Latest research in football - week 16 - 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 Association between Cumberland Ankle Instability Tool score and postural stability in collegiate soccer players with and without functional ankle instability
Reference: Phys Ther Sport. 2018 Mar 23;32:29-33. doi: 10.1016/j.ptsp.2018.03.002. [Epub ahead of print]
Authors: Kunugi S, Masunari A, Yoshida N, Miyakawa S
Summary: The purpose of this study was to investigate the association between Cumberland Ankle Instability Tool (CAIT) scores and postural stability during a diagonal landing, and to investigate whether postural stability is altered in collegiate soccer players with and without functional ankle instability (FAI). Ninety-one soccer players were classified into a FAI group (history of at least two ankle sprains and a CAIT-Japanese version score ≤25, n = 28), a copers group (history of one ankle sprain and a CAIT-Japanese version score ≥26, n = 32), or a control group (no history of ankle sprain, n = 31). Time to anteroposterior stabilisation (TTSAP) and mediolateral stabilisation (TTSML) were measured during the diagonal single-leg landing. The CAIT scores were correlated with TTSAP (P < 0.05, rs = -0.214) and TTSML (P < 0.01, rs = -0.566). TTSAP was longer in the FAI group than in the control group, and TTSML was longer in the FAI group than in the other groups. Our findings indicate the presence of an association between the CAIT-J score and TTSML, as well as postural stability deficits in collegiate soccer players with FAI during diagonal landings.

#2 Isolated Subscapularis Tendon Tear in a Skeletally Immature Soccer Player
Reference: Joints. 2017 Dec 11;6(1):68-70. doi: 10.1055/s-0037-1608952. eCollection 2018 Mar.
Authors: Avanzi P, Dei Giudici L, Giovarruscio R, Gigante A, Zorzi C
Download link:
Summary: Subscapularis injury in adolescents, usually associated to an avulsion fracture of the lesser humeral tuberosity, accounts for less than 2% of all fractures of the proximal humerus. Isolated tears of the subscapularis tendon without a history of dislocation and associated avulsion fractures are an even rarer occurrence, and treatment is controversial. This article describes a rare case of a 12-year-old suffering from an isolated subscapularis tear and discusses its management. The patient was evaluated at presentation, and at 1 to 2.5 months after he underwent a cuff tear arthroscopic repair with a single "all suture" anchor loaded with two wires, active/passive range of motion (A/PROM), Constant-Murley score, and American Shoulder and Elbow Surgeons (ASES) score were noted. Patient reported an excellent outcome, recovered the whole ROM, was pain free, and returned to the previous level of activity. Isolated avulsion of the subscapularis tendon requires a high index of suspicion for a proper diagnosis as early treatment is required for a good recovery. Arthroscopy reserves more advantages in proper hands, restoring the previous levels of function and activity. An increase in attention for this condition is mandatory in a society where many adolescents are getting more and more active in high levels of sport activities.

#3 The relative age effect is larger in Italian soccer top-level youth categories and smaller in Serie A
Reference: PLoS One. 2018 Apr 19;13(4):e0196253. doi: 10.1371/journal.pone.0196253. eCollection 2018.
Authors: Brustio PR, Lupo C, Ungureanu AN, Frati R, Rainoldi A, Boccia G
Download link:
Summary: The relative age effect (RAE; i.e., an asymmetry in the birth distribution) is a bias observed in sport competitions that may favour relatively older athletes in talent identification. Therefore, the aim of this study was to investigate the presence of RAE in elite soccer players competing in the Italian championships, even considering the discriminations of younger and older Serie A players (in relation to the median age of the sample), and different positional roles (i.e., goalkeeper, defender, midfielder, forward) for each observed category. A total of 2051 players competing into the 2017-2018 Italian under-15 (n = 265), under-16 (n = 362), under-17 (n = 403), Primavera (n = 421) and Serie A (n = 600) championships were analysed. The birth-date distributions, grouped in four quartiles (i.e., January-March, Q1; April-June, Q2; July-September, Q3; October-December, Q4), were compared to a uniform distribution using Chi-squared analysis. The week of birth was analysed using Poisson regression. The results showed a large over-representation of players born in Q1 in all soccer player categories. However, the effect size of this trend resulted smaller as age increased. Individuals born in Q1 have about two-folds more chances to become a Serie A player compared to those born in Q4. The Poisson regression analysis showed that RAE was greater for defenders than for forwards among all categories. Therefore, a strongly biased selection emerged among elite soccer players competing in Italian championships, highlighting how young individuals born in the first three months have many more chances to become elite players compared to the others.

#4 Ratios of torques of antagonist muscle groups in female soccer players
Reference: Acta Bioeng Biomech. 2018;20(1):153-158.
Authors: Struzik A, Siemienski A, Bober T, Pietraszewski B
Summary: An increase in the value of the hamstring-to-quadriceps (H/Q) ratio with an increase in angular velocity may effectively prevent injuries of the back of the thigh. Previous studies have found that the conventional H/Q ratio was unaltered along with an increasing angular velocity in females. Therefore, this study aimed to investigate the relationships between the conventional H/Q ratio and angular velocity in a group of female soccer players. The study was carried out on a group of 16 female soccer players (age: 20.7 ± 3.9 years, body height: 166.1 ± 5.8 cm, body mass: 58.4 ± 6.2 kg, training experience: 8.8 ± 4.1 years). Measurements of peak torque of extensors and flexors of the knee joint under static conditions and under isokinetic conditions (at angular velocities of 30°/s, 60°/s, 90°/s and 120°/s) were carried out using a Biodex dynamometer. There was a statistically significant increase in the conventional H/Q ratio with an increase in angular velocity. These differences occurred between measurements at angular velocities of 0°/s and 30°/s, and 30°/s and 60°/s. As previously found for males, an increase in conventional H/Q ratio with increased angular velocity was also present in this group of female players. This phenomenon should reduce the number of injuries of the muscles of back of the thigh. Coaches should pay attention to increasing the level of strength in the group of knee joint flexor muscles so as to make the value of the H/Q ratio appropriately high and increasing with increasing angular velocity.

#5 Investigation of knee control as a lower extremity injury risk factor: A prospective study in youth football
Reference: Scand J Med Sci Sports. 2018 Apr 19. doi: 10.1111/sms.13197. [Epub ahead of print]
Authors: Raisanen AM, Arkkila H, Vasankari T, Steffen K, Parkkari J, Kannus P, Forsman H, Pasanen K
Summary: This prospective study in youth football examined the relationship between frontal plane knee projection angle (FPKPA) during the single-leg squat and sustaining an acute lower extremity injury or acute non-contact lower extremity injury. Secondly, side-to-side asymmetry in FPKPA and sex as injury risk factors were explored. In addition, we investigated the influence of age, sex and leg dominance on the FPKPA. A total of 558 youth football players (U11 to U14), participated in the single-leg squat test and prospective injury registration. FPKPA was not found as a risk factor for injuries at this age. There was no difference in the mean FPKPA between sexes. However, FPKPA was associated with age; oldest subjects displayed the smallest FPKPA. Among boys, the frontal plane knee control improved by age. Among girls, the relationship between age and FPKPA was not as clear but the oldest girls displayed the smallest mean FPKPA in the study (12.2°+ 8.3°). The FPKPA was greater on the dominant kicking leg compared to the non-dominant support leg (P<0.001 for boys, P=0.001 for girls). However, side-to-side asymmetry in FPKPA was not associated with future injuries. In conclusion, frontal plane knee control in the single-leg squat was not associated with lower extremity injuries among young football players. As the single-leg squat to 90° knee flexion was too demanding for many subjects, easier single-leg squat test procedure or a different movement control test, such as a double-legged squat, could be more suitable for the young football players.

#6 Is the message getting through? Awareness and use of the 11+ injury prevention programme in amateur level football clubs
Reference: PLoS One. 2018 Apr 19;13(4):e0195998. doi: 10.1371/journal.pone.0195998. eCollection 2018.
Authors: Wilke J, Niederer D, Vogt L, Banzer W
Download link:
Summary: A large body of evidence suggests that the 11+ warm-up programme is effective in preventing football-related musculoskeletal injuries. However, despite considerable efforts to promote and disseminate the programme, it is unclear as to whether team head coaches are familiar with the 11+ and how they rate its feasibility. The present study aimed to gather information on awareness and usage among German amateur level football coaches. A questionnaire was administered to 7893 individuals who were in charge of youth and adult non-professional teams. Descriptive and inferential statistics were used to analyse the obtained data. A total of 1223 coaches (16%) returned the questionnaire. There was no risk of a non-response bias (p>.05). At the time of the survey, nearly half of the participants (42.6%) knew the 11+. Among the coaches who were familiar with the programme, three of four reported applying it regularly (at least once per week). Holding a license (φ = .28, p < .0001), high competitive level (Cramer-V = .13, p = .007), and coaching a youth team (φ = .1, p = .001) were associated with usage of 11+. Feasibility and suitability of the 11+ were rated similarly by aware and unaware coaches. Although a substantial share of German amateur level coaches is familiar with the 11+, more than half of the surveyed participants did not know the programme. As the non-usage does not appear to stem from a lack of rated feasibility and suitability, existing communication strategies might need to be revised.

#7 Muscle injuries in professional football : Treatment and rehabilitation
Reference: Unfallchirurg. 2018 Apr 17. doi: 10.1007/s00113-018-0501-z. [Epub ahead of print]  [Article in German]
Authors: Riepenhof H, Del Vescovo R, Droste JN, McAleer S, Pietsch A
Summary: Muscle injuries are common in professional sports, especially in football. Recent epidemiological studies showed that muscle injuries account for more than 30% of professional football injuries (1.8-2.2/1000 h exposure); however, even though there are significant differences within a European comparison, a single professional football team diagnosed on average 12 muscle injuries per season, corresponding to more than 300 availability days lost. The aim of this work is to present the diagnosis, general treatment and comprehensive management of muscle injuries in professional football. The present work is based on current scientific findings, experiences of the authors and examples from routine practice in the management of muscle injuries in a professional sports environment. The authors present a model of gradual progression for the treatment of muscular injuries and their rehabilitation. Due to the time-pressured nature of the professional sports environment, often promoted by coaches and media, this model could help lead players to recover as quickly as possible and return to competitive sports without relapse or sequel injury. This model integrates the player into the treatment plan. The progression sequences in the rehabilitation should be made clear to players and other parties involved, which are crucial for optimal healing. Even if absolute certainty cannot be achieved, i.e. the occurrence of re-injury or secondary injury, this model attempts to minimize the level of risk involved for the returning athlete. Since it is hardly possible to act strictly in line with more conservative guidelines due to the particular circumstances of the professional sport environment, the experiences of the authors are presented in the sense of best practice in order to support future decision-making processes.

#8 Post-Game High Protein Intake May Improve Recovery of Football-Specific Performance during a Congested Game Fixture: Results from the PRO-FOOTBALL Study
Reference: Nutrients. 2018 Apr 16;10(4). pii: E494. doi: 10.3390/nu10040494.
Authors: Poulios A, Fatouros IG, Mohr M, Draganidis DK, Deli C, Papanikolaou K, Sovatzidis A, Nakopoulou T, Ermidis G, Tzatzakis T, Laschou VC, Georgakouli K, Koulouris A, Tsimeas P, Chatzinikolaou A, Karagounis LG, Batsilas D, Krustrup P, Jamurtas AZ
Download link:
Summary: The effects of protein supplementation on performance recovery and inflammatory responses during a simulated one-week in-season microcycle with two games (G1, G2) performed three days apart were examined. Twenty football players participated in two trials, receiving either milk protein concentrate (1.15 and 0.26 g/kg on game and training days, respectively) (PRO) or an energy-matched placebo (1.37 and 0.31 g/kg of carbohydrate on game and training days, respectively) (PLA) according to a randomized, repeated-measures, crossover, double-blind design. Each trial included two games and four daily practices. Speed, jump height, isokinetic peak torque, and muscle soreness of knee flexors (KF) and extensors (KE) were measured before G1 and daily thereafter for six days. Blood was drawn before G1 and daily thereafter. Football-specific locomotor activity and heart rate were monitored using GPS technology during games and practices. The two games resulted in reduced speed (by 3-17%), strength of knee flexors (by 12-23%), and jumping performance (by 3-10%) throughout recovery, in both trials. Average heart rate and total distance covered during games remained unchanged in PRO but not in PLA. Moreover, PRO resulted in a change of smaller magnitude in high-intensity running at the end of G2 (75-90 min vs. 0-15 min) compared to PLA (P = 0.012). KE concentric strength demonstrated a more prolonged decline in PLA (days 1 and 2 after G1, P = 0.014-0.018; days 1, 2 and 3 after G2, P = 0.016-0.037) compared to PRO (days 1 after G1, P = 0.013; days 1 and 2 after G2, P = 0.014-0.033) following both games. KF eccentric strength decreased throughout recovery after G1 (PLA: P=0.001-0.047-PRO: P =0.004-0.22) in both trials, whereas after G2 it declined throughout recovery in PLA (P = 0.000-0.013) but only during the first two days (P = 0.000-0.014) in PRO. No treatment effect was observed for delayed onset of muscle soreness, leukocyte counts, and creatine kinase activity. PRO resulted in a faster recovery of protein and lipid peroxidation markers after both games. Reduced glutathione demonstrated a more short-lived reduction after G2 in PRO compared to PLA. In summary, these results provide evidence that protein feeding may more efficiently restore football-specific performance and strength and provide antioxidant protection during a congested game fixture.

#9 Hip and groin time-loss injuries decreased slightly but injury burden remained constant in men's professional football: the 15-year prospective UEFA Elite Club Injury Study
Reference: Br J Sports Med. 2018 Apr 24. pii: bjsports-2017-097796. doi: 10.1136/bjsports-2017-097796. [Epub ahead of print]
Authors: Werner J, Hagglund M, Ekstrand J, Walden M
Summary: Hip and groin injuries are common in men's professional football, but the time-trend of these injuries is not known. The aim of the study was to investigate hip and groin injury rates, especially time-trends, in men's professional football over 15 consecutive seasons. 47 European teams were followed prospectively for a varying number of seasons between 2001/2002 and 2015/2016, totalling 268 team seasons. Time-loss injuries and individual player exposure during training and matches were recorded. Injury rate was defined as the number of injuries/1000 hours and injury burden as the number of lay-off days/1000  hours. Time-trends for total hip and groin injuries and adductor-related injury rates were analysed using Poisson regression, and injury burden was analysed using a negative binomial regression model. Hip and groin injuries contributed 1812 out of 12 736 injuries (14%), with adductor-related injury as the most common of hip and groin injuries (n=1139, 63%). The rates of hip and groin injury and adductor-related injury were 1.0/1000 hours and 0.6/1000 hours, and these rates decreased significantly with on average 2% (Exp(b)=0.98, 95% CI 0.97 to 0.99, P=0.003) and 3% (Exp(b)=0.97, 95% CI 0.95 to 0.99, P<0.001) per season (year on year), respectively. The seasonal trend of hip and groin injury burden did not improve (Exp(b)=0.99, 95% CI 0.97 to 1.01, P=0.40). Hip and groin injuries constitute a considerable part of all time-loss injuries in men's professional football. Although there was a promising slight decreasing trend in the rates of hip and groin injury (as a category) and adductor-related injury (as a specific diagnosis), the injury burden remained at a consistent level over the study period.

#10 Body composition and somatotypes of male Zimbabwean Premier League football referees
Reference: J Sports Med Phys Fitness. 2018 Apr 20. doi: 10.23736/S0022-4707.18.08326-3. [Epub ahead of print]
Authors: Banda M, Grobbelaar HW, Terblanche E
Summary: Elite athletes need to optimise their body composition to deliver world class performances and this argument could be extended to elite referees as well. Unfortunately, there is a scarcity of body composition information among football referees. The aim of the study was to determine and compare the body composition and somatotypes of male football referees and assistant referees who officiated in the 2013 Zimbabwe Premier Football League. Forty-one participants (21 referees, 20 assistant referees; 8 FIFA, 33 ZIFA licenced referees) with a mean age of 34.89 ± 5.13 years took part. They had on average 10.85 ± 3.85 years of refereeing experience. The ISAK restricted anthropometric profile was used to measure body mass, height, skinfolds, girths and bone breadths, from which body mass index (BMI), waist-to-hip ratio (WHR), percentage body fat and somatotype were calculated. The referees were significantly taller than the assistant referees. The FIFA referees had moderately more desirable anthropometric profiles than the ZIFA referees. With a mean somatotype of 2.62-4.65-2.65, the total sample could be classified as balanced mesomorphs. They had lower BMI and body fat percentages than that observed among referees from other nationalities in the available literature. The results add to the paucity of information on the body composition of football officials. Referees aiming to excel at higher levels need to obtain and maintain an ideal body composition since elite level football is intense and requires high fitness levels.

The Training Manager -