Latest research in football - week 47 - 2018

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 High-Intensity Demands of 6-a-Side Small-Sided Games and 11-a-Side Matches in Youth Soccer Players
Reference: Pediatr Exerc Sci. 2018 Nov 30:1-6. doi: 10.1123/pes.2018-0122. [Epub ahead of print]
Authors: Goto H, King JA
Summary: The purposes of the present study were to examine high-intensity running distance during 6-a-side small-sided games (SSGs) and 11-a-side matches (11M) in youth soccer players using speed and metabolic power approaches and the magnitude of difference between the high-intensity running distance calculated with the 2 approaches. A total of 11 outfield players (age = 16.3 [0.6] y) performed SSGs with 3 pitch sizes (small SSG [SSGS], medium SSG, and large SSG [SSGL]) and 11M. A Global Positioning System (15 Hz) was employed to calculate total distance covered, distance covered at a speed ≥4.3 m·s-1 (TS), and metabolic power of ≥20 W·kg-1 (TP). The total distance covered increased from SSGS through to SSGL (P < .001) and was greater during 11M and SSGL compared with other SSGs (P < .01). TS and TP increased from SSGS (TS vs TP = 98 [55] vs 547 [181] m) through to SSGL (538 [167] vs 1050 [234] m; P < .001). TS and TP during 11M (370 [122] vs 869 [233] m) was greater than SSGS (P < .001 for both) and less than SSGL (P < .05 for both). The magnitude of difference between TS and TP (as a percentage) was lower with an increase in pitch size during SSGs and was greater in SSGS (615% [404%]; P < .001), medium SSG (195% [76%]; P < .05), and smaller in SSGL (102% [33%]; P < .01) compared with 11M (145% [53%]). SSGs can replicate the high-intensity demands of 11M and the speed approach underestimates the high-intensity demands of SSGs and 11M compared with the metabolic power approach.

#2 Injury prevalence and risk factors in a Greek team's professional football (soccer) players: a three consecutive seasons survey
Reference: Res Sports Med. 2018 Nov 30:1-13. doi: 10.1080/15438627.2018.1553779. [Epub ahead of print]
Authors: Smpokos E, Mourikis C, Theos C, Linardakis M
Summary: This study investigated the prevalence and risk factors of injuries on a cohort of 123 Greek team's professional football players during three consecutive seasons, 2015/16-to-2017/18. Injuries were assessed and regression analysis was used to evaluate the potential risk factors. Three-quarters of the players were recorded as injured with 2.3 injuries/injured player, and the injury incidence was 55 injuries/1,000 match-playing-exposure-hours. The mean rehabilitation days were 29.3/injured player (95%CI 22.4-36.8) and 13.0/injury (95%CI 8.6-17.4). The majority of injured players has been found to have moderate-to-major/severe injuries and most of the injuries were traumatic than overuse (p < 0.05). The number of injuries were related to the recurrence of injury (beta = 0.646, p < 0.001) and the rehabilitations days (beta = 0.271, p < 0.001). High prevalence of injuries was found as the recurrence of injury and rehabilitation days were their main predictive risk factors. In order to reduce the risk of injuries, continuous effort is required in the rehabilitation of players.

#3 ACL injury incidence, severity and patterns in professional male soccer players in a Middle Eastern league
Reference: BMJ Open Sport Exerc Med. 2018 Oct 23;4(1):e000461. doi: 10.1136/bmjsem-2018-000461. eCollection 2018.
Authors: Rekik RN, Tabben M, Eirale C, Landreau P, Bouras R, Wilson MG, Gillogly S, Bahr R, Chamari K
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Summary: The purpose was to ascertain ACL injury incidence, severity (injury burden) and patterns (contact/non-contact and reinjuries) in a professional male football league in the Middle East over five consecutive seasons. Prospective epidemiological study reporting ACL injuries in professional male soccer players in the Qatar Stars League, with complete matches/training exposure over five seasons (2013-2014 to 2017-2018), corresponding to 2243 player seasons and 729 team months. 37 complete ACL ruptures occurred in 37 players during 486 951  hours of player exposure. The overall ACL injury rate was 0.076 injuries/1000  hours of exposure (season range 0.045-0.098). Injury incidence during matches and training was 0.41 and 0.04 injuries/1000  hours of exposure, respectively. Match injury incidence was greater than that of training (OR 11.8, 95%  CI 6.21 to 23.23, p<0.001). Average injury-related time-loss following ACL injury was 225 days±65 (range 116-360). Overall injury burden was 16.3 days lost/1000  hours of exposure. The overall ACL injury rate in professional male soccer players competing in the Middle East was 0.076 injuries/1000  hours of exposure, match injury incidence was greater than training, while the average ACL time-loss was 225 days.

#4 Normative Data of the Wingate Anaerobic Test in 1 Year Age Groups of Male Soccer Players
Reference: Front Physiol. 2018 Nov 15;9:1619. doi: 10.3389/fphys.2018.01619. eCollection 2018.
Authors: Nikolaidis PT, Matos B, Clemente FM, Bezerra P, Camões M, Rosemann T, Knechtle B
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Summary: The Wingate anaerobic test (WAnT) has been used extensively to evaluate performance in soccer, however, a comprehensive sport-specific normative database has not been available so far. Therefore, the main aim of the present study was to develop norms of the main indices of the WAnT with regards to age in soccer. A secondary aim was to examine the relationship of WAnT with two common field tests, 20 m sprint and vertical jump, and study the variation of this relationship by age and playing position. Hundred and ninety five male soccer players (age 18.1 ± 4.9 years) performed the WAnT, and a sub-sample of 190 soccer players (age 19.4 ± 5.1 years) performed 20 m sprint, squat (SJ) and countermovement jump (CMJ). Age was related very largely with peak power (R 2 = 0.57) and mean power of the WAnT (R 2 = 0.60) when they were expressed in W, and largely (R 2 = 0.41 and R2 = 0.33, respectively) when they were expressed in, whereas it did not relate with fatigue index. After being adjusted for age, a relationship of SJ (B = 3.91, 90% CI: 2.49, 5.32; R 2 = 0.26), CMJ (B = 3.59, 90% CI: 2.22, 4.95; R 2 = 0.24) and 20 m sprint (B = -0.06, 90% CI: -0.10; -0.01; R 2 = 0.19) with peak power of the WanT was observed. In summary, Ppeak and Pmean were related very largely to age, especially during adolescence, and percentile norms of these indices were developed for 1-year age groups from 11 to 21 years old and for a single adult age group (22-39 years old). These findings on the largest dataset of soccer players ever studied would be expected to offer a practical tool to the members of the sports medicine team (e.g., exercise physiologists, fitness trainers, and coaches) working with them.

#5 Sprint Mechanical Properties of Female and Different Aged Male Top-Level German Soccer Players
Reference: Sports (Basel). 2018 Nov 28;6(4). pii: E161. doi: 10.3390/sports6040161.
Authors: Baumgart C, Freiwald J, Hoppe MW
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Summary: This study compared the sprint mechanical properties of female and different aged male top-level soccer players. A total of 14 adult females (FEM) and 115 different aged male field players, competing at German top levels, participated in this study. The males belonged to teams of under 12, 13, 14, 15, 17, 19, and 23 years (U 12⁻23) and professionals (PRO). All players were tested for a 30 m linear sprint. From timing gate derived sprint times, force-velocity and power-velocity relationships, as well as theoretical maximum running velocity, force, and power data were computed by an inverse dynamic approach applied to the center of mass. The approach was optimized for taking the starting time into account, which is a progress in the present research field, when aiming to compute sprint mechanical properties by different methodological approaches under field conditions. Sprint mechanical properties of FEM were lower than those of PRO. Compared to other age groups, sprint mechanical properties of FEM were similar to those of U 14 and U 15. An increase in sprint mechanical properties was found from U 12 to U 17. The study shows that sprint mechanical properties differ according to gender and age in top-level soccer players.

#6 Combination of Agility and Plyometric Training Provides Similar Training Benefits as Combined Balance and Plyometric Training in Young Soccer Players
Reference: Front Physiol. 2018 Nov 13;9:1611. doi: 10.3389/fphys.2018.01611. eCollection 2018.
Authors: Makhlouf I, Chaouachi A, Chaouachi M, Ben Othman A, Granacher U, Behm DG
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Summary: Studies that combined balance and resistance training induced larger performance improvements compared with single mode training. Agility exercises contain more dynamic and sport-specific movements compared with balance training. Thus, the purpose of this study was to contrast the effects of combined balance and plyometric training with combined agility and plyometric training and an active control on physical fitness in youth. Fifty-seven male soccer players aged 10-12 years participated in an 8-week training program (2 × week). They were randomly assigned to a balance-plyometric (BPT: n = 21), agility-plyometric (APT: n = 20) or control group (n = 16). Measures included proxies of muscle power [countermovement jump (CMJ), triple-hop-test (THT)], muscle strength [reactive strength index (RSI), maximum voluntary isometric contraction (MVIC) of handgrip, back extensors, knee extensors], agility [4-m × 9-m shuttle run, Illinois change of direction test (ICODT) with and without the ball], balance (Standing Stork, Y-Balance), and speed (10-30 m sprints). Significant time × group interactions were found for CMJ, hand grip MVIC force, ICODT without a ball, agility (4 m × 9 m), standing stork balance, Y-balance, 10 and 30-m sprint. The APT pre- to post-test measures displayed large ES improvements for hand grip MVIC force, ICODT without a ball, agility test, CMJ, standing stork balance test, Y-balance test but only moderate ES improvements with the 10 and 30 m sprints. The BPT group showed small (30 m sprint), moderate (hand grip MVIC, ICODTwithout a ball) and large ES [agility (4 m × 9 m) test, CMJ, standing stork balance test, Y-balance] improvements, respectively. In conclusion, both training groups provided significant improvements in all measures. It is recommended that youth incorporate balance exercises into their training and progress to agility with their strength and power training.

#7 Use of Musculoskeletal Ultrasound and Regenerative Therapies in Soccer
Reference: Am J Orthop (Belle Mead NJ). 2018 Oct;47(10). doi: 10.12788/ajo.2018.0093.
Authors: Centurion AJ, Youmans H, Zeini IM
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Summary: Improvements in ultrasound technology have increased the popularity and use of ultrasound as a diagnostic and therapeutic modality for many soccer-related musculoskeletal (MSK) injuries. As a dynamic imaging modality, ultrasound offers increased accuracy and efficacy with minimally invasive procedures, such as guided injections, percutaneous tenotomy, and regenerative therapies, in the clinical setting. Emerging evidence indicates that regenerative therapies, such as platelet-rich-plasma (PRP), mesenchymal stem cells, and amniotic products, are a promising treatment for many MSK injuries and are gaining popularity among professional athletes. PRP is a safe treatment for a number of MSK conditions and has been included in the standard of care. However, conflicting evidence on return-to-play timeframes and efficacy in certain MSK conditions have led to inconsistent recommendations on indications for use, dose, and timing of treatment. Mesenchymal stem cell therapy, while promising, lacks high-level evidence of efficacy despite its increasing use among athletes. Currently, no data are available regarding the outcome of the use of amniotic products for the treatment of injuries in athletes. Furthermore, preparation of many regenerative therapies eclipses the concept of minimal manipulation and is subject to US Food and Drug Administration phase I to III trials. High-level research on regenerative medicine therapies should be continuously conducted to establish their clinical efficacy and safety data.

#8 Upper Extremity Injuries in Soccer
Reference: Am J Orthop (Belle Mead NJ). 2018 Oct;47(10). doi: 10.12788/ajo.2018.0091.
Authors: Marom N, Williams RJ 3rd
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Summary: Upper limb injuries in soccer represent only a marginal portion of injuries, however this is mainly true for outfield players. Goalkeepers are reported to have up to 5 times more upper extremity injuries, many of them requiring substantial time-loss for treatment and rehabilitation. The most common upper extremity injury locations are the shoulder/clavicle followed by the hand/finger/thumb, elbow, wrist, forearm, and upper arm. The mechanism of injury, presentation, physical examination, and imaging features all play a significant role in reaching the correct diagnosis. Taking to consideration the position the player plays and his demands will also enable tailoring the optimal treatment plan that allows timely and safe return to play. This article discusses common upper extremity injuries observed in soccer players, focusing on proper diagnosis and optimal management.

#9 The Three H's: Head, Heart, and Heat Considerations in Soccer
Reference: Am J Orthop (Belle Mead NJ). 2018 Oct;47(10). doi: 10.12788/ajo.2018.0087.
Authors: Whipple MT, Baggish AL, Pieroth EM, Chiampas GT
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Summary: Soccer requires significant physical conditioning and endurance, as well as the physicality required for contact play. In order to keep athletes safe, it is important that coaches, medical staff, and the players themselves are educated on the most common dangers to their health that they may encounter on a soccer pitch. This article aims to review the current literature and recommendations on concussion, cardiovascular considerations, and heat-related illness as they relate to competitive soccer, with a goal of educating all those who help to keep athletes healthy and competing to their full potential.

#10 The Effect of Playing Position on Injury Risk in Male Soccer Players: Systematic Review of the Literature and Risk Considerations for Each Playing Position
Reference: Am J Orthop (Belle Mead NJ). 2018 Oct;47(10). doi: 10.12788/ajo.2018.0092.
Authors: Della Villa F, Mandelbaum BR, Lemak LJ
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Summary: Soccer (football) is a complex contact sport with a substantial risk of injury. As injury surveillance is the first step of the injury prevention paradigm, soccer epidemiology is well reported in the existing literature, but less is known about the actual role of player position on the general injury risk. The goal of this study is to present the existing evidence regarding the influence of player's position on general injury risk in male soccer. A systematic review of the Medline database was carried out. Only English written studies on male soccer and citing playing position as a possible determinant of injury risk were included. One hundred and two full texts were evaluated for eligibility, and 11 studies were selected for the qualitative synthesis. Of the 11 studies included in the systematic review, 5 didn't find any significant correlation with between player's position and general injury risk, while the remaining 6 studies found player's position to be correlated with injury risk, with mixed findings depending on each study. The most consistent finding was a tendency for goalkeepers (GKs) to sustain less injuries compared to outfield players. When considering only the studies reporting just the match injury risk, forwards seemed to be at higher risk, even if there wasn't a complete agreement. Few studies have evaluated a possible effect of playing position on general injury risk in male soccer. There is no agreement if weather or not different playing positions are associated to a higher injury risk. GKs seem to be at lower risk of injury when compared to outfield players.

#11 Soccer or Football Medicine? Global Sports Medicine for a Global Game
Reference: Am J Orthop (Belle Mead NJ). 2018 Oct;47(10). doi: 10.12788/ajo.2018.0089.
Authors: Osbahr DC
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#12 Knee Injuries in Elite Level Soccer Players
Reference: Am J Orthop (Belle Mead NJ). 2018 Oct;47(10). doi: 10.12788/ajo.2018.0088.
Authors: Roth TS, Osbahr DC
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Summary: As one of the most popular sports in the world, soccer injury rates involving the knee continue to rise. An alarming trend of knee injuries, including increased anterior cruciate ligament ruptures, underscores the need to review our current understanding of these injuries in soccer players. This article includes a critical review of the epidemiology of knee injuries in soccer, anterior cruciate ligament and other ligamentous injuries, cartilage and meniscal injury, post-traumatic osteoarthritis, as well as current prevention initiatives.

#13 Hip and Core Muscle Injuries in Soccer
Reference: Am J Orthop (Belle Mead NJ). 2018 Oct;47(10). doi: 10.12788/ajo.2018.0094.
Authors: Sherman B, Chahla J, Hutchinson W, Gerhardt M
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Summary: Soccer is the most popular sport in the world and has the fourth highest number of sports injuries. Hip and groin injuries account for 14% of soccer injuries and can be difficult to recognize and treat as they often require a high level of suspicion and advanced imaging. Groin pain can be separated into 3 categories: (1) defined clinical entities for groin pain (adductor-related, iliopsoas-related, inguinal-related [sports hernias/athletic pubalgia], and pubic-related groin pain), (2) hip-related groin pain (hip morphologic abnormalities, labral tears, and chondral injuries), and (3) other causes of groin pain. Conservative approaches are typically the first line of treatment, but operative intervention has been reported to result in higher rates of return to sport in athletes with hip-related and inguinal-related groin pain injuries. In patients with concurrent hip-related and inguinal-related groin pain, the failure to recognize the relationship and treat both conditions may result in lower rates of return to sport. Preseason screening programs can identify high-risk athletes, who may benefit from a targeted prevention program. Further study on exercise therapy, early surgical intervention, and potential biologic intervention are needed to determine the most effective methods of preventing groin injuries in athletes.

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