Player Psyche and Injury Risk

Many consider injuries as an accepted part of the game. Despite this, coaches and researchers work together to reduce the risk of players sustaining an injury. Much of the focus has been on external factors such as equipment and playing field as well as internal factors such as fitness. As a result, successful advancements have been made in equipment and training routines. However, psychological issues are sometimes overlooked as a risk factor. Players often cope with events outside of soccer. For some players, these stressors can increase their anxiety level, which can increase injury risk. Two recent studies of Swedish youth and professional players show that these psychological issues are important internal factors in increasing injury risk. The authors of the studies also provide some insight into how coaches may play a role in reducing this risk factor.

The first study focused on high school male and female players in Sweden whereas the second study examined professional players from the Swedish Premier leagues. At the beginning of the study, players completed a series of psychological and personality questionnaires designed to identify characteristics of stress, anxiety, daily hassle and coping. Over the course of the season, injuries were recorded by the team’s medical personnel. The researcher then compared the various psychological traits between those athletes sustained an injury during play and those who did not.

The studies showed that a key predictor of injury risk is a concept called “somatic trait anxiety”. This can be described as long-term stress that results in physical changes. That is, athletes who demonstrate somatic stress anxiety are often chronically anxious and may show physical signs ranging from sweaty palms to muscle tension. Daily hassles were also a factor. For the younger players, trust in the coach played a role in predicting injury. Lastly, poor coping skills also raised the risk of injury in the young players but not the professionals. It is likely that upon reaching the professional level, these highly experienced players have developed effective skills needed to cope with anxiety. Taken together, the researchers found that these factors, especially anxiety, daily hassles and poor coping skills, accounted for about 25% of the injuries sustained.

The source of stress and anxiety for the players may stem from a variety of pressures. For the younger athletes, schoolwork and the pressure to succeed academically as well as social relationships with peers can create anxiety in many athletes. In addition the pressures of playing well can mount. Pressure from parents and coaches along with the desire to be “seen” at college showcase events or to be “identified” by regional or national coaches can be great. These pressures often result in the players dealing with what they perceive as a variety of daily hassles such as interactions with family, friends, coaches and teachers, completing homework assignments, studying for exams and balancing social relationship. The net result of this affects the players focus and concentration on the game. It can also alter the athlete’s physical nature which then affects their play.

The result of stress, anxiety and daily hassles can lead to one of two risky scenarios. The first is a loss of concentration and focus on the game. Losing focus during a match can prevent the player from identifying cues and avoiding risky situations such as a blind-side tackle. The second is more aggressive physical play that creates risky encounters such as an overly aggressive tackle or header. In either case, the player is unable to identify and analyze situations that may put him or her as risk of injury.

The authors of the studies do offer some suggestions to minimize injury risk. First, coaches should consider the athlete as a whole person. In addition to fitness and technical abilities, coaches should pay close attention to their players psyche and look for signs of stress and anxiety. Identify those players who seem to be struggling with life events or daily hassles, those who show physical or emotional signs or stress. Perhaps a day off is needed to restore their focus and balance. Second, help players develop effective coping skills to reduce the level of stress and worry. Creating an open atmosphere where athletes can express their worries, feelings and concerns could be a step in that direction. Third, help athletes learn muscle relaxation techniques to reduce the level of physical anxiety. Muscle tension is a common physical response to stress and anxiety. By controlling muscle tension, injury risk may be reduced. The overall goal is to provide the tools and avenues for each player to reduce or deal with their stress, anxiety and daily hassles in a healthy manner.

The take home message from these two studies is that the psychological profile of an athlete is an important risk factor for injury. Be they a youth player or a professional, anxiety and life stress that leads to daily hassles can cause the player to either respond or lose to focus, both of which can increase the chances of sustaining an injury.

References:

Johnson U, Ivarsson A (2011) Psychological predictors of sport injuries among junior soccer players. Scandinavian Journal of Medicine and Science in Sports, 21: 129-136.

Ivarsson A, Johnson U, Podlog L (2012) Psychological predictors of injury occurrence: A prospective investigation of Swedish soccer players. Journal of Sport Rehabilitation, in press.

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Nutrient Intake of Spanish Youth Players

It is clear that a player’s diet can affect his or her performance on the field. A diet that is high in fat and low and carbohydrates can leave a player lethargic and without enough “energy” to compete at a high level. This idea is backed by years of research both in the laboratory and on the playing field. Despite this, players still do not eat a proper diet. In a new study, Researchers at the Universidad CEU San Pablo in Madrid performed a detailed analysis of the dietary habits of youth players. As with previous studies, they found that the diets of these players lacked the optimal amounts of carbohydrates, fats and proteins.

The subjects of the study were young male players (aged 16-21 years) from a junior Spanish First Division club. All were asked to self-record their dietary intake for six consecutive days (a full week, excluding match day). What makes this study unique is the level of detail and precision in the dietary records. Players were given food record questionnaires as well as food-weighing scales. They were then instructed on how to record both the types and precise amounts of foods eaten during the week. They were also instructed not to change their eating habits but to eat the same foods that they normally eat. After the recording week, food records were analyzed by the research group to determine how many calories were consumed and whether those calories came from carbohydrates, fats or proteins.

This group of subjects was clearly fit. The average body fat percentage was 10.5%, with goalkeepers having slightly higher values (11.8%) and fullbacks slightly lower (9.9%). All positions also scored high on the Yo-Yo test of intermittent endurance, with the goalkeeper slightly less fit.

As a group, these players consumed nearly 3000 calories per day (38.5 cal per kg of body weight or 17.5 cal per lb). This did not vary between field positions but the goalkeepers consumed fewer total calories that the other positions. While energy expenditure was not measured, this amount of calories consumed per day is probably below what is needed to replenish the energy expended on a daily basis (>3500 cal per day).

The analysis of dietary components showed that as a group, these players consumed less than the recommended amounts of carbohydrates and more than the recommended amounts of fat. For trained soccer players, it is recommended that 55-65% of total calories come from carbohydrates and less than 25-30% from fat. In this group of players, only 45% of their calories come from carbohydrate and 37% from fat. Protein intake was also slightly higher than recommended, 17% versus 10-15%. Thus, the macronutrient intake (carbohydrates, fats and proteins) was less than ideal.

The researchers also found that 55% of the players’ calories came from cereals, potatoes, meat, poultry, milk and dairy products. Without taking preparation into account (e.g. fried chicken versus baked), these are all solid choices that should be included in the diet. However, the researchers also found that 25% of calories came from oils, biscuits, sweets, sweeteners, and pre-cooked foods. Since these items tend to be high in fat or high in simple sugars, they are not solid choices and should be limited to far less that 25%. What is more troubling is that only 1-2% of the players’ calories came from vegetables. A lack of vegetables in the diet not only reduces carbohydrate intake but also limits vitamin and mineral intake.

The overall conclusion from this study is that the caloric intake of these players is less than needed and the macronutrient intake (carbohydrates, fats and proteins) is less than optimal. This conclusion has been reached by others and highlighted on the SSO (Article 1, Article 2). Clearly players need to improve their diets. How can this be accomplished? The authors of the study suggest that the answer lies in education. Players need to understand how the composition of their diet affects their game, that a diet high in carbohydrates and low in fats yields peak performance.

Players also need to understand the food selection process. This is often overlooked in many educational programs – the concepts are taught but specifics are lacking. Few players realize what types of foods that they eat on a regular basis and many do not understand how to make proper food choices. For example, using the food records take from the Spanish players, an obvious suggestion is to reduce the amount of sweets and precooked meals eaten as well as foods cooked in oil (fried). These should be replaced by increased servings of vegetables (preferably fresh). Not only would this reduce the intake of fats but increase the percentage of carbohydrates in the diet (as well as add vitamins and minerals). The researchers emphasize that such a focus on the selection of specific foods and behaviors should be the focal point with young players.

Coaches can play a unique role in affecting the diets of young players, specifically players in their early teens. By making players be aware of what types of foods should be eaten and which should be avoided, it may be possible to improve their diets in terms of both total calories and the optimal percentages of carbohydrates, fats and proteins. There is little doubt that will improve performance. More importantly, instilling proper nutritional habits early in the player’s life can carry into adulthood and led to a healthy lifestyle. Thus, nutritional education can have both immediate and life-long benefits.

Reference:
Iglesias-Gutierrez E, Garcia A, Garcia-Zapico P, Perez-Landaluce J, Patterson A, Garcia-Roves M (2012) Is there a relationship between the playing position of soccer players and their food and macronutrient intake? Applied Physiology, Nutrition and Metabolism, 37: 225-232.

Further Reading:

The SCIENCE Behind Soccer Nutrition
The SCIENCE Behind Soccer Nutrition: Diet and Training Journal

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Translating Sports Science at The Huffines Institute

A word of thanks to the Huffines Institute for Sports Medicine and Human Performance at Texas A&M University for featuring the Science of Soccer Online during their weekly podcast. The Director of the Institute, Dr. Tim Lightfoot and I discussed the use of the internet and social media as a way to communicate with coaches and athletes. We also talked about some of the stumbling blocks that lead to the “information gap” between researchers and coaches.

The Huffines Institute is part of the Health and Kinesiology Department at Texas A&M. Its mission is “Facilitating research, application and communication between sports scientists, practitioners and the world”. On their website, you will find a wealth of information about sports science and human performance, presented in a variety of practical formats. What is unique about their site is that it is not just scientists discussing the latest findings. The site also contains pieces written by or featuring coaches, trainers and students. Through the use of short articles, video and audio interviews, blogs, Twitter and Facebook, the Huffines Institute is making headway in moving science out of the lab and onto the field.

The links to the Huffines Institute and our podcast are below. Visit their site often. Read and listen to the latest in sport science research.

Huffines Institute Website

Weekly Podcast with The SSO


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Traveling the Information Superhighway

It is estimated that 50-80% of the American public uses the Internet to obtain medical and health information. A single Google search using the term “soccer” returns nearly 850 million sites. Combining soccer with terms like nutrition, training or injury returns more than 10-20 million sites. While many of these sites are duplicates and news articles, it is clear that there is a tremendous amount of information about soccer available on the Internet. This raises a number of important questions. How accurate, reliable and complete is information posted on websites? Are some sites more reliable than others? Given the emergence of the information age, studies of website content are now being published. In general, these studies examine the quality and completeness of information found on various sites. The results are troubling. For the most part, traveling the information superhighway is littered with potholes. However, there are some bright spots along the way.

A 2010 survey asked more than 300 registered fitness professionals about where they obtain information on obesity (1). A large percentage these individuals utilize textbooks, class notes, journals and workshops. However, a significant portion also use the Internet and mass media. Those professionals without degrees in exercise science were more likely to utilize the Internet than those with formal education.

Unfortunately the information that these trainers find is relatively poor. A survey of physical activity sites found that less than 2% are considered accurate and 78% are characterized as having low accuracy (2). The researchers conclude that the quality of physical activity information found on the Internet is “dismal”. As a result, many fitness professionals may be utilizing and promoting inaccurate information about exercise training.

The same can be said for nutritional information found on the Internet. Commercial and sponsored sites could account for 80% of the visits and time spent seeking nutritional information (3). That is, Internet users are more likely to use websites that have a commercial investment and promote their product or service. Of these, only 31% have purely correct information. The worst sites are commercial site that contain articles written by “expert” journalists, professionals who write “scientific” articles but have little or no formal training in the medical or health field (3). Articles are often written in an attempt to entice readers to purchase a product rather that to educate them. News sites or sites featuring “news” articles about nutrition also provide questionable information. The investigators specifically mention sites such as Yahoo and MSN as publishing inaccurate or misleading articles.

While accuracy is a key problem, omission also raises concern. That is, the information is often incomplete and unable to answer the questions raised by readers. An example of this is found in a recent survey of sites focused on asthma (4). Researchers found that while many sites contain accurate information, less than 9% provide comprehensive information on the educational concepts provided by the National Heart, Lung and Blood Institute. That is, critical information was omitted. A second potential problem found is the owner of the website. Sponsored sites (those with a commercial interest) or those owned by a single individual are the least accurate and least comprehensive. Sites sponsored by governmental organizations (such as the National Institutes of Health) and professional organizations (like the American Lung Association) provide the most accurate and most complete information.

The problems obtaining accurate and complete information from the Internet are highlighted in a 2010 study (5). The investigators performed Google searches to answer five common child-health related questions. These questions ranged from MMR vaccines to infant sleeping positions. They entered search terms for each question then analyzed the first 500 sites that appeared on the search results.

Of the websites surveyed, 39% gave correct information, 11% gave incorrect information and 49% did not answer the question at all. Governmental sites (those ending in .gov) tended to be the most accurate. Educational sites (.edu) were the second most reliable. News sites provide correct information slightly more than half of the time and none of the sponsored sites surveyed provide accurate information. In particular, sponsored sites suffer from glaring conflicts of interest with many offering products or services that did not conform to sound medical advice.

From these studies, four trends emerge regarding health, nutrition and exercise information posted on the World Wide Web. First, be wary - many websites do not provide complete or accurate information about health conditions or treatments. Many are inaccurate and most suffer from a problem of omission. That is, the lack of information is as problematic as accuracy. Second, articles authored media experts can be unreliable in terms of accuracy and completeness. Most lay authors are not trained in exercise science, nutrition or injury management biology. Complex health issues such as these should be addressed by someone who is an expert in the field rather than someone who is an expert writer. Third, commercial and sponsored websites are rife with conflicts of interest. The problem here is that it is very difficult to determine if the information provided is accurate or if it is designed to entice the reader to purchase a product or service. Many times, misleading information can appear to be sound advice. Sponsored sites should not be used for advice on training because their primary goal is commerce, not necessarily improving performance.

Is there hope? How can one go about finding credible and complete information about issues like soccer, diet, training and injury prevention? The most reliable sites are governmental and educational (typically ending in .gov or .edu). A number of universities have sports science centers that regularly post well-researched information about improving performance and avoiding injury. For example, the Soccer and Health Research Project at the University of Copenhagen has an excellent site that presents soccer-specific information. Professional organizations (not advocacy groups) are also provide sound web-based information. The American College of Sports Medicine’s Access Public Information website provides a number of excellent resources that coaches and players can use. Their sites provide accurate information and the information provided is thorough and complete. The articles are either written by or thoroughly reviewed by experts in the field rather than a copy editor. Likewise, FIFA and the FIFA FMARC group provide excellent information. The advantage of these sites is that they do not suffer from conflicts of interest. Their goal is to provide unbiased, educational information, not to sell a product or sway an opinion.

It is also important be skeptical and look for multiple points of view. It is also important to ask some simple questions when reading information posted online. First, what is the goal of the article? Is the objective to promote a product or to educate the reader? Second, ask who is writing the article? Is the author trained is the topic? Expert coaches are excellent resources for coaching information such as tactical formations, motivating players, etc. However, they may not be the best experts on issues such as supplement use or injury prevention. Likewise, scientists can explain what research says about diet, training and injuries but they may lack context or a sense of how research findings fit into the game. Often considering both a coach’s and researcher’s points of view give the best answer. Lastly, consider what the information is based on. Is the article simply the author’s opinion or is the info based on credible research? Opinions can be biased and sometimes wrong. Look for articles that provide references or list additional resources.

The bottom line, surfing the web for information about soccer, diet and exercise is a case of “reader beware”. The search for accurate information can be difficult. It is a process that must be carried out with care. However, by looking in the right places and asking a few questions, information that is accurate and complete as well as useful to the player and coach can be found in the World Wide Web.

REFERENCES

Stacey D, Hopkins M, Adamo KB, Schorr R, Prud’homme D (2010) Knowledge translation to fitness trainers: A systematic review. Implementation Science, 5: 28.

Bonnar-Kidd KK, Black DR, Mattson M, Coster D (2009) Online physical activity information: Will typical users find quality information. Health Communication, 24: 165-175.

Ostry A, Young ML, Hughes M (2007) The quality of nutritional information available on popular websites: a content analysis. Health Education Research, 23: 648-655.

Meadows-Oliver M, Banasiak NC (2010) Accuracy of asthma information on the world wide web. Journal for Specialists in Pediatric Nursing, 15: 211-216.

Scullard P, Peacock C, Davies P (2010) Googling children’s health: reliability of medical advice on the internet. Archives of Disease in Childhood. 95: 580-582.

NOTE

This article was extracted and modified from the new book, Questioning Research, recently published by Jay Williams.

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More Evidence Supporting Injury Prevention Training: Cost Effectiveness

Over the past years, the SSO has posted several articles about neuromuscular training programs designed to reduce the risk of injury. We have been especially concerned about preventing non-contact injuries to the anterior cruciate ligament (ACL) in female players. An ACL tear can be personally devastating to the athlete and result in significant financial costs. Fortunately, the overwhelming consensus is that neuromuscular training programs are highly effective in reducing risk factors as well as occurrence of ACL injuries. A new study by researchers at Northwestern University and the Children’s Memorial Hospital in Chicago trained urban-area, high school basketball and soccer coaches in using a neuromuscular warm-up program. They found teams that using the program substantially reduced injuries to both the knee and ankle. What is unique about this study is that for a small financial investment in training coaches, a large return in injury prevention was realized.

The study was conducted in the Chicago public school system. This is an urban school district that enrolls predominantly low-income students. This is an important aspect of the study as the investigators point out that these schools and athletic teams often have erratic practice conditions (times, equipment and facilities), no athletic trainers on staff and access to health care is lacking for most of the players. Given this, it is clear that the athletes in this school system could benefit greatly from a program designed to reduce the rate of injuries.

All of the 258 head girl’s soccer and basketball coaches in the school district (varsity, junior varsity, sophomore and freshman teams) were contacted and asked to participate in the study. Of those, 95 coaches (37%) representing 111 teams and almost 1500 athletes agreed to participate. The coaches were then randomly divided into control and intervention groups.

The coaches in the intervention group attended a 2-hour training session where they were instructed on how to use the 20-minute neuromuscular warm-up program. A similar program mentioned on the SSO is the FIFA 11+. They were taught the specific exercise that should be used before each practice as well as before games. They were also taught how to distinguish between correct and incorrect form and how to use verbal cues to encourage proper form. Each coach also received a DVD with narrated videos of the exercises, a laminated card for use on the field or court and printed educational materials about knee injuries and neuromuscular training. The compliance rate was very high. The coaches in the intervention group reported that they used the program at 80% of their practices.

The control group coaches received no training in injury prevention and simply went about coaching their teams as done previously.

All of the coaches were asked to complete weekly injury reports. In addition, the researchers met with the coaches and athletes to discuss injuries and to determine the type of injury and how the injury occurred. The investigators were interested in non-contact knee and ankle injuries and whether they were acute (due to a single event) or gradual-onset (developed over the course of several days). No additional information or encouragement to use the warm-up program was provided to the coaches of the intervention group.

The effectiveness of the warm-up program was impressive. The intervention group experienced a 65% reduction in gradual-onset injuries a 56% reduction in acute injuries. Ankle injuries were reduced by 66% in the intervention group. In addition, all athletes sustaining an ACL injury that required surgery were in the control group.

Overall, a 20-minute neuromuscular warm-up program, used prior to training reduced the rate of non-contact knee and ankle injuries by almost two-thirds.

An interesting aspect of the study is the cost effectiveness of the program. The investigators report that the cost of training each coach and providing him/her with a DVD and printed materials was $80 per coach ($4 for each soccer player). The return on this investment was a substantial reduction in medical costs used to treat knee and ankle injuries. For example, using data for ACL tears, for every 11 soccer coaches trained, one ACL injury could be prevented. To put that into perspective, a 6-team high school league could invest $960 towards training 6 varsity and 6 junior varsity coaches in neuromuscular injury prevention (12 X $80). That investment could result in one less torn ACL during the upcoming season. That doesn’t seem like a big impact, but given the costs of ACL surgery and rehabilitation, it translates into a savings of $17,000 to $25,000 in medical costs. Add to that, the personal costs associated with recovery and the increased risk of developing knee osteoarthritis later in life, the total cost savings could be considerable.

It should also be pointed out that this study examined injuries during a single school year or a single season. It seems reasonable that coaches who are trained in the warm-up program would continue to use it during the following seasons. Thus, the cost effectiveness becomes even greater. For example, over a four-year period, the medical cost savings on ACL ruptures alone could potentially approach $100,000. If the costs of other injuries such as ankle and knee sprains are considered, there could be a tremendous return for less than $1000 invested in prevention.

This notion can also be extended to local soccer clubs. Taking into account both recreational and competitive programs, a large club could easily enroll 100-150 high school aged girls. Thus, for a small financial investment in training coaches on injury prevention, there is the potential of lowering knee and ankle injuries by nearly two-thirds as well as reducing health care costs for a number of young female athletes.

In a follow-up commentary, clinicians at the University of Wisconsin at Madison point out that there has been a large increase in the number of for-profit sports performance-training programs available to young athletes. These programs typically emphasize performance but the types of exercises used (strengthening, balance, plyometrics flexibility and agility) mimic the components of a comprehensive neuromuscular injury prevention program. The costs of these programs can range from $100-200 per month or $20-50 per session. This is clearly out of reach for low-income families and young athletes such as those in the Chicago public school system. Thus, a low-cost, school-based training program could provide athletes from low-income families much needed access to injury prevention. Recall that athletes in urban school systems may not have access to athletic trainers. Also, financial situation may prevent them from seeking proper evaluation and treatment by a medical professional. Given this, it is easy to see the potential benefit of such a program in such a population of athletes cannot be underestimated.

The authors of the commentary also point out that more coaches and administrators might be more interested in injury prevention if the program was repackaged as a sport enhancement program. After all, “we play to win the game” and coaches are often more keen to work on sport-specific skills than injury prevention. There is scientific support for this marketing idea. Multiple studies show that neuromuscular training designed to reduce injury risk also improves performance in soccer players as well as volleyball, basketball and tennis athletes. Thus, emphasizing that a neuromuscular training program could improve match performance might entice more coaches to make it a part of their regular training session.

The evidence continues to mount. Neuromuscular training programs are successful in reducing the risk of knee and ankle injuries. In addition, they have the added benefit of being both cost-effective and improving performance in the field or on the court.

REFERENCES

LaBella CR, Huxford MR, Grissom J, Kim K-Y, Peng J, Christoffel KK (2011) Effect of neuromuscular warm-up on injuries in female soccer and basketball athletes in urban public high schools. Archives of Pediatric and Adolescent Medicine, 165, 1033-1040.

Brooks MA, McGuine TA (2011) Translating cost-effective injury prevention research into sustainable change on the playing field. The youth injury epidemic. Archives of Pediatric and Adolescent Medicine, 165, 1050-1049.

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What Separates the Professionals from the Amateurs?

Talent identification in youth soccer is an ongoing debate among the coaching community. What characteristics separate those players who will succeed at the next level from those who will struggle? Factors such as physical size, speed, fitness and technical ability are all important attributes of success. But how important? Many coaches also consider the ability to “read the game” as a critical trait. That is, “off-the-ball” skills are needed to be successful. Researchers at the University of Groningen in the Netherlands looked at this later concept as a predictor of future success. They found that the tactical ability of “positioning and deciding” is a key factor determining which players will reach the professional level and those who will not.

The study focused on elite youth players from Dutch premier league clubs who trained with their club’s talent development program. The authors note that the players’ level of performance placed them in the top 0.5% of all other players at their age. Bottom line - these were highly talented youth players preparing to play that the professional level.

At 17-18 years of age, the players were given the Tactical Skills Inventory for Sports (TACSIS) survey. This survey asks players about their knowledge of the game as well as their confidence in executing specific tactical actions. The goal is to determine their knowledge, decision-making and execution abilities performed during a match.

The players were later tracked into adulthood. At that point, they were divided into two groups based on their adult performance – those who played on a professional team (Premier or national league) and those who played for an amateur club.

The investigators found that the knowledge of the game did not differ between the players who reached the professional level and those who did not. However, those players who scored highest in the area of “positioning and deciding” as a youth player were almost seven times more likely to reach the professional level that those who scored lowest. This was especially true for the midfielders. Even though all of the players had more than 10 years of training and were some of the most talented players in the Netherlands, half of them did not reach the professional level. What separated the professional from the armatures was the ability to make correct decisions and position themselves correctly on the field.

The authors argue that tactical skills involve both the ability to decide the right action as well as the ability to execute it. That is, being able to make the right decision does not always translate into being able to carry out the right maneuver. This component is what the investigators called “positioning and deciding” and what they found to be highly important for success. For example, players may all understand what to do strategically when shifting from a 4-4-2 to a 3-4-3 system. The may also have the technical skills to execute it. However, it is the ability to put that strategy into play during the course of the match that separates the truly talented players. Positioning oneself in the right place making the right decision is essential. That is, seeing the making the correct run or playing the correct ball separates the professionals from the amateurs. In fact, the authors suggest that it may be impossible for midfielders who lack this ability to ever succeed as a professional player.

This study focused on players in the Dutch youth system that trained at the highest level. So, it is not clear if the results are applicable for identifying success at other levels. For example, does positioning and deciding ability determine which US youth players will be successful at the college level? This study suggests it might but more research is needed. Nevertheless the investigators stress that coaches should pay attention to the concept of positioning and deciding when evaluating and training young players. Given that this characteristic impacts future success, fostering that ability is essential in developing young players into successful adults.

References

Kannekens R, Elfernik-Gemser MT, Visscher C (2011) Positioning and deciding: key factors for talent development in soccer. Scandinavian Journal of Medicine and Science in Sports, 21: 846-852.

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The Diets of Female Players Are Also Left Wanting

A sound nutritional strategy is a critical component of any athletes training program. Unfortunately, this is one aspect of a player’s game that is often overlooked. Over the years, research has examined the diets of both youth and professional male players (Click here for a recent SSO article). However, very few studies have focused on female athletes. Female players have unique influences on nutritional choices compared males. Increased risk of iron depletion, a need for calcium and vitamin D to support bone heath as well as social pressures to maintain a low body weight can all affect diet their choices. A recent study published in the International Journal of Sports Nutrition and Exercise Metabolism found that similar to their male counterparts, female diets are lacking in key components that could affect both health and performance on the field.

The study was conducted by researchers at the University of Victoria in British Columbia, Canada. It focused on junior female players who play at the highest regional competitive level in Canada. The ages of the players ranged from 14 to 17 years and they trained an average of 12 hours per week.

The investigators asked the players to record their food choices during four different days – two training days, one competition day and one rest day. All players and their parents attended a seminar to insure that they understood how to accurately record the types of foods eaten and the serving sizes. The diets were analyzed by the researchers to determine total calories eaten as well as the amounts of vitamins and minerals. The researchers also estimated the players’ energy expenditure on those same days.

The results are quite interesting. The average amount of foods and beverages consumed (total energy intake) amounted to slightly more than 2,000 calories per day. This was less that the estimated amount of energy expended, 2,546 calories per day. Thus, these players are not consuming enough calories to match the demands of training and other daily activities. They are left with a caloric deficit of more than 500 calories per day. It is important to point out that the players in the study are not considered over weight or overly lean. Thus, the caloric deficit recorded during the study period is probably being gained on other days so that weight is maintained. However, over the long-term, a daily reduction in energy intake (especially in lean players) can add up and eventually affect performance.

More than 50% of the players consumed fewer carbohydrates than recommended for female athletes. Fiber intake was very low with only one-quarter of those studied eating the recommended amounts. Fortunately, fat and protein intakes were within the normal range, with only a few players eating too few proteins or too many fats. Thus, the caloric deficit mentioned above probably results from inadequate carbohydrate intake.

As for vitamins and minerals, not a single player consumed the recommended amounts of vitamins D and E. Folate and calcium intake was also remarkably low with only one-third taking in the recommended amounts. Several players’ diets were also lacking in zinc, magnesium and vitamin A. On the other hand, a large number exceeded the recommended amounts of the B vitamins, iron and copper.

The authors of the study conclude that the female players’ diets are lacking in key components needed to fuel performance as well as support proper growth and development. As for performance, the total calories consumed do not match the energy expended. Also, the low amount of carbohydrates eaten may leave players with reduced muscle glycogen levels. Given that muscle glycogen depletion has a dramatic affect on performance, a diet lacking carbohydrates can hinder performance. This is especially true during the later stages of training or match play.

They also raise concern that the low intakes of vitamin D and calcium can impact bone growth. Both of these are essential for proper bone health. Low intakes of these components could lead to lower bone density and raise the risk of stress fractures. Vitamin E is a powerful antioxidant that is essential to preventing cellular damage aiding repair.

What can be done to correct the problems outlined in this study? The optimal strategy to counter these findings is to focus on a proper diet with adequate carbohydrates, vitamins and minerals. Lean meats, fresh fruits and vegetables as well as whole grain breads and pastas are the best approach. A daily multivitamin supplement can help insure that recommended amounts of vitamins and minerals are taken in. However, eating a proper diet can supply these key components.

The researchers also suggest that athletes should be taught the importance of a healthy diet, one that can meet the unique demands of soccer. Coaches often assume that players understand what types of foods to eat and when to eat them. However, that is often not the case (as suggested by this study). Because diet and performance are integrally linked, players should also closely monitor their daily nutritional habits. They can then compare the types of foods eaten with their performance on the pitch. By understanding how diet affects performance, players can begin to make both wise and healthy nutritional choices. Instilling habits that improve athletic performance will also set in place a health dietary routine that can last a lifetime.

Reference

Gibson JC, Stuart-Hill L, Martin S, Gaul C (2011) Nutritional status of junior elite Canadian female soccer athletes. International Journal of Sports Nutrition and Exercise Metabolism. 21: 507-514.

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Does the Game Improve Fitness?

There is little argument that peak performance in soccer requires a high level of fitness. Soccer fitness includes a variety of components from cardiovascular fitness, strength, power and agility. How to best improve these components is a question that is debated among coaches and trainers. On the Science of Soccer Online, we have discussed the value of strength training (weight lifting), sprint training, balance and agility training and small-sided games as ways to improve performance during a match. All have their benefits and can lead to gains in one or more soccer fitness components. But what about full-sided, competitive matches? Competition imposes a considerable “physiological load” on the athlete. But is it great enough to affect fitness? Recent research suggests that the answer is yes, playing competitive matches on a weekly basis can positively benefit strength, speed and agility.

Two recent studies examined the relationship between match play and fitness. The first study, performed at the University of Porto (Portugal), examined various marker of fitness over the course of a professional season (1-2 matches per week). Players were tested before the start of the season, at mid-season and at the end of the season. The researcher found that short spring speed (5 meters, a measure of acceleration) was related to the number of minutes played. More minutes played lead to greater improvements in speed. Also, changes in quadriceps and hamstring muscle strength were correlated with the number of minutes played during the season – strength improved in players who played the greatest number of minutes. This was particularly true for hamstring strength.

The second study, carried out by researcher at the University of Zagreb (Croatia), compared changes in fitness markers over the course of the season between starters and non-starters. The starters played more than 1000 minutes in official matches (the equivalent of 11 90-min matches) while the non-starters played fewer minutes. Over the course of the season, the starters were able to maintain and improve their agility and overall power performance more so than the reserves. Tests of sprinting, jumping and kicking the ball were all improved by match play.

A 90 minute match may require players to cover as much as 10 kilometers (6.2 miles). This includes high-intensity running every 70 seconds, up to 20 sprints, as well as many changes in direction. While the required efforts vary between playing position, it is clear that the physical demands of a match are considerable. Thus, it is not surprising that those players who play the most minutes enjoy the greater benefit to fitness. A greater physiological lead translates into improved fitness.

It should be pointed out that both studies used highly trained, adult players as subjects. So, it is possible that younger players may respond differently to matches. In fact, the distance covered, the number of high-intensity sprints performed and the number of jumps, stops and turns are all less during a youth game compared to a professional match. Liberal substitution rules and shorter matches can also affect the amount of time players spend on the field. Thus the impact of playing weekly matches on a young player’s fitness might be smaller than on an adult’s. A 2008 study showed that young starting players (10-14y) improved various fitness components over the course of a season whereas reserve players did not.  While this might be due to growth, more match play may have been responsible. Therefore, given this and the demands of a youth match, it seems reasonable to suggest that playing competitive matches would also improve or maintain several fitness components in young players.

These studies suggest that over the course of a season, match play can improve (or maintain) various components of soccer fitness. Specifically, strength, agility and speed are all positively affected by competitive games. As for training, the authors also suggest that coaches should consider including completive training matches for those players whose playing time may be limited (non-starters or reserves). In addition, these types of matches might also be considered during weeks when the team is not scheduled to play a competitive, weekend match. This would provide players with the training stimulus that is missed during the weekend match.

References:

Gravina L, Gil SM, Ruiz F, Zubero J, Gil J, Irazusta J (2008) Anthropometric and physiological differences between first team and reserve soccer players aged 10-14 years at the beginning and end of the season. J Strength Cond Res, 22: 1308-1314.

Silva JR, Magalhães JF, Ascensão AA, Oliveira EM, Seabra AF, Rebelo AN (2011) Individual match playing time during the season affects fitness-related parameters of male professional soccer players. J Strength Cond Res, DOI: 10.1519/JSC.0b013e31820da078

Sporis G, Jovanovic M, Omrcen D, Matkovic B (2011) Can the official soccer game be considered the most important contribution to player's physical fitness level?, J Sports Med Phys Fitness, 51: 374-380.

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Preventing Hamstring Injuries With Eccentric Training

As mentioned earlier on this site, hamstring injuries are one of the most common injuries in soccer. Research says that they account for about 1 in 7 injuries. Depending on the severity of the injury, recovery from a hamstring pull can take from a few days to several months. The re-injury rate is also high with about 25% of players suffering a recurrent injury. Given this, there is a clear need to reduce the rate of hamstring strains. The hamstring muscles are often injured while running or sprinting, during the late swing phase of the stride. During that period, the hamstring muscles generate force to slow hip flexion and knee extension while they are being stretched. That is, are undergoing an eccentric contraction. Some speculate that by increasing eccentric strength of the hamstring muscles, injuries might be prevented. A new study performed at the University of Copenhagen examined this idea. The researchers show that a program of eccentric hamstring training can dramatically reduce the rate of injuries.

The Danish researchers carried out a very large-scale study. Fifty teams playing in the top five men’s Danish soccer divisions participated. The teams were first clustered based on playing level (division) and geographical location. Then 23 teams were assigned to the treatment group and 27 teams to the control group. In all, 461 players received hamstring injury prevention training and 481 served as control subjects.

The training program consisted of “Nordic hamstring exercises”. To do this exercise, the player assumes a kneeling position with his trunk upright and back straight. A second player holds his feet securely on the ground. The player then leans forward and resists a falling motion using his hamstring muscles for as long as possible. This maximizes the loading on the hamstring muscles. He uses his hands/arms to cushion the fall, lets his chest touch the ground then uses the hands to push himself back to the starting position. This exercise is also referred to as “Russian curls”.

The program was carried out for 10 weeks. During week one, players performed two sets of five repetitions, once during the week. Training progressed so that during weeks 5-6 they were performing 3 sets of 12-10-8 reps, three times per week. After the 10 week program, hamstrings exercises were performed only once each week (3 sets of 12-10-8 reps).

The program was started after the start of the second half of the teams’ season (January) and continued until the end of the fall season later that year (December). It was not conducted during the 2-3 week vacation prior to the start of fall preseason training. The control group did not undergo any hamstring training except for traditional static and dynamic stretching exercises.

The results, recorded over the course of the year were impressive. For the entire group of players, the hamstring injury rate for the training group was 3.8, compared to 13.1 for the control group (normalized values based on the number of players and length of each team’s season). That is a 71% decrease in the rate of injury using a simple program of Nordic hamstring training. For new injuries, eccentric training reduced the injury rate by more than 60%. For recurrent injuries, the rate was lowered by about 85%!

The researchers also found that the greatest number of injuries in both the training and control groups occurred during the preseason period prior to the start of the fall season. Interestingly, this was the period after the 2-3 week break from regular training and the absence of the hamstring exercises.

These results clearly show that the risk of hamstring pulls can be greatly reduced using an eccentric training program involving the Nordic hamstring exercises.

Most hamstring injuries occur when the knee is being extended and hip flexed. This can happen during sprinting and reaching for a ball. Under either of these conditions, movements of the knee and hip are being “braked” by contraction of the hamstring muscles. Thus, they are undergoing an eccentric or lengthening contraction. The results of this study show that the force these muscles exert during these eccentric contractions may hold the key to preventing strains. By increasing eccentric strength, damage to the muscle as it is contracting and being stretched may be prevented.

Nordic hamstring exercises are also a key component of ACL injury prevention programs. Increasing strength of the hamstring muscles helps stabilized the knee by providing “backward” forces on the lower leg (tibia). They protect the ACL from being stretched and ruptured as the quadriceps muscles contract and pull the tibia forward and twist it. Given this, eccentric training of the hamstrings may offer players a two-for-one - prevention of both hamstring pulls and ACL injuries.

The bottom line, eccentric hamstring training can be very beneficial for the players in reducing the risk of hamstring pulls. The Nordic exercises are simple, require no additional equipment and can be performed in a very short period of time. Low cost with a high payoff.

Reference:

Petersen J, Thorberg K, Nielson MB, Budtz-Jørgensen E, Hölmich P (2011) Preventive effect of eccentric training on acute hamstring injuries in men’s soccer. A cluster-randomized controlled trial. American Journal of Sports Medicine, DOI: 10.1177/0363546511419227.

Note: Nearly a year ago, we reported a study that showed a similar reduction in hamstring injuries using a balance training program. Perhaps both strength and neuromuscular control of the hamstrings are important in preventing injuries.


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How Fast Can Players Run? How Fast Do They Run?

High-speed running is an integral part of a soccer match. As such, a player’s sprint speed is considered as critical to success. Players are often tested and short sprint times are recorded. Team and positional selections may then be made by picking the fastest players. However, it is not clear how raw sprint speed translates to sprinting during a match. Do faster players use that speed by sprinting at maximal velocity? Do slower players compensate for a lack of raw speed by running at higher percentages of their maximal? Lastly, do the match sprint characteristics of players vary by playing position? Researchers at the Academy for Sports Excellence in Doha, Qatar provide an answer these questions. They found that sprint speed is an important component of a match and that some players do indeed take advantage of that ability.

The study recorded and compared sprint speeds during sprint tests and during match play. The subjects were 16-17 year old members of a high performance academy team Maximal sprint speed was determined as the fastest 10m split time of a 40m sprint. After sprint testing, wide midfield players and central defenders were grouped as the fastest and slowest for their position. A portable GPS system was then used to record player movements during a match and to determine match speed.

The investigators found that the fastest players on the team reached higher absolute running speeds during the match than the slowest players. This was the case regardless of playing position. As for the wide midfielders, both the fastest and slowest players achieved peak match speeds that were about 90% of maximal. Thus, the slower players did not compensate for their lack of foot-speed by running at a higher relative velocity (that is, a higher percentage of their maximal). This may be due to the fact that both run at such a high percentage of maximal. Also, running at greater than 90% of maximal may adversely affect other movements (cutting and stopping) or limit soccer skills such as receiving the ball or shooting.

As for central defenders, the fastest players reached peak sprint speeds during the match of about 84% of maximal. The slower defenders however, compensated for their lack of speed by sprinting at relatively higher velocities, around 89% of maximal.

When comparing the two positions, the fastest midfielders and fastest central defenders had almost identical maximal sprint speeds. However, the midfielders ran at a higher percentage of their maximum. Perhaps the space provided for outside midfielders allows them to reach higher speeds. However, slower central defenders were able to achieve high relative match speeds than the faster defenders. The investigators suggest that for successful central defenders, a “speed threshold” is needed. That is, a certain pace is required for optimal performance and that faster players can reach this pace at a lower percentage of their maximal speed. On the other hand, no such threshold seems to exist for wide midfielders. They are less likely to restrain their speed during play. That is, midfielders run at ~90% of maximal regardless of their maximal ability.

The authors conclude that high relative running speeds are reached during a match (~90% of maximal). Acceleration of the first step is traditionally seen a critical to performance. This study adds to that by stressing the importance of absolute sprint speed as well. As such, coaches should emphasize development of both acceleration (10m) and peak speed (>30m). Drills that include maximal 30-60m sprints as well as other training strategies such as plyometrics and weight training should be used to develop maximal running speed.

Reference:

Mendez-Villanueva A, Buchheit M, Simpson B, Peltola E, Bourdon P (2011) Does on-field sprinting performance in young soccer players depend on how fast they can run or how fast they do run? Journal of Strength and Conditioning Research, DOI: 10.1519/JSC.0b013e318201c281 (e-published ahead of print).

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