Latest research in football - week 50 - 2015

#1 Short biceps femoris fascicles and eccentric knee flexor weakness increase the risk of hamstring injury in elite football (soccer): a prospective cohort study
Reference: Br J Sports Med. 2015 Dec 16. pii: bjsports-2015-095362. doi: 10.1136/bjsports-2015-095362. [Epub ahead of print]
Authors: Timmins RG, Bourne MN, Shield AJ, Williams MD, Lorenzen C, Opar DA
Summary: The aim of the study was to investigate the role of eccentric knee flexor strength, between-limb imbalance and biceps femoris long head (BFlh) fascicle length on the risk of future hamstring strain injury (HSI). Elite soccer players (n=152) from eight different teams participated. Eccentric knee flexor strength during the Nordic hamstring exercise and BFlh fascicle length were assessed at the beginning of preseason. The occurrences of HSIs following this were recorded by the team medical staff. Relative risk (RR) was determined for univariate data, and logistic regression was employed for multivariate data. Twenty seven new HSIs were reported. Eccentric knee flexor strength below 337 N (RR=4.4; 95% CI 1.1 to 17.5) and possessing BFlh fascicles shorter than 10.56 cm (RR=4.1; 95% CI 1.9 to 8.7) significantly increased the risk of a HSI. Multivariate logistic regression revealed significant effects when combinations of age, history of HSI, eccentric knee flexor strength and BFlh fascicle length were explored. From these analyses the likelihood of a future HSI in older athletes or those with a HSI history was reduced if high levels of eccentric knee flexor strength and longer BFlh fascicles were present. The presence of short BFlh fascicles and low levels of eccentric knee flexor strength in elite soccer players increases the risk of future HSI. The greater risk of a future HSI in older players or those with a previous HSI is reduced when they have longer BFlh fascicles and high levels of eccentric strength.


#2 Relationship between y-balance test scores and soft tissue injury incidence in a soccer team
Reference: Int J Sports Phys Ther. 2015 Dec;10(7):955-66.
Authors: Gonell AC, Romero JA, Soler LM
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4675196/pdf/ijspt-10-955.pdf
Summary: Although the dynamic balance has been proposed as a risk factor for sports-related injuries, few researchers have used the Y balance test to examine this relationship. The purpose of this study was to determine if the Y Balance Test (YBT) is a valid test for determining subjects susceptible to soft tissue injury among soccer players on a professional team. Prior to the 2011 football (soccer) season, the anterior, posteromedial and posterolateral YBT reach distances and limb lengths of 74 soccer players were measured. Athletes' physiotherapists documented how many days the players were unable to play due to the injuries. After normalizing for lower limb length, each of the reach distances, right/left reach distance difference and composite reach distance were examined using odds ratios and logistic regression analysis. Logistic regression models indicated that players with a difference of equal or greater than 4cm between lower limbs in posteromedial direction were 3.86 more likely to sustain a lower extremity injury (p=0.001). Results indicate that players who had lower scores than the mean in each reach direction, independently, were almost two times more likely to sustain an injury.


#3 Soccer vs. running training effects in young adult men: which programme is more effective in improvement of body composition? Randomized controlled trial
Reference: Biol Sport. 2015 Nov;32(4):301-5. doi: 10.5604/20831862.1163693. Epub 2015 Aug 4.
Authors: Milanović Z, Pantelić S, Kostić R, Trajković N, Sporiš G
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4672161/pdf/JBS-32-1163693.pdfAbstract
Summary: The aims of this study were: 1) To determine the effects of a 12-week recreational soccer training programme and continuous endurance running on body composition of young adult men and 2) to determine which of these two programmes was more effective concerning body composition. Sixty-four participants completed the randomized controlled trial and were randomly assigned to one of three groups: a soccer training group (SOC; n=20), a running group (RUN; n=21) or a control group performing no physical training (CON; n=23). Training programmes for SOC and RUN lasted 12-week with 3 training sessions per week. Soccer sessions consisted of 60 min ordinary five-a-side, six-a-side or seven-a-side matches on a 30-45 m wide and 45-60 m long plastic grass pitch. Running sessions consisted of 60 min of continuous moderate intensity running at the same average heart rate as in SOC (~80% HRmax). All participants, regardless of group assignment, were tested for each of the following dependent variables: body weight, body height, body mass index, percent body fat, body fat mass, fat-free mass and total body water. In the SOC and RUN groups there was a significant decrease (p < 0.05) in body composition parameters from pre- to post-training values for all measures with the exception of fat-free mass and total body water. Body mass index, percent body fat and body fat mass did not differ between groups at baseline, but by week 12 were significantly lower (p < 0.05) in the SOC and RUN groups compared to CON. To conclude, recreational soccer training provides at least the same changes in body composition parameters as continuous running in young adult men when the training intensity is well matched.


#4 Effect of restricted hip flexor muscle length on hip extensor muscle activity and lower extremity biomechanics in college-aged female soccer players
Reference: Int J Sports Phys Ther. 2015 Dec;10(7):946-54.
Authors: Mills M, Frank B, Goto S, Blackburn T, Cates S, Clark M, Aguilar A, Fava N, Padua D
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4675195/pdf/ijspt-10-946.pdf
Summary: Hip flexor tightness is theorized to alter antagonist muscle function through reciprocal inhibition and synergistic dominance mechanisms. Synergistic dominance may result in altered movement patterns and increased risk of lower extremity injury. The aim was to compare hip extensor muscle activation, internal hip and knee extension moments during double-leg squatting, and gluteus maximus strength in those with and without clinically restricted hip flexor muscle length. Using a modified Thomas Test, female soccer athletes were assigned to a restricted (>0 ° of sagittal plane hip motion above the horizontal; n=20, age=19.9 ± 1 years, ht=167.1 ± 6.4 cm, mass=64.7 ± 8.2kg) or normal (>15 ° of sagittal plane hip motion below horizontal; n=20, age=19.4 ± 1 years, ht=167.2 ± 5.5 cm, mass=61.2 ± 8.6 kg) hip flexor muscle length group. Surface electromyographic (sEMG) activity of the gluteus maximus and biceps femoris, and net internal hip and knee extension moments were measured between groups during a double-leg squat. Isometric gluteus maximus strength was assessed using handheld dynamometry. Individuals with restricted hip flexor muscle length demonstrated less gluteus maximus activation (p=0.008) and a lower gluteus maximus : biceps femoris co-activation ratio (p=0.004). There were no significant differences (p>0.05) in hip or knee extension moments, isometric gluteus maximus strength, or biceps femoris activation between groups. Female soccer athletes with hip flexor muscle tightness exhibit less gluteus maximus activation and lower gluteus maximus : biceps femoris co-activation while producing similar net hip and knee extension moments. Thus, individuals with hip flexor muscle tightness appear to utilize different neuromuscular strategies to control lower extremity motion.


#5 Psychological Gender and Emotional Intelligence in Youth Female Soccer Players
Reference: J Hum Kinet. 2015 Oct 14;47:285-91. doi: 10.1515/hukin-2015-0084. eCollection 2015.
Authors: Rutkowska K, Bergier J
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4633264/pdf/jhk-47-285.pdf
Summary: Many sports (for instance soccer) are stereotypically perceived as a male activity. Even so, more and more women decide to become competitive athletes. Since the theory of sport requires comprehensive explanations and the practice of sport needs clear guidelines, interdisciplinary studies into the nature of sport, including its psychological aspects, are necessary. Analysing the psychological profile of female soccer players, particularly those who are about to become professional athletes, can provide many interesting insights into the specific character of female youth sport and show where improvements can be made in athletic training programmes (especially in mental training). It is therefore important to study psychological gender that determines social behaviours and to analyse female athletes' emotional intelligence. Emotional intelligence is defined as a set of emotional competencies that determine the effectiveness of human behaviours. Psychological gender and emotional intelligence have a significant effect on human adaptability and the efficiency of psychosocial functioning. This research was undertaken with the dual purpose of identifying the psychological gender and emotional intelligence of female soccer players. It involved 54 secondary-school girls, some of whom attended a sports class and others played on the Polish national team. The following tools were used to carry out the research: the Gender Assessment Inventory (IPP [This and the other acronyms derive from the Polish language]-developed by Kuczyńska) and the Emotional Intelligence Questionnaire (INTE; created by Jaworowska and Matczak). As shown by the analysis of the results, most female soccer players in the study were androgynous and the level of their emotional intelligence was significantly higher than in other participants. This also seems to point to their significantly greater adaptability. At the same time, the level of emotional intelligence in many players was average or low, which seems insufficient and calls for adequate intervention measures to be taken.

#6 Hip Range of Motion Is Lower in Professional Soccer Players With Hip and Groin Symptoms or Previous Injuries, Independent of Cam Deformities
Reference: Am J Sports Med. 2015 Dec 16. pii: 0363546515617747. [Epub ahead of print]
Authors: Tak I, Glasgow P, Langhout R, Weir A, Kerkhoffs G, Agricola R
Summary: Soccer (football) players often have hip and groin symptoms (HGS), and a previous groin injury is a risk factor for a relapse. Decreased hip range of motion (HROM) has been related to both hip and groin pain and the presence of a cam deformity. How these factors interact is unknown. The first aim was to study whether HGS are associated with HROM. The second aim was to study the association of the presence of a cam deformity with HROM. Additionally, the influence of a cam deformity on the relationship between HGS and HROM was examined. Seasonal screening data of 2 professional soccer clubs were used. Variables for HGS were current hip or groin pain, the Copenhagen Hip and Groin Outcome Score (HAGOS), and previous hip- and groin-related time-loss injuries (HGTIs). HROM was determined for hip internal rotation (IR), external rotation, and total rotation (TR) in the supine position and for the bent knee fall out (BKFO) test. A cam deformity was defined by an alpha angle >60° on standardized anteroposterior pelvic and frog-leg lateral radiographs. Sixty players (mean [±SD] age, 23.1 ± 4.2 years) were included. All were noninjured at the time of screening. Current hip or groin pain was not associated with HROM. Hips of players in the lowest HAGOS interquartile range (thus most affected by complaints; n = 12) showed less IR (23.9° ± 8.7° vs 28.9° ± 7.8°, respectively; P = .036) and TR (58.2° ± 13.5° vs 65.6° ± 11.8°, respectively; P = .047) than those in the highest interquartile range (n = 29). No such differences were found for BKFO (P = .417). Hips of players with a previous HGTI showed less IR (21.1° ± 6.8° vs 28.3° ± 8.9°, respectively; P < .001) and TR (56.0° ± 8.2° vs 64.5° ± 13.6°, respectively; P < .001) than those without a previous HGTI. This was independent of the presence of a cam deformity. BKFO did not differ between groups (P = .983). Hips with a cam deformity showed less but nonsignificant IR (25.5° ± 10.3° vs 29.0° ± 7.1°, respectively; P = .066) and TR (P = .062) and higher but nonsignificant BKFO values (17.1 cm ± 3.4 cm vs 14.2 cm ± 4.6 cm, respectively; P = .078) than those without a cam deformity. Decreased HROM in professional soccer players is associated with more hip- and groin-related symptoms and with previous injuries, independent of the presence of a cam deformity.


#7 Comparison of Retinal Sensitivity between Professional Soccer Players and Non-athletes
Reference: Int J Sports Med. 2015 Dec 15. [Epub ahead of print]
Authors: Pereira VB, Pereira VB, Pereira RA, Kasahara N
Summary: The purpose of the study was to compare the peripheral retinal sensitivity of the visual field between professional soccer players and age-gender matched non-athlete subjects. All participants underwent a complete eye evaluation. The visual field was evaluated with the achromatic program 60-4 from the Humphrey automated perimetry. The binocular visual field was created with the best location model. It was divided into 4 quadrants (left superior, right superior, left inferior, and right inferior) and compared between groups. The study group comprised 29 professional male football players and the control group comprised 26 age-matched male non-athletes. Mean age was 25.8±4.7 years in the study group and 26.3±5.1 for controls. The average of retina sensitivity in the left inferior and right inferior quadrants was higher in the study group (27.2±1.2 dB and 27.0±1.4 dB) as compared to controls (26.1±1.9 dB and 25.5±2.1 dB). (Student's t test, P=0.011 and P=0.004, respectively). In this small cohort, professional soccer players presented higher retina sensitivity in the inferior quadrants when compared to non-athletes.


#8 Symptoms of Common Mental Disorders in Professional Football (Soccer) Across Five European Countries
Reference: J Sports Sci Med. 2015 Nov 24;14(4):811-8. eCollection 2015.
Authors: Gouttebarge V, Backx FJ, Aoki H, Kerkhoffs GM
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4657424/pdf/jssm-14-811.pdf
Summary: Evidence on the prevalence of symptoms related to distress, anxiety/depression or substance abuse/dependence, - typically referred to as symptoms of common mental disorders (CMD) - is lacking in European professional football (soccer). The aims of the present study were to investigate the prevalence of symptoms related to CMD (distress, anxiety/depression, sleeping disturbance, adverse alcohol behaviour, and adverse nutrition behaviour) in professional footballers from five European countries, and to explore associations of the outcome measures under study with life events and career dissatisfaction. A cross-sectional design was used. Questionnaires were distributed among professional footballers by the national players' unions in Finland, France, Norway, Spain and Sweden. The highest prevalence of symptoms related to common mental disorders were 18% for distress (Sweden), 43% for anxiety/depression (Norway), 33% for sleeping disturbance (Spain), 17% for adverse alcohol behaviour (Finland), and 74% for adverse nutrition behaviour (Norway). In Finland, France and Sweden, both life events and career dissatisfaction were associated with distress, anxiety/depression, adverse alcohol behaviour, and adverse nutrition behaviour. Results suggest the need for self-awareness in professional football about common mental disorders and a multidisciplinary approach by the medical team. Key pointsThe highest prevalence of symptoms related to common mental disorders were 18% for distress (Sweden), 43% for anxiety/depression (Norway), 33% for sleeping disturbance (Spain), 17% for adverse alcohol behaviour (Finland), and 74% for adverse nutrition behaviour (Norway).In Finland, France and Sweden, both life events and career dissatisfaction were associated with distress, anxiety/depression, adverse alcohol behaviour, and adverse nutrition behaviour.Our results suggest the need for self-awareness in professional football about common mental disorders and a multidisciplinary approach by the medical team.Further research based on longitudinal design should be conducted in order to acquire an insight into the causal relationship between symptoms related to common mental disorders and risk factors.


#9 Prevalence and severity of hip and groin pain in sub-elite male football: a cross-sectional cohort study of 695 players
Reference: Scand J Med Sci Sports. 2015 Dec 8. doi: 10.1111/sms.12623. [Epub ahead of print]
Authors: Thorborg K, Rathleff MS, Petersen P, Branci S, Hölmich P
Summary: The purpose of this study was twofold: (a) to investigate the prevalence of hip and groin pain in sub-elite male adult football in Denmark and (b) to explore the association between prevalence and duration of hip and groin pain in the previous season with the Copenhagen Hip and Groin Outcome Score (HAGOS) in the beginning of the new season. In total 695 respondents from 40 teams (Division 1-4) were included. Players completed in the beginning of the new season (July-Sept 2011) a self-reported paper questionnaire on hip and/or groin pain during the previous season and HAGOS. In total 49% (95% CI: 45-52%) reported hip and/or groin pain during the previous season. Of these, 31% (95% CI: 26-36%) reported pain for >6 weeks. Players with the longest duration of pain during the previous season had the lowest HAGOS scores, when assessed at the beginning of the new season, P < 0.001. This study documents that half of sub-elite male adult football players report pain in the hip and/or groin during a football season. The football players with the longest duration of pain in previous season displayed the lowest HAGOS scores in the beginning of the new season.


#10 The Effect of Body Mass on Eccentric Knee Flexor Strength Assessed With an Instrumented Nordic Hamstring Device (Nordbord) in Football Players
Reference: Int J Sports Physiol Perform. 2015 Dec 2. [Epub ahead of print]
Authors: Buchheit M, Cholley Y, Nagel M, Poulos N.
Summary: The aims of the present study were to 1) examine the effect of body mass (BM) on eccentric knee flexor strength using the Nordbord, and 2) offer simple guidelines to control for effect of BM on knee flexors strength. Data from 81 soccer players (U17, U19, U21, senior 4th French division and professionals) and 41 Australian Football League (AFL) players were used for analysis. They all performed one set of three maximal repetitions of the bilateral Nordic hamstring exercise, with the greatest strength measure used for analysis. The main regression equation obtained from the overall sample was used to predict eccentric knee flexor strength from a given BM (moderate TEE, 22%). Individual deviations from the BM-predicted score were used as a BM-free index of eccentric knee flexor strength. There was a large (r = 0.55, 90% confidence limits: 0.42;0.64) correlation between eccentric knee flexor strength and BM. Heavier and older players (professionals, 4th French division and AFL) outperformed their lighter and younger (U17-U21) counterparts, with the soccer professionals presenting the highest absolute strength. Professional soccer players were the only ones to show strength values likely slightly greater than those expected for their BM. Eccentric knee flexor strength, as assessed with the Nordbord, is largely BM-dependent. To control for this effect, practitioners may compare actual test performances with the expected strength for a given BM, using the following predictive equation: eccentric strength (N) = 4 x BM (kg) + 26.1. Professional soccer players with specific knee flexors training history and enhanced neuromuscular performance may show higher than expected values.