Latest research in football - week 27 - 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 Coping with COVID-19: Can a Sense of Coherence and Social Support Play a Protective Role in the Perception of COVID-19 by Polish Women Football Players? A Cross-Sectional Study

Reference: Int J Environ Res Public Health. 2023 Jul 6;20(13):6308. doi: 10.3390/ijerph20136308.

Authors: Anna Ussorowska-Krokosz, Jan Blecharz, Malgorzata Siekanska, Monika Grygorowicz

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Summary: Athletes have demonstrated a significant increase in anxiety and stress connected to the COVID-19 pandemic. Drawing on the theory of salutogenesis, this study examined the relationship between the sense of coherence and social support and competitive elite-level athletes' perception of the COVID-19 pandemic situation. The perceived secondary gains associated with the pandemic were analysed with a quasi-qualitative research methodology. The sample consisted of 204 competitive elite-level female football players aged 14-36 (M = 17.61, SD = 4.42) who completed the Sense of Coherence Questionnaire (SOC-29), the Berlin Social Support Scales (BSSS), and the researchers' own questionnaire to assess the perception of the COVID-19 situation. The results confirmed a relationship between a sense of coherence and coping better with the difficult situation caused by the coronavirus pandemic. No protective role of social support in the adaptive perception of the pandemic situation was identified. The data from the quasi-qualitative study testify to the use of the adversity of the pandemic to grow in many areas of female football players' lives. The sense of coherence was a protective factor in mitigating the negative consequences of the COVID-19 pandemic situation.



#2 Carbohydrate Nutrition and Skill Performance in Soccer

Reference: Sports Med. 2023 Jul 8. doi: 10.1007/s40279-023-01876-3. Online ahead of print.

Authors: Ian Rollo, Clyde Williams

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Summary: In soccer, players must perform a variety of sport-specific skills usually during or immediately after running, often at sprint speed. The quality of the skill performed is likely influenced by the volume of work done in attacking and defending over the duration of the match. Even the most highly skilful players succumb to the impact of fatigue both physical and mental, which may result in underperforming skills at key moments in a match. Fitness is the platform on which skill is performed during team sport. With the onset of fatigue, tired players find it ever more difficult to successfully perform basic skills. Therefore, it is not surprising that teams spend a large proportion of their training time on fitness. While acknowledging the central role of fitness in team sport, the importance of team tactics, underpinned by spatial awareness, must not be neglected. It is well established that a high-carbohydrate diet before a match and, as a supplement during match play, helps delay the onset of fatigue. There is some evidence that players ingesting carbohydrate can maintain sport-relevant skills for the duration of exercise more successfully compared with when ingesting placebo or water. However, most of the assessments of sport-specific skills have been performed in a controlled, non-contested environment. Although these methods may be judged as not ecologically valid, they do rule out the confounding influences of competition on skill performance. The aim of this brief review is to explore whether carbohydrate ingestion, while delaying fatigue during match play, may also help retain sport soccer-specific skill performance.



#3 Head movement direction in football - a field study on visual scanning activity during the UEFA-U17 and -U21 European Championship 2019

Reference: J Sports Sci. 2023 Jul 13;1-11. doi: 10.1080/02640414.2023.2235160. Online ahead of print.

Authors: Marius Pokolm, Marie Kirchhain, Daniel Müller, Geir Jordet, Daniel Memmert

Summary: Visual exploration (scanning) of one's environment is a key aspect in team sports. Based on Gibson's (1979) ecological approach of visual perception, this study aims to advance the understanding of scanning by focusing on the direction of head movements in football and its implications for subsequent on-ball actions. The video-based data analysis consisted of nine selected matches and 162 players of the Union of European Football Associations (UEFA) U17 and U21 European Championship 2019. The results indicate that the direction of the last scan prior to receiving the ball is related to the foot used for the first ball contact. This relationship was further analysed in view of the game context (direction of play and opponent pressure) and with information about the player's dominant foot. The findings reveal a relationship between the direction of the last scan before receiving the ball and the direction the game is proceeded in. Further, when a player performs the last scan to the side of their dominant foot, the probability increases that their dominant foot is used for the subsequent first ball contact. Depending on the direction of the last scan, opponent pressure had various effects on the foot used for the first contact.



#4 Assessing the agreement between a global navigation satellite system and an optical-tracking system for measuring total, high-speed running, and sprint distances in official soccer matches

Reference: Sci Prog. 2023 Jul-Sep;106(3):368504231187501. doi: 10.1177/00368504231187501.

Authors: Piotr Makar, Ana Filipa Silva, Rafael Oliveira, Marcin Janusiak, Przemysław Parus, Małgorzata Smoter, Filipe Manuel Clemente

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Summary: This study aimed to compare the agreement of total distance (TD), high-speed running (HSR) distance, and sprint distance during 16 official soccer matches between a global navigation satellite system (GNSS) and an optical-tracking system. A total of 24 male soccer players, who are actively participating in the Polish Ekstraklasa professional league, were included in the analysis conducted during official competitions. The players were systematically monitored using Catapult GNSS (10-Hz, S7) and Tracab optical-tracking system (25-Hz, ChyronHego). TD, HSR distance, sprint distance, HSR count (HSRC), and sprint count (SC) were collected. The data were extracted in 5-min epochs. A statistical approach was employed to visually examine the relationship between the systems based on the same measure. Additionally, R2 was utilized as a metric to quantify the proportion of variance accounted for by a variable. To assess agreement, Bland-Altman plots were visually inspected. The data from both systems were compared using the estimates derived from the intraclass correlation (ICC) test and Pearson product-moment correlation. Finally, a paired t-test was employed to compare the measurements obtained from both systems. The interaction between Catapult and Tracab systems revealed an R2 of 0.717 for TD, 0.512 for HSR distance, 0.647 for sprint distance, 0.349 for HSRC, and 0.261 for SC. The ICC values for absolute agreement between the systems were excellent for TD (ICC = 0.974) and good for HSR distance (ICC = 0.766), sprint distance (ICC = 0.822). The ICC values were not good for HSRCs (ICC = 0.659) and SCs (ICC = 0.640). t-test revealed significant differences between Catapult and Tracab for TD (p < 0.001; d = -0.084), HSR distance (p < 0.001; d = -0.481), sprint distance (p < 0.001; d = -0.513), HSRC (p < 0.001; d = -0.558), and SC (p < 0.001; d = -0.334). Although both systems present acceptable agreement in TD, they may not be perfectly interchangeable, which sports scientists and coaches must consider when using them.



#5 Horizontal jump asymmetries are associated with reduced range of motion and vertical jump performance in female soccer players

Reference: BMC Sports Sci Med Rehabil. 2023 Jul 8;15(1):80. doi: 10.1186/s13102-023-00697-1.

Authors: Alberto Roso-Moliner, Demetrio Lozano, Hadi Nobari, Chris Bishop, Antonio Carton-Llorente, Elena Mainer-Pardos

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Summary: Performance in jumping and change of direction tests are good proxies to reflect the skill level during soccer-specific actions. Greater inter-leg asymmetries have been identified as a risk factor for developing acute and overuse injuries and jeopardizing soccer performance. The aim of this study was to assess the association between asymmetry in the unilateral vertical and horizontal jump tests, ankle range of motion, linear velocity, and change of direction in a sample of highly trained adult female soccer players. Thirty-eight highly trained female soccer players underwent a testing protocol including ankle dorsiflexion, single leg jumps for height (CMJ), distance (HJ), 40 m sprint and 180° change of direction tests. Within-session reliability was acceptable (CV ≤ 7.9%), and relative reliability showed good to excellent (ICC: 0.83 to 0.99). The one-way ANOVA reported higher inter-limb differences for change of direction deficit (10.9 ± 8.04%) and single leg CMJ (5.70 ± 5.22%). Pearson correlations highlighted significant relationships between horizontal jump asymmetries and ankle dorsiflexion (r = -0.41), CMJ (r = -0.36 to -0.49) and HJ (r = -0.28 to -0.56). Assessing inter-limb asymmetries through different methods can help scientists understand the specificity of their detrimental effects on soccer performance. Practitioners should be aware of these specificities as well as the magnitude and direction of the asymmetries when aiming to improve specific on-field skills.



#6 Evaluating the Suitability of the Low Energy Availability in Females Questionnaire (LEAF-Q) for Female Football Players

Reference: Sports Med Open. 2023 Jul 13;9(1):54. doi: 10.1186/s40798-023-00605-4.

Authors: Marcus S Dasa, Oddgeir Friborg, Morten Kristoffersen, Gunn Pettersen, Jørn V Sagen, Jorunn Sundgot-Borgen, Jan H Rosenvinge

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Summary: The Low Energy Availability in Females Questionnaire (LEAF-Q) is a screening tool developed to detect endurance athletes and dancers at risk for development of persistent low energy availability (LEA) and the female athlete triad (Triad). This study investigated the applicability of the LEAF-Q in a cohort of sixty professional female football players. The participants were classified as at risk (≥ 8) or not at risk (< 8) for persistent LEA and the Triad according to their LEAF-Q score, before being compared. Receiver operating curves were then conducted to examine the ability of the overall LEAF-Q and subcategories to correctly determine the presence of clinically defined markers of the Triad. Additionally, Youden's index was calculated to determine the best fitting cut-off values. Thirty-two percent of participants were classified as at risk by the LEAF-Q. We found no statistically significant differences between the two groups for any markers associated with persistent LEA. Except for acceptable accuracy in determining menstrual status, all other LEAF-Q components exhibited poor accuracy and predictive values. Youden's index scores imply that increasing the overall and injury cut-off values to ≥ 10 and ≥ 5 respectively, would yield increased performance. Our findings do not support the use of the LEAF-Q for the purpose of detecting LEA and Triad conditions among female football players.



#7 Qatar 2022: challenges and implications related to the medical follow-up of a national football team

Reference: Rev Med Suisse. 2023 Jul 12;19(835):1374-1377. doi: 10.53738/REVMED.2023.19.835.1374. [Article in French]

Authors: Pierre-Étienne Fournier, Markus Tschopp, Philippe M Tscholl

Summary: The preparation and medical follow-up of a national team during a major tournament, in particular climatic conditions and at an unusual date posed several problems, acclimatization, recovery in connection with a busy championship game, seasonal risk of infection, which had to be resolved. Close collaboration between the various people involved, team manager, coaches, physiologist, fitness coach and doctors is essential in order to prepare to face the challenges to be met to accompany an ambitious team.



#8 The impact of COVID-19 lockdown on the quality of life of Chinese football referees: the chain mediating role of occupational stress and job burnout

Reference: BMC Public Health. 2023 Jul 10;23(1):1314. doi: 10.1186/s12889-023-16248-9.

Authors: Xianliang Wang, Kehao Zong, Yubo Gao, Bochen Li, Shuzhen Wang, Liguo Zhang

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Summary: COVID-19 lockdown measures have had a great negative impact on the development of sports competition in China, as well as on the quality of life of football referees. This study aims to explore the impact of lockdown measures implemented in response to the COVID-19 pandemic on the quality of life of football referees in China and its mechanism of action. The Impact of Event Scale-Revised (IES-R), the Effort-Reward Imbalance Scale (ERI), the Maslach Burnout Inventory General Survey (MBI-GS), and the World Health Organization Quality of Life Brief Version (WHOQOL-BREF). The scale was used from August to September 2022. Using an online questionnaire, 350 questionnaires were sent out and 338 were returned, for a return rate of 96.57%. Invalid questionnaires were excluded, and 307 football referees with referee grades in 29 provinces registered with the CFA were surveyed. SPSS 24.0 and Mplus 8.0 were used for data analysis and structural equation model testing in this study. The results showed that the COVID-19 lockdown had no significant impact on the quality of life of Chinese football referees. However, the COVID-19 lockdown can affect the quality of life of Chinese football referees through occupational stress or job burnout. Occupational stress and job burnout also play a chain intermediary role between the COVID-19 lockdown and the quality of life of Chinese football referees. In addition, this study further explores the quality of life by dividing it into four dimensions (physical, social, psychological, and environmental). The results show that all four dimensions satisfy the chain mediation model. Therefore, the quality of life of Chinese football referees can be improved by reducing their occupational stress and job burnout during the COVID-19 lockdown.



#9 Isokinetic Assessment of Knee Flexor and Extensor Strength and Lower Extremity Flexibility Assessment of an NCAA Division III Men's Soccer Team

Reference: Int J Sports Phys Ther. 2023 Jun 1;V18(3):626-635. doi: 10.26603/001c.74971. eCollection 2023.

Authors: Savanna Perkins, Paul Canavan

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Summary: Strength imbalances and flexibility deficits of the hamstrings and hip flexors have been identified as potential risk factors for hamstring injuries, but research on athletes at the Division III level are limited, potentially due to a lack of resources and technology. The purpose of this study was to conduct isokinetic and flexibility assessments to screen male soccer athletes at risk of sustaining a hamstring injury. Standardized isokinetic testing of concentric muscle performance, measured by peak torque of the quadriceps and hamstrings and hamstring-to-quadriceps ratios, was conducted using a Biodex isokinetic dynamometer at speeds of 60 and 180°/sec. Additionally, the Active Knee Extension (AKE) test and the Thomas test were performed bilaterally to objectively measure flexibility. Paired sample t-tests were used to compare left and right lower extremities for all outcomes, with the level of significance set at p<0.05. Participants were ranked for risk and given a set of exercises sourced from the FIFA 11 Injury Prevention Program. At 60°/sec, the mean PT/BW bilateral deficit was 14.1% for extension and 12.9% for flexion. At 180°/sec, the mean deficit was 9.9% for extension and 11.4% for flexion. The team's average for left and right H:Q ratios for each speed were 54.4 and 51.4 at 60°/sec and 61.6 and 63.1 at 180°/sec, respectively. The team's average AKE range of motion was 158° for the left leg and 160° for the right leg. The mean Thomas test measurements were 3.6° away from the neutral position on the right and 1.6° on the left, with nine positive tests. There were no statistically significant differences between left and right knee extension or flexion PT/BW or H:Q ratios at either speed. There was no significant difference between left and right AKE measurements (p=0.182). The results of this screening suggest that isokinetic testing and flexibility testing may be useful to identify non-optimal strength ratios and flexibility deficits in male collegiate soccer players. The benefits of this research have direct implications, as participants received both their screening data and a set of exercises aimed to help decrease their injury risk, in addition to the offering data that is useful for determining what normative values for flexibility and strength profiles might look like for Division III male soccer players.



#10 Incidence, characteristics and cost of head, neck and dental injuries in non-professional football (soccer) using 3 years of sports injury insurance data

Reference: Dent Traumatol. 2023 Jul 10. doi: 10.1111/edt.12869.

Authors: Mille Greve Hansen, Andrew George Ross, Tim Meyer, Christian Knold, Ian Meyers, Kerry Peek

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Summary: This descriptive epidemiological study aimed to quantify the incidence, characteristics and costs of head, neck and dental injuries in non-professional football players. Injury data were coded (using Orchard Sports Injury and Illness Classification System) from a de-identified insurance database containing three seasons (2018-2020) of data. Cost data included direct and indirect costs presented by type of injury, age group and sex using means ± SD, range of costs ($AU) and total costs ± SE. Chi-squared tests were used to analyse the data (significance level p < .05) with injury incidence rates (IR) calculated per 1000 match hours and per 1000 injury insurance claims. A total of 388 injuries affecting 240 players were sustained. Of these, 43% (n = 102) of players also sustained one or more secondary injuries, mainly to the head or neck area. Dental injuries (n = 143, 39%, IR = 0.008) accounted for the highest number of primary and secondary injuries and the highest mean direct cost per injury ($AU1152), while head and facial injuries accounted for the highest proportion of total costs ($AU434,101). Players who sustained one or more secondary injuries had the highest direct and indirect mean cost per injury. Given the frequency and cost of dental injuries in non-professional football players, injury prevention initiatives warrant further investigation.



#11 The relationship between ambient temperature and match running performance of elite soccer players

Reference: PLoS One. 2023 Jul 11;18(7):e0288494. doi: 10.1371/journal.pone.0288494. eCollection 2023.

Authors: Ryland Morgans, Eduard Bezuglov, Dave Rhodes, Jose Teixeira, Toni Modric, Sime Versic, Rocco Di Michele, Rafael Oliveira

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Summary: The influence of environmental factors on key physical parameters of soccer players during competitive match-play have been widely investigated in the literature, although little is known on the effects of sub-zero ambient temperatures on the performance of adult elite soccer players during competitive matches. The aim of this study was to assess how the teams' match running performance indicators are related to low ambient temperature during competitive matches in the Russian Premier League. A total of 1142 matches played during the 2016/2017 to 2020/2021 seasons were examined. Linear mixed models were used to assess the relationships between changes in ambient temperature at the start of the match and changes in selected team physical performance variables, including total, running (4.0 to 5.5 m/s), high-speed running (5.5 to 7.0 m/s) and sprint (> 7.0 m/s) distances covered. The total, running and high-speed running distances showed no significant differences across temperatures up to 10°C, while these showed small to large decreases at 11 to 20°C and especially in the >20°C ranges. On the contrary, sprint distance was significantly lower at temperature of -5°C or less compared to higher temperature ranges. At sub-zero temperatures, every 1°C lower reduced team sprint distance by 19.2 m (about 1.6%). The present findings show that a low ambient temperature is negatively related to physical match performance behavior of elite soccer players, notably associated with a reduced total sprint distance.



#12 Description of the menstrual cycle status, energy availability, eating behavior and physical performance in a youth female soccer team

Reference: Sci Rep. 2023 Jul 11;13(1):11194. doi: 10.1038/s41598-023-37967-4.

Authors: Ana Carolina Paludo, Marta Gimunová, Marcos Michaelides, Magdalena Kobus, Koulla Parpa

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Summary: The aim of the study was to describe the menstrual status and perception, risk of low energy availability (LEA) and the presence of orthorexia nervosa (ON) in youth female from a soccer team. Also, verify the possible effect of LEA and ON on physical performance. Data from 19 female players (14.6 ± 1.42 yr) belonging to a soccer team from Cyprus was taken during pre-season. The menstrual cycle status was evaluated by specific questions, LEA by the Low Energy Availability in Females Questionnaire (LEAF-Q), ON by the ORTO-R questionnaire and physical performance by jump, handgrip and cardiorespiratory exercise tests. Players were separated into the risk of LEA and ON. Comparison and correlation tests were performed with a significance set at p < 0.05. As the main results, 66.7% of players perceived that the menstrual period affects their performance in the game, 83.3% did not communicate with coaches about their menstrual cycle; the prevalence of risk of LEA was 26.3%; players with risk of LEA also presented higher scores ON; neither LEA nor ON presented a significant association with players performance. The findings highlighted that youth players perceived an impact of the menstrual period on performance, but did not communicate with the coach about it. Players with the risk of LEA and high values of ON seem not to be associated with a decrease in physical performance during the pre-season evaluation. Attention is required as the players were assessed once. Monitoring these parameters throughout the sports season is recommended to obtain better clarification about the topic.



#13 Landing Posture in Elite Female Athletes During a Drop Vertical Jump Before and After a High-Intensity Ergometer Fatigue Protocol: A Study of 20 Japanese Women's Soccer League Players

Reference: Orthop J Sports Med. 2023 Jun 2;11(6):23259671231171859. doi: 10.1177/23259671231171859. eCollection 2023 Jun.

Authors: Aguri Kamitani, Kunio Hara, Yuta Fujii, Shohei Yoshida

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Summary: Even elite athletes, who usually show stable postural control, sometimes cannot control their posture after high-load training. This instability may contribute to anterior cruciate ligament injury. The purpose of this study was to evaluate the landing posture of elite female soccer players before and after a novel high-intensity fatigue-inducing exercise protocol. We hypothesized that the landing posture will change before versus after the fatigue protocol. The study participants were 20 female elite soccer players. All athletes performed 3 drop vertical jumps (DVJs), pedaled an ergometer 8 times with full force for 10 seconds each (fatigue protocol), and then repeated the 3 DVJs. We measured and compared the athletes' blood lactate levels before and after the fatigue protocol, as well as the hip flexion, knee flexion, and ankle dorsiflexion angles and final landing posture during the DJVs. Blood lactate levels increased significantly pre- to postprotocol (from 2.7 ± 1.9 to 15.0 ± 3.6 mmol/L; P < .001), while there were decreases in hip flexion angle (from 35.0° ± 11.2° to 22.4° ± 8.8°; P < .001) and ankle dorsiflexion angle (from 26.4° ± 3.9° to 20.0° ± 3.7°; P < .001). The number of athletes who could not maintain a stable DVJ final landing posture increased from 10% before the fatigue protocol to 70% after. The elite female athletes in our study showed significant decreases in hip flexion and ankle dorsiflexion angles in the DVJ landing after a fatigue-inducing protocol. Most elite athletes were unable to maintain a stable posture on the DVJ landing after the fatigue protocol. 



#14 Asymmetries of foot strike patterns during running in high-level female and male soccer players

Reference: BMC Sports Sci Med Rehabil. 2023 Jul 14;15(1):86. doi: 10.1186/s13102-023-00696-2.

Authors: Stanislav Dimitri Siegel, Joel Mason, Daniel Hamacher, Anna Lina Rahlf, Astrid Zech

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Summary: Foot strike pattern (FSP) is defined by the way the foot makes initial ground contact and is influenced by intrinsic and extrinsic factors. This study investigated the effect of running speed on asymmetries of FSP. Seventeen female and nineteen male soccer players performed an incremental running test on an instrumented treadmill starting at 2.0 m/s until complete exhaustion. Force plate data were used to categorize foot strikes into rearfoot (RFS) and non-rearfoot strikes. Additionally, peak vertical ground reaction force (peakGRF) and stride time were calculated. The symmetry index (SI) was used to quantify lateral asymmetries between legs. The SI indicated asymmetries of the rate of RFS (%RFS) of approximately 30% at slow running speed which decreased to 4.4% during faster running speed (p = 0.001). There were minor asymmetries in peakGRF and stride time at each running stage. Running speed influenced %RFS (p < 0.001), peakGRF (p < 0.001) and stride time (p < 0.001). Significant interaction effects between running speed and sex were shown for %RFS (p = 0.033), peakGRF (p < 0.001) and stride time (p = 0.041). FSP of soccer players are asymmetric at slower running speed, but symmetry increases with increasing speed. Future studies should consider that FSP are non-stationary and influenced by running speed but also differ between legs.



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