Latest research in football - week 39 - 2016

#1 Repeated-sprint sequences during female soccer matches using fixed and individual speed thresholds
Reference: J Strength Cond Res. 2016 Sep 20. [Epub ahead of print]
Authors: Nakamura FY, Pereira LA, Loturco I, Rosseti M, Moura FA, Bradley PS
Summary: The main objective of this study was to characterize the occurrence of single sprint and repeated-sprint sequences (RSS) during elite female soccer matches, using fixed (20 kmh) and individually based speed thresholds (>90% of the mean speed from a 20 m sprint test). Eleven elite female soccer players from the same team participated in the study. All players performed a 20 m linear sprint test, and were assessed in up to 10 official matches using Global Positioning System (GPS) technology. Magnitude-based inferences were used to test for meaningful differences. Results revealed that irrespective of adopting fixed or individual speed thresholds, female players produced only a few RSS during matches (2.3 ± 2.4 sequences using the fixed threshold and 3.3 ± 3.0 sequences using the individually based threshold), with most sequences composing of just two sprints. Additionally, central defenders performed fewer sprints (10.2 ± 4.1) than other positions (full backs: 28.1 ± 5.5; midfielders: 21.9 ± 10.5; forwards: 31.9 ± 11.1; with likely to almost certainly differences associated with effect sizes ranging from 1.65 to 2.72) and sprinting ability declined in the second half. The data do not support the notion that RSS occurs frequently during soccer matches in female players, irrespective of using fixed or individual speed thresholds to define sprint occurrence. However, repeated sprint ability development cannot be ruled out from soccer training programs due to its association with match-related performance.


#2 The use of vanishing spray reduces the extent of rule violations in soccer
Reference: Springerplus. 2016 Sep 15;5(1):1572. doi: 10.1186/s40064-016-3274-2. eCollection 2016
Authors: Kolbinger O, Link D
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5023644/pdf/40064_2016_Article_3274.pdf
Summary: More and more sport associations introduce innovative devices to support referees and umpires respectively, affecting a strong need for the evaluation of these devices. This study evaluates the use of the new vanishing spray for free kicks in the German Bundesliga. In more detail, the aim of the study is to investigate if the spray reduces violations of the required minimum distance and consequently the respective punishments, if it reduces errors concerning the distance set by the referee and if it leads to a higher success rate of free kicks. Therefore, 1833 free kicks of the 2013/2014 and 2014/2015 season of the German Bundesliga were screened using a self-designed observational system. For the statistical analysis two parallel samples were built of 299 free kicks each. The results showed no decrease of free kicks with distance violations but a significantly lower extent of these violations (χ(2) = 4.58; p < .05). However, none of these violations were punished appropriately. Concerning the success of free kicks, no significant impact was found neither for shots nor for crosses. In addition, no influence on the distance set by the referee could be identified. The main objective of the vanishing spray was basically realized, but the use didn't lead to any further positive (side) effects. Due to the lack of punishment, the authors raise concerns about the current application of the minimum distance rule.


#3 Flu vaccination in elite athletes: A survey among Serie A soccer teams
Reference: Acta Biomed. 2016 Sep 13;87(2):117-20.
Authors: Signorelli C, Odone A, Miduri A, Cella P, Pasquarella C, Gozzini A, Tamburrino P, Castellacci E
Summary: Scant data is available on immunization policies and practices among professional athletes. Following up on a recent review on the topic, we conducted a survey among Italian Serie A soccer teams during the influenza season 2015-16, to explore vaccination practices and attitudes as well as influenza vaccine uptake. The survey covered a sample of over 600 professional athletes from 20 teams and was carried out in collaboration with the Italian Association of Physicians of Professional Football Teams (L.A.M.I.CA.). For each team, the head of the medical staff was interviewed (structured telephone interviews, 100% response rate). Seasonal influenza vaccine was actively offered in 75% of Serie A teams with a median coverage rate of 40% (range 0%-100%). Vaccines are often administered after matches or training sessions. We report vaccine hesitancy associated with fear of adverse events, poor communication and other selected determinants. Vaccination in elite athletes, if correctly managed, represents a powerful, cost-effective and long lasting preventive tool. In times where vaccines are losing public confidence, our findings are a useful basis to inform the planning, implementation and evaluation of interventions to promote prevention in sports medicine.


#4 The effect of low back pain on trunk muscle size/function and hip strength in elite football (soccer) players
Reference: J Sports Sci. 2016 Sep 19:1-9. [Epub ahead of print]
Authors: Hides JA, Oostenbroek T, Franettovich Smith MM, Mendis MD
Summary: Low back pain (LBP) is a common problem in football (soccer) players. The effect of LBP on the trunk and hip muscles in this group is unknown. The relationship between LBP and trunk muscle size and function in football players across the preseason was examined. A secondary aim was to assess hip muscle strength. Twenty-five elite soccer players participated in the study, with assessments conducted on 23 players at both the start and end of the preseason. LBP was assessed with questionnaires and ultrasound imaging was used to assess size and function of trunk muscles at the start and end of preseason. Dynamometry was used to assess hip muscle strength at the start of the preseason. At the start of the preseason, 28% of players reported the presence of LBP and this was associated with reduced size of the multifidus, increased contraction of the transversus abdominis and multifidus muscles. LBP decreased across the preseason, and size of the multifidus muscle improved over the preseason. Ability to contract the abdominal and multifidus muscles did not alter across the preseason. Asymmetry in hip adductor and abductor muscle strength was found between players with and without LBP. Identifying modifiable factors in players with LBP may allow development of more targeted preseason rehabilitation programmes.


#5 Quantifying the high-speed running and sprinting profiles of elite female soccer players during competitive matches using an Optical Player Tracking System
Reference: J Strength Cond Res. 2016 Sep 6. [Epub ahead of print]
Authors: Mara JK, Thompson KG, Pumpa KL, Morgan S
Summary: The aim of this study was to determine the high-speed running and sprinting profiles of elite female soccer players during competitive matches using a new Optical Player Tracking System. Eight stationary video cameras were positioned at vantage points surrounding the soccer field so that when each camera view was combined the entire field could be viewed simultaneously. Following each match, an optical player tracking system detected the coordinates (x,y) of each player for every video frame. Algorithms applied to the x and y coordinates were used to determine activity variables for twelve elite female players across seven competitive matches. Players covered 9,220-10,581 m of total distance, 1,772-2,917 m of high-speed running (3.4-5.3 m·s) distance and 417-850 m of sprinting (>5.4 m·s) distance, with variations between positional groups (p < 0.001, partial η = 0.444-0.488). Similarly, the number of high-speed runs differed between positional groups (p = 0.002, partial η = 0.342) and a large proportion of high-speed runs (81-84 %) and sprints (71-78 %) were performed over distances less than 10 m. Mean time between high-speed runs (13.9 s ± 4.4) and sprints (86.5 s ± 38.0) varied according to playing position (p < 0.001, partial η = 0.409) and time period of the match (p < 0.001, partial η = 0.113 - 0.310). The results of this study can be used to design match-specific conditioning drills, and shows that coaches should take an individualised approach to training load monitoring according to position.


#6 The peak velocity derived from the Carminatti Test is related to physical match performance in young soccer players
Reference: J Sports Sci. 2016 Aug 10:1-8. [Epub ahead of print]
Authors: Fernandes-da-Silva J, Castagna C, Teixeira AS, Carminatti LJ, Guglielmo LG
Summary: The aim of this study was to examine the relationship between the peak velocity derived from the Carminatti Test (T-CAR) (PVT-CAR) and physical match performance in young soccer players. Thirty-three youth soccer players were recruited from 2 non-professional clubs. Friendly matches and small-sided game were performed. Physical match demands were assessed using Global Positioning System (GPS) technology. On a separate occasion, the players were submitted to the T-CAR. Players were categorised into 3 groups based on their T-CAR performance: Low (PVT-CAR ≤ P33), Intermediate (P33 > PVT-CAR < P66) and High (PVT-CAR ≥ P66). The PVT-CAR (15.5 ± 0.7 km·h-1) was significantly related to high-intensity activities (HIA; r = 0.78, P < 0.001), high-intensity running (HIR; r = 0.66, P < 0.001), sprinting (r = 0.62, P < 0.001) and total distance (TD) covered (r = 0.47, P < 0.01) during friendly matches. The PVT-CAR was strongly correlated with the amount of HIA (r = 0.81, P < 0.001), HIR (r = 0.85, P < 0.001) and TD covered (r = 0.81, P < 0.001) during small-sided game. No significant correlation was observed between the PVT-CAR and distance of sprinting (r = 0.49, P = 0.067) during small-side game. Furthermore, players in the High group covered significantly more TD (10%) and did more HIA (42%), sprinting (31%) and HIR (25%) during friendly matches compared to the players classified as having Low performance on the T-CAR. These differences still remained after adjusting for chronological age (CA), maturity and body size. In conclusion, the current study gives empirical support to the ecological and construct validity of this novel field test (T-CAR) as an indicator of match-related physical performance in young soccer players during pubertal years.


#7 Effect of Dry Needling on Thigh Muscle Strength and Hip Flexion in Elite Soccer Players
Reference: Med Sci Sports Exerc. 2016 Sep 28. [Epub ahead of print]
Authors: Haser C, Stöggl T, Kriner M, Mikoleit J, Wolfahrt B, Scherr J, Halle M, Pfab F
Summary: Increase in muscle force, endurance and flexibility is desired in elite athletes in order to improve performance and avoid injuries but often hindered by occurence of myofascial trigger points. Dry needling (DN) has been shown effective in eliminating myofascial trigger points. This randomized controlled study in 30 elite youth soccer players of a professional soccer Bundesliga Club investigated the effects of four weekly sessions of DN plus water-pressure-massage on thigh muscle force and range-of-motion of hip flexion. A group receiving placebo-LASER plus water-pressure-massage and a group with no intervention served as controls. Data was collected at baseline (M1), treatment end (M2) and four-week follow-up (M3). Furthermore a 5-month muscle injury follow-up was performed. DN showed significant improvement of muscular endurance of knee extensors at M2 (p=0.039) and M3 (p=0.008) compared to M1 (M1:294.6±15.4nm/s, M2:311±25Nm/s; M3:316.0±28.6nm/s) and knee flexors at M2 compared to M1 (M1:163.5±10.9Nm/s, M2:188.5±16.3Nm/s) as well as hip flexion (M1:81.5±3.3°, M2:89.8±2.8°; M3:91.8±3.8°). Compared to placebo (3.8±3.8°) and control (1.4±2.9°) DN (10.3±3.5°) showed a significant (p=0.01 and p=0.0002) effect at M3 compared to M1 on hip flexion; compared to non-treatment control (-10±11.9Nm) DN (5.2±10.2Nm) also significantly (p=0.049) improved maximum force of knee extensors at M3 compared to M1. During the rest of the season muscle injuries were less frequent in the DN group compared to control groups. DN showed a significant effect on muscular endurance and hip flexion range-of-motion that persisted 4 weeks post-treatment. Compared to placebo it showed a significant effect on hip flexion that persisted 4 weeks post-treatment and compared to non-intervention control a significant effect on maximum force of knee extensors 4 weeks post-treatment in elite soccer players.


#8 Epidemiology of football (soccer) injuries in the 2012/2013 and 2013/2014 seasons of the Italian Serie A
Reference: Res Sports Med. 2016 Sep 29:1-7. [Epub ahead of print]
Authors: Falese L, Della Valle P, Federico B
Summary: Epidemiological studies on football (soccer) injuries are needed to assess both the magnitude of the problem and the effectiveness of preventive programmes. However, few data are available for Italy, which hosts one of the main football leagues in Europe. In this study, we aimed to describe the epidemiology of football injuries in the 2012/2013 and 2013/2014 seasons of the Italian Serie A. Information about injury location, type, date of occurrence and duration of absence was obtained from www.football-lineups.com , a free collaborative international database on football. Overall, 363 injuries occurred throughout the two seasons affecting 286 players. The most commonly reported injuries were thigh-strain and knee injury, which accounted for 42% and 19% of all injuries, respectively. Injury incidence increased with age and was particularly higher from August to October. Results suggest that injury prevention strategies should be introduced from the preseason to reduce the risk of injuries, especially muscle strains.


#9 Isokinetic hip in soccer players: Moroccan experience about 36 cases
Reference: Ann Phys Rehabil Med. 2016 Sep;59S:e16. doi: 10.1016/j.rehab.2016.07.039
Authors: Belhaj K, Meftah S, Zahi S, Lmidmani F, Elfatimi A
Summary: Isokinetic evaluation allows accurate and reproducible measurement of dynamic muscle strength. It has several application areas, especially in sports, it allows the evaluation, rehabilitation and re-entrainment. It is rarely used for the hip joint. The objective of this study was to report the isokinetic profile of the abductor and adductor muscles of the hip in Moroccan professional players, while comparing players with a history of groin for those without medical history at the hip. This is a prospective study in physical medicine and rehabilitation, including 36 professional footballers who have been performed concentric isokinetic evaluation mode abductor and adductor muscles of the hip at 60°/s and 120°/s. The distribution of variables was verified by the normality test of Shapiro, Wilk. The Wilcoxon test and U Mann-Whitney test were used to compare different isokinetic variables of the two groups evaluated. There was no statistically significant difference between dominant and non-dominant side in terms of the maximum peak torque, work, power, and adductor/abductor ratios. There was a significant difference between the players with a history of groin and those who showed no pathological history at the hip. A weak adductors compared to hip abductors may be involved in the development of the groin, especially an eccentric force deficit. The isokinetic allows the establishment of specific profiles and can be applied preventively early in the season to objectify and correct anomalies, particularly agonists/antagonists imbalances sometimes responsible for further damage. It allows a customized physical preparation, predicting the return to competition.


#10 Hormonal (cortical-gonadotropic axis) and physical changes with two years intense exercise training in elite young soccer players
Reference: J Strength Cond Res. 2016 Sep 23. [Epub ahead of print]
Authors: Ali Hammami M, Abderrahman AB, Hackney AC, Kebsi W, Owen AL, Nebigh A, Racil G, Tabka Z, Zouhal H
Summary: The aim of this study was to investigate the effects of two soccer-training seasons on physical fitness and hormone concentrations in elite youth soccer players. Twenty male elite soccer players (SP, age 14.5 ± 0.4 years) and 20 male control subjects (CS, age 14.3 ± 0.3years) participated to the study. Anthropometric measurements, aerobic (Yo-Yo Intermittent Recovery Test Level 1 (YYIRT1)) and anaerobic soccer relevant performances (jump and sprint tests), blood testosterone (T), cortisol (C),sex hormone binding globulin (SHBG) and T/C ratio were assessed 5 times (from T0 to T4) during two competitive seasons. Significant differences from basal values (Δ) of T, SHBG and C between SP and CS were observed (p<0.01). Additionally, T and T/C ratio changes were positively correlated to physical performance (p<0.05). In conclusion, as expected, higher T concentration and greater power performance were observed in the soccer players group compared to controls. Our findings also show that the T concentrations and power performance outcomes covary positively over the two soccer seasons in soccer players.