#ReadyToplay: hamstring injuries in women's football - a two-season prospective cohort study in the Norwegian women's premier league.

In this two-season prospective cohort study (2020-2021), we aimed to describe the characteristics, clinical findings and magnetic resonance imaging (MRI) findings of hamstring injuries in the Norwegian women's premier league. Hamstring injuries were examined by team physiotherapists using a standardised clinical examination and injury form. Injury location and severity (modified Peetrons classification) were graded based on MRI by two independent radiologists. Fifty-three hamstring injuries were clinically examined, 31 of these with MRI. Hamstring injuries caused 8 days (median) lost from football (interquartile range: 3-15 days, range: 0-188 days), most were non-contact and occurred during sprinting. Gradual-onset (53%) and sudden-onset injuries (47%) were evenly distributed. The injuries examined with MRI were classified as grade 0 (52%), grade 1 (16%) or grade 2 (29%). One proximal tendinopathy case was not graded. Grade 2 injuries caused more time loss than grade 0 (19 ± 8 vs. 7 ± 7 days, p = 0.002). Of injuries with MRI changes, 60% were in the m. biceps femoris, mainly the muscle-tendon junction, and 40% in the m. semimembranosus, most in the proximal tendon. Compared to previous findings from men's football, a higher proportion of hamstring injuries in women's football had a gradual onset and involved the m. semimembranosus, particularly its proximal tendon.

Reciprocal associations of pain and post-traumatic stress symptoms after whiplash injury: A longitudinal, cross-lagged study.

BACKGROUND: The objectives of the current study were to investigate (1) the longitudinal, reciprocal associations between pain and post-traumatic stress symptoms as proposed by the mutual maintenance model, and (2)  to assess the predictive value of the three clusters of post-traumatic stress, where the model revealed that post-traumatic stress symptoms maintained pain in a consecutive cohort of whiplash-injured. METHODS: Participants (n = 253; 66.4% women) were people with WAD grades I-III following motor vehicle crashes in Australia. Pain and post-traumatic stress symptoms were assessed by questionnaires over the course of a year (at baseline (<4 weeks), 3, 6 and 12 months post-injury). The objectives were tested using auto-regressive cross-lagged modelling and two additional structural equation models. RESULTS: The analyses revealed that post-traumatic stress symptoms at baseline predicted an increase in pain between baseline and 3 months and that post-traumatic stress symptoms at 6 months predicted an increase in pain between 6 and 12 months, beyond the stability of pain over time. Furthermore, hyperarousal at baseline significantly predicted pain at 3 months and hyperarousal at 6 months significantly predicted pain at 12 months with 16 and 23% explained variance, respectively. [Correction added on 2 March 2018 after first online publication: the explained variance for hyperarousal symptoms at 6 months was previously given incorrectly and has been corrected to 23% in this version.] CONCLUSIONS: The results point to a temporal main effect of post-traumatic stress symptoms on pain over and above the stability of pain itself within the first 3 months post-injury and again in the chronic phase from 6 to 12 months with hyperarousal symptoms driving these effects. From 3 to 6 months, there was a slip in the maintenance patterns with no cross-lagged effects. SIGNIFICANCE: Investigating mutual maintenance of pain and PTSS in whiplash, the present study found evidence suggesting a maintaining effect of PTSS on pain within the first 3 months post-injury and from 6 to 12 months driven by hyperarousal, highlighting the importance of addressing PTSS.

A novel in vitro model for haematogenous spreading of S. aureus device biofilms demonstrating clumping dispersal as an advantageous dissemination mechanism.

Staphylococcus aureus is able to disseminate from vascular device biofilms to the blood and organs, resulting in life-threatening infections such as endocarditis. The mechanisms behind spreading are largely unknown, especially how the bacterium escapes immune effectors and antibiotics in the process. Using an in vitro catheter infection model, we studied S. aureus biofilm growth, late-stage dispersal, and reattachment to downstream endothelial cell layers. The ability of the released biofilm material to resist host response and disseminate in vivo was furthermore studied in whole blood and phagocyte survival assays and in a short-term murine infection model. We found that S. aureus biofilms formed in flow of human plasma release biofilm thromboemboli with embedded bacteria and bacteria-secreted polysaccharides. The emboli disseminate as antibiotic and immune resistant vehicles that hold the ability to adhere to and initiate colonisation of endothelial cell layers under flow. In vivo experiments showed that the released biofilm material reached the heart similarly as ordinary broth-grown bacteria but also that clumps to some extend were trapped in the lungs. The clumping dispersal of S. aureus from in vivo-like vascular biofilms and their specific properties demonstrated here help explain the pathophysiology associated with S. aureus bloodstream infections.

Pain-catastrophizing and fear-avoidance beliefs as mediators between post-traumatic stress symptoms and pain following whiplash injury - A prospective cohort study.

BACKGROUND: Knowledge about the course of recovery after whiplash injury is important. Most valuable is identification of prognostic factors that may be reversed by intervention. The mutual maintenance model outlines how post-traumatic stress symptoms (PTSS) and pain may be mutually maintained by attention bias, fear, negative affect and avoidance behaviours. In a similar vein, the fear-avoidance model describes how pain-catastrophizing (PCS), fear-avoidance beliefs (FA) and depression may result in persistent pain. These mechanisms still need to be investigated longitudinally in a whiplash cohort. METHODS: A longitudinal cohort design was used to assess patients for pain intensity and psychological distress after whiplash injury. Consecutive patients were all contacted within 3 weeks after their whiplash injury (n = 198). Follow-up questionnaires were sent 3 and 6 months post-injury. Latent Growth Mixture Modelling was used to identify distinct trajectories of recovery from pain. RESULTS: Five distinct trajectories were identified. Six months post-injury, 64.6% could be classified as recovered and 35.4% as non-recovered. The non-recovered (the medium stable, high stable and very high stable trajectories) displayed significantly higher levels of PTSS, PCS, FA and depression at all time points compared to the recovered trajectories. Importantly, PCS and FA mediated the effect of PTSS on pain intensity. CONCLUSIONS: The present study adds important knowledge about the development of psychological distress and pain after whiplash injury. The finding, that PCS and FA mediated the effect of PTSS on pain intensity is a novel finding with important implications for prevention and management of whiplash-associated disorders. WHAT DOES THIS STUDY ADD?: The study confirms the mechanisms as outlined in the fear-avoidance model and the mutual maintenance model. The study adds important knowledge of pain-catastrophizing and fear-avoidance beliefs as mediating mechanisms in the effect of post-traumatic stress on pain intensity. Hence, cognitive behavioural techniques targeting avoidance behaviour and catastrophizing may be beneficial preventing the development of chronic pain.

Injuries in male professional football: A prospective comparison between individual and team-based exposure registration.

Methodological considerations of football injury epidemiology have only scarcely been described. The aim of this study was to evaluate the inter-rater agreement in injury capture rate and injury categorization for data registered in two different prospective injury surveillance audits studying the same two Norwegian male professional football clubs for two consecutive seasons, 2008-2009. One audit used team-based exposure (TBE) recording and the other individual-based exposure (IBE). The number of injuries recorded and corresponding injury rates (injuries/1000 h exposure) were compared between audits. Cohen's kappa and prevalence-adjusted bias-adjusted kappa (PABAK) coefficients were calculated for injury variables. Of 323 injuries included, the IBE audit captured 318 (overall capture rate 98.5%, training 98.9%, match 97.8%) and the TBE audit 303 injuries (overall capture rate 93.8%, training 91.4%, match 97.1%). Agreement analysis showed kappa and PABAK coefficients regarded as almost perfect (> 0.81) for 8 of 9 injury variables, and substantial (ƙ 0.75) for the variable injury severity. In conclusion, the capture rate for training injuries was slightly higher with IBE recording, and inter-agreement in injury categorization was very high.

Atrial Size and Function in Athletes.

We wanted to explore whether change in LA (left atrium) size would influence LA function, or increase regurgitation in the atrioventricular valves. 595 male elite football players and 47 non-athletic controls were included. End-systolic LA volume and RA area and end-diastolic LV volume and RV area were measured by 2-dimensional (2D) echocardiography Pulsed and colour Doppler were used to estimate tricuspid and mitral regurgitations. 2D longitudinal strain of the 50 football players with the largest LA volumes were compared with the 50 players with the smallest LA volumes. The LA volumes in some athletes with large atria were more than tripled, compared to athletes with small atria. 2D strain however, could not reveal any impairment of LA function in the players with the largest atria, compared to those with the smallest LA. Tricuspid valve regurgitation was found in 343 (58%) of the athletes, compared to 17 (36%) of the controls (p<0.01), while mitral regurgitation was found in 116 (20%) football players and 7 (15%) controls (NS). Furthermore, the RA area was significantly larger in athletes with tricuspid regurgitation compared to athletes without. The present study demonstrated a huge variation in atrial size between the athletes. This variation, however, had no impact on LA function. Tricuspid regurgitation was significantly more prevalent among the athletes, than among the controls.

Motives for sports participation as predictions of self-reported outcomes after anterior cruciate ligament injury of the knee.

Aim of the study was to access how individual's motives for participation in sports impact on self-reported outcomes 2 years after an anterior cruciate ligament injury. Based on a longitudinal cohort study, this secondary analysis present data from the Knee Anterior Cruciate Ligament, Nonsurgical versus Surgical Treatment (KANON) study, a randomized controlled trial. At baseline, 121 patients recorded in an initial questionnaire that their motives for sports participation fell into four categories: achievement, health, social integration, or fun and well-being. These four categories were used as variables in the analyses. All 121 subjects completed the 2-year follow-up. The largest improvement was seen in the Knee Injury and Osteoarthritis Outcome Score (KOOS) subscale sports and recreation function, with an effect size of 2.43. KOOS sports and recreation function was also the subscale score best predicted by the motives for sports participation. Baseline motives achievement and fun and well-being predicted worse levels of pain and function 2 years after the injury, even after adjusting for age, gender, treatment and baseline scores. Psychological aspects, such as motives for participation in sport, can be factors in predicting of patient-reported outcomes 2 years after injury. Evaluating motives for sports participation may help predict the outcome 2 years after ACL injury.

Prevalence of abnormal ECGs in male soccer players decreases with the Seattle criteria, but is still high.

Electrocardiogram (ECG) and echocardiography are mandatory in preparticipation cardiac screening in soccer players. Abnormal ECG findings usually require follow-up investigations. The main aim of this study was to compare the prevalence of abnormal ECG findings in male professional soccer players according to European Society of Cardiology's (ESC) recommendations and the Seattle criteria, and to assess the need for echocardiography. ECGs from 587 of 595 (99%) players were recorded with ClickECG, and measurements were derived with visually adjusted on-screen calipers on the computer-based averaged PQRST complex. Echocardiographic recordings were performed with Vivid 7/i and categorized according to reference values for athlete's heart. After the initial screening, 32 (5.5%) players were recommended for follow-up. The prevalence of abnormal ECGs was 29.3% vs 11.2% according to the ESC's recommendations and the Seattle criteria, respectively. None of the players with abnormal ECGs only according to the ESC's recommendations had abnormal echocardiograms. Echocardiography alone detected one player with abnormalities (athlete's heart). The Seattle criteria reduced the number of athletes with abnormal ECGs considerably compared with the ESC recommendations. Based on echocardiographic evaluations, this increased the specificity of the Seattle criteria, without increasing the number of false-negative ECGs. The need for mandatory echocardiography in soccer players seems limited.

Visual or computer-based measurements: important for interpretation of athletes' ECG.

BACKGROUND: ECG is recommended for preparticipation health examination in athletes. Owing to a lack of consensus on how to read and interpret athletes' ECGs, different criteria for abnormality are used. AIMS: To compare the prevalence of abnormal ECGs and test the correlation between visual and computer-based measurements. METHODS: In a preparticipation cardiac screening examination of 595 male professional soccer players aged 18-38 years, ECGs were categorised according to the European Society of Cardiology's (ESC) recommendations and the Seattle criteria, respectively. Visual measurements were conducted with callipers on-screen on the averaged PQRST complex in each lead, calculated by the trimmed mean. Computer-based measurements were derived from the medium beat. Heart rhythm and conduction were scored visually by a cardiologist. Categorical variables were compared by κ statistics (K) and continuous variables by intraclass correlation. RESULTS: ECGs of good quality were available from 579 players. According to the ESC's recommendations and Seattle criteria, respectively, ECGs were categorised as abnormal in 171 (29.5%) vs 64 (11.1%) players after visual assessment, and in 293 (50.6%; K=0.395) vs 127 (21.9%; K=0.564) after computer-based measurements. Intraclass correlation was very good for measurements of R and S wave amplitudes and moderate to very good for intervals. K was very good for pathological Q wave amplitudes and moderate for T wave inversions. CONCLUSIONS: Abnormal ECGs were more than twice as common after computer-based than after visual measurements. Such a difference will markedly influence the number of athletes who need further examinations. Reference values may need adjustments dependent on measurement methods.

The Scandinavian athlete's heart; echocardiographic characteristics of male professional football players.

This investigation explores the cardiac four-chamber remodeling response to training in male players in Norwegian professional football league, and ethnicity as determinants in the development of athlete's heart. Standard 2D echocardiographic examination and analysis of all four cavities were performed in 504 football players of Caucasian origin, 49 of African origin, and 47 matched Caucasian controls (<3 h training /week). All results were indexed to body surface area (BSA). Most athletes exhibited BSA-indexed values within normal ranges. Left ventricle (LV) mass was equally enlarged in both groups of athletes, but LV relative wall thickness and right ventricular (RV) relative wall thickness were increased in Africans compared with Caucasian athletes (0.37 ± 0.06 vs 0.33 ± 0.06 and 0.25 ± 0.06 vs 0.22 ± 0.04, respectively). Both LV and RV were smaller in Africans than in Caucasian athletes (67.8 ± 12.0 ml/m(2) vs 73.6 ± 13.2 ml/m(2) and 12.8 ± 2.1 vs 13.7 ± 2.4 cm(2) /m(2) , respectively, both P < 0.05), while left and right atria increased similarly. This first large-scale echocardiographic survey of elite football players in a Scandinavian league suggests use of BSA-indexed upper normal limits for both LV and RV in athletes. African athletes had significantly more concentric remodeled LV and RV than the Caucasian athletes.

Text messaging as a new method for injury registration in sports: a methodological study in elite female football.

Methodological differences in epidemiologic studies have led to significant discrepancies in injury incidences reported. The aim of this study was to evaluate text messaging as a new method for injury registration in elite female football players and to compare this method with routine medical staff registration. Twelve teams comprising 228 players prospectively recorded injuries and exposure through one competitive football season. Players reported individually by answering three text messages once a week. A designated member of the medical staff conducted concurrent registrations of injuries and exposure. Injuries and exposure were compared between medical staff registrations from nine teams and their 159 affiliated players. During the football season, a total of 232 time-loss injuries were recorded. Of these, 62% were captured through individual registration only, 10% by the medical staff only, and 28% were reported through both methods. The incidence of training injuries was 3.7 per 1000 player hours when calculated from individual registration vs 2.2 from medical staff registration [rate ratio (RR): 1.7, 1.2-2.4]. For match injuries, the corresponding incidences were 18.6 vs 5.4 (RR: 3.4, 2.4-4.9), respectively. There was moderate agreement for severity classifications in injury cases reported by both methods (kappa correlation coefficient: 0.48, confidence interval: 0.30-0.66).

Gradual increase in the risk of match injury in Norwegian male professional football: a 6-year prospective study.

The aim of this study was to monitor injury incidence and pattern in Norwegian male professional football over six consecutive seasons and compare the risk of injury between the preseason and competitive season. All time loss injuries were recorded by the medical staff of each club. In total, 2365 injuries were recorded. The incidence of acute injuries was 15.9/1000 match hours [95% confidence interval (CI): 14.9-16.8], 1.9/1000 training hours (95% CI: 1.7-2.0), and 1.4 (95% CI: 1.3-1.5) overuse injuries/1000 h. A linear regression model found an annual increase of 1.06 acute match injuries/1000 h (95% CI: 0.40-1.73), corresponding to a total increase of 49% during the 6-year study period. When accounting for interteam variation and clustering effects using a general estimating equation model, the increase in injury incidence was 0.92 (95% CI: -0.11-1.95, P = 0.083). No difference in the risk of acute match injuries (rate ratio (RR): 0.86, 95% CI: 0.73-1.01), acute training injuries (RR: 1.16, 95% CI: 0.99-1.36), or overuse injuries (RR: 1.04, 95% CI: 0.89-1.21) was observed between the preseason and competitive season. In conclusion, the overall risk of acute match injuries in Norwegian male professional football increased by 49% during the study period, although this increase was not fully consistent across teams. We detected no change in the risk of training and overuse injuries or any difference between the preseason and competitive season.

Injury risk on artificial turf and grass in youth tournament football.

The aim of this prospective cohort study was to investigate the risk of acute injuries among youth male and female footballers playing on third-generation artificial turf compared with grass. Over 60,000 players 13-19 years of age were followed in four consecutive Norway Cup tournaments from 2005 to 2008. Injuries were recorded prospectively by the team coaches throughout each tournament. The overall incidence of injuries was 39.2 (SD: 0.8) per 1000 match hours; 34.2 (SD: 2.4) on artificial turf and 39.7 (SD: 0.8) on grass. After adjusting for the potential confounders age and gender, there was no difference in the overall risk of injury [odds ratio (OR): 0.93 (0.77-1.12), P=0.44] or in the risk of time loss injury [OR: 1.05 (0.68-1.61), P=0.82] between artificial turf and grass. However, there was a lower risk of ankle injuries [OR: 0.59 (0.40-0.88), P=0.008], and a higher risk of back and spine [OR: 1.92 (1.10-3.36), P=0.021] and shoulder and collarbone injuries [OR: 2.32 (1.01-5.31), P=0.049], on artificial turf compared with on grass. In conclusion, there was no difference in the overall risk of acute injury in youth footballers playing on third-generation artificial turf compared with grass.

Cardiovascular pre-participation screening does not distress professional football players.

BACKGROUND: It has been debated whether cardiovascular screening of athletes creates negative psychological reactions in those being screened. Neither the athletes' level of distress towards, nor their opinion about screening has actually been examined. Therefore, the aim of this study was to assess the level of distress among Norwegian elite male football players and their experiences of screening. METHODS: After screening, players completed a 10-item scale assessing their experience on a Likert scale. Their level of distress was measured with the intrusion sub-scale of Impact of Event Scale (IES) (7 items) on a six-point scale (grade 0-5). A sum score of ≥19 indicates a clinical stress problem. Twenty-five out of 28 teams, 441 of 591 players (75%, mean age 26 [18-39] years) consented to participate. RESULTS: Sixty-four percent felt more confident when playing football and 88% were satisfied having completed the screening. The majority (77%) felt a need for the screening and 84% would strongly recommend it to others. Sixteen percent were afraid that the screening result might have consequences for their own health, and 13% were afraid of losing their license to play football. Less than 3% experienced distress (IES ≥ 19). CONCLUSIONS: The majority of the players were satisfied having completed the screening, felt more confident and would recommend it to other players. Only a marginal proportion of the players were distressed by the screening, but were at least as likely to recommend it.

Injury surveillance in male professional football; is medical staff reporting complete and accurate?

Since the 2000 season, an injury surveillance system has been established to monitor injury risk and injury patterns in the Norwegian professional football league. The aim of this study was to assess the accuracy of routine injury registration performed by medical staff in professional football. The team medical staff completed injury registration forms on a monthly basis throughout the 2007 season (January-October). Players were interviewed at the end of the season (October/November) about all injuries that occurred from July through September. Thirteen of fourteen teams, 296 of 310 A-squad players were interviewed. An injury was recorded when a player was unable to take fully part in football training or match the day after injury. A total of 174 injuries were registered, 123 acute injuries and 51 overuse injuries. Of these, 141 were reported by medical staff and 122 by players. Eighty-nine injuries (51%) were registered using both methods, 52 (30%) by medical staff only and 33 (19%) by player interviews only. Prospective injury surveillance by team medical staff in Norwegian male professional football underestimates the incidence of time-loss injuries by at least one-fifth.

An intermittent running test to estimate maximal oxygen uptake: the Andersen test.

AIM: Monitoring of height and weight in children in schools has been discussed to get data on trends in obesity. Physical fitness may be just as important to monitor and a simple reliable test will therefore be important. The aim of this paper was to analyze the association between VO2max measured during maximal work on a treadmill and running distance in an intermittent running test. METHODS: Three different groups conducted an intermittent running test VO2max was measured directly during treadmill running. The groups were 27 physical education students (age 20.0-27.0 years), 57 children (age 9.9-11.0 years), and 14 male elite soccer players (age 14.2-15.0 years). RESULTS: The reproducibility of the Andersen test was good (r=0.84). Subjects ran 15 m (SD 61 m) longer the second time, but this difference was not significant (P=0.102). The association between running distance in the Andersen test and VO2max measured on the treadmill showed a correlation coefficient of 0.87 in university students, 0.68 in children, and 0.60 in soccer players. For the whole group: VO2max= 18.38 + (0.03301*distance) - (5.92*sex) (boys=0;girls=1) (r=0.84). CONCLUSION: The test may provide teachers and health care professionals with an important tool to estimate physical fitness in children and adolescents in a fast, non-expensive and reliable way.

Prevention of hamstring strains in elite soccer: an intervention study.

The purpose was to test the effect of eccentric strength training and flexibility training on the incidence of hamstring strains in soccer. Hamstring strains and player exposure were registered prospectively during four consecutive soccer seasons (1999-2002) for 17-30 elite soccer teams from Iceland and Norway. The first two seasons were used as baseline, while intervention programs consisting of warm-up stretching, flexibility and/or eccentric strength training were introduced during the 2001 and 2002 seasons. During the intervention seasons, 48% of the teams selected to use the intervention programs. There was no difference in the incidence of hamstring strains between teams that used the flexibility training program and those who did not [relative risk (RR)=1.53, P=0.22], nor was there a difference compared with the baseline data (RR=0.89, P=0.75). The incidence of hamstring strains was lower in teams who used the eccentric training program compared with teams that did not use the program (RR=0.43, P=0.01), as well as compared with baseline data for the same intervention teams (RR=0.42, P=0.009). Eccentric strength training with Nordic hamstring lowers combined with warm-up stretching appears to reduce the risk of hamstring strains, while no effect was detected from flexibility training alone. These results should be verified in randomized clinical trials.

Consensus statement on injury definitions and data collection procedures in studies of football (soccer) injuries.

Variations in definitions and methodologies have created differences in the results and conclusions obtained from studies of football injuries; this has made inter-study comparisons difficult. An Injury Consensus Group was established under the auspices of FIFA Medical Assessment and Research Centre. Using a nominal group consensus model approach, a working document that identified the key issues related to definitions, methodology and implementation was discussed by members of the group during a 2-day meeting. Following this meeting, iterative draft statements were prepared and circulated to members of the group for comment before the final consensus statement was produced. Definitions of injury, recurrent injury, severity and training and match exposures in football together with criteria for classifying injuries in terms of location, type, diagnosis and causation are proposed. Proforma for recording players' baseline information, injuries and training and match exposures are presented. Recommendations are made on how the incidence of match and training injuries should be reported and a checklist of issues and information that should be included in published reports of studies of football injuries is presented. The definitions and methodology proposed in the consensus statement will ensure that consistent and comparable results will be obtained from studies of football injuries.

Consensus statement on injury definitions and data collection procedures in studies of football (soccer) injuries.

Variations in definitions and methodologies have created differences in the results and conclusions obtained from studies of football (soccer) injuries, making interstudy comparisons difficult. Therefore an Injury Consensus Group was established under the auspices of Fédération Internationale de Football Association Medical Assessment and Research Centre. A nominal group consensus model approach was used. A working document on definitions, methodology, and implementation was discussed by the group. Iterative draft statements were prepared and circulated to members of the group for comment before the final consensus statement was produced. Definitions of injury, recurrent injury, severity, and training and match exposures in football together with criteria for classifying injuries in terms of location, type, diagnosis, and causation are proposed. Proforma for recording players' baseline information, injuries, and training and match exposures are presented. Recommendations are made on how the incidence of match and training injuries should be reported and a checklist of issues and information that should be included in published reports of studies of football injuries is presented.