Latest research in football - week 13 - 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 Effects of congested match periods on acceleration and deceleration profiles in professional soccer

Reference: Biol Sport. 2022 Mar;39(2):307-317. doi: 10.5114/biolsport.2022.103725. Epub 2021 Apr 9.

Authors: Léo Djaoui, Adam Owen, Matt Newton, Pantelis Theodoros Nikolaidis, Alexandre Dellal, Karim Chamari

Download link:

Summary: The aim of the present study was to analyse the influence of congested periods of matches on the acceleration (Acc) and deceleration (Dec) profiles of elite soccer players. Twenty-three elite male professional soccer players participated in the study across 31 official matches. Assessed periods included: (i) congested periods (three to four days between games), and (ii) non-congested periods (more than four days between games). Physical activity during matches was recorded during games using a 10Hz global positioning system device, coupled with a 100 Hz accelerometer, and was analysed according to the periods. Maximal Acc- (73.2 ± 20.3 vs. 84.918.5 m), high Acc- (244.0 ± 49.5 vs. 267.0 ± 37.8 m), maximal Dec- (139.0 ± 44.8 vs. 152.039.3 m) and the total decelerating- distance (5132 ± 690 vs. 5245 ± 552 m) were lower in congested than in non-congested periods (p < 0.05, effect size 0.31-0.70). Neither a main effect of playing position nor a period*playing position interaction on Acc and Dec were observed (p > 0.05). It was concluded that Acc and Dec match activities were significantly affected during congested periods compared to non-congested highlighting a possible fatigue accumulation being responsible for the observed decrement in physical activity. Monitoring Acc and Dec metrics throughout particular periods of congested fixtures amongst professional soccer teams is advised and may be a way to assess physical and fatigue status.



#2 Characteristics of the Kicking Motion in Adolescent Male Soccer Players Who Develop Osgood-Schlatter Disease: A Prospective Study

Reference: Orthop J Sports Med. 2022 Mar 14;10(3):23259671221083567. doi: 10.1177/23259671221083567. eCollection 2022 Mar.

Authors: Seira Takei, Shuji Taketomi, Suguru Torii, Michio Tojima, Koji Kaneoka, Sakae Tanaka

Download link:

Summary: Osgood-Schlatter disease (OSD) is an apophysitis of the tibial tubercle caused by repeated traction of the patellar tendon during adolescence. Although OSD is associated more with sports such as soccer, it remains unclear whether the kicking motion itself is related to OSD onset. The purpose was to prospectively evaluate the kicking motion in adolescent soccer players who later developed OSD. The authors observed 47 Japanese adolescent male soccer players (mean age, 12 years) over 6 months in 2018-2019; none of the participants had OSD at study onset. The players underwent tibial tubercle ultrasound at baseline, and their kicking motion was evaluated using 3-dimensional (3D) motion analysis with 65 reflective markers. The 3D angle of the lumbar spine, thorax, and pelvis and the angular velocity of the hips, knees, and ankles were calculated for the support leg. The kicking motion was divided into 8 phases, and ball speed, kicking time, and positions of the support (nonkicking) leg and center of mass (COM) from the ball were calculated for each phase. Six months later, the players underwent another ultrasound and were divided into 2 groups: those diagnosed with OSD in the support leg (OSD group) and those without OSD (normal [NRL] group). All factors calculated using the kicking motion analysis at the baseline were compared between groups. There were 19 players in the OSD group and 28 players in the NRL group. Anthropometric measurements, ball speed, and kicking time were similar between the 2 groups. The forward translation of the COM and the support leg, the flexion angle of the thorax, and the rotation angle of the pelvis before impact with the ball were all significantly smaller in the OSD group than in the NRL group (P < .05). Moreover, the knee extension angular velocity of the support leg was significantly larger in the OSD group (P < .05) at ball impact. A kicking motion with small COM translation, small thoracic flexion, and small pelvic rotation before ball impact, as well as large knee extension angular velocity of the support leg at ball impact, may be associated with OSD onset.



#3 Leveling the Playing Field: A New Proposed Method to Address Relative Age- and Maturity-Related Bias in UK Male Academy Soccer Players

Reference: Front Sports Act Living. 2022 Mar 3;4:847438. doi: 10.3389/fspor.2022.847438. eCollection 2022.

Authors: Sofie Bolckmans, Janet L Starkes, Chris Towlson, Chris Barnes, Guy Parkin, Werner F Helsen

Download link:

Summary: Relative age selection bias persists within all major soccer leagues and youth soccer academies across the globe, with the relative age effect (RAE) being typically characterized as the over selection of relatively older players (who have sometimes also been shown to be early maturing). The aim of this study was to examine if a new allocation method (i) eliminates the RAE, and (ii) reduces the presence of any additional maturity-related differences in anthropometric and physical fitness characteristics which may exist between players within the same selection category. In the first phase, 1,003 academy soccer players [under (U) 9-16] from 23 UK professional soccer clubs were sampled and a clear RAE per birth quarter (Q) was observed for the overall sample (Q1 = 45.0% vs. Q4 = 9.8%) as well as for the different age categories. Using the newly suggested reallocation method, youth players were divided by allocation date which was defined as the midway point between the chronological age and the estimated developmental (ED) birthdate. Stature was used as an anthropometric reference point on the P50 of the growth curve to determine the developmental birthdate for this new method. After the reallocation of the players using ED, the distribution of players was more equally spread (Q1 = 25.3%, Q2 = 25.6%, Q3 = 22.4%, Q4 = 26.7%). After reallocation, the mean delta stature was reduced by 16.6 cm (from 40.3 ± 7.08 to 23.7 ± 4.09 cm, d = 2.87). The mean delta body mass difference after allocation was reduced by 6.7kg (from 33.2 ± 6.39 to 26.5 ± 4.85 kg, d = 1.18). The mean age difference increased from 1.8 to 3.9 years. A total of 42.7% of the sample would have been reallocated to a different age group compared to the current one. After reallocation, 45% of the anthropometric and physical fitness comparisons showed reductions in the within-group variation expressed as a percentage of coefficient of variation (CV%). The U10 players demonstrated the largest reduction in CV% (-7.6%) of the anthropometric characteristics. The U10 squad also showed the largest reduction in CV% for various physical fitness characteristics (-7.5%). By both eliminating the RAE and reducing temporary maturity-related anthropometric and physical fitness differences, soccer academies across the world may diversify and increase the size of the talent pool both for clubs and national youth teams. In conclusion, this study provides further evidence that the newly proposed allocation method shows the potential to remove the RAE and to create a more "leveled playing field" by reducing the within-group variation of anthropometric and physical fitness characteristics affording relatively younger, and eventually, late-maturing players the opportunity to develop their talent fairly.



#4 No sport for old players. A longitudinal study of aging effects on match performance in elite soccer

Reference: J Sci Med Sport. 2022 Mar 9;S1440-2440(22)00046-9. doi: 10.1016/j.jsams.2022.03.004.

Authors: Ezequiel Rey, Miguel Lorenzo-Martínez, Roberto López-Del Campo, Ricardo Resta, Carlos Lago-Peñas

Summary: This study aimed to examine the effects of age on match-related physical and technical-tactical performance in elite soccer players using a longitudinal design. Data were collected from 154 players who competed in the Spanish first division (LaLiga) between the 2012-13 and 2019-20 seasons. A total of 14,092 individual match observations were analyzed using a computerized tracking system (TRACAB, Chyronhego, New York, NY). The players were classified into five positional roles: central defenders (n = 37); external defenders (n = 44); central midfielders (n = 34); external midfielders (n = 22); and forwards (n = 17). The main results showed that (a) soccer players decreased by an average of 0.56% their total distance covered for each year that they got older. Similarly, the number of high-intensity efforts and distance covered at high-intensity running decreased by 1.80% and 1.42% per year, respectively; (b) players significantly increased their pass accuracy by an average of 0.25% each year that they got older; (c) the detrimental effect of age on total distance and high-intensity running was greater for external defenders, external midfielders, and forwards; and (d) the positive effect of age on pass accuracy was greater for central defenders and central midfielders. Elite soccer players with long-term careers were unable to maintain their match-related physical performance as they got older. However, players can annually improve their technical-tactical skills with increasing age as a possible compensation mechanism against physical performance declines related to aging.



#5 Management of anterior thigh injuries in soccer players: practical guide

Reference: BMC Sports Sci Med Rehabil. 2022 Mar 18;14(1):41. doi: 10.1186/s13102-022-00428-y.

Authors: Lasse Lempainen, Sandra Mechó, Xavier Valle, Stefano Mazzoni, Jose Villalon, Marco Freschi, Luca Stefanini, Alvaro García-Romero-Pérez, Maria Burova, Pavel Pleshkov, Ricard Pruna, Giulio Pasta, Jussi Kosola

Download link:

Summary: Most of the anterior thigh injuries are contusions or strains, however, some of these injuries can be career ending. Early diagnosis and correct treatment are key to successful outcome. Analyzing injury mechanism and adding both clinical and imaging findings, clinicians can make the right treatment decisions already often in the acute phase of the injury. Low grade contusions and muscle strains are treated well with planned rehabilitation, but complete tendon injuries or avulsions can require operative treatment. Also, neglected minor injuries could lead to chronic disabilities and time lost from play. Typical clinical presentation of anterior thigh injury is swelling and pain during hip flexion or knee extension. In more severe cases a clear gap can be palpated. Imaging methods used are ultrasound and magnetic resonance imaging (MRI) which are helpful for clinicians to determine more exact the extent of injury. MRI can identify possible tendon retractions which may need surgery. Clinicians should also be aware of other traumatic lesions affecting anterior thigh area such as myositis ossificans formation. Optimal treatment should be coordinated including acute phase treatment with rest, ice, and compression together with designed return-to-play protocol. The anatomical structure involved lines the treatment pathway. This narrative review describes these more common reasons for outpatient clinical visits for anterior thigh pain and injuries among soccer players.



#6 Small-Sided Games in Elite Football: Practical Solutions to Replicate the 4-min Match-Derived Maximal Intensities

Reference: J Strength Cond Res. 2022 Mar 23. doi: 10.1519/JSC.0000000000004249. Online ahead of print.

Authors: Andrea Riboli, Fabio Esposito, Giuseppe Coratella

Summary: The purpose of the study was to determine the area per player (ApP, m2·player-1) to replicate the maximal 4-min match-play period (4-minPeak) using small-sided or large-sided games (SSGs) lasting the same duration in elite football players. Twenty players (age: 26 ± 5 years) competing in European championship and international UEFA competitions were monitored during SSGs with (SSGwith) or without (SSGwithout) goalkeepers, both lasting 4-min. A total of 1,724 and 561 individual observations for SSGwith and SSGwithout across 99 and 34 different SSGs formats were undertaken. Whole (90-minavg) and 4-minPeak match demands were calculated. Relative (m·min-1) total, high-speed (HSRD), very high-speed (VHSRD), sprint, and acceleration/deceleration distance were collected. For both SSGwith and SSGwithout, ApP was small-to-very-largely correlated with TD, HSRD, VHSRD, and sprint, whereas an inverse trivial-to-small correlation with acceleration/deceleration was found. In SSGwith, the ApP to replicate 4-minPeak was larger (p < 0.001, effect size [ES]: 0.33-5.80) than that to mimic 90-minavg for total distance, HSRD, VHSRD, and sprint, whereas for acceleration/deceleration the ApP was lower (p < 0.001, ES: -3.13 to 0.48) for 4-minPeak. In SSGwithout, the ApP to replicate 4-minPeak was larger (p < 0.001, ES: 0.04-3.72) than that to mimic 90-minavg for HSRD, VHSRD, and sprint. Some positional differences (p < 0.05, ES: 0.22-1.10) in ApP were found. The ApP to replicate 4-minPeak was higher for SSGwith than SSGwithout (p < 0.001, ES: 0.67-3.58). These findings may help practitioners to recreate the 4-minPeak to manage ApP during SSGs in elite football.



#7 A Bayesian Approach to Predict Football Matches with Changed Home Advantage in Spectator-Free Matches after the COVID-19 Break

Reference: Entropy (Basel). 2022 Mar 4;24(3):366. doi: 10.3390/e24030366.

Authors: Jaemin Lee, Juhuhn Kim, Hyunho Kim, Jong-Seok Lee

Download link:

Summary: Since the coronavirus disease 2019 (COVID-19) pandemic, most professional sports events have been held without spectators. It is generally believed that home teams deprived of enthusiastic support from their home fans experience reduced benefits of playing on their home fields, thus becoming less likely to win. This study attempts to confirm if this belief is true in four major European football leagues through statistical analysis. This study proposes a Bayesian hierarchical Poisson model to estimate parameters reflecting the home advantage and the change in such advantage. These parameters are used to improve the performance of machine-learning-based prediction models for football matches played after the COVID-19 break. The study describes the statistical analysis on the impact of the COVID-19 pandemic on football match results in terms of the expected score and goal difference. It also shows that estimated parameters from the proposed model reflect the changed home advantage. Finally, the study verifies that these parameters, when included as additional features, enhance the performance of various football match prediction models. The home advantage in European football matches has changed because of the behind-closed-doors policy implemented due to the COVID-19 pandemic. Using parameters reflecting the pandemic's impact, it is possible to predict more precise results of spectator-free matches after the COVID-19 break.



#8 Change of Direction Speed and Reactive Agility in Prediction of Injury in Football; Prospective Analysis over One Half-Season

Reference: Healthcare (Basel). 2022 Feb 25;10(3):440. doi: 10.3390/healthcare10030440.

Authors: Dragan Mijatovic, Dragan Krivokapic, Sime Versic, Goran Dimitric, Natasa Zenic

Download link:

Summary: Agility is an important factor in football (soccer), but studies have rarely examined the influences of different agility components on the likelihood of being injured in football. This study aimed to prospectively evaluate the possible influences of sporting factors, i.e., flexibility, reactive agility (RAG), and change of direction speed (CODS), on injury occurrence over one competitive half-season, in professional football players. Participants were 129 football professional players (all males, 24.4 ± 4.7 years), who underwent anthropometrics, flexibility, and RAG and CODS (both evaluated on non-dominant and dominant side) at the beginning of second half-season 2019/20 (predictors). Over the following half-season, occurrence of injury was registered (outcome). To identify the differences between groups based on injury occurrence, t-test was used. Univariate and multivariate logistic regressions were calculated to identify the associations between predictors and outcome. Results showed incidence of 1.3 injuries per 1000 h of training/game per player, with higher likelihood for injury occurrence during game than during training (Odds Ratio (OR) = 3.1, 95%CI: 1.63-5.88) Univariate logistic regression showed significant associations between players' age (OR = 1.65, 95%CI: 1.25-2.22), playing time (OR = 2.01, 95%CI: 1.560-2.58), and RAG (OR = 1.21, 95%CI: 1.09-1.35, and OR = 1.18, 95%CI: 1.04-1.33 for RAG on dominant- and non-dominant side, respectively), and injury occurrence. The multivariate logistic regression model identified higher risk for injury in those players with longer playing times (OR = 1.81, 95%CI: 1.55-2.11), and poorer results for RAG for the non-dominant side (OR = 1.15, 95%CI: 1.02-1.28). To target those players who are more at risk of injury, special attention should be paid to players who are more involved in games, and those who with poorer RAG. Development of RAG on the non-dominant side should be beneficial for reducing the risk of injury in this sport.



#9 Effects of Mobile-Based Rehabilitation in Adolescent Football Players with Recurrent Lateral Ankle Sprains during the COVID-19 Pandemic

Reference: Healthcare (Basel). 2022 Feb 22;10(3):412. doi: 10.3390/healthcare10030412.

Authors: Xiaobo Qu, Kai Li, Sangcheul Nam

Download link:

Summary: Football is a sport involving dynamic movements, and ankle sprains are common sports injuries experienced by football players. Ankle sprains exhibit a high recurrence rate, and rehabilitation training is effective; however, expert-supervised rehabilitation (SVR) at training centers is difficult due to the recent COVID-19 pandemic. This study investigated the effects of mobile-based rehabilitation (MBR) performed at home by high school football players. Sixty players (SVR: 30 and MBR: 30) with recurrent ankle sprains were analyzed. The rehabilitation program consisted of strength and balance training, and the training intensity was gradually increased from week 1 to week 8. The SVR group underwent training at the center with experts, and the BMR group were provided with programs and feedback using mobile devices. Ankle muscle strength was evaluated by measuring isometric eversion, inversion, plantarflexion, and dorsiflexion contraction using a hand-held dynamometer, and dynamic balance was assessed using the Y-balance test (YBT; anterior, posteromedial, and posterolateral); the Foot and Ankle Outcome Score (FAOS) was used for the subjective evaluation. Measurements were conducted at weeks 1, 4, and 8. The patients visited the clinic within 1 week after the injury, and the first test was conducted after consent to participate in the research. Patients underwent the second test at an average of 3.2 weeks after the first test, and the last test at an average of 4.4 weeks after the second test. Although only the SVR group exhibited improvement in strength (eversion and dorsiflexion), YBT and subjective satisfaction at week 4, these measurements improved in both the SVR and MBR groups at week 8. Therefore, mobile-based rehabilitation could be a suitable alternative for high school athletes with ankle sprains who cannot undergo supervised rehabilitation.



#10 Does Femoroacetabular Impingement Syndrome Affect Self-Reported Burden in Football Players With Hip and Groin Pain?

Reference: Sports Health. 2022 Mar 23;19417381221076141. doi: 10.1177/19417381221076141. 

Authors: Mark J Scholes, Joanne L Kemp, Benjamin F Mentiplay, Joshua J Heerey, Rintje Agricola, Adam I Semciw, Richard B Souza, Thomas M Link, Sharmila Majumdar, Matthew G King, Peter R Lawrenson, Kay M Crossley

Summary: It is unknown if football players with femoroacetabular impingement (FAI) syndrome report worse burden than those with other causes of hip/groin pain, and to what extent this is mediated by cartilage defects and labral tears. Football players with FAI syndrome would report worse burden than other symptomatic players, with the effect partially mediated by cartilage defects and/or labral tears. Football (soccer and Australian football) players (n = 165; 35 women) with hip/groin pain (≥6 months and positive flexion-adduction-internal rotation test) were recruited. Participants completed 2 patient-reported outcome measures (PROMs; the International Hip Outcome Tool-33 [iHOT-33] and Copenhagen Hip and Groin Outcome Score [HAGOS]) and underwent hip radiographs and magnetic resonance imaging (MRI). FAI syndrome was determined to be present when cam and/or pincer morphology were present. Cartilage defects and labral tears were graded as present or absent using MRI. Linear regression models investigated relationships between FAI syndrome (dichotomous independent variable) and PROM scores (dependent variables). Mediation analyses investigated the effect of cartilage defects and labral tears on these relationships. FAI syndrome was not related to PROM scores (unadjusted b values ranged from -4.693 (P = 0.23) to 0.337 (P = 0.93)) and cartilage defects and/or labral tears did not mediate its effect (P = 0.22-0.97).

Conclusion: Football players with FAI syndrome did not report worse burden than those with other causes of hip/groin pain. Cartilage defects and/or labral tears did not explain the effect of FAI syndrome on reported burden.

Clinical relevance: FAI syndrome, cartilage defects, and labral tears were prevalent but unrelated to reported burden in symptomatic football players.



#11 The Effectiveness of Psychological Workshops for Coaches on Well-Being and Psychomotor Performance of Children Practicing Football and Gymnastics

Reference: J Sports Sci Med. 2021 Oct 1;20(4):586-593. doi: 10.52082/jssm.2021.586. eCollection 2021 Dec.

Authors: Dominika Wilczyńska, Anna Łysak-Radomska, Magdalena Podczarska-Głowacka, Wojciech Skrobot, Katarzyna Krasowska, Ewelina Perzanowska, Tomasz Dancewicz, Patrycja Lipińska, Will G Hopkins

Download link:

Summary: Coach workshops based on seven principles (inspiration, explanation, expectation, support, reward, appreciation, growth and winning) enhance the sport experience of adult athletes. Therefore, we have investigated the effects of such workshops with coaches of child athletes. Study participants were coaches of 57 9- to 12-year old girls (practicing gymnastics) and boys (practicing football). Three coaches of 28 children attended three workshops over 12 weeks, while a control group of 5 coaches of 29 children attended no workshops. Measures of well-being and psychomotor performance were taken on the children before and after the intervention; differences in mean changes between intervention and control groups were adjusted for baseline, standardized, and assessed with a conservative magnitude-based decision method. There were clear substantial effects of the workshop on motivation averaged across several dimensions (girls, large, most likely beneficial), on a decision test (boys, small-moderate, very likely beneficial), on state anxiety self-reflection (girls, moderate, likely harmful), and on reaction time (boys, small, possibly harmful). The beneficial effects of the workshop in this pilot study are encouraging, but the unclear and potentially harmful effects and the roles of presenter- and coach-specific effects need to be investigated further with a representative sample of coaches and more children before the workshop is recommended for implementation.



#12 International football players with cerebral palsy maintained their physical fitness after a self-training program during the COVID-19 lockdown

Reference: PeerJ. 2022 Mar 17;10:e13059. doi: 10.7717/peerj.13059. eCollection 2022.

Authors: Iván Peña-González, José Manuel Sarabia, Agustín Manresa-Rocamora, Manuel Moya-Ramón

Download link:

Summary: The COVID-19 global pandemic caused a complete stop in sport participation which meant a detraining period for athletes. High-level athletes had to train at home guided by their coaches and conditioning trainers in an effort to maintain their physical fitness. The aim of maintaining the training adaptations and physical fitness during the COVID-19 mandatory lockdown was especially important for CP athletes, in which the detraining period was expected to cause early declines in motor function, poor coordination and muscle weakness due to their disability. The present study assessed the effect of a guided self-training program on international CP football players' physical fitness during the COVID-19 mandatory lockdown. Fifteen CP football players from the Spanish National Team participated in the study. An experimental design with a pre- (T1) and a post-intervention (T2) assessment was carried out, with a 12-week period of players' self-training (divided in two periods of 6 weeks) which combined strength and endurance training. Physical performance assessment consisted in the free countermovement jump (CMJ), 5, 10 and 20-m sprint, the modified agility T-test (MAT) and a dribbling test. The Kruskal-Wallis test was used for between-group comparisons, while the Student's paired t test or the Fisher Pitman permutation test, based on the normality of the data, were used for within-group comparisons. The results showed no differences between sport classes (FT1, FT2 and FT3) in physical fitness change after the training program (Chi2 = 0.16 to 1.73; p = 0.42 to 0.92). Within-group comparisons showed an increase of jump height in the CMJ (4.19 cm [2.46, 5.93]; p < 0.001) and a maintenance of the 5, 10 and 20-m sprint, MAT and dribbling ability (<0.01 to 0.09 s; p = 0.19 to 0.97). To the authors' knowledge, this is the first study that examined the physical fitness adaptations to a training program with CP football players. The results show that a 12-week guided self-training program without football-specific stimulus may be effective to maintain or even improve the specific physical performance of international CP football players during a non-competitive period (as the COVID-19 lockdown). This study reveals that CP football players are able to show adaptations to the strength and endurance training and this could be the basis for future research regarding training adaptations in CP football players.



#13 Return to match running performance after a hamstring injury in elite football: a single-centre retrospective cohort study

Reference: BMJ Open Sport Exerc Med. 2022 Feb 24;8(1):e001240. doi: 10.1136/bmjsem-2021-001240. eCollection 2022.

Authors: Marloes I Hoppen, Gustaaf Reurink, Vosse A de Boode, Lisanne van der Kaaden, Lotte Jagtman, Tim Glazenburg, Bastiaan Bruning, Johannes L Tol

Download link:

Summary: The aim was to determine the number of matches to return to pre-injury match running performance after sustaining an acute hamstring injury. In this retrospective cohort study, the injuries of the players of the first, Under21, Under19, Under18 and Under17 teams of a professional football club in the period 2017-2020 were analysed. Acute hamstring injuries with a minimal absence from training or match play of 7 days were included. For running performance, we assessed the following variables: maximal velocity (km/hour), total distance, high-intensity distance (17.5-22.5 km/hour) and sprint distance (>22.5 km/hour). We calculated the average and 95% CI for these variables during the last five matches before the injury. The primary outcome was the number of matches to reach maximal velocity within the 95% CI of the player's individual pre-injury performance. Secondary outcome scores included the duration (in days and matches) to reach the other running performance variables. 18 hamstring injuries in 15 players were included. 15 out of 18 injuries (83%) showed a return to pre-injury maximal velocity in the second match after return to play. The median number of matches to return to pre-injury maximal velocity was 2 (IQR 1-2). In the first match after return to play, pre-injury total distance was reached in 100% of the injuries, pre-injury sprint distance was reached in 94% of the injuries and pre-injury high-intensity distance was reached in 89% of the injuries. Following an acute hamstring injury in elite football, pre-injury match running performance is reached in the first or second match.



#14 The Faroe Islands COVID-19 Recreational Football Study: Player-to-Player Distance, Body-to-Body Contact, Body-to-Ball Contact and Exercise Intensity during Various Types of Football Training for Both Genders and Various Age Groups

Reference: Biomed Res Int. 2022 Mar 17;2022:6822385. doi: 10.1155/2022/6822385. eCollection 2022.

Authors: Magni Mohr, Tórur Sjúrðarson, Eli N Leifsson, Morten B Randers, Nikolas Sten Knudsen, Manuel Mounir Demetry Thomasen, Jeppe Panduro, Malte Nejst Larsen, Thomas Bull Andersen, Peter Krustrup

Download link:

Summary: We determined player-to-player distance, body-to-ball contact, and exercise intensity during three training modalities in various football populations. 213 participants were recruited, ranging from 9-year-old boys to young men and 11-year-old girls to middle-aged women. All groups were analysed with video-filming and GPS-based Polar Pro monitors during three types of football training for 20 min, i.e., COVID-19-modified training (CMT) with >2-metre player-to-player distance, small-sided games (SSG), and simulated match-play with normal rules (SMP), in randomised order. Time spent in a danger zone (1.5 m) per-percent-infected-player (DZ PPIP) ranged from 0.015 to 0.279% of playing time. DZ PPIP for SSG was higher (P < 0.05) than CMT and SMP. The average number of contacts (within 1.5 m) with a potentially infected player ranged from 12 to 73 contacts/hour. SSG had more (P < 0.05) contacts than CMT and SMP, with SMP having a higher (P < 0.05) number of contacts than CMT. Time/contact ranged from 0.87 to 3.00 seconds for the groups. No player-to-player and body-to-ball touches were registered for CMT. Total player-to-player contacts were 264% higher (P < 0.05) in SSG than SMP, ranging from 80 to 170 and 25 to 56 touches, respectively. In all groups, a greater total distance was covered during SMP compared to CMT (38-114%; P < 0.05). All groups performed more high-intensity running (33-54%; P < 0.05) and had higher heart rates during SMP compared to CMT. Different types of football training all appear to exert a minor COVID-19 infection risk; however, COVID-19-modified training may be safer than small-sided game training, but also match-play. In contrast, exercise intensity is lower during COVID-19-modified training than match-play.



#15 Osgood-Schlatter Disease in youth elite football: Minimal time-loss and no association with clinical and ultrasonographic factors

Reference: Phys Ther Sport. 2022 Mar 9;55:98-105. doi: 10.1016/j.ptsp.2022.02.024. Online ahead of print.

Authors: Mohamed Schultz, Johannes L Tol, Linda Veltman, Lisanne Kaaden van der, Gustaaf Reurink

Download link:

Summary: Osgood-Schlatter Disease is the most common cause of knee pain in youth. Scientific research in youth elite football is limited. The aim was to assess clinical and ultrasonographic factors associated with Osgood-Schlatter Disease and calculate point prevalence of clinical diagnosis and time-loss in youth elite male football. We obtained data during the pre-season periodic health evaluation. Osgood-Schlatter Disease diagnosis was defined as (1) athlete-reported anterior knee pain and (2) clinical confirmation by pain provocation at the tibial tuberosity. Time-loss was defined as inability to participate in team training and/or competition. For the nested-case control study, we examined clinical and ultrasonographic factors in the U13 to U16 teams. We matched on calendar-age. The clinical factors were: self-reported history of Sever's disease, growth measures, leg muscles flexibility and strength and ultrasonographic bone maturity stages according to Ehrenborg, For the cross-sectional study, we included players of the U13 to U19 teams to calculate the point prevalence. The case-control study consisted 30 players and the cross-sectional study 127 players. Previous Sever's disease was strongly associated with Osgood-Schlatter Disease (OR = 16.8; p = 0.02; 95% CI = 1.6-174.5). None of the other clinical or ultrasonographic factors were associated. The point prevalence was 17% and 80% had no time-loss despite presence of clinical symptoms. Considering the 16.8OR, previous Sever's disease indicates a strong association with Osgood-Schlatter Disease. Although generally suggested, growth velocity and bone maturity are not associated in an age-matched comparison.



#16 Cognitive and Physical Effects of Warm-Up on Young Soccer Players

Reference: Motor Control. 2022 Mar 29;1-19. doi: 10.1123/mc.2021-0128. Online ahead of print.

Authors: Francisco Tomás González-Fernández, Hugo Sarmento, Sixto González-Víllora, Juan Carlos Pastor-Vicedo, Luis Manuel Martínez-Aranda, Filipe Manuel Clemente

Summary: This study analyzed the effects of with (WC) or without conducting a warm up on youth soccer players immediately before performing physical and cognitive tests. Fourteen youth soccer player (age 11.64 ± 0.50) participated in a counterbalanced cross-sectional study in which three conditions were tested: (a) basal lineal condition; (b) WC (immediately before the physical and cognitive tests); and (c) without WC (passive resting for 15 min between the warm-up and physical and cognitive tests). A 30-m sprint test, countermovement jump, and psychomotor vigilance task were also applied. The WC revealed significant improvements in countermovement jump (p < .05), 30-m sprint test performance (p < .05), and reaction time in psychomotor vigilance task (p < .05) in comparison to basal lineal condition and without WC. A 15-min rest after a warm-up has a meaningfully decremental effect on the physical and cognitive readiness of youth soccer players, in comparison with when they warm-up immediately before the demands are imposed.



#17 Acute Effects of Soleus Stretching on Ankle Flexibility, Dynamic Balance and Speed Performances in Soccer Players

Reference: Biology (Basel). 2022 Feb 26;11(3):374. doi: 10.3390/biology11030374.

Authors: Shi Huang, Hong-Jia Zhang, Xin Wang, Winson Chiu-Chun Lee, Wing-Kai Lam

Download link:

Summary: Most dynamic stretching protocols include the gastrocnemius muscle, but soleus stretches are often neglected, which is the key powerful muscle for the push-off (concentric) of all speed movements. The purpose of this study was to examine whether the added soleus stretch in a regular stretching protocol would have greater benefits for ankle flexibility, dynamic balance and functional performance. Fourteen healthy male soccer players received each of the stretching conditions (regular stretching only (Regular), regular stretching with soleus stretching (Soleus) and no stretching (Control)) randomly on different training days, with two-day separation. The ankle flexibility, standing heel-lift balance and speed performances were assessed following each stretching intervention. The active dynamic stretches were performed for 30 s with three repetitions on each of the three (Regular) and four (Soleus) muscles. One-way ANOVA with repeated measures (or the Friedman non-parametric test) was performed to determine any significant effect with alpha = 0.05. Our findings revealed that both the Regular and Soleus stretching groups showed an increased active range of ankle motion compared to the no-stretching control (Ps &lt; 0.05). In the heel raise balance test, both stretching groups experienced a significant increase in maximum plantarflexion strength as well as resultant anterior-posterior and medial-lateral CoP excursions compared to the no-stretching control (Ps &lt; 0.05). In the sprinting tasks, both the Soleus and Regular stretching groups induced faster linear and curved running times (Ps &lt; 0.05). When comparing the two stretching groups, Soleus stretching led to better ankle flexibility, maximum plantarflexion strength and curved running time (Ps &lt; 0.05). Thus, added stretches on the soleus muscles can provide further benefits to speed performances in soccer.



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

Reference: Biology (Basel). 2022 Mar 18;11(3):467. doi: 10.3390/biology11030467.

Authors: Hadi Nobari, Roghayyeh Gholizadeh, Alexandre Duarte Martins, Georgian Badicu, Rafael Oliveira

Download link:

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



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

Reference: Res Q Exerc Sport. 2022 Mar 28;1-9. doi: 10.1080/02701367.2021.1964697. Online ahead of print.

Authors: Adam Field, Liam David Corr, Hugo Sarmento, Robert Naughton, Tom Clifford, Matthew Haines, Richard Michael Page, Liam David Harper

Summary: 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. 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. 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). 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.



#20 Are acute:chronic workload ratios of perceived exertion and running based variables sensible to detect variations between player positions over the season? A soccer team study

Reference: BMC Sports Sci Med Rehabil. 2022 Mar 28;14(1):51. doi: 10.1186/s13102-022-00445-x.

Authors: Hadi Nobari, Ersan Arslan, Alexandre Duarte Martins, Rafael Oliveira

Download link:

Summary: The aim of this study was to describe and compare the in-season variations of acute: chronic workload ratio (ACWR) coupled, uncoupled, and exponentially weighted moving average (EWMA) through session rating of perceived exertion (s-RPE), total distance (TD), high-speed running distance (HSRD) and sprint distance (SPRINT) in three different periods of an elite soccer season according to player positions. Twenty male elite players (age: 29.4 ± 4.4) from an Asian First League team were daily monitored for twenty consecutive weeks during the 2017-2018 in-season. Forty-seven trainings and twenty matches were monitored using global positioning system units (GPS) to collect TD, HSRD and SPRINT. Through the collection of s-RPE, TD, HSRD, and SPRINT by ACWR and EWMA were calculated for each training session. The results revealed that according to different periods of the season, workload measures observed in mid-season were meaningfully higher compared with early-season (g = ranging from 0.53 to 4.98) except for EWMASPRINT. In general, wingers and strikers tended to have greater scores in workload measures compared to the defenders and midfielders (g = ranging from 0.41 to 5.42). These findings may provide detailed information for coaches and sports scientists regarding the variations of acute and chronic workload ratio and external loading in-season and between player positions in an elite soccer team.



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

Reference: Res Sports Med. 2022 Mar 28;1-15. doi: 10.1080/15438627.2022.2052069. Online ahead of print.

Authors: Renêe de Caldas Honorato, Alex Soares Marreiros Ferraz, Witalo Kassiano, Priscila Custódio Martins, Diego Augusto Santos Silva, Vânia Marilande Ceccatto

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



#22 Does anticipation of penalty kicks in soccer transfer across similar and dissimilar sports?

Reference: Cogn Process. 2022 Mar 30. doi: 10.1007/s10339-021-01073-y. Online ahead of print.

Authors: Matthew Andrew, Joe Causer

Download link:

Summary: The aim of the present study was to examine whether anticipation skill associated with penalty-kick scenarios is sport-specific, or whether it transfers between sports that have similar elements. A shortened participation history questionnaire was used to identify 97 soccer players, 47 invasion sport players (e.g., rugby), and 72 other sport players (e.g., swimming), as well as skill level (hours of engagement/competition level). These participants completed a video-based temporal occlusion anticipation test that required them to select the destination of the ball across a series of soccer penalty scenarios. Results indicated that the skilled soccer players were more accurate than the skilled and less-skilled invasion sport players and skilled and less-skilled other sport players. Skilled soccer players were also more accurate than the less-skilled soccer players, with less-skilled soccer players exhibiting similar accuracy to both the skilled and less-skilled invasion sport and other sport players indicating that processes associated with anticipation of penalty kicks may be specific to their sport.


The Training Manager -