Latest research in football - week 14 - 2020

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 Understanding the presence of mental fatigue in English academy soccer players
Reference: J Sports Sci. 2020 Mar 25:1-7. doi: 10.1080/02640414.2020.1746597. [Epub ahead of print]
Authors: Thompson CJ, Noon M, Towlson C, Perry J, Coutts AJ, Harper LD, Skorski S, Smith MR, Barrett S, Meyer T
Summary: Research has demonstrated that induced mental fatigue impairs soccer-specific technical, tactical and physical performance in soccer players. The findings are limited by the lack of elite players and low ecological validity of the tasks used to induce mental fatigue, which do not resemble the cognitive demands of soccer. The current study collected survey data from English academy soccer players (n = 256; age groups - U14 - U23), with questions comprising of five themes (descriptors of physical and mental fatigue, travel, education, match-play and fixture congestion). The survey consisted of multiple choice responses, checkboxes and blinded/unblinded (for duration based questions) 0-100 arbitrary unit (AU) slider scales. Listening to music (81.6% of players), using social media (58.3%) and watching videos (34.3%) were the most common pre-match activities. Pre-match subjective mental fatigue was low (18.7±18.8 AU), and most frequently reported at the end of a match (47±26 AU) and remained elevated 24-hours post-match (36±27 AU). Travel (29±24 AU), fixture congestion (44±25 AU) and education (30±26 AU) demonstrated a low to moderate presence of subjective mental fatigue. These findings provide an overview of activities performed by English academy soccer players pre-match, and demonstrate that mental fatigue is experienced as a result of match-play.

#2 Small-Sided Games are More Enjoyable Than High-Intensity Interval Training of Similar Exercise Intensity in Soccer
Reference: Open Access J Sports Med. 2020 Mar 4;11:77-84. doi: 10.2147/OAJSM.S244512. eCollection 2020.
Authors: Selmi O, Ouergui I, Levitt DE, Nikolaidis PT, Knechtle B, Bouassida A
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Summary: High-intensity interval training (HIIT) and small-sided games (SSG) have been applied and tested for athletes in order to enhance the soccer performance. For this reason, this experimental study aimed to compare the effects of SSGs and HIIT on power, physiological responses and perceived enjoyment. Sixteen youth soccer players (age, 17.5±0.6 years, mean±standard deviation; height, 178.2±6.4 cm; body mass, 70.4±5.4 kg; body fat, 10.6±0.8%) completed one session each of HIIT and SSG on separate days with 1 week between sessions. Each session lasted 25 mins (4x4 mins work with 3 mins of passive recovery in-between). SSGs consisted of 4 versus 4 player games on a 25×35 m pitch, and HIIT consisted of intermittent 15-s runs at 110% maximal aerobic speed separated by 15 s of passive recovery. Psychological responses following each protocol were assessed using the Physical Activity Enjoyment Scale (PACES). Heart rate (HR) was continuously recorded, rating of perceived exertion (RPE) and lactate concentration [La] were measured after each training session. Lower body muscular power was assessed using the 5-jump test relative to leg length (5JT-relative) before and after each training session, where greater average distance per stride over five sequential jumping strides indicated greater muscular power. HIIT and SSG showed no significant difference in HR, RPE and [La] responses (p=0.70, ES=0.11; p=0.61, ES=0.08 and p=0.38, ES=0.21, respectively). 5JT-relative decreased significantly for SSG and HIIT (p<0.05, ES=0.50 and p<0.05, ES=0.40, respectively). PACES score was greater in SSG compared to HIIT (ES=5.35, p<0.001). HIIT and SSG sessions induced similar physiological responses; however, SSGs induced a higher enjoyment level than HIIT. Coaches could choose between these training modalities according to the objective of their training session, considering the enjoyment-related advantages of SSGs.

#3 Effects of muscular injuries on the technical and physical performance of professional soccer players
Reference: Phys Sportsmed. 2020 Mar 21:1-5. doi: 10.1080/00913847.2020.1744485. [Epub ahead of print]
Authors: Portillo J, Abián P, Calvo B, Paredes V, Abián-Vicén J
Summary: The aim of this study was to determine the effects of muscular injuries in the lower limbs on the technical and physical performance of professional soccer players when they return to the league competition. Seventy-six muscular injuries incurred by Spanish male professional soccer players (Age: 27.5 ± 3.5 years) were analyzed during two consecutive competitive seasons: 2014-2015 and 2015-2016. The players' performance was studied during Spanish First Division competitive matches using a multi-camera computerized tracking system (Mediacoach Desktop). After muscular injury relative total distance covered in sprints decreased by 8.6 ± 30.2% (P = 0.013) in the first half and 7.7 ± 36.6% (P = 0.038) in the second half. Similarly, maximal running speed decreased by 2.78 ± 6.91 km.h-1 (pre: 27.3 ± 6.4 km.h-1 vs. post: 24.5 ± 6.6 km.h-1, P = 0.013) in the first half, and 1.50 ± 5.68 km.h-1 (29.1 ± 3.9 km.h-1 vs. 27.6 ± 5.3 km.h-1, P = 0.043) in the second half. Muscle injury also affected technical performance significantly decreasing successful passes (P = 0.045). There were no differences in the number of possession gains (P = 0.277), and possession losses (P = 0.178). After a moderate or severe muscular injury (causing >8 days lay off), player performance is significantly lower in high-intensity efforts and technical skills such as sprints, maximal running speed, or successful passes.

#4 Age-related differences in torque in angle-specific and peak torque hamstring to quadriceps ratios in female soccer players from 11 to 18 years old: Α Cross-sectional study
Reference: Res Sports Med. 2020 Mar 22:1-13. doi: 10.1080/15438627.2020.1742713. [Epub ahead of print]
Authors: Andrade MS, Junqueira MS, Andre Barbosa De Lira C, Vancini RL, Seffrin A, Nikolaidis PT, Rosemann T, Knechtle B
Summary: The aim of this study was to evaluate and compare the hamstring (H) and quadriceps (Q) strength, bilateral difference and balance ratios in female soccer players. Ninety-three athletes from three age groups: under 13 (U13), 15 (U15) and 18 (U18) participated in the study performing isokinetic tests to measure peak torque, total work, average power and torque at 30º of thigh muscles. Conventional strength balance ratios, angle-specific balance ratio and bilateral strength difference were evaluated. There was bilateral strength difference for extensor muscles total work (p = 0.02) in U13 and flexor muscles peak torque (p = 0.02) in U15. All variables were superior in U15 than U13 (p <.05). There was no strength difference between U15 and U18. Balance ratios did not differ between sides or age groups. The study showed that although peak torque values were higher in U15 than in U13, balance ratios were similar.

#5 Acceleration intensity is an important contributor to the external and internal training load demands of repeated sprint exercises in soccer players
Reference: Res Sports Med. 2020 Mar 22:1-10. doi: 10.1080/15438627.2020.1743993. [Epub ahead of print]
Authors: Beato M, Drust B
Summary: The aim of this study was to evaluate the effect of acceleration on the external and internal load during repeated sprint exercises (RSE). This study used a cross-over design. Sixteen soccer players were included (mean ± SDs: age 21 ± 1 years; weight 71.1 ± 7.7 kg). RSE was 3 sets of 7 × 30 m sprints with 25 s and 3 min recovery between sprints and sets, respectively. RSE was performed using two protocols requiring either 10 m maximal acceleration (2.12 m.s-2 [RSE-MA]) or 10 m submaximal acceleration (1.66 m.s-2 [RSE-SA]). Global positioning systems (10 Hz; STATSports, Viper) were utilized to collect: high speed running (HSR), dynamic stress load (DSL), Heart Rate (HR) peak, time >85% HR peak, respiratory (RPEres) and muscular (RPEmus) rating of perceived exertion. RSE-MA induced higher load than RSE-SA in HSR (p = 0.037, ES = 0.20), DSL (p = 0.027, ES = 0.43), HR peak (p = 0.025, ES = 0.47), Time >85% HR peak (p = 0.028, ES = 1.11), RPEres (p = 0.001, ES = 1.10), and RPEmus (p = 0.001, ES = 0.73). This study shows that a different acceleration intensity in a RSE (MA vs. SA) impacts external and internal training load parameters.

#6 Perceptual-cognitive processes underlying creative expert performance in soccer
Reference: Psychol Res. 2020 Mar 21. doi: 10.1007/s00426-020-01320-5. [Epub ahead of print]
Authors: Roca A, Ford PR, Memmert D
Summary: Creativity is one of the key parts of expert performance in sport and other domains. The aim of this study was to determine the underlying perceptual and cognitive processes that underpin creative expert performance in the sport of soccer. Forty skilled adult soccer players participated. In the experimental task, they interacted with representative video-based 11 vs. 11 attacking situations whilst in possession of a ball. Clips were occluded at a key moment and participants were required to play the ball in response to each presented scenario as they would in a real-game situation. Moreover, they were required to name other additional actions they could execute for each situation. Their solutions on the task were measured using the three observation criteria for creativity of originality, flexibility, and fluency of decisions. Using these criteria, players were categorized into either high- or low-creative groups. Visual search and cognitive thought processes were recorded during the task using a portable eye-movement registration system and retrospective verbal reports. The creativity-based between-group differences in decision making were underpinned by differences in visual search strategy. Compared to the low-creative group, the high-creative players made more fixations of shorter duration in a different sequential order and to more task-relevant locations of the display, indicating a broader attentional focus. They also generated a greater number of verbal reports of thoughts related to the assessment of the current task situation and planning of future decisions when compared with the low-creative players. Our findings highlight the perceptual-cognitive processes that underlie creative expert performance in a sport-specific domain.

#7 Short-Term FIFA 11+ Improves Agility and Jump Performance in Young Soccer Players
Reference: Int J Environ Res Public Health. 2020 Mar 18;17(6). pii: E2017. doi: 10.3390/ijerph17062017.
Authors: Trajković N, Gušić M, Molnar S, Mačak D, Madić DM, Bogataj Š
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Summary: Studies dealing with the effectiveness of the Fédération Internationale de Football Association (FIFA) 11+ prevention program to improve performance outcomes in children aged < 14 years are limited. This study aimed to point out the effects of the application of short-term FIFA 11+ warm-up program on physical performance in young football players. Participants were 36 youth male football players, divided into a FIFA 11+ (n = 19; mean (SD) age: 11.15 (0.79) y) and a control group (CG: n = 17; age: 10.87 (0.8) y) and trained for 4 weeks. Before and after the training period, standing long jump performance, agility, repeated sprint ability, sit and reach, and "30-15" intermittent fitness tests were assessed. A mixed ANOVA showed significant differences between the groups in the standing long jump test (FIFA 11+: 5.6% vs. CG: -1.9%) in favor of FIFA 11+ over CG. Additionally, the FIFA 11+ performance of the Illinois agility test was significantly better compared to the CG performance (FIFA 11+: -1.9% vs. CG: 0.03%). The main findings of this study suggest that just 4 weeks of implementation of the FIFA 11+ improves physical performance compared with traditional warm-up routines in young soccer players.

#8 Football cannot restart soon during the COVID-19 emergency! A critical perspective from the Italian experience and a call for action
Reference: Br J Sports Med. 2020 Mar 24. pii: bjsports-2020-102306. doi: 10.1136/bjsports-2020-102306. [Epub ahead of print]
Authors: Corsini A, Bisciotti GN, Eirale C, Volpi P
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#9 Does a recent hamstring muscle injury affect the timing of muscle activation during high speed overground running in professional Australian Football players?
Reference: Phys Ther Sport. 2020 Mar 18;43:188-194. doi: 10.1016/j.ptsp.2020.03.005. [Epub ahead of print]
Authors: Crow J, Semciw A, Couch J, Pizzari T
Summary: The purpose was to investigate if the temporal characteristics of hamstring and gluteal muscle activation are altered during high speed overground running in professional Australian Football players following hamstring muscle injury. Elite professional Australian Football players who had sustained a hamstring muscle injury in the six months prior to testing (n = 7) and a group of players from the same club who had no history of hamstring muscle injury (n = 8) participated in this study. Muscle onset timing, muscle offset timing and muscle onset duration of the medial hamstrings, biceps femoris and gluteus maximus muscles during high-speed running using electromyographic data were used.  No significant differences in any of the temporal aspects of muscle activation were found between groups for any of the muscles tested (p > 0.05). Persistent alterations to the timing of muscle activation following hamstring muscle injury that have been reported in recreational athletes were not observed during high speed running in professional athletes who have completed comprehensive rehabilitation programs.

#10 The relationship between cam morphology and hip and groin symptoms and signs in young male football players
Reference: Scand J Med Sci Sports. 2020 Mar 22. doi: 10.1111/sms.13660. [Epub ahead of print]
Authors: van Klij P, Ginai AZ, Heijboer MP, Verhaar JAN, Waarsing JH, Agricola R
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Summary: Conflicting and limited high quality prospective data is available on the associations between cam morphology and hip and groin symptoms and range of motion (ROM). This cross-sectional cohort study investigated associations between cam morphology presence, size and duration and symptoms and ROM. Academy male football players (n=49, 17-24 years) were included. Standardised anteroposterior pelvic and frog-leg lateral radiographs were obtained at baseline, 2.5 and 5-year follow-up. The femoral head-neck junction was quantified by: Visual score. Cam morphology (flattening or prominence), large cam (prominence). Alpha angle.Cam morphology (≥60°), large cam (≥78°). Cam morphology duration was defined as long (first present at baseline) or short (only from 2.5 or 5-year follow-up). Current symptoms at 5-year follow-up were assessed using a hip and groin pain question and by the 'Hip and Groin Outcome Score' (HAGOS). HAGOS-scores were categorised into: most symptoms (≥2 domains in lowest interquartile range [IQR]), least symptoms (≥2 domains in highest IQR). Hip ROM was measured by goniometry at 5-year follow-up. Large cam morphology based on visual score was associated with hip and groin pain (23.8% vs. 7.1%, OR: 3.17, CI: [1.15-8.70], P=.026), but not with HAGOS-scores. Cam morphology presence, size and duration were associated with limited flexion of around 6° and/or 3° to 6° for internal rotation. Cam morphology presence, size and duration were associated with limited hip flexion and/or internal rotation, but differences might not exceed the minimal clinical important difference. Whether cam morphology results in symptoms is uncertain.

#11 Novel Methodology for Football Rebound Test Method
Reference: Sensors (Basel). 2020 Mar 18;20(6). pii: E1688. doi: 10.3390/s20061688.
Authors: Colino E, Corral-Gómez L, Rodríguez-Rosa D, Juárez-Pérez S, García-Unanue J, González-Rodríguez A, Sánchez-Sánchez J, Felipe JL, Gallardo L, Castillo-García FJ
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Summary: Assessing and keeping control of the mechanical properties of sport surfaces is a relevant task in sports since it enables athletes to train and compete safely and under equal conditions. Currently, different tests are used for assessing athlete- and ball-surface interactions in artificial turf pitches. In order to make these evaluations more agile and accessible for every facility, it is important to develop new apparatus that enable to perform the tests in an easier and quicker way. The existing equipment for determining the vertical ball behavior requires a complex and non-easily transportable device in which the ball must be fixed to the upper part of the frame in a very precise position by means of a magnet. The rebound height is determined by capturing the acoustic signal produced when the ball bounces on the turf. When extended tests are conducted, the time required to evaluate a single field is too high due to the non-valid trials. This work proposes a novel methodology which allows to notoriously decrease the time of testing fields maintaining the repeatability and accuracy of the test method together with a compact device for improving its mobility and transport. Simulations and experiments demonstrates the repeatability and accuracy of the results obtained by the proposed device, which decreases the non-valid trials and notoriously reduces the time for field evaluation.

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