Latest research in football - week 15 - 2021

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 Sport-Specific Functional Tests and Related Sport Injury Risk and Occurrences in Junior Basketball and Soccer Athletes

Reference: Biomed Res Int  2020 Dec 11;2020:8750231. doi: 10.1155/2020/8750231. eCollection 2020. 

Authors: Wen-Dien Chang, Chi-Cheng Lu

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Summary: Sport-specific functional tests were used to assess the power, speed, and agility of the lower extremity for a specific sport, but comparison of the differences and association with sport injury was rare. The aim of this study was to investigate the differences in sport-specific functional tests between junior basketball and soccer athletes and analyze the sport injury risk and occurrences. All participants were evaluated using the sprint test, vertical jump (VJ) test, agility T test, and functional movement screen (FMS). There were significant intergroup differences in the sprint test, VJ test, agility T test, and FMS. Specific functional tests were compared against FMS score, either FMS ≤ 14 or FMS > 14. The FMS subtests, namely, in-line lunge, trunk stability push-up (TSPU), and quadruped rotary stability, were also performed. In one-year follow-up, the sport injury incidence was also recorded. Significant differences in sprint, agility, and FMS performance were found between the junior basketball and soccer athletes. Individual FMS scores of the in-line lunge, TSPU, and quadruped rotary stability were evaluated. No significant differences in sprint, VJ, and agility scores were found between FMS ≤ 14 and FMS > 14. FMS total score ≤ 14 was significantly associated with high sport injury occurrence. The scores of sprint, agility, and FMS performance were differed between basketball and soccer athletes. The scores of sprint, VJ, and agility tests did not have differences with sport injury risks and occurrences, but the FMS score was associated with sport injury occurrence. 



#2 Nonunion of a Stress Fracture at the Base of the Second Metatarsal in a Soccer Player Treated by Osteosynthesis with the Bridging Plate Fixation Technique 

Reference: Case Rep Orthop. 2020 Dec 22;2020:6649443. doi: 10.1155/2020/6649443. eCollection 2020. 

Authors: Futoshi Morio, Shota Morimoto, Shintaro Onishi, Toshiya Tachibana, Tomoya Iseki

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Summary: A stress fracture of the second metatarsal base in soccer players is extremely rare. In this case study, we report a nonunion of a stress fracture at the base of the second metatarsal in a female soccer player who had persistent pain despite continued conservative treatment, who then was treated with the bridging plate fixation technique. A 19-year-old female college soccer player complained of pain on the dorsum of her right midfoot during a game without history of trauma and was conservatively treated for 6 months. Radiographic examination showed an oblique fracture with small bone fragment at the proximal base of the second metatarsal and computed tomography demonstrated sclerotic change around the fracture site. We diagnosed her with nonunion of a stress fracture at the base of the second metatarsal and performed operative treatments using autogenous cancellous iliac bone grafting and plate fixation bridging a second metatarsal and medial cuneiform with a locking plate. At 4 months after the initial surgery, she was able to return to playing soccer at preinjury level without complications or pain. We report a rare case of nonunion of a stress fracture at the base of the second metatarsal in a female soccer player without underlying diseases. Surgical treatment was applied, because the conservative treatment was ineffective for 6 months and led to nonunion. The plate fixation technique bridging the second metatarsal and medial cuneiform was a useful option to attain the bone fusion for small fracture fragment for a treatment of nonunion of a stress fracture at the base of the second metatarsal. 



#3 A Preliminary Analysis of the Importance of Distance, Angle, and Insight When Soccer Referees Make Penalty Decisions

Reference: Front Sports Act Living. 2021 Jan 8;2:595703. doi: 10.3389/fspor.2020.595703. eCollection 2020. 

Authors: Bjørn Tore Johansen, Martin Kjeøen Erikstad

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Summary: Soccer referees move freely on the pitch to place themselves in the best location for making decisions. While Football Association UK (FA) highlights that a referee should never be more than 20 m away from the playing situation, previous studies have been inconsistent in indicating appropriate distance to a situation for increasing the likelihood of a correct decision. Further, appropriate angle and insight are also likely to influence the correctness of referees' decisions. The aim of this study was to provide an initial investigation of elite referees' positioning in the field (distance, angle, and insight) when making correct and erroneous decisions in potential penalty situations. An expert panel (EP) consisting of two active referees with relevant academic background analyzed referees positioning when making correct or erroneous decisions regarding penalties. The EP were asked to qualitatively analyze referees positioning in selected video clips by using recommended technical refereeing criteria and practical guidelines (i.e., the referee's distance from, angle to, and insight into the penalty situations). Of the 42 situations evaluated, the results revealed that the EP termed the referees positioning as good in terms of angle and insight in 25 and 21 situations, respectively. The angle was average in seven situations and poor in 10 situations, and the insight were average in 10 situations and poor in 11 situations. The match referee was <10 meters away in 12 situations, 10-20 m away in 22 situations, and >20 meters away in eight situations. Results revealed that referees' positioning that resulted in the highest rate of correct decisions were when the distance were under 10 meters (83% correct decisions), good angle (88%), and good insight (86%). In contrast, referees were poorly positioned in terms of angle and/or insight in nine of the 15 erroneous decisions made. Although the present study was a preliminary qualitative investigation containing a limited number of potential penalty situations, the findings indicated that soccer referees are more likely to produce a correct decision in potential penalty situations when the distance to the situation is under 10 meters, when the insight to the situation is good and the angle to the incident is good. In contrast, the match referees generally had a poor starting position to assess the penalty situations where they landed on a wrong decision. While previous studies have been somewhat inconsistent in indicating optimal referee positioning in soccer, the present study highlights the potential value of a more qualitative approach to understand referees' positioning and subsequent decision-making accuracy. 



#4 The Influence of Injury History on Countermovement Jump Performance and Movement Strategy in Professional Soccer Players: Implications for Profiling and Rehabilitation Foci

Reference: J Sport Rehabil. 2021 Jan 25;1-6. doi: 10.1123/jsr.2020-0243. Online ahead of print. 

Authors: Andy Mitchell, Craig Holding, Matt Greig 

Summary: Professional soccer players who have sustained a lower limb injury are up to 3× more likely to suffer a reinjury, often of increased severity. Previous injury has been shown to induce compensatory strategies during neuromuscular screening tests, which might mask deficits and lead to misinterpretation of readiness to play based on task outcome measures. The aim was to investigate the influence of previous injury in professional soccer players on countermovement jump (CMJ) performance and movement strategy. Professional soccer club competing in the English Championship (tier 2). Outfield players with a minimum of 6 years as a professional. Players were categorized as previously injured (n = 10) or not injured (n = 10). All players completed double- and single-leg CMJ trials. CMJ performance was quantified as jump height and flight time:contraction time ratio. CMJ movement strategy was quantified as force-time history, differentiating eccentric and concentric phases and CMJ depth. Double-leg CMJ was not sensitive to previous injury in performance or movement strategy. In contrast, single-leg CMJ performance was impaired in players with previous injury, who generated significantly lower eccentric and concentric peak force and rate of force development, and a deeper countermovement. Impaired single-leg CMJ performance was also evident in the nonaffected limb of previously injured players, suggesting cross-contamination. Hierarchical ordering revealed that the eccentric phase of the CMJ contributed little to performance in previously injured players. In noninjured players, the eccentric rate of force development and concentric peak force were able to account for up to 89% of the variation in CMJ performance. Single-leg CMJ is advocated for player profiling, being more sensitive to previous injury, and negating the opportunity for interlimb compensation strategies. Movement strategy deficits in previously injured players suggest rehabilitation foci specific to eccentric force development. 



#5 Testing protocol affects the velocity at VO 2max in semi-professional soccer players

Reference: Res Sports Med. 2021 Jan 25;1-11. doi: 10.1080/15438627.2021.1878460. Online ahead of print. 

Authors: Andrea Riboli, Giuseppe Coratella, Susanna Rampichini, Eloisa Limonta, Fabio Esposito

Summary: The aim was to compare three different protocols to assess the velocity associated with the maximal oxygen uptake (Vmax) in soccer players. Sixteen semi-professional soccer players performed three maximum incremental tests on treadmill: two continuous protocols [1 km·h-1·min-1 (CP1); and 1 km·h-1 every 2 min (CP2)], and one discontinuous (DP) protocol to determine Vmax, maximum oxygen uptake (VO2max) and oxygen cost of running (i.e., the slope of the VO2 vs velocity relationship at submaximal exercise). Vmax was higher in CP1> CP2> DP (19.4 ± 1.7, 17.4 ± 1.2, 16.1 ± 1.1 km·h-1 for CP1, CP2, and DP, respectively; P < 0.05 ES: 0.09 to 3.36). No difference in VO2max was found between CP1, CP2 and DP (P > 0.05). Oxygen cost of running showed between-protocol differences (CP1> CP2> DP; P < 0.05; ES: 0.28 to 3.30). Vmax was higher when determined using continuous vs discontinuous protocols due to the greater overestimation in oxygen cost of running. Such differences in Vmax should be considered to optimize acute physiological responses during high-intensity running activities. 



#6 How does the mid-season coach change affect physical performance on top soccer players? 

Reference: Physiol Behav. 2021 Jan 21;232:113328. doi: 10.1016/j.physbeh.2021.113328. Online ahead of print. 

Authors: Berni Guerrero-Calderón, Adam Owen, José Alfonso Morcillo, Alfonso Castillo-Rodríguez

Summary: The aim of this study was to analyze the locomotion and metabolic responses of professional players in the top three competitive standards of Spanish soccer (First, Second and Second 'B' division) during the four weeks before and after dismissal the coach. Training and match load data were analyzed separately (n = 1189 events) by coach (dismissed coach and the new coach) and Wilcoxon-test was performed to compare data between coaches. In training, players covered longer distance in all speed ranges >14 km•h - 1 with the coach dismissed; medium (14-18 km•h - 1), high (18-21 km•h - 1), very-high (21-24 km•h - 1) and sprint running distance (>24 km•h - 1) (d = 0.53, 0.46, 0.58 and 0.54; respectively) on first division; and equivalent distance index and accelerations events (d = 0.63 and 0.50; respectively) on second division. Lower differences were found in matches, in which the dismissed coach showed higher equivalent distance index, accelerations and decelerations events (d = 0.69, 0.68 and 0.61; respectively) compared to the new coach in the second division. Therefore, the players covered longer high-intensity distance with the dismissed coach than the new coach in training, whilst a similar performance was found in the competition. These results suggest that the coach turnover at mid-season did no increase the players' physical performance either in training or in competition. 



#7 An 11-week school-based 'health education through football programme' improves health knowledge related to hygiene, nutrition, physical activity and well-being-and it's fun! A scaled-up, cluster-RCT with over 3000 Danish school children aged 10-12 years old 

Reference: Br J Sports Med. 2021 Jan 28;bjsports-2020-103097. doi: 10.1136/bjsports-2020-103097.

Authors: Malte Nejst Larsen, Anne-Marie Elbe, Mads Madsen, Esben Elholm Madsen, Christina Ørntoft, Knud Ryom, Jiri Dvorak, Peter Krustrup

Summary: Our large-scale cluster randomised controlled trial aimed to investigate the effects on health knowledge and enjoyment of an 11 week 'health education through football' programme for children aged 10-12 years old. 3127 Danish school children (49% girls) aged 10-12 years from a total of 154 schools located in 63% of the Danish municipalities (69 of 98) took part in the analysis. A 5:1 cluster randomisation was performed at school level for the intervention group (IG) or the control group (CG). The twice-weekly 45 min intervention was the '11 for Health in Denmark' programme, which includes health education, football drills and small-sided games. The health education element focused on hygiene, nutrition, physical activity and well-being. Outcomes: The participants completed a 34-item multiple-choice computer-based health knowledge questionnaire preintervention and postintervention. IG also evaluated whether the programme was enjoyable. Between-group differences (p<0.05) were observed in overall health knowledge in favour of IG (+7.2% points, 95% CI 6.1% to 8.4%, effect size, ES:0.59), with similar effects for girls (+7.4% points, 95% CI 5.9% to 9.0%, ES:0.57) and for boys (+7.0% points, 95% CI 5.3% to 8.7%, p<0.05, ES:0.51). Marked between-group differences were observed in favour of IG, for health knowledge related to hygiene (IG vs CG:+13.9% points, 95% CI 11.1% to 16.7%, ES:0.53), nutrition (+10.3% points, 95% CI 8.5% to 12.1%, ES:0.53), physical activity (+5.9% points, 95% CI 4.1% to 7.7%, ES:0.36) and well-being (+4.4% points, 95% CI 2.7% to 6.1%, ES:0.28). Both girls and boys gave the programme moderate to high scores for enjoyment (3.6±1.0 and 3.7±1.1, respectively). Health education through sport, using the '11 for Health' model, was enjoyable for girls and boys aged 10-12 years old, and improved health knowledge related to hygiene, nutrition, physical activity and well-being. 



#8 Elite football of 2030 will not be the same as that of 2020: What has evolved and what needs to evolve?

Reference: Scand J Med Sci Sports. 2021 Feb;31(2):493-494. doi: 10.1111/sms.13876. 

Authors: Damian J Harper, Gareth N Sandford, Jo Clubb, Megan Young, Matt Taberner, Dave Rhodes, Chris Carling, John Kiely



#9 The 2015 U.S. Soccer Federation header ban and its effect on emergency room concussion rates in soccer players aged 10-13

Reference: J Can Chiropr Assoc. 2020 Dec;64(3):187-192. 

Authors: Rahim Lalji, Hayden Snider, Noah Chow, Scott Howitt

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Summary: In 2015, the U.S. Soccer Federation banned heading for players aged 10-13. The purpose was to assess the change in proportion of children aged 10-13 playing soccer in the US presenting to an Emergency Department (ED) with a concussion in relation to any other injury before and after the ban. Analysis was restricted to soccer athletes between 10-13 years that reported to a National Electronic Injury Surveillance System (NEISS) participating hospital ED following injury in 2013-2014 and 2016-2017. Multivariable logistic regression was performed to assess the association between year of injury and concussion diagnosis in relation to other injury diagnosis after adjusting for age, sex, and ethnicity. Concussion in relation to other injuries showed a significant increase in 2016-2017 when compared to 2013-2014 after adjustment (OR= 1.286, 95%CI = 1.090-1.517). These results suggest that banning heading may not reduce concussion within this population. However, significant confounders, including increased reporting, were not controlled for. 



#10 Implementing Strength Training Strategies for Injury Prevention in Soccer: Scientific Rationale and Methodological Recommendations 

Reference: Int J Sports Physiol Perform. 2021 Jan 27;1-6. doi: 10.1123/ijspp.2020-0862. Online ahead of print. 

Authors: Marco Beato, Sergio Maroto-Izquierdo, Anthony N Turner, Chris Bishop 

Summary: Due to the negative effects that injuries have on performance, club finances, and long-term player health (permanent disability after a severe injury), prevention strategies are an essential part of both sports medicine and performance. Purpose: To summarize the current evidence regarding strength training for injury prevention in soccer and to inform its evidence-based implementation in research and applied settings. Conclusions: The contemporary literature suggests that strength training, proposed as traditional resistance, eccentric, and flywheel training, may be a valid method to reduce injury risk in soccer players. Training strategies involving multiple components (eg, a combination of strength, balance, plyometrics) that include strength exercises are effective at reducing noncontact injuries in female soccer players. In addition, the body of research currently published supports the use of eccentric training in sports, which offers unique physiological responses compared with other resistance exercise modalities. It seems that the Nordic hamstring exercise, in particular, is a viable option for the reduction of hamstring injuries in soccer players. Moreover, flywheel training has specific training peculiarities and advantages that are related to the combination of both concentric and eccentric contraction, which may play an important role in injury prevention. It is the authors' opinion that strength and conditioning coaches should integrate the strength training methods proposed here in their weekly training routine to reduce the likelihood of injuries in their players; however, further research is needed to verify the advantages and disadvantages of these training methods to injury prevention using specific cohorts of soccer players. 



#11 The Moral Gatekeeper: Soccer and Technology, the Case of Video Assistant Referee (VAR) 

Reference: Front Psychol. 2021 Jan 12;11:613469. doi: 10.3389/fpsyg.2020.613469. eCollection 2020. 

Authors: Ilan Tamir, Michael Bar-Eli

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Summary: Video assistant referee was officially introduced into soccer regulations in 2018, after many years in which referee errors were justified as being "part of the game." The technology's penetration into the soccer field was accompanied by concerns and much criticism that, to a large degree, continues to be voiced with frequency. This paper argues that, despite fierce objections and extensive criticism, VAR represents an important revision in modern professional soccer, and moreover, it completes a moral revolution in the evolution of the sport as a whole. Theoretically speaking, this technology enables an improvement in the sport's professional standards and its public image and prestige, and especially its moral standards - Fair play. Furthermore, the introduction of this technology makes it possible to discover additional weaknesses (Standardization for extra time, a clear definition of a handball offense and more) that professional soccer regulations will probably be forced to address in the future. 



#12 The Goal Scale: A New Instrument to Measure the Perceived Exertion in Soccer (Indoor, Field, and Beach) Players 

Reference: Front Psychol. 2021 Jan 7;11:623480. doi: 10.3389/fpsyg.2020.623480. eCollection 2020. 

Authors: Luis Felipe Tubagi Polito, Marcelo Luis Marquezi, Douglas Popp Marin, Marcelo Villas Boas Junior, Maria Regina Ferreira Brandão

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Summary: The rating of perceived exertion (RPE) can be used to monitor the exercise intensity during laboratory and specific tests, training sessions, and to estimate the internal training load of the athletes. The aim of the present study was to develop and validate a specific pictorial perceived exertion scale for soccer players (indoor, field, and beach soccer) called GOAL Scale. The pictorial GOAL Scale (six drawings; 1 "low exertion" to 6 "exhaustion") was validated for twenty under-17 soccer players (16.4 ± 0.68 years; 175.4 ± 9 cm; 66.4 ± 7.7 kg; % fat mass 12.4 ± 3.3). In the validation phase, the athletes were evaluated in a progressive protocol involving stimuluses of 3 min with 1 min for the rest into the stages until the voluntary exhaustion in Maximal Cardiopulmonary Effort Test (MCET), and in the Yo Yo Intermittent Recovery Test - Level 1 (Yo-Yo). The RPE identified by the GOL Scale, by the Borg Scale 6 - 20 and by the Cavasini Scale, as well as the heart rate (HR), perceptual of the heart rate (%HRmax) and the blood lactate concentration ([La]) were immediately evaluated after each stage of both tests. Spearman's correlation coefficient (p < 0.05) was used. Construct scale validity was examined by regressing GOAL Scale against Borg Scale 6 - 20 and Cavasini Scale and concurrent scale validity was investigated by regressing GOAL Scale against HR, beats/min and blood lactate concentration (mmol/L) during two progressive tests. There was a significant correlation values of the GOAL Scale with Borg Scale (r = 0.93; r = 0.88), Cavasini Scale (r = 0.91; r = 0.90), %HRmax (r = 0.91; r = 0,86), HR (r = 0.87; r = 0.83) and lactate (r = 0.68; r = 0.83) during tests (Maximal Incremental Cardiopulmonary Test and Yo-Yo test, respectively). The results evidenced concurrent and construct validity of the GOAL Scale across a wide range of exercise intensity. The absence of verbal anchors makes the use of this instrument to soccer, futsal and beach soccer athletes of different languages and different literacy levels possible. 


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