CI 0.48 to 0.84) and balance-training exercises alone cause a 42% reduction in ankle injury (IRR 0.58, 95% CI 0.41 to 0.84). This meta-analysis demonstrates that balance exercises alone or as part of an injury prevention program decrease the risk of ankle injuries. PROSPERO CRD42017054450.



#11 Traumatic biceps femoris tendon subluxation in a young football player

Reference: Orthop Rev (Pavia). 2022 Apr 20;14(2):34184. doi: 10.52965/001c.34184. eCollection 2022.

Authors: Luca Padovani, Venanzio Iacono, Ludovica Auregli, Amedeo Guarino, Simone Natali, Claudio Zorzi, Massimo Mariconda

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Summary: Snapping a knee related to a biceps femoris tendon subluxation is an uncommon syndrome that could be disabling in patients with high functional requirements such as athletes. We report a case of a 21-year-old soccer player with a painful left snapping biceps femoris tendon due to a varus trauma. He underwent knee arthroscopy and surgical exploration of the knee: the long head of the biceps femoris tendon was partially detached from his fibular insertion and there was a prominence on the fibular head. Reinsertion of the tendon and osteotomy of the fibular head allowed for resolution of all symptoms and the return to sport.



#12 Forecasting football injuries by combining screening, monitoring and machine learning

Reference: Sci Med Footb. 2022 Jul 4;1-15. doi: 10.1080/24733938.2022.2095006. Online ahead of print.

Authors: Anne Hecksteden, Georges Pierre Schmartz, Yanni Egyptien, Karen Aus der Fünten, Andreas Keller, Tim Meyer

Summary: Identifying players or circumstances associated with an increased risk of injury is fundamental for successful risk management in football. So far, time-constant and volatile risk factors are generally considered separately in either a screening (constant) or a monitoring (volatile) approach each resulting in a restricted set of explanatory variables. Consequently, improvements in predictive accuracy may be expected when screening and monitoring data are combined, especially when analysed with current machine learning (ML) techniques.This trial was designed as a prospective observational cohort study aiming to forecast non-contact time-loss injuries in male professional football (soccer). Injuries were registered according to the Fuller consensus. Gradient boosting with ROSE upsampling within a leave-one-out cross-validation was used for data analysis. The hierarchical data structure was considered throughout. Different splits of the original dataset were used to probe the robustness of results.Data of 88 players from 4 teams and 51 injuries could be analysed. The cross-validated performance of the gradient boosted model (ROC area under the curve 0.61) was promising and higher compared to models without integration of screening data. Importantly, holdout test set performance was similar (ROC area under the curve 0.62) indicating prospect of generalizability to new cases. However, the variation of predictive accuracy and feature importance with different splits of the original dataset reflects the relatively low number of events.It is concluded that ML-based injury forecasting based on the integration of screening and monitoring data is promising. However, external prospective verification and continued model development are required.



#13 Return to sport and beyond following intramuscular tendon hamstring injury: A case report of an English Premier League football player

Reference: Phys Ther Sport. 2022 May 31;56:38-47. doi: 10.1016/j.ptsp.2022.05.013. Online ahead of print.

Authors: M Taberner, J O'keefe, A Dunn, D D Cohen

Summary: Hamstring strain injuries are the most common type of injury in elite football and are associated with a high risk of reinjury, particularly those involving the intramuscular tendon (IMT). Limited information is available regarding the rehabilitation and return to sport (RTS) processes following such injuries. This case study describes the clinical presentation of an elite football player following IMT hamstring injury, their on- and off-pitch rehabilitation alongside performance monitoring throughout RTS and beyond. An elite football player suffered a grade 2c hamstring injury during an English Premier League (EPL) match. The player underwent early post-injury management, alongside progressive off-pitch physical preparation. The 'control-chaos continuum' was used as a framework for on-pitch rehabilitation to prepare the player for a return to full team training and competition. Objective and subjective markers of the player's response to progressive on- and off-pitch loading were monitored throughout RTS and beyond. The player returned to on-pitch rehabilitation after 11 days, to full team training having achieved weekly pre-injury chronic running load outputs after 35 days and played in the EPL 40 days post-injury. The player did not suffer reinjury for the rest of the EPL season. An understanding the unique structural and mechanical properties of the IMT, alongside expected RTS timeframes are important to inform rehabilitation and decision-making processes post-injury. Performance and frequent load-response monitoring throughout RTS and beyond, in conjunction with practitioner experience and effective communication are critical in facilitating effective RTS and reduce risk of reinjury following IMT injury.



#14 Relative skeletal maturity status affects injury burden in U14 elite academy football players

Reference: Scand J Med Sci Sports. 2022 Jun 24. doi: 10.1111/sms.14204. Online ahead of print.

Authors: X Monasterio, I Bidaurrazaga-Letona, J Larruskain, J A Lekue, G Diaz-Beitia, J Santisteban, I Martin-Garetxana, S M Gil

Summary: Maturation progresses at different times and at different rates between individuals. Thus, differences in maturity status exist among players in the same chronological age-based category, especially in U14 players. The purpose of this prospective study was to describe injury burden according to the relative skeletal maturity status in U14 elite academy football players. From 2011 to 2020 injuries and individual exposure (training and match) were prospectively recorded in 183 male U14 players. Skeletal age (SA) was assessed using the Tanner-Whitehouse 2 method. Relative skeletal maturity status [SA minus chronological age (CA)] was classified as follows: early (SA-CA > 0.5), on-time (SA-CA ± 0.5) and late (SA-CA < -0.5). Overall and specific injury burden (days lost/1000h) and rate ratios for comparisons between groups were calculated. Overall injury burden was 2.8-times higher (3.6-times in training) in early maturers compared with late maturers. Growth-related injuries were the most burdensome injuries in all three groups, but significant differences were not found between groups. Muscle injuries were 4-times more burdensome in early maturers compared with on-time and late maturers. Besides, joint/ligament injuries were 7- and 12- times less burdensome in late maturers than in on-time and late maturers, respectively. Significant differences between groups in overall and specific injury burden were not found in matches. Our results showed different injury patterns in U14 early, on-time and late maturers. Hence, monitoring maturity seems crucial to detect potential injuries that cause the greatest disruption, and facilitate design of targeted injury prevention programs.



#15 Wellness Forecasting by External and Internal Workloads in Elite Soccer Players: A Machine Learning Approach

Reference: Front Physiol. 2022 Jun 15;13:896928. doi: 10.3389/fphys.2022.896928. eCollection 2022.

Authors: Alessio Rossi, Enrico Perri, Luca Pappalardo, Paolo Cintia, Giampietro Alberti, Darcy Norman, F Marcello Iaia

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Summary: Training for success has increasingly become a balance between maintaining high performance standards and avoiding the negative consequences of accumulated fatigue. The aim of this study is to develop a big data analytics framework to predict players' wellness according to the external and internal workloads performed in previous days. Such a framework is useful for coaches and staff to simulate the players' response to scheduled training in order to adapt the training stimulus to the players' fatigue response. 17 players competing in the Italian championship (Serie A) were recruited for this study. Players' Global Position System (GPS) data was recorded during each training and match. Moreover, every morning each player has filled in a questionnaire about their perceived wellness (WI) that consists of a 7-point Likert scale for 4 items (fatigue, sleep, stress, and muscle soreness). Finally, the rate of perceived exertion (RPE) was used to assess the effort performed by the players after each training or match. The main findings of this study are that it is possible to accurately estimate players' WI considering their workload history as input. The machine learning framework proposed in this study is useful for sports scientists, athletic trainers, and coaches to maximise the periodization of the training based on the physiological requests of a specific period of the season.



#16 Injury incidence, severity, and burden in elite youth soccer players - A 3-year prospective study

Reference: J Sci Med Sport. 2022 Jun 11;S1440-2440(22)00174-8. doi: 10.1016/j.jsams.2022.06.003.

Authors: Ludwig Ruf, Stefan Altmann, Ferdinand Graf, Christian Romeike, Christian Wirths, Oliver Wohak, Sascha Härtel

Summary: This study aimed to investigate age-related injury incidence, severity, and burden over a 3-year period in U14 to U19 elite male soccer players in a German youth academy. Time-loss injuries of 166 unique players were prospectively documented and injury incidence, severity, and burden were calculated for each age group, body part, and type of injuries. A total of 562 time-loss injuries were recorded. Across all age groups (U14 to U19), injury incidence was 42.2 per squad season (ranging from 30.5 in the U19 to 67.7 in the U15), severity was 11.0 days lost (ranging from 8.0 in the U15 to 17.0 in the U17), and burden was 464.1 days lost per squad season (ranging from 304.9 in the U19 to 756.7 in the U14). The thigh, knee and ankle were the body parts with the highest injury incidence (9.2; 5.9; 5.9), severity (11.0; 16.0; 13.0), and burden (101.6; 94.9; 76.1). Cruciate ligament injuries had both the highest burden (164.4) and severity (137.0), and muscle injuries the highest incidence (11.0) of all types of injuries. U15 had the highest injury incidence (67.7) of all age groups. U14 and U17 had both the highest injury severity (15.0; 17.0) and burden (756.7; 618.8) of all age groups. Age-related patterns were observed for selected types of injuries such as muscle injuries, tendinopathy, bone-stress injury, and fractures. Injury incidence, severity, and burden substantially differed descriptively between age groups and clear age-related patterns for selected types of injuries were evident.



#17 Ultrasound imaging of patellar tendon thickness in elite sprint track cyclists and elite soccer players: An intra-rater and inter-rater reliability study

Reference: PLoS One. 2022 Jul 5;17(7):e0270871. doi: 10.1371/journal.pone.0270871. eCollection 2022.

Authors: Sebastian Klich, Aureliusz Kosendiak, Igor Krymski, Adam Kawczyński, Pascal Madeleine, Cesar Fernández-de-Las-Peñas

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Summary: The goal of our study was to investigate the relative and absolute intra-rater and inter-rater reliability of ultrasound assessment of patellar tendon (PT) thickness assessed over four locations, in track cyclists and soccer players. Fifteen male elite track cyclists and 15 male elite soccer players participated. Tendon thickness was measured over 4 locations placed at 5-10-15-20 mm inferior to the apex of the patella by two experienced examiners. Each examiner took two US images for the test measurements with a 10-min rest period. After a 30-min period, the subjects underwent a retest measurements that were also repeated 1-week after. A two-way analysis of variance revealed a significant group x location interaction on PT thickness for Examiner 1 (p = .001, η2 = .81) and Examiner 2 (p = 0.001, η2 = 0.78). Intra-rater reliability ranged from good to excellent (ICC2,k ≥ 0.75), whereas inter-rater reliability was good (ICC2,k ≥ 0.75) in both groups. Ultrasonographic assessment of PT was found to be a reliable method to assess tendon thickness. The middle location of the PT (corresponding to 15 and 20 mm) can be considered the most reliable spot to measure PT thickness. The PT thickness was larger among track cyclists than soccer players, with larger differences over the distal location (15 mm). Ultrasonographic assessment of PT was found to be a reliable method to assess tendon thickness. The middle location of the PT corresponding to 15 mm and 20 mm can be considered the most reliable area to measure PT thickness.



#18 Executive Functions, Physical Abilities, and Their Relationship with Tactical Performance in Young Soccer Players

Reference: Percept Mot Skills. 2022 Jul 6;315125221112236. doi: 10.1177/00315125221112236.

Authors: Daniel Carnevale, Marije Elferink-Gemser, Alberto Filgueiras, Barbara Huijgen, Caique Andrade, Julia Castellano, Davi SiIva, Fabrício Vasconcellos

Summary: While tactical performance in soccer is associated with the players' and teams' collective actions in the context of game stimuli, how tactical performance relates to players' executive functions (EFs) and physical abilities should be examined. In this study, we examined these relationships among 81 Under-15 male soccer players who underwent tactical evaluation (FUT-SAT), EF tests (i.e.,(Stop-Signal Test and Design Fluency Test)), and physical tests (i.e.,(Maturity Offset, Yoyo Endurance Test II, Sargent Jump Test, and Sprint Test)). Multiple linear regression modeling with the stepwise method showed that approximately 48% of overall game tactical performance variance was explained by inhibitory control, biological maturation, and sprint capacity (p = .004; d = .54; r2 = .479), whereas 35% of offensive tactical performance variance was explained by the same dimensions (p = .001; d = .91; r2 = .353). In addition, approximately 28% of defensive tactical performance variance was explained by cognitive flexibility and aerobic resistance (p = .007; d = .39; r2 = .280). These results reflect the combined importance of EFs and physical abilities for tactical performance in young soccer players, suggesting that these abilities may be targets for training when trying to improve young players' performance.



#19 Fractures in soccer: The current evidence, and how this can guide practice

Reference: J Orthop. 2022 Jun 24;33:25-30. doi: 10.1016/j.jor.2022.06.010. eCollection Sep-Oct 2022.

Authors: Greg A J Robertson, Kok K Ang, Bilal Jamal

Summary: This article reviews the current evidence on traumatic fractures in soccer, and assesses how this can guide practice. The incidence of traumatic soccer-related fractures was found to be 0.64 to 0.71/1000 in the general population. Demographics vary between the general population and professional soccer players, with 68% of traumatic soccer fractures occurring in the upper extremity in the general population, and only 23% of traumatic soccer fractures occurring in the upper extremity in professional players. Within the general population, around 80% of traumatic soccer-related fractures are managed non-operatively, with 20% managed operatively. The optimal treatment method is determined by fracture location and configuration. There is an increasing role for primary operative treatment in unstable, non-displaced fracture types, to facilitate an accelerated return to soccer. Around 86% of soccer players return to sport post-fracture. Return times vary by fracture locations and playing level, with elite players having quicker return times than the general population. Regarding injury prevention, shin guards appear to confer substantial benefit against tibial diaphyseal fractures. However, further research is required to determine the optimal preventative measures against fractures in soccer.


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