Studying professional and recreational female footballers: A bibliometric exercise.

OBJECTIVES: Research directed at soccer has seen dramatic growth in the last decade. While published research on soccer has shown exponential growth, the proportion of articles addressing females is lagging behind research addressing males. The purpose of this paper is to explore how the literature on soccer, female soccer, and professional female soccer has changed over time. METHODS: The Web of Science (WoS) was queried for all "articles" about soccer and association football from 1970 to 2019. This set of records was then queried to collect subsets of papers about females, professional/elite, and female professional/elite. Each of these data subsets was then queried for a number of characteristics and topics. The results were submitted to bibliometric analysis. RESULTS: WoS returned 16,822 "articles" about soccer from 1970 to 2019, 3242 of which addressed females. A total of 5924 "articles" about professional players was found, of which 919 had a female focus. Articles about anterior cruciate ligament injuries and concussion were the topics with the highest proportion of papers involving females. Articles directed at selective areas of training and performance were relatively infrequent. Prominent journals, authors, affiliations, and influential papers are presented. CONCLUSIONS: A bibliometric analysis of the published research presents a high-level overview of trends in soccer research. Overall, studies about women accounted for around 20% of all soccer research and about 15% of studies on professional players. There were a number of topics where studies on females account for less than 10%-15% of the research on all professionals, and opens opportunities for future study.

Relative Age Effect: Beyond the Youth Phenomenon.

Introduction. The relative age effect (RAE) refers to performance advantage of youth born in the first quarter of the birth year when auditioning for select, age-restricted sports. This advantage conferred to the older athlete is a result of being more physically and emotionally mature, therefore, assumed to be a more advanced player. We hypothesize an RAE exists in Olympic athletes, and this extends across selected categories of athletes (by gender), such as team versus individual sports, winter versus summer athletes, and sports using a ball versus those not using a ball. Methods. We extended the exploration of an RAE beyond specific sports by examining the birth quarter of more than 44 000 Olympic athlete's birthdates, born between 1964-1996. The data were summarized by birth quarter (January 1 to March 31, etc) and presented as percentages and 95% confidence intervals. Results. The fractions of births in the first versus the fourth quarter were significantly different ( P < .001) from each other for the summer and winter Olympians, ball and nonball sports, and team as well as individual sports. Conclusions. The general presence of an RAE in Olympic athletes exists regardless of global classification.

Evolution of soccer as a research topic.

Soccer has not only the largest number of worldwide participants, it is also the most studied sport, with nearly 14,000 citations listed on Pubmed and nearly 60% more articles than the next most studied sport. Research about soccer was limited until the late 1970s when exponential growth began; approximately 98% of all soccer-related research publications have occurred since 1980. This vast repository of soccer research shows trends in various major (e.g., 'sex' or 'age group' or 'performance' or 'injury') and specialty (e.g., agility, deceleration, elbow-head impact injuries, behavior) topics. Examining trends of the various topics provides insights into which subjects have come in and out of favor as well as what topics or demographics have been neglected and worthy of inquiry. A further examination can be used by students to learn the most productive researchers, which programs have a strong history of inquiry, and what journals have demonstrated a commitment to publishing research on soccer.

Rotator Cuff Matrix Augmentation and Interposition: A Systematic Review and Meta-analysis.

BACKGROUND: Surgical management of rotator cuff tears is controversial and complex, ranging from nonoperative management to reverse shoulder arthroplasty. PURPOSE: To systematically review and evaluate the outcomes of graft augmentation or interposition versus rotator cuff repair (RCR) alone and evaluate via meta-analysis whether the use of a graft leads to superior outcomes versus RCR alone. STUDY DESIGN: Systematic review and meta-analysis. METHODS: An electronic literature search (Medline, Embase, CINAHL) was conducted. Studies with a minimum follow-up of 1 year and minimum sample size of 10 that provided clinical results of RCR or rotator cuff reconstruction using any type of augmentation tissue or matrix were included. Methodological quality was evaluated by assessment of the risk of bias in the included studies. Studies comparing outcomes of RCR with graft augmentation or interposition versus repair alone (control group) were subjected to meta-analysis. RESULTS: The authors identified 774 articles and included 36 in the systematic review; 5 of the 36 studies underwent meta-analysis. Except for one outcome measure in a single study, all surgical interventions (RCR alone, RCR with augmentation, and RCR with interposition) improved clinical scores and outcome measures. Because of variability in study outcomes, no graft option was found to be superior. Compared with RCR alone, graft augmentation or interposition provided significantly lower retear rates ( P = .05) and higher American Shoulder and Elbow Surgeons (ASES) scores ( P = .005), but improvements in UCLA (University of California, Los Angeles) scores ( P = .29) and pain scores ( P = .1) did not reach statistical significance. CONCLUSION: In the meta-analysis, graft augmentation or interposition appeared to provide a lower retear rate and improved ASES scores when compared with RCR alone. Future prospective, randomized, controlled, and appropriately powered trials are needed for more definitive recommendations.

Muscle changes in aging: understanding sarcopenia.

UNLABELLED: Muscle physiology in the aging athlete is complex. Sarcopenia, the age-related decrease in lean muscle mass, can alter activity level and affect quality of life. This review addresses the microscopic and macroscopic changes in muscle with age, recognizes contributing factors including nutrition and changes in hormone levels, and identifies potential pharmacologic agents in clinical trial that may aid in the battle of this complex, costly, and disabling problem. LEVEL OF EVIDENCE: Level 5.

"Real world" treatment of metastatic renal cell carcinoma in a joint community-academic cohort: progression-free survival over three lines of therapy.

BACKGROUND: New targeted therapeutics approved for metastatic renal cell carcinoma (mRCC) offer multiple options in each line of therapy; however, there are few prospective data beyond the first-line settings, and overall comparative effectiveness data are limited. In the targeted therapy era, progression-free survival (PFS) has been the most common regulatory end point for demonstrating the benefit of new therapies. PATIENTS AND METHODS: Drawing on a joint community-academic retrospective mRCC registry, we analyzed all patients who had undergone at least 1 line of systemic therapy (N = 325) for PFS. Patients were grouped according to treatment choice (sorafenib, sunitinib, temsirolimus, everolimus, and "other") for up to 3 lines of therapy. PFS by treatment choice and line of therapy was evaluated using Kaplan-Meier and Cox regression analyses. RESULTS: PFS was longest in patients treated with sunitinib in the first and second lines of therapy. First-line PFS for sorafenib, sunitinib, temsirolimus, everolimus, and "other" was 6.9, 8.9, 4.2, not analyzed (too few patients), and 10.8 months, respectively. Second-line PFS was 4.6, 7.0, 3.2, 3.8, and 4.1 months, respectively. Third-line PFS was 4.5, 4.6, 9.9, 4.2, and 2.9, months, respectively. The risk of progression in patients treated with temsirolimus was about twice that of patients treated with sunitinib in the first and second lines of therapy. CONCLUSION: Patients treated with sunitinib had the longest PFS in the first and second lines of therapy. PFS from practice-based data appear consistent with trial-based expectations; however, practice variation was still evident.

Strategies for maintaining fitness and performance during Ramadan.

The Muslim athlete, whether living in a Muslim majority country or in a non-Muslim country, face unique challenges to faithfully follow one of the pillars of their faith - Ramadan - while attempting to maintain their participation in sports training and competition. There are conflicting reports on the effects of Ramadan on fitness and physical performance in general and in football in particular. In general, the impact of a brief daytime fast has minor effects on health or factors of physical fitness. Add physical training and now a new set of barriers to both performance and the observance of Ramadan begin to interact. Practising athletes have worked out strategies to cope with the rigors of Ramadan; strategies that have both physical (training modifications, dietary habits, rest and recovery) and emotional (patience, emotional preparations) domains. Carefully blending strategies like these can help the football player be true to their faith and follow the tenants of Ramadan hopefully, with a minimum of impact on their physical performance. In this context, science can help coaches improve their training plans and educate players with respect to the challenges presented by Ramadan to all levels of sports participation.

Management of the Retired Athlete with Osteoarthritis of the Knee.

PURPOSE: Osteoarthritis of the knee is a complex interaction of biological, mechanical, and biochemical factors that are further complicated by injury, which accelerates pathological processes within the joint. As a result, athletes, particularly those with a history of knee injury, have an earlier onset and higher prevalence of osteoarthritis that would be expected based on their age. This can present a clinical dilemma to the physician managing the patient who, despite the presence of radiologically confirmed disease, has few symptoms and wishes to maintain an active lifestyle. METHODS: We reviewed meta-analyses and systematic reviews of randomized controlled trials about clinical management of knee osteoarthritis with special interest on effect sizes. RESULTS: Numerous management options have undergone the rigor of clinical trials and subsequently have been summarized in meta-analyses and systematic reviews, the results of which offer evidence regarding varying degrees of effect. Based on the available evidence, most summaries and clinical practice guidelines suggest a regimen of patient education, self-management, weight control, and exercise supported by individualized pain management strategies. Other noninvasive or less invasive strategies are available that have varying degrees of effect. CONCLUSIONS: Although the evidence supporting many of the clinical management options might be considered modest, those effects are sufficient to permit an active lifestyle and have, given the prevalence of the disease, a public health impact.

Effective injury prevention in soccer.

Sports participation is accompanied by risk of injury, and each specific sport has its own unique injury profile. One of the goals of a sports medicine professional is injury prevention, and the past decade has seen numerous reports on the outcomes of injury-prevention studies. Health care professionals have been particularly vigilant in attempting to reduce common injuries in soccer, beginning with work in the early 1980s to the rigorous randomized trials of today. The use of a structured, generalized warm-up program has been shown to be effective in preventing common soccer injuries, reducing overall injury rates by approximately 30%. Given the number of individuals who play soccer worldwide, any injury reductions will likely have an impact on public health. It is an important goal of the sports medicine community to inform physicians and other sports medicine professionals about the effectiveness of prevention programs to increase use and compliance.

Prevention of football injuries.

PURPOSE: Every sport has a unique profile of injury and risk of injury. In recent years, there have been numerous attempts at conducting injury prevention trials for specific injuries or for injuries within specific sports to provide evidence useful to the sports medicine and sport community. Football has been a focus of a number of randomized injury prevention trials. METHODS: MEDLINE was searched with the first order keywords of "injury prevention" and "sport". This list was restricted to "clinical trial" or "randomized controlled trial" which had been conducted on children and adults whose goal was preventing common football injuries. Our objective was to find studies with an exercise-based training program, thus projects that used mechanical interventions were excluded. RESULTS: A structured, generalized warm-up has been shown to be effective at preventing common injuries in football, reducing injuries by about one-third. CONCLUSION: The huge participation numbers in the worldwide family of football would suggest that any reduction in injury should have a public health impact. Professionals in sports medicine need to promote injury prevention programs that have been shown to be effective.

The F-MARC study on Ramadan and football: research design, population, and environmental conditions.

Ramadan is a month of penance during which Muslims take food or drink only after sunset and before the sun rises. This fast can present a considerable challenge to the Muslim athlete. Sports performance in those who observe Ramadan and those who do not has not been formally compared. Four Tunisian junior football squads participated in the study, and it was the individual's choice whether they observed the Ramadan fast. In this study, 64 players fasted while 36 players did not. Players completed daily questionnaires on perception of training difficulty before and during Ramadan. Anthropometric data were recorded 3 weeks before Ramadan, during the second and fourth weeks of Ramadan, and into the third week after Ramadan. Performance tests (sprint, leg power, agility, aerobic endurance, football-specific skills) were also measured on these test days. Nutritional intake was recorded by recall three times during each phase of the study. Haematological and biochemical analyses were performed on a 7-ml blood sample taken from each participant on each of the test days. Sweat samples were collected during a training session in the third week of Ramadan, when heart rate was also measured. The data analyses are presented and discussed elsewhere in this issue.

Influence of Ramadan fasting on physiological and performance variables in football players: summary of the F-MARC 2006 Ramadan fasting study.

The timing of food and liquid intake depends on the times of sunset and sunrise during the month of Ramadan. The current body of knowledge presents contradicting results as to the effect of Ramadan fasting on body mass, body composition and metabolic changes. The main objective of the present investigation was to gain additional information and scientific data in conformity with the philosophical background of Islam to allow optimisation of the daily training and dietary regimen in relation to the mental and physical performance of football players. The four teams, along with their coaches and trainers, attended a residential training camp at training centre 3 weeks before the start of Ramadan and throughout the study. Energy intake was relatively stable in the fasting group, but there was a small, albeit significant, decrease of approximately 0.7 kg in body mass. Water intake increased on average by 1.3 l/day in line with the greater energy intake in the non-fasting group in Ramadan. Daily sodium intake fell during Ramadan in the fasting players but increased slightly in the non-fasting group. Fasting players trained on average 11 h after their last food and drink, and reported that they felt slightly less ready to train during the Ramadan fast. None of the assessed performance variables was negatively affected by fasting while nearly all variables showed significant improvement at the third test session, indicating a training effect. Heart rate measurements in one training session during the third week of Ramadan appeared to suggest that the training load during training was marginally greater for the fasting than for the non-fasting players. However, the overall exercise load measures indicated that there was no biologically significant difference between the fasting and non-fasting groups. In the present study, biochemical, nutritional, subjective well-being and performance variables were not adversely affected in young male football players who followed Ramadan fasting in a controlled training camp environment. Physical performance generally improved, but match performance was not measured. We recommend that players should ensure adequate sleep and good nutrition during Ramadan to preserve football performance and general health.

The influence of Ramadan on physical performance measures in young Muslim footballers.

Ramadan alters the normal patterns of food intake and sleep. The aim of this study was to describe the impact of Ramadan on physical performance in youth Muslim athletes. The members of four Tunisian teams (age 18 years, N = 85) resided at the Tunisian Football Federation training ground. Each player chose either to fast or not fast during the 4-week period of Ramadan. Two teams were randomly chosen for morning testing; the remaining teams were tested in the afternoon. Testing took place 3 weeks before and in the second and fourth weeks of Ramadan. A subgroup of 45 players was tested again 3 weeks after Ramadan. Each player was assessed for speed, power, agility, endurance, and for passing and dribbling skills. No variables were negatively affected by fasting. Almost all variables had improved significantly by the third test session (training effect). A limited number of variables were also significant for time of day or in an interaction with week of testing. Changes in performance were most likely due to the effects of training and familiarity with the test methods. Based on these data, Ramadan had little effect on objective tests of physical performance in this sample of youth players observing Ramadan.

Issues in training the female player.

On the surface, the women's game appears to be similar to the men's game. On closer examination, there are subtle differences in the nature of how each gender plays the game, which are evident in the disparity between skills, tactics and fitness. The technical weaknesses of women include the first touch, dribbling, long passing and goal keeping. These skill limitations have dictated specific tactical approaches towards both attack and defence. Specific biological limitations inherent in the female player affect the pace and total work output in the women's game. Although it is unrealistic to expect the women's game to approach the work output of the men's game, specific training of skills and fitness will influence the tactical approach to the game.

Head injuries in the female football player: incidence, mechanisms, risk factors and management.

Although all injuries in sports are a concern for participants, head injuries are particularly troublesome because of the potential for long-term cognitive deficits. To prevent any specific injury, it is important to understand the basic frequency and incidence of injury and then the mechanism of injury. Once these are established, prevention programmes can be tested to see if the rate of injury changes. A primary problem with head injuries is recognising that the injury has occurred. Many athletes are not aware of the seriousness of concussive injury, thus this type of injury is probably under-reported. Once the diagnosis of a concussion is made, the next difficult decision is when to return a player to the game. These two management issues dominate the continuing development of understanding of concussive head injury. This paper explores the known gender differences between head injuries and highlights the areas that need to be considered in future research.

Age and gender effects on lower extremity kinematics of youth soccer players in a stop-jump task.

BACKGROUND: Gender differences in lower extremity motion patterns were previously identified as a possible risk factor for non-contact anterior cruciate ligament injuries in sports. HYPOTHESIS: Gender differences in lower extremity kinematics in the stop-jump task are functions of age for youth soccer players between 11 and 16 years of age. STUDY DESIGN: Descriptive laboratory study. METHODS: Three-dimensional videographic data were collected for 30 male and 30 female adolescent soccer players between 11 and 16 years of age performing a stop-jump task. The age effects on hip and knee joint angular motions were compared between genders using multiple regression analyses with dummy variables. RESULTS: Gender and age have significant interaction effects on standing height (P = .00), body mass (P = .00), knee flexion angle at initial foot contact with the ground (P = .00), maximum knee flexion angle (P = .00), knee valgus-varus angle (P = .00), knee valgus-varus motion (P = .00), and hip flexion angle at initial foot contact with the ground (P = .00). CONCLUSION: Youth female recreational soccer players have decreased knee and hip flexion angles at initial ground contact and decreased knee and hip flexion motions during the landing of the stop-jump task compared to those of their male counterparts. These gender differences in knee and hip flexion motion patterns of youth recreational soccer players occur after 12 years of age and increase with age before 16 years. CLINICAL RELEVANCE: The results of this study provide significant information for research on the prevention of noncontact anterior cruciate ligament injuries.

Effect of fatigue on knee kinetics and kinematics in stop-jump tasks.

BACKGROUND: Altered motor control strategies in landing and jumping maneuvers are a potential mechanism of noncontact anterior cruciate ligament injury. There are biomechanical differences between male and female athletes in the landing phase of stop-jump tasks. Fatigue is a risk factor in musculoskeletal injuries. HYPOTHESIS: Lower extremity muscle fatigue alters the knee kinetics and kinematics during the landing phase of 3 stop-jump tasks and increases an athlete's risk of anterior cruciate ligament injury. STUDY DESIGN: Controlled laboratory study. METHODS: Three-dimensional videography and force plate data were collected for 20 recreational athletes (10 male and 10 female athletes) performing 3 stop-jump tasks before and after completing a fatigue exercise. Knee joint angles and resultant forces and moments were calculated. RESULTS: Both male and female subjects had significantly increased peak proximal tibial anterior shear forces (P = .01), increased valgus moments (P = .03), and decreased knee flexion angles (P = .03) during landings of all 3 stop-jump tasks when fatigued. Fatigue did not significantly affect the peak knee extension moment for male or female athletes. CONCLUSION: Fatigued recreational athletes demonstrate altered motor control strategies, which may increase anterior tibial shear force, strain on the anterior cruciate ligament, and risk of injury for both female and male subjects. CLINIC RELEVANCE: Fatigued athletes may have an increased risk of noncontact anterior cruciate ligament injury.

Effectiveness of a neuromuscular and proprioceptive training program in preventing anterior cruciate ligament injuries in female athletes: 2-year follow-up.

BACKGROUND: Among female athletes it has not been established whether a neuromuscular and proprioceptive sports-specific training program will consistently reduce the incidence of anterior cruciate ligament injuries. PURPOSE: To determine whether a neuromuscular and proprioceptive performance program was effective in decreasing the incidence of anterior cruciate ligament injury within a select population of competitive female youth soccer players. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: In 2000, 1041 female subjects from 52 teams received a sports-specific training intervention in a prospective non-randomized trial. The control group consisted of the remaining 1905 female soccer players from 95 teams participating in the same league who were age and skill matched. In the 2001 season, 844 female athletes from 45 teams were enrolled in the study, with 1913 female athletes (from 112 teams) serving as the age- and skill-matched controls. All subjects were female soccer players between the ages of 14 and 18 and participated in either their traditional warm-up or a sports-specific training intervention before athletic activity over a 2-year period. The intervention consisted of education, stretching, strengthening, plyometrics, and sports-specific agility drills designed to replace the traditional warm-up. RESULTS: During the 2000 season, there was an 88% decrease in anterior cruciate ligament injury in the enrolled subjects compared to the control group. In year 2, during the 2001 season, there was a 74% reduction in anterior cruciate ligament tears in the intervention group compared to the age- and skill-matched controls. CONCLUSION: Using a neuromuscular training program may have a direct benefit in decreasing the number of anterior cruciate ligament injuries in female soccer players.

Immediate effects of a knee brace with a constraint to knee extension on knee kinematics and ground reaction forces in a stop-jump task.

BACKGROUND: A small knee flexion angle in landing tasks was identified as a possible risk factor for noncontact anterior cruciate ligament injuries that are common in sports. HYPOTHESIS: A specially designed knee brace with a constraint to knee extension would significantly increase the knee flexion angle at the landing of athletic tasks preceded with horizontal movement components, such as stop-jump tasks. STUDY DESIGN: Repeated measure design for brace effects. METHODS: Three-dimensional videographic and force plate data were collected for 10 male and 10 female recreational athletes performing a stop-jump task with and without the specially designed brace. Knee flexion angle at landing, maximum knee flexion angle, and peak ground reaction forces during the stance phase of the stop-jump task were determined for each subject with and without the knee brace. RESULTS: The knee brace decreased the knee flexion angle at the landing by 5 degrees for both genders but did not significantly affect the peak ground reaction forces during the landing. CONCLUSIONS: The specially designed knee brace may be a useful device in the prevention and rehabilitation of noncontact anterior cruciate ligament injuries in sports.