Latest research in football - week 25 - 2013

Latest research in football

As previous literature updates, we have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.
Following studies were retrieved for this week:

#1 Anxiety and injuries in soccer players
Reference: Br J Sports Med. 2013 Jul;47(10):e3. doi: 10.1136/bjsports-2013-092558.86.
Authors: Vago P, Casolo F, Lovecchio N, Colombo L, Gatti M.
Summary: Soccer is among the most played and most popular sports in the world. The average incidence of injuries per game is 2.7 and that an adult soccer player has at least one injury per year (Roi G.S., Della Villa S., 2011). Findings from recent studies suggest that psychological factors such as somatic trait anxiety and daily hassles are associated with increased risk of injury (Johnson and Ivarsson, 2013). The purpose of this study was to examine the relationship between anxiety and injury in adult male soccer players. The participants of the study were 100 amauteur male soccer players (aged 18 to 45). Each player filled in a qualitative questionnaire about his personal characteristics and sport practice (training, matches, etc.) and previous injuries (muscle, meniscal, injuries, tendinopathies, fractures, etc.). The participants also completed the Stai-State-Trait Anxiety Inventory (Spielberger et al, 1968). This questionnaire investigates the anxiety level, both in a specific situation (before the match, in this study) and in everyday life. The data were tested for correlations between anxiety (state and trait) levels and number of injuries (divided in specific types). Tendinopathies positively correlated both with state (rho=0.243; p<0.05) and trait anxiety (rho=0.205; p<0.05). Also fractures positively correlated both with state (rho=0.295; p<0.01) and trait anxiety (rho=0.368; p<0.01). Differences in injuries between participants who reported high or low anxiety levels were also explored. Players with higher level of state anxiety (N=35) reported more tendinopathies (p<0.01) and fractures (p<0.01). Similarly, players with higher levels of trait anxiety (N=33) reported more tendinopathies (p<0.05) and fractures (p<0.01). The present results support the contention that anxiety is an important factor, significantly associated with injuries, such as tendinopathies and fractures. In addict, several studies have shown that lack of readiness to take action, tough-mindedness or presence of a generalized high status of muscle tone, might be factors related to injury in a player with anxiety traits. Hence, with respect to psychological components, situation-related emotional states and coping resources may represent important avenues for interventions aimed at preserving health status and preventing injuries in soccer players

#2 Return-to-play criteria after hamstring injury: actual medicine practice in professional soccer teams

Reference: Br J Sports Med. 2013 Jul;47(10):e3. doi: 10.1136/bjsports-2013-092558.57.
Authors: Delvaux F, Rochcongar P, Bruyère O, Bourlet G, Daniel C, Diverse P, Reginster JY, Croisier JL.
Summary: The purpose was to analyze how clinicians decide, in their daily practice, when a hamstring injured professional soccer player is fully able to get back to competitive activities. Thirty-seven doctors for French and Belgian professional soccer clubs filled in a questionnaire formulated with multiple choice questions. Nearly 80% of the questioned doctors declared to use at least 7 criteria in order to assess player's ability to return to competitive soccer after a hamstring injury. The most important ones are: complete pain relief, normalized muscle strength assessment, subjective feeling reported by the player, normalized flexibility and achievement of a specific soccer test. For some of these criteria, most notably muscle strength assessment, there is a lack of consensus about the choice of assessment parameters and the limit value allowing doctors to authorize or forbid RTP. Our study also highlighted the interest for clinicians to consider the opinion of physical therapists and physical trainers. After a hamstring injury, clinicians for professional soccer clubs assess player's ability to return to full sport according to a "criteria-approach" instead of a "timed-based" approach. However, even if the scientific evidence about this topic is not sufficient at the moment, the implementation, in daily practice, of scientifically demonstrated assessment parameters and limit values should help the RTP decision and decrease the risk of re-injury

#3 Effect of complex and contrast training on the physiological and bio-motor variables of men soccer players
Reference: Br J Sports Med. 2013 Jul;47(10):e3. doi: 10.1136/bjsports-2013-092558.26.
Authors: Kanniyan AS, Syed I.
Summary: Complex training is a workout comprising of resistance exercise followed by a matched plyometric exercise whereas Contrast training is a set of heavy resistance repetitions followed immediately by an unloaded, explosive exercise utilizing the same movement pattern ( There are different viewpoints on the effects of complex and contrast training on different components of sports performance variables. The purpose of the study was to find out the effect of complex and contrast training on selected physiological and bio-motor variables of men soccer players. To achieve the purpose of the study, 36 men players between the age group 18 and 25 were selected as subjects. They were divided into three equal groups (n=12). Group-1 underwent complex training; Group-2 underwent contrast training and Group-3 acted as control group which only took part in their normal playing session. The subjects were tested on selected criterion variables viz, speed, muscular endurance, cardio-respiratory endurance, blood pressure and resting pulse rate. The duration of training was 10 weeks for all the three groups. The analysis of covariance (ANCOVA) was used to find out the significant difference if any, among the experimental and control groups on the selected criterion variables separately. The level of significance was fixed at 0.05 at all levels. Sheffe's test was used as post hoc test. The results of the study indicate that there are significant differences among complex training group and contrast training group and the control group in all of the physiological and bio-motor variables selected for the study. Though for some of the variables, complex training group has better improvement, contrast training group has also showed significant performance in most of the physiological and bio-motor variables. It is concluded that the complex and contrast training is beneficial for training groups that seek improvements in the selected criterion variables

#4 Lower Running Performance and Exacerbated Fatigue in Soccer Played at 1600 m
Reference: Int J Sports Physiol Perform. 2013 May 22. [Epub ahead of print]
Authors: Garvican LA, Hammond K, Varley MC, Gore CJ, Billaut F, Aughey RJ.
Summary: This study investigated the decrement in running performance of elite soccer players competing at low altitude and time-course for abatement of these decrements. Twenty elite youth soccer players had their activity profile, in a sea level (SL) and two altitude (Alt, 1600 m, d4 and d6) matches measured with a global positioning system. Measures expressed in metres per minute of match time (m.min-1) were: total distance; low and high-velocity running (LoVR, 0.01-4.16 m.s-1; HiVR, 4.17-10.0 m.s-1) and frequency of maximal accelerations (Accel, >2.78 m.s-2). The peak and subsequent stanza for each measure were identified and a transient fatigue index calculated. Mean heart rate (HR) during the final minute of a sub-maximal running task (5-min, 11 km.h-1) was recorded at SL and for 10d at Alt. Differences were determined between SL and Alt using percentage change, and effect size statistic with 90% confidence intervals. Mean HR almost certainly increased on d1 (5.4%, ES 1.01±0.35) and remained probably elevated on both d2 (ES 0.42±0.31) and d3 (ES 0.30±0.25) returning to baseline at d5. Total distance was almost certainly lower than SL (ES -0.76±0.37) at d4, and remained probably reduced on d6 (ES -0.42±0.36). HiVR probably decreased at d4 vs. SL (-0.47±0.59), with no clear effect of altitude at d6 (-0.08±0.41). Transient fatigue in matches was evident at SL and Alt with a possibly greater decrement at Alt. a Despite some physiological adaptation, match running performance of youth soccer players is compromised for at least six days at low altitude

#5 Role of free testosterone in interpreting physical performance in elite young brazilian soccer players

Reference: Pediatr Exerc Sci. 2013 May;25(2):186-97.
Authors: Moreira A, Mortatti A, Aoki M, Arruda A, Freitas C, Carling C.
Summary: This study investigated the contribution of salivary testosterone (sT) concentration, years from peak height velocity (YPHV) and height by body mass interaction on jumping performance (Countermovement jump; CMJ) and aerobic fitness (Yo-Yo intermittent endurance test, level 1) in young elite soccer players. Forty-five participants (age: 12.5 ± 0.5y; body mass: 48.6 ± 10.2kg, height: 155.7 ± 10.0cm) belonging to a top level Brazilian soccer club were evaluated at four time points across a single semester. None of the assessed players had reached PHV. The data from the four evaluations were averaged and multiple linear regression analysis conducted. For CMJ, the model explained 42.88% of the variance (R2 = 42.88; p < .000); sT concentration was the primary contributor (R2 = 32.84) and the YPHV contributed 9.95% of the variance. The model explained 28.50% (p < .000) of the variance in Yo-Yo. The sT was the primary and single significant contributor (R2 = 21.32). A significant difference was noted between high and low testosterone groups divided a posteriori to CMJ performance (t = 3.35; p = .001). These results suggest an important role for hormonal status in interpreting physical performance in preadolescent soccer players.

#6 The Nordic Football Injury Audit: higher injury rates for professional football clubs with third-generation artificial turf at their home venue
Reference: Br J Sports Med. 2013 Jun 15. [Epub ahead of print]
Authors: Kristenson K, Bjørneboe J, Waldén M, Andersen TE, Ekstrand J, Hägglund M.
Summary: The purpose of the study was to compare acute injury rates in professional football played on AT and NG at the individual player level; and to compare, at club level, acute and overuse injury rates between clubs that have AT at their home venue (AT clubs) and clubs that have NG (NG clubs). 32 clubs (AT, n=11; NG, n=21) in the male Swedish and Norwegian premier leagues were followed prospectively during the 2010 and 2011 seasons. Injury rate was expressed as the number of time loss injuries/1000 h and compared with rate ratio (RR) and 99% CI. No statistically significant differences were found in acute injury rates on AT compared with NG during match play (RR 0.98, 99% CI 0.79 to 1.22) or training (RR 1.14, 99% CI 0.86 to 1.50) when analysing at the individual player level. When analysing at the club level, however, AT clubs had a significantly higher acute training injury rate (RR 1.31, 99% CI 1.04 to 1.63) and overuse injury rate (RR 1.38, 99% CI 1.14 to 1.65) compared with NG clubs. At the individual player level, no significant differences were found in acute injury rates when playing on AT compared with NG. However, clubs with AT at their home venue had higher rates of acute training injuries and overuse injuries compared with clubs that played home matches on NG.

#7 Osgood schlatter's syndrome and functional impairment of the knee in young football players
Reference: Br J Sports Med. 2013 Jul;47(10):e3. doi: 10.1136/bjsports-2013-092558.88.
Authors: Domingues M.
Summary: Football, like any contact sport it is susceptible to various kinds of injuries. Long-term planning is a characteristic and requirement of modern training as it can greatly increase training efficiency for future competitions (Bompa, 1999). Epidemiological findings suggest that little is known about the injury risk among the youngest players between six and twelve years and also the injury risk is low (Froholdt, Olsen and Bahr, 2009). This article focus on the understanding of microtraumatology in youth sports and examines one specific injury Osgood Schlatter disease, and the main mechanisms whereby such injury occur. It is referred the link between methodology of training and the prevention of overuse injuries in youth as it relates to maladaptive sport programs. There is an increasing awareness to growth related conditions and the relation of musculoskeletal development and the onset of youth related conditions. The aethology is complex and the risk factors underpinning injury occurrence are considered, along with injury avoidance tactics. Functional treatment is justified even if there is an increased formation of ossicles on non-immobilization of the joint, since such ossification occurs with only 20-25% of all cases of Osgood-Schlatter disease and the duration of the complaints is markedly less enhanced than with immobilization measures (Engel & Windhager, 1987). Treatment and recovery should attend to athletes specific conditions and involves activity modification and pain relief.

#8 Growth and functional capacities in 8-10 year old children who practice football-an overview
Reference: Br J Sports Med. 2013 Jul;47(10):e3. doi: 10.1136/bjsports-2013-092558.76.
Author: Domingues M.
Summary: Sport and more specifically football is an important asset in youth lives. Much has been written regarding functional capacities and dimensions in pre-adolescence and adolescence but there's a consistent lack of information concerning the ages of 6-10 years of age. Biological factors, such as body size and maturity status, have been documented as predictors of athlete selection and performance in several sports (Malina, Bouchard, & Bar-Or, 2004). As some authors contest, advanced biological maturity status constitutes an asset positively associated with selection process and success in several sports in early adolescence (Malina, Pena Reyes, Eisenmann, Horta, Rodrigues, & Miller, 2000), as chronological age and sport specialization increase. Children are very responsive to systematic instructional and training programs for the development of motor skills. Moreover, studies of youth football players start to consider the potential influence of variation in growth and biological maturity status upon sport-specific football skills. Attention is given to functional capacities and performance outcomes in young athletes at relatively young age as they relate to growth and maturation. The multilateral development emphasis should be placed ahead when elaborating youth programs as coaches should be careful in using body size as cut-points in sport and should be aware of individual differences (Malina, 2004). Care should therefore be taken in developing football skills regarding performance with full respect to youth development.

#9 Influence of negative pre-match mental States on coping with psychological burden during football match
Reference: Br J Sports Med. 2013 Jul;47(10):e3. doi: 10.1136/bjsports-2013-092558.29.
Authors: Zeman T, Voborny J, Králík M, Blahutková M.
Summary: For football referees supervision of a match means significant mental burden. Referees experience higher level of anxiety and fear(1) which are typical manifestations of negative pre-match states.(2) As a result of a completed match levels of components of depression and exhaustion increase.(1) Our goal was to verify the correlation between these two components. Our research sample consisted of 26 male football referees who supervise football competitions in one of the 14 regions of the Czech Republic. For evaluation of their subjective psychological experiences and states the standardised questionnaire SUPSO(3) was used. The questionnaire was filled in twice: before the match and immediately after the match. Ratio of predominant temperament components was evaluated using standardised Belov's temperament test.(4) In the statistical analysis Spearman's coefficient of rank correlation and partial correlation coefficient were used. Pre-match values of anxiety and fear component statistically significantly correlate with the values of component of depression and exhaustion. This serial dependence remained stastically significant even after exclusion of implications of referees' temperament. Negative pre-match mental states of football referees worsen their ability to cope with the supervised match on a psychological level. "Pre-match fever" can lead to premature exhaustion, while apathy can lead to insufficient activation. Regulation of these negative pre-match states can improve coping with mental burden during a football match. Pre-match preparation should therefore focus more on regulating the referees' actual mental state ("pre-start mental state").

#10 Isokinetic strength and ratio of professional football players in UAE
Reference: Br J Sports Med. 2013 Jul;47(10):e3. doi: 10.1136/bjsports-2013-092558.24.
Authors: Ghrairi M, Chomier P, Khelifa M, Ferret JM.
Summary: Numerous research studies examined muscles strength among professional football players worldwide. However, little or no research studies exist on this issue with relation to Arabian Gulf players. Therefore, the purpose of this study was to provide reference data for peak isokinetic muscle strength and ratio of hamstring and quadriceps in professional Emirati footballers. The study was conducted within Alshabab Football Club (AFC) of Dubai, one of twelve clubs evolving then in the United Arab Emirates (UAE) professional football league. As part of AFC's 2011-2012 preseason program, 36 professional footballers underwent an isokinetic assessment. Peak Torque and Ratio of left and right thigh muscles, i.e. quadriceps and hamstrings, were assessed using a Cybex Norm machine following a standardized protocol at 3 different speeds, namely 60, 180, and 240°/s. The results for the right thigh showed that the maximum peak torque at the speed of 60°/sec was 195.77 N.m. for the quadriceps and 173.2 N.m for the Hamstring. For the left thigh, the values were 193.3 N.m for the quadriceps and 171.6 N.m for the hamstrings. As our main focus was to assess the balance of the thigh muscles, the recorded average ratio hamstrings/quadriceps was 95.6 for the right thigh and 94.4 for the left one. In comparison with the available literature in other professional football leagues, the obtained values indicate that the Emirati player is characterized with a lack of strength and thigh muscles imbalance. Data obtained in this study was used to educate players and football technicians on the need to rigorously strength train to reach the ideal muscle profile as observed in reputed professional football leagues. The obtained values were also used as a reference for the prevention and rehabilitation of muscle injuries.

#11 Incidence of Sports-Related Concussion among Youth Football Players Aged 8-12 Years
Reference: J Pediatr. 2013 Jun 7. pii: S0022-3476(13)00428-9. doi: 10.1016/j.jpeds.2013.04.011. [Epub ahead of print]
Authors: Kontos AP, Elbin RJ, Fazio-Sumrock VC, Burkhart S, Swindell H, Maroon J, Collins MW.
Summary: The purpose of the study was to determine the risk of concussion among youth football players (ages 8-12 years). Participants included 468 male youth football players in western Pennsylvania during the 2011 youth football season. Incidence rates (IRs) and incidence density ratios (IDRs) of concussion were calculated for games and practices and for age groups.There was a total of 11 338 (8415 practice and 2923 game) athletic exposures (AEs) in the study period, during which 20 medically diagnosed concussions occurred. A majority of concussions were the result of head-to-head (45%) contact. The combined concussion IR for practices and games was 1.76 per 1000 AEs (95% CI 0.99-2.54). The concussion IR was 0.24 per 1000 AEs (95% CI 0.04-0.79) in practices and 6.16 per 1000 AEs (95% CI 3.76-9.54) in games. The IDR for concussions in games to practices was 25.91 (95% CI 6.01-111.70). The IDR of concussions for youth aged 11-12 years compared with youth aged 8-10 years was 2.72 (95% CI 0.66-4.78). The overall IR for concussion in youth football players aged 8-12 years was comparable with that reported previously for high school and collegiate samples. However, participation in games was associated with an increase in risk of concussion compared with practices, which was higher than rates previously reported for high school and collegiate athletes. Younger players were slightly less likely to incur a concussion than were older players.

#12 Isokinetic strength of knee flexors and extensors in very young soccer players
Reference: Br J Sports Med. 2013 Jul;47(10):e3. doi: 10.1136/bjsports-2013-092558.62.
Authors: Maly T, Zahalka F, Mala L, Teplan J.
Summary: Monitoring of physical fitness characteristics in very young players could be helpful for the selection of talented youth or identification of the strengths and weaknesses in motor predispositions for physical performance. Muscular strength tested on an isokinetic dynamometer belongs to the most widely used methods of the identification of knee extensors (KE) and flexors (KF) strength in adult soccer players It appears that there is the lack of information concerning monitoring of isokinetic strength of lower limbs and its parameters in very young soccer players. The purpose of the study was to find out the level of isokinetic strength (IS) of KE and KF and to compare the selected characteristics of IS related to the movement velocity and limb dominancy in very young players. Young players (n=16, age 8.8±0.4 years, body height=137.5±6.2 cm, body weight=30.7±4.1 kg) were tested on an isokinetic dynamometer Cybex Humac Norm. Maximum peak muscle torque (PT) of KE and KF, their mutual ratio (H:Q) and bilateral ratio between Q:Q or H:H were assessed during concentric contraction at different velocities (60,180,300°.s-1) in the dominant leg (DL) and non-dominant leg (NL). Mixed-design ANOVA was used for evaluation of PT differences between the factors (angular velocity, limb dominancy, muscle groups-KE, KF). For multiple comparisons we used Bonferonni's post-hoc test. Statistical significance was set at p≤0.05. Effect size was assessed using the ηp2 coefficient. The results of PT during 60,180 and 300°.s-1 were (KE [DL]: 60.9±11.6, 39.2±7.3, 30.9±5.4 N•m, [NL]: 60.8±12.2, 41.1±7.8, 33.6±6.3 N•m and for KF [DL]: 34.5±6.2, 24.5±4.1, 19.7±4.3 N•m, [NL]: 33.2±5.7, 24.6±5.8, 20.0±4.8 N•m). Movement velocity had a significant effect on the level of PT (peak torque) in the players F(1.3, 77.9)=414.9, p<0.01, ηp2=0.874 and HQ ratio (F(1.7, 49.8)=7.6, p<0.01, ηp2=0.202. With increasing velocity, significant differences were revealed in PT (L vs M, L vs H, M vs. H p<0.01) and HQ ratio (L vs M, L vs H p <0.05). Limb dominancy did not significantly influence the level of PT F(1, 60)=0.180, p>0.05, ηp2=0.687 or H:Q F(1, 30)=0.760, p>0.05, ηp2=0.025. Movement velocity and limb dominancy did not have any significant effect on the bilateral ratio between QQ and HH in young soccer players (p>0.05). The results indicated significant differences in PT and HQ in relation to movement velocity. On the contrary, no significant differences were found in bilateral ratio (Q:Q, H:Q). Limb dominancy did not significantly affect any of the observed characteristics. The presented data may contribute to comparison or establishment of standards for strength profile in this age category

#13 Sacral fatigue fracture in an amateur soccer player
Reference: Case Rep Med. 2013;2013:985310. doi: 10.1155/2013/985310. Epub 2013 May 23.
Authors: Tzoanos G, Tsavalas N, Manidakis N, Karantanas A.
Summary: Sacral fatigue fractures represent a frequently overlooked cause of low-back and buttock pain in athletes. A high index of clinical suspicion and MRI utilization can provide the accurate diagnosis. A 38-year-old male amateur, midfielder, soccer player presented to our department with aggravating right buttock pain during the previous month, following an increase in training intensity and frequency on an artificial turf field. A point of maximal tenderness was demonstrated over the area of the right sacroiliac joint. No radiographic abnormalities were observed. MRI of the pelvis revealed the presence of a stress fracture in the right sacral ala. The patient underwent conservative treatment and resumed playing soccer 12 weeks later, with no residual or recurrent clinical complaints. Apart from the recent change in training regimen, decreased shock absorption related to the physical properties of old generation artificial turf may have also been involved in this case.

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