Latest research in football - week 23 - 2023

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 External and internal maximal intensity periods of elite youth male soccer matches

Reference: J Sports Sci. 2023 Jun 20;1-10. doi: 10.1080/02640414.2023.2227539. Online ahead of print.

Authors: Songmi Kim, Stacey Emmonds, Paul Bower, Dan Weaving

Summary: Understanding the maximal intensity periods (MIP) of soccer matches can optimise training prescription. The aim was to establish differences between positions and other contextual factors (match location, match outcome, playing formation and score line) for both external and internal MIP variables and to investigate the differences in the match start time between MIP variables. Maximal moving averages (1 to 10 min) for average speed, high-speed running (5.5-7 m·s-1), sprinting (>7 m·s-1; all m·min-1), average acceleration/deceleration (m·s-2) and heart rate (bpm, % maximal) were calculated from 24 professional youth players across 31 matches. Linear mixed models determined differences in MIP variables between positions, contextual factors and in the match start time of MIPs. Trivial to large positional differences existed in maximal external intensities while central defenders presented the lowest heart rate. It was unclear whether maximal intensities were influenced by contextual factors. MIPs for average speed, acceleration/deceleration and heart rate tend to occur concurrently (ES = trivial) within the first 30 min, while high-speed running and sprinting are likely to occur concurrently (ES = trivial) throughout a whole match. Practitioners could target maximising average speed and average acceleration/deceleration in technical-tactical based training to maximise heart rate responses.



#2 Investigation of concussion knowledge and attitudes of Chinese amateur adolescent soccer athletes

Reference: Medicine (Baltimore). 2023 Jun 9;102(23):e33972. doi: 10.1097/MD.0000000000033972.

Authors: Yue Li, Jiaxing Tang, Xiaomin Zhang, Dawei Cao, Teng Lyu

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Summary: Concussions are a common traumatic brain injury in soccer games but are often ignored by coaches and athletes. The purpose of our study is to assess the concussion knowledge and attitudes among amateur adolescent soccer athletes in China. Data was collected from questionnaire surveying (Rosenbaum Concussion Knowledge and Attitudes Survey (Student Version)) and semi-structured interviews completed by 69 amateur adolescent soccer athletes who participated in the U17 and U15 male groups of the 2022 China Youth Soccer League. The study followed a mixed methodology cross sectional study design. The concussion knowledge index (0-25) and concussion attitude index (15-75) scores were derived from the questionnaire and descriptive statistics were used for data analysis. The mean score of concussion knowledge is 16.8 ± 2.4 (range 10-22), and the mean score of concussion attitude is 61.3 ± 8.8 (range 45-77). Thematic analysis was used to categorize the participant's responses of the semi-structured interview and the results were compared with their survey answers of questionnaire. Interestingly, the interviews revealed the inconsistencies between the questionnaire responses and intended behaviors, and multiple factors (injury severity, the importance of the game and substitution rules) influencing concussion-reporting behaviors were identified. In addition, athletes hope to acquire concussion knowledge through formal education. Our study lay the foundation for educational interventions to potentially improve concussion-reporting behaviors among amateur adolescent soccer athletes.



#3 Incidence of concussion and associated risk factors in collegiate soccer: findings from the NCAA-DoD CARE consortium

Reference: Sci Med Footb. 2023 Jun 23;1-7. doi: 10.1080/24733938.2023.2227134. Online ahead of print.

Authors: Anthony P Kontos, Shawn R Eagle, Sara P D Chrisman, Margot Putukian, Lisa Manderino, Cyndi Holland, Michael W Collins, Steven P Broglio, Thomas W McAllister, Michael A McCrea, Paul Pasquina, Thomas W Kaminski; CARE Consortium Investigators

Summary: This retrospective cohort study aims to examine concussion incidence rates (IR) in collegiate soccer players and compare IRs based on risk factors including sex, competition level, games/practices, history of concussion, and playing position. Collegiate soccer players were recruited (n = 2,471) from 23 institutions from the NCAA-DoD Concussion Assessment, Research, and Education (CARE) Consortium. Incidence rates for concussion per 1000 athlete exposures (AEs) were calculated across the 2015-16/2016-17 seasons. Incidence rates (IR) comparing risk factor groups were also calculated. A total of 162 concussions occurred during the study, for an IR of 0.08/1000 AEs. Females were more likely to have a concussion than males overall (IR = 1.47) and were more likely to have a concussion in games (IR = 1.42) and practices (IR = 2.91). Concussions were more likely during competition compared to practice (IR = 2.53), and less likely in Division III, compared to Divisions I and II, χ2 = 6.5, p > .05. In the concussed group, male sex was associated with 2.47 times higher odds of playing defender and 2.29 times higher odds of a collision mechanism. Results confirm previous findings that females and game exposures have higher concussion IR than males and practice exposures. Findings also supported sex differences in IRs based on exposure type, position, and mechanism.



#4 Effects of horizontal compared to vertical-based plyometric jump training on semi-professional soccer player's performance

Reference: Sci Rep. 2023 Jun 20;13(1):10039. doi: 10.1038/s41598-023-37213-x.

Authors: Hadi Nobari, Filipe Manuel Clemente, Norodin Vali, Ana Filipa Silva, Daniel van den Hoek, Rodrigo Ramirez-Campillo

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Summary: This study aimed to compare the effects of horizontal (HJ) and vertical (VJ)-based plyometric jump training on male semi-professional soccer player's performance (e.g., change-of-direction speed [5-0-5 test]; 10-m, 20-m, and 30-m linear sprint speed). A parallel-study design was conducted. Participants were organized into HJ (n = 10) or VJ (n = 9) during 12 weeks. Measures of athletic performance were obtained in four phases: (i) before and (ii) end of the pre-season, (iii) during (weeks 7th), and (iv) after the intervention. The within-group analysis revealed that both HJ and VJ improved change of direction ([Formula: see text] = 27.783; p < 0.001 ([Formula: see text] = 21.635; p < 0.001),), 10-m linear sprint time ([Formula: see text] = 28.576; p < 0.001), 20-m linear sprint time ([Formula: see text] = 28.969, p < 0.001), and 30-m linear sprint time ([Formula: see text] = 26.143; p < 0.001). Similarly, the VJ-group also imposed significant changes on 5-0-5 time, 10-m linear sprint time ([Formula: see text] = 25.787; p < 0.001), 20-m linear sprint time ([Formula: see text] = 24.333, p < 0.001), and 30-m linear sprint time ([Formula: see text] = 22.919; p < 0.001). Between-group analysis revealed no significant differences in any of the assessment moments. HJ and VJ plyometric jump training are effective for improving the change-of-direction and a linear sprint of semi-professional players with no difference between types of intervention.



#5 Knowledge of traumatic dental injuries and mouthguard behavior among Croatian soccer players

Reference: Dent Traumatol. 2023 Jun 21. doi: 10.1111/edt.12862. Online ahead of print.

Authors: Marin Kasum, Lidia Gavic, Petra Mandic, Antonija Tadin

Summary: Sports-related dental injuries occur frequently among athletes due to inadequate knowledge and prevention measures. The aim of the study was to assess knowledge, attitudes, and practices of active soccer players from all leagues in Croatia regarding traumatic dental injuries and the use of mouthguards. 393 respondents completed a questionnaire-based online survey from March 2022 to April 2022. The questionnaire consisted of 37 questions divided in four sections: demographic characteristics, experience with orofacial injuries, knowledge of emergency therapeutic procedures for dental injuries, and behaviors related to the use of a mouthguard. Insufficient knowledge was confirmed by a total score of 2.8 ± 2.8 points, with a possible maximum of 11. Respondents' better knowledge can be associated with educational level (p = .002), playing position (p = .046), and personally experienced injuries to the face and jaw (p ≤ .001) and teeth (p = .022). Less than 40% of respondents suffered facial and jaw injuries while playing football and 18.6% suffered dental injuries. Although most respondents (93.9%) were familiar with mouthguards and 68.9% believed that they help prevent injuries while playing football, only 16% used them. The study revealed significant gaps in knowledge regarding dental injuries and the practice of mouthguard usage among Croatian soccer players. Therefore, it is evident that additional education is needed to prevent dental injuries and take proper procedures when taking care of them among the examined population.



#7 SUPER rehabilitation of hamstring strain injuries in soccer players: Delphi consensus study

Reference: Physiother Theory Pract. 2023 Jun 21;1-11. doi: 10.1080/09593985.2023.2226732.

Authors: Murat Emirzeoğlu, Özlem Ülger

Summary: Hamstring strain injuries (HSI) are one of the most common injuries for soccer players and there is a need for new clinical-based studies on the rehabilitation of these injuries. This study aimed to create a consensus on physiotherapy and rehabilitation approaches used in HSI by physiotherapists with super league experience in Turkey. Twenty-six male physiotherapists (duration of experience in professional life, on athlete health, and in the super league: 12.84 ± 6.04 years, 12.19 ± 5.96 years, 8.71 ± 5.31 years, respectively) from different institutions participated in the study. The research was carried out in three rounds using the Delphi method. Data collected using LimeSurvey and Google Forms were analyzed using the Microsoft Excel and SPSS 22 software. The response rates over the three rounds were 100%, 96%, and 96%, respectively. The 10 main items that were agreed upon in Round 1 were divided into 93 sub-items. Their numbers in the second and third Rounds were 60 and 53, respectively. At the end of Round 3, the highest consensus was on eccentric exercise, dynamic stretching, interval running, and movement-enhancing field training. All sub-items at this round were classified as SUPER (S: Soft tissue restoration techniques; U: Using supportive approaches; P: Physical fitness exercises; E: Electro-hydro-thermal methods; and R: Return to sport activities). SUPER rehabilitation provides a new conceptual framework in terms of approaches used by clinicians in rehabilitation for athletes with HSI. Recognizing the lack of evidence for the various approaches involved, clinicians can modify their practice and researchers can explore whether these approaches are scientifically correct.



#8 Do you have a good all-around view? Evaluation of a decision-making skills diagnostic tool using 360° videos and head-mounted displays in elite youth soccer

Reference: Front Sports Act Living. 2023 Jun 5;5:1171262. doi: 10.3389/fspor.2023.1171262. eCollection 2023.

Authors: Oliver Höner, Damir Dugandzic, Thomas Hauser, Michael Stügelmaier, Nico Willig, Florian Schultz

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Summary: Elite youth players' decision-making skills are considered important predictors of adult performance in soccer. The presentation of 360° videos in head-mounted displays offers new potential for the diagnostic of these skills in talent development programs. This study evaluated a new diagnostic tool using soccer-specific 360° videos for assessing decision-making skills in youth academy (YA) players. The evaluation consisted of players' subjective feedback as well as the analysis of diagnostic and prognostic validity. It was hypothesized that high-level YA players achieve better diagnostic results than regional-level players, and U19 outperform U17 players. Moreover, YA players' diagnostic results should be positively associated with future adult performance level. During the 2018/19 season, N = 48 youth players participated in the diagnostic procedures (split-half reliability r = .78). Participants were shown 54 videos which terminated when the central midfielder received a teammate's pass. Participants were then asked how to best continue playing. The subjective evaluation explored YA players' experiences with the diagnostic tool via quantitative ratings (e.g., "How exciting was the task?", "How involved did you feel in the game situation?") and additional interviews. Diagnostic validity was examined in a balanced cross-sectional 2 × 2-design (performance level x age group) and prognostic validity in a 3-year prospective design. Sensitivity and case-by-case analyses completed the evaluation. The YA players provided positive quantitative ratings regarding their experienced immersion into the environment. Players' qualitative feedback indicated general acceptance of the diagnostic tool as well as it offered recommendations for improvements. Confirming the diagnostic validity, ANOVA revealed significant main effects for performance level (p < .001, η2 = .29) and age group (p < .01, η2 = .14). Contributing to the prognostic validity, the diagnostic results discriminated between YA players achieving a higher and a lower adult performance level ("League 1-4" vs. "League 5 or below") in adulthood (p < .05; d = 0.80). A ROC curve and the AUC showed that the correct assignment to the adult performance levels is possible with a 71% probability. YA players with a high decision-making accuracy had a six times higher chance of playing in "League 1-4". The results demonstrated empirical evidence for the new diagnostic tool in terms of YA players' acceptance and validity coefficients exceeding effect sizes of former studies. The technology provides opportunities to test soccer-specific situations demanding an all-around view that were not testable in former experimental settings. Further technological advancements will enable the realization of improvements recommended by the players. Nonetheless, case-by-case analyses suggest caution in using such a diagnostic as a selection tool in talent development programs.



#9 Soccer-drill specificity in top-class male players with reference to peak match locomotor demands

Reference: J Sports Sci. 2023 Jun 21;1-11. doi: 10.1080/02640414.2023.2228131. Online ahead of print.

Authors: Andrea Riboli, Carlo Castagna

Summary: The aim was too compare the locomotor demands of several ball/running drills with the official match peak, locomotor demands determined across different time-windows of the same duration in top-class male soccer players (n = 40). Total distance (TD), high-speed running (HSR, 15-20 km⋅h-1), very high-speed running (VHSR, 20-24 km⋅h-1), sprint and acceleration+deceleration (Acc+Dec >±3 m⋅s-2) distances were measured during training and official matches. A total of 9372 individual observations were classified as technical-tactical drills, small-sided games (SSGs), super-SSGs (pitch-area >340 m2·player), SSGs with rules modifications (SSGmodified), individual positional drills or running drills. The relative (m·min-1) TD, HSR, VHSR, sprint and Acc+Dec were compared with the peak locomotor demands determined during official matches across different time-windows (1, 2, 3, 4 and 5-min). Individual position-specific drill, super-SSGs, SSGmodified and running drills showed similar (P > 0.05) or higher (P < 0.05; ES:1.17/4.61) than match TD, HSR and VHSR, while sprint and Acc+Dec were lower (P < 0.05). Conversely, technical-tactical drills and SSGs showed lower (P < 0.05; ES:-1.00/-3.45) TD, HSR, VHSR, sprint and Acc+Dec than official match peak demands. Locomotor loads during technical-tactical drills and SSGs were lower than peak demands, particularly for VHSR and sprint. Since training intensity is a key factor for high-performance development, these results may help to prepare top-class players for the official match peak demands.



#10 Effects of different training schedules based on distance and accelerometry measures: A full-season case study in professional soccer players

Reference: Sci Rep. 2023 Jun 23;13(1):10193. doi: 10.1038/s41598-023-37337-0.

Authors: Hadi Nobari, Nader Alijanpour, Amirhossein Talvari, Rafael Oliveira

Summary: This study aimed to evaluate external load based on distance and accelerometry measures in six different microcycle schedules with congested (CW2, CW3, and CW4) and regular weeks (RW4, RW5, and RW6) in professional soccer players. Twelve Iranian First League players (age: 28.2 ± 3.8 years; body mass: 77.92 ± 4.72 kg, and height: 183.2 ± 0.06 cm) participated in this study. A GPSPORTS system was used to collect training/match durations, total distance, distance covered at different speeds, number of accelerations, delecelerations and body load over 29 weeks, 40 matches, and 121 training sessions. Data were analysed by weekly mean and accumulated weekly values. The results showed a tendency for higher values in CWs than RWs. Regarding mean total distance, RW4 and RW5 presented lower values with very large effect size than CW2 (all, p < 0.05). The mean distance covered between 16 and 23 km/h showed that all RWs presented significantly lower values than all CWs (p < 0.05 with considerable effect size). In addition, mean acceleration values at < 2 m/s2 showed significantly lower values than all CWs (p < 0.05 with a very large effect size). Therefore, it is recommended to coaches pay special attention to players who participate in matches to reduce fatigue and improve the performance of professional soccer players. Ensuring recovery mechanisms are in place to minimize the external load is recommended. Coaches arrange practice sessions for non-starters who do not experience similar external loads compared to starters to prepare them for potential competition.



#11 A comparison of FELS and Tanner-Whitehouse II skeletal ages in male youth soccer players from the Middle East

Reference: Am J Hum Biol. 2023 Jun 24;e23941. doi: 10.1002/ajhb.23941. Online ahead of print.

Authors: Lorenzo Lolli, Valter Di Salvo, Mauricio Monaco, Amanda Johnson, Warren Gregson

Summary: The aim was to assess measurement agreement between FELS and Tanner-Whitehouse (TW) II skeletal ages in male youth soccer players from the Middle East. We examined agreement between FELS and TW-II skeletal ages using data collected between- and within-subjects (n = 1057 observations) for 409 male, full-time, academy student-athletes recruited as part of the Qatar Football Association national soccer development programme (chronological age range, 9.8 to 18 years; annual screening range, one to seven visits). The Bland-Altman method for repeated measurements estimated the limits of agreement describing the expected range of differences for 95% of pairs of future FELS and TW-II skeletal ages determined on similar individuals from the reference population. The mean difference for TW-II versus FELS protocols was 0.02 years (95% confidence interval, -0.04 to 0.08 years) with lower and upper limits of agreement ranging from -1.39 years (95% confidence interval, -1.48 to -1.30 years) to 1.43 years (95% confidence interval, 1.34 to 1.52 years). Differences for 95% of pairs of future skeletal ages determined with FELS and TW-II methods in this population could be as high as ~3 years for some people that suggested protocols may not be interchangeable in youth Middle Eastern athletes. Justification of skeletal age protocol selection rests on knowledge of measurement bias and variability of expected growth estimations for rationalized application to a population of interest.



#12 24 h Hydration profile of collegiate soccer players training once versus twice per day in the heat

Reference: Physiol Behav. 2023 Jun 16;269:114273. doi: 10.1016/j.physbeh.2023.114273. Online ahead of print.

Authors: Tate M Dean, Savanna N Knight, Marcus J Robinson, Lynnsey R Bowling, Angela R Russell, Eric K O'Neal, Brett A Davis

Summary: This study examined 24-h hydration parameters among collegiate, male soccer players (n = 17) during twice (X2) and once (X1) per day practice schedules in the heat. Urine specific gravity (USG) and body mass were measured before morning practices, afternoon practice (X2)/team meeting (X1), and the next morning practices. Fluid intake, sweat losses, and urinary losses were assessed during each 24-h window. Pre-practice body mass or USG did not differ among the timepoints. Sweat losses differed among all practices (p < 0.05) and averaged approximately 2.181±0.693 (X2AM) 1.710±0.474 (X2PM), and 3.361±0.956 L (X1AM), but players averaged replacing >50% of sweat losses with fluid intake every practice. Fluid intake during and between practices from practice 1 to the afternoon practice for X2 resulted in a positive fluid balance for X2 (+0.446±0.916 L). However, higher sweat loss during the initial morning practice and lower relative fluid intake prior to the afternoon team meeting the following morning resulted in a negative fluid balance (-0.304±0.675 L; p < 0.05: Cohen's d = 0.94) over the same time period for X1. By the start of the next morning practice sessions, both X1 (+0.664±1.051 L) and X2 (+0.446±0.916 L) were in positive fluid balance, respectively. Ample fluid consumption opportunities, scaled down practice intensities during X2, and potentially intentional greater relative fluid intake during X2 training resulted in no difference in fluid shift versus an X1 schedule before the start of practices. The majority of players maintained fluid balance drinking ad libitum regardless of practice schedule.



#13 Effects of eccentric-emphasized leg curl intervention on muscle strength imbalance markers in professional soccer players during pre-season

Reference: J Bodyw Mov Ther. 2023 Jul;35:28-32. doi: 10.1016/j.jbmt.2023.04.012. Epub 2023 Apr 14.

Authors: Rafael Grazioli, Martinho Inácio, Pedro Lopez, Sandro R Freitas, Giovani Dos Santos Cunha, Carlos L F Machado, Filipe Veeck, Bruno Manfredini Baroni, Eduardo L Cadore, Ronei S Pinto

Summary: The effects of strength training on muscle strength imbalance are unclear in professional soccer players. As a result, this study examined the effects of an 8-week strength training program comprising eccentric-emphasized prone leg curl adjusted according to the individual strength imbalance status. Ten professional soccer players (26.0 ± 3.6 yrs) participated in the study. Players who had a ≥ 10% contralateral imbalance in knee flexors eccentric peak torque (n = 6) performed two additional repetitions per set in the low-strength limb (high-volume, HV) compared to the high-strength limb (low-volume, LV). Isokinetic concentric knee extension and concentric and eccentric knee flexion peak torque (PT) and derived contralateral imbalances and conventional and functional hamstring-to-quadriceps ratios (H:Q) were assessed at baseline and after 8 weeks. Differences at baseline were assessed using paired-sample T-tests, and a two-way (limb x time) repeated measures analysis of covariance (ANCOVA) for changes over time. A significant improvement in the eccentric knee flexion PT was observed in both limbs after 8 weeks (P < 0.05), with greater effects observed in the HV limb (25.0 N m, 95% CI: 15.1-34.9 N m). Significant decreases were also observed in the contralateral imbalances from concentric knee extension and flexion and eccentric knee flexion PT (P < 0.05). Differences were not observed in concentric knee extension and flexion PT (P > 0.05). A short-term eccentric-emphasized leg curl intervention adjusted by the initial knee flexors eccentric strength was an efficient method to improve knee flexors strength imbalance in professional soccer players.



#14 Knee osteoparthritis in the former elite football players and the ordinary population – a comparative cross-sectional study

Reference: Sci Med Footb. 2023 Jun 23. doi: 10.1080/24733938.2023.2228279. Online ahead of print.

Authors: Aljaž Merčun, Matej Drobnič, Nik Žlak, Zmago Krajnc

Summary: A cross-sectional case-control study compared subjective knee function, quality of life and radiographic knee osteoarthritis (OA) between forty-five former elite football players and an age-matched general male population. Participants completed the Knee OA Outcome Score (KOOS), a quality-of-life assessment (EQ-5D-3 L) and standing knee radiographs. Among the players twenty-four (53%) sustained at least one moderate or severe knee injury, while 21 (47%) did not recall any injury. Players with previous knee injuries reported significantly lower knee-specific and general quality-of-life scores (KOOS 69; EQ-5D-3 L 0.69 (0.2)) compared to the non-injured players (KOOS 92; EQ-5D-3 L 0.81 (0.2)) or the control population (KOOS 90; EQ-5D-3 L 0.83 (0.2)). The injured knees had higher radiographic OA Kellgren-Lawrence (KL) scale grades 1.7 (1.3) than the knees of the non-injured players 0.8 (1.0) or the control knees 0.8 (1.0)Former elite football players who had previously sustained a moderate or severe knee injury reported inferior knee function and lower quality of life. Injured knees had higher levels of radiographic OA. Non-injured players reported similar knee and general function and their knees had similar grades of OA to those in the control group. The defining moment for long-term knee preservation in football should be injury prevention protocols.



#15 Sentiment Analysis of Social Media Users' Emotional Response to Sudden Cardiac Arrest During a Football Broadcast

Reference: JAMA Netw Open. 2023 Jun 1;6(6):e2319720. doi: 10.1001/jamanetworkopen.2023.19720.

Authors: Nino Fijacko, Robert Greif, Gregor Štiglic, Primož Kocbek, Benjamin S Abella

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