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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The Placebo Effect and Performance

In the 2006 book Harry Potter and the Half Blood Prince, Ron Weasly was struggling with low self-confidence. Harry then pretends to give Ron felix felicis, a potion that makes one lucky. Believing that he has taken in a dose of liquid luck, Ron performs brilliantly in the day’s Quidditch match. This is a classic example of a placebo effect, an improvement in performance due to expectations or beliefs rather than to biology. In fictional tales (movies and books), placebos are often used to help characters win the day. Could the placebo effect actually impact a player’s performance during a soccer match? Research suggests yes, the placebo effect may be beneficial to sports performance. Also, the use of a "verbal placebo" may already be commonplace among coaches.

The use of placebos is a hotly debated issue in the field of medicine and pain management. Two recent research reviews highlight the effect placebo medications can have on a chronic pain sufferer’s perception of pain (Benedetti, 2011; Pollo et al, 2011). Giving some patients a placebo pill while telling them that it is a drug designed to reduce pain can reduce their pain perception. That is, the patient feels better even though he received no medication. The mere expectation of a positive effect actually elicited one. This concept is called placebo analgesia – reducing pain using a placebo. Clinicians are currently debating the ethics of using deception to reduce the symptoms of a disease. Some argue that it should not be done. Others argue that non-pharmacological treatments for pain management are preferable to drug therapy.

Placebo effects are thought to be “all in your head”. Both articles however, discuss several biological effects that placebos can exert. Brain chemicals, stress hormones as well as the immune system can be affected by the power of suggestion. Placebo effect may be more complex than a simple psychological phenomenon.

As for athletics, the placebo effect can also lead to improved physical performance. For example, one study showed that when subjects were told that they were given a caffeine supplement but were actually given a sugar pill, strength performance improved (Pollo et al., 2008). Another showed that endurance performance was improved when cyclists were told they were provided a carbohydrate supplement during exercise but were actually drinking a placebo  beverage(Clark et al., 2000). In both cases, the athletes were fully aware of how the substances might affect performance. Thus, the expectation that a substance will improve performance actually benefits the athlete.

It should be pointed out that research into placebos and exercise performance is somewhat inconsistent. Not all studies show a clear placebo effect in all subjects. It appears that some are more susceptible to the power of suggestion than are others. Also, the placebo effect may be stronger in some types of activities that others. Nevertheless, there is evidence that the use of placebos may benefit the athlete as demonstrated by Ron Weasly’s match performance.

The discussion on placebo medication, pain and performance is provided to illustrate a point. There is a powerful link between the brain and the body. It is not meant as an endorsement of “performance enhancing” substances. It cannot be emphasized strongly enough – providing young athletes with drugs or even placebo drugs is not an appropriate way to improve performance. No coach, parent or fellow athlete should provide a player any substance (such as caffeine) with the suggestion that it will improve performance. Fostering a dependency on pharmaceuticals or other substances, whether real of imagined, is well beyond the limits of ethical behavior. And, the long-term effects on the athlete’s health can be dangerous.

An alternative to a placebo substance is what researchers call a “verbal placebo”. Many coaches already use the verbal placebo effect to improve their team’s performance. Teams are often faced with a match against a far superior opponent. On paper, there is little hope that the underdog team can prevail. In the days leading up to the match, coaches try to build confidence in their players, individually and as a team. They spend hours trying to build self-efficacy. That is, the players’ belief that they have the skills to compete with and defeat a more talented opponent. Building self-efficacy is simply instilling an expectation that the team can compete without actually improving their skills. In effect, they are trying to elicit a placebo effect.  Coaches are trying to get the team to “play over their heads” and achieve an expectation that, on paper, may not be possible. In essence, the coach is using a verbal placebo to enhance performance.

There is a scientific basis for verbal placebos affecting performance. In an interesting study of naval cadets, researchers experimentally improved self-efficacy by convincing the sailors that they would not experience seasickness on their maiden voyage and if they did, it would not affect performance (Eden & Zuk, 1995). At the end of the cruise, the treated cadets experienced less seasickness and showed better performance than untreated, control sailors. Thus verbally improving self-efficacy prevented seasickness and its adverse effects. To further emphasize that point, a study on exercise training, showed that emphasizing the goals and expected outcomes of the training program resulted in those outcomes being achieved (Desharnias et al. 1993).

Building self-confidence and self-efficacy is a cornerstone of coaching. Research shows that these concepts are integral components of peak performance (Vealey, 2009; Zinsser et al., 1998). Recovering lost confidence after an injury or surgery is also critical in helping the player regain his or her playing form. The mind is a powerful organ. While most training sessions are spent on fitness, technical skills and technical approaches, it seems that training the mind is equally important. To achieve peak performance, superior abilities should be matched with self-confidence.

References:

Benedetti F (2011) Is there a place for placebo analgesia in everyday clinical practice? Pain Management, 1: 211-212.

Clark VR, Hopkins WG, Hawley JA, Burke LM (2000) Placebo effect of carbohydrate feedings during a 40-km cycling time trial. Medicine and Science in Sports and Exercise, 32: 1642-1647.

Desharnias R, John J, Cote C, Levesque L, Godin G (1983) Aerobic exercise and the placebo effect: A controlled study. Psychosomatic Medicine, 55: 149-154.

Eden D, Zuk Y (1995) Seasickness as a self-fulfilling prophecy: Raising self-efficacy to boost performance at sea. Journal of Applied Psychology, 5: 628-635.

Pollo A, Carlino E, Benedetti (2008) The top-down influence of ergogenic placebos on muscle work and fatigue. European Journal of Neuroscience. 28: 379-388.

Pollo A, Carlino E, Benedetti (2011) Placebo mechanisms across different conditions: from the clinical setting to physical performance. Philosophical Transactions of the Royal Society B, 366: 1790-1798.

Vealey, RS (2009) Confidence in Sport. In: Sport Psychology , Ed: BW Brewer), Wiley-Blackwell, Oxford, UK. doi: 10.1002/9781444303650.ch5

Zinsser, N., Bunker, L., & Williams, J. M. (1998). Cognitive techniques for building confidence and enhancing performance. In: Applied Sport Psychology: Personal Growth to Peak Performance, Ed: JM Williams, pp. 270-295. Mountain View,CA: Mayfield.

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Can Pomegranate Juice Improve Soccer Performance?

Pomegranates have been described as the new “super fruit”. Their juice contains high levels of polyphenols, which have powerful antioxidant effects. It is also high in vitamins A, C and E, high in folic acid and potassium. Drinking pomegranate juice has been linked to several health benefits including reduced risk of cancer, lowered blood pressure and improved blood cholesterol. Given the health benefits of pomegranate juice it seems likely to ask the question, will pomegranate juice improve exercise performance? For some time, scientists have suggested that polyphenols may aid in recovery from intense exercise. Researchers at the University of Texas recently completed a pair of studies designed to determine if pomegranate juice affects muscle strength and soreness during recovery from intense exercise. Their findings suggestthat the juice may have some small effect but they also raise several questions.

The two studies, funded by the POM Wonderful company (producers of PomX), focused on the recovery of muscle strength and soreness after intense, strenuous exercise. The design was a bit different than other supplement studies. Instead of providing the treatment only after exercise, the researchers gave the pomegranate juice well in advance of the exercise bout and continued through the recovery period.

In the first study, untrained subjects drank 500 ml (~2 cups) of either pomegranate juice or a placebo drink for five days prior to the intense exercise bout. They continued consuming the juice for the remainder of the experiment (four more days). On day five, baseline measurements of strength and soreness were measured. After baseline measurements, subjects performed a series of eccentric or lengthening contractions with the elbow flexor muscles (biceps muscle). This “negative rep” protocol is traditionally used as a high-intensity exercise bout to induce both muscle fatigue and delayed onset muscle soreness. Immediately after exercise and over the next four days, strength and soreness measurements were repeated.

Under both conditions, muscle force declined by about 30% immediately after exercise. The following day, these untrained subjects regained some strength and force steadily improved over the following days. The pomegranate juice had no effects on strength after exercise but did lead to small improvements on days two and three. As for soreness, discomfort was felt after exercise but pain peaked 24-48 hours later then subsided by day four. Pomegranate juice slightly reduced the level of muscle soreness immediately after exercise but did not affect delayed-onset soreness (days 1-4). Interestingly, blood markers of muscle damage were slightly elevated in the pomegranate juice trial.

In the second study, weight trained subjects drank 250 ml (~1 cup) of either pomegranate juice or a placebo drink twice daily for 15 days. Eight days into the experiment, baseline measurements were performed and the subjects performed the eccentric contraction protocol using both the elbow flexor and the knee extensor muscles (quadriceps). Strength and soreness were again measured after exercise and for the next seven days.

In these trained subjects, arm strength was reduced immediately after exercise by about 35% in the placebo condition and about 25% in the pomegranate juice condition, a statistically significant difference. Strength recovered over the next six days but was always slightly greater when the subjects drank the pomegranate juice. At two and three days post-exercise, pomegranate juice slightly reduced the perception soreness.

Leg strength was also reduced by about 20% under both conditions and slowly recovered over the next week. Soreness also followed the same pattern as the arm, described above. However, pomegranate juice had no effect on leg strength or soreness across the duration of the study.

The results of these two studies are somewhat confusing. On the one hand, they suggest that pomegranate juice may aid in the recovery of strength and soreness after intense exercise. This appears to be the case in both trained and untrained subjects. On the other hand, the effect seems to occur only in the arm muscles but not in the leg muscles. And, the effect is variable, being greater at different times in the trained and untrained subjects. Nevertheless, there may be some important benefits to drinking pomegranate juice.

Two key issues should be pointed out before players start on pomegranate juice regimen. First, the studies show that the effects on the arms were quite small and somewhat variable. Soreness was minimally affected. In fact, on a scale of 1-10 (with 10 being “unbearable soreness”), the pain perception was improved, at most from a 4 to a 3. Many feel that while this difference may be statistically significant, it is probably too small to be noticed by athletes during training or competition. Further, strength of the arm muscles was improved by, at most, 8-10%. Again, this is a fairly small improvement in performance. One could argue that in a sport where victory may be determined by inches, a 10% gain is meaningful. One could also argue that other factors such as diet and fitness level affect performance by a greater margin. Given this, it is too early to say that the observed in the two studies would translate into noticeable improvements on the pitch.

Second, pomegranate juice did not affect recovery of the leg muscles. This is an important point. Soccer is a sport played primarily with the legs. Thus, it is quite possible that drinking the juice would have no beneficial effects on soccer skill or fitness. In other sports, say tennis or swimming where the arms are used extensively, there may be a performance advantage. Again, improvements in training or match performance are questionable.

Third, the authors of the studies suggest that there is a clear need for more research. These are the first two studies looking at pomegranate juice and exercise performance. Questions remain about the effects on other aspects and types of exercises. For example, would fitness or skill, as opposed to strength be improved? Given the lack of research, it is difficult to make firm conclusions about pomegranate juice as a supplement.

Back to the title of this post, can pomegranate juice improve soccer performance? Unfortunately, the jury is still out on this question. Research suggests that drinking it before the start of preseason training and continuing through the first week or so might help recovery between training days. However, given the small improvements in the arm muscles only, improvements on the pitch may not be noticeable.

References:

Trombold JR, Barnes JN, Critchley L, Coyle EF (2010) Ellagitannin consumption improves strength recovery 2-3 d after eccentric exercise. Medicine and Science in Sports and Exercise, 42:493-498.

Trombold JR, Reinfeld AS, Casler JR, Coyle EF (2011) the effect of pomegranate juice supplementation on strength and soreness after exercise. Journal of Strength and Conditioning Research, 25: 1782-1788.

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Avoiding the Pre-Season Injury Bug

As the fall approaches, players begin preparing for the upcoming soccer season. Pre-season training is a time to develop fitness, fine-tune technical skills and improve tactical abilities. It can be a physically demanding time of the player’s year. Unfortunately, it is also a time where injuries can be a problem. Studies of soccer as well as other sports show that athletes tend to be more susceptible to injuries during the pre-season than at other times during the year. This is true for muscle and joint injuries as well as overuse injuries. A recent study focused on the incidence of injury in youth players during pre-season training. The results show that young players are quite susceptible to certain types of injuries during this period. This study, coupled with the results of others provides some insight into how the risk of injury might be reduced.

The study, published in the Clinical Journal of Sports Medicine, examined the incidence of various injuries during the soccer pre-season period. It focused on “sub-elite” youth players from 40 different teams in the U13-U19 age groups. Each team trained 3-4 times per week during the 6-week pre-season period and played several matches. Injuries that required a player to miss at least one day of training were recorded along with the type of injury, the body part injured along with the number of days sidelined.

The researchers found that, on average, each team suffered 1-2 injuries during the preseason period. Of the injuries recorded, 34% required players to miss only a single day of training. However, 55% forced them to sit out for 8 or more days. To put it into a team perspective, more than half of the teams had at least one player miss more than a week of training due to an injury.

The most common injury was a "thigh muscle" strain (this was most likely hamstring strain or pulls). Bruises were almost as common with ligament sprains the third most likely to have occurred. This is consistent with other research studies of professionals that show pre-season is a time where players are very susceptible to hamstring injuries. Studies also show that players who suffer a hamstring strain are far more likely to re-injure the muscle during the next year. Thus, the impact of a pre-season hamstring injury can extend well beyond the immediate recovery period.

This raises the question as to how best to prevent pre-season injuries, particularly hamstring injuries. Unfortunately, only a handful of studies focused on hamstring injury prevention have been published. A few studies provide some insight but most of the recommendations are based on reducing the risk factors. Researchers in Greece found that hamstring injury risk is associated with lack of hamstring strength, flexibility and neuromuscular control. Fatigue also seems to play a role. Most importantly, the lack of hamstring strength, particularly eccentric strength, creates a muscle imbalance with the quadriceps muscles. That is, weak hamstrings coupled with strong quadriceps seem to be a key risk factor.

Using this information, hamstring injury prevention should include exercises designed to strengthen the hamstrings and increase hip range of motion (i.e. flexibility).  For example, exercises such as Russian curls will increase eccentric strength,  while static and dynamic stretching will improve flexibility. Researchers in Germany also suggest that training include balance and agility activities such hopping and jumping exercises along with balancing on one foot.

Coaches should be aware that hamstring injuries often occur when players are fatigued. Gradually increasing fitness over the pre-season may reduce the risk of injury. Avoiding high speed sprinting and other “high risk” activities when players are fatigued might also help.

Players can also play a role in injury prevention. They can reduce their risk by using the off-season to correct certain risk factors. Improving hamstring strength and flexibility during summer months, before pre-season begins can go a long way towards preventing injury. Including balance and agility training can also help with injury prevention as well as improve other aspects of their game.

Interestingly, the training components listed above are included in most anterior cruciate injury prevention programs. For example, FIFA’s 11+ recommends hamstring strengthening and flexibility training as well as balance and agility training. This program is designed as a short (15-20 minutes) warm-up program to be used at the start of each training session. Several research studies have shown that it is effective in reducing he risk of ACL injury as well as improving various components of soccer performance. Thus, including this type of training as a part of a pre-season program can reduce the risk of both knee and hamstring injuries and improve performance the field.

Avoiding the injury bug is an important part of pre-season training. Not only can a severe hamstring pull sideline a player for more than a week, it can be a recurrent problem for much of the season. Given that players are susceptible to these injuries during pre-season training, coaches should focus on prevention and avoid placing players at risk (such as high speed sprinting when they are fatigue). Hopefully, these strategies will prevent players from missing this important period of preparation for the upcoming season.

References:

Brito J, Rebelo A, Soares JM, Seabra A, Krustrup P, Malina RM (2011) Injuries in youth soccer during the preseason. Clinical Journal of Sports Medicine, 21:259-260.

Croisier J-L, Ganteaume S, Binet J, Gentry M, Ferret J-M (2008) Strength imbalances and prevention of hamstring injury in professional soccer players: A prospective study. American Journal of Sports Medicine, 36:1469-1475.

Elliott MC, Zarins B, Powell JW, Kenyon CD (2011) Hamstring muscle strains in professional football players: a 10-year review. American Journal of Sports Medicine, 39: 843-850

Fousekis K, Tsepis E, Poulmedis P, Athanasopoulos S, Vagenas G (2011) Intrinsic risk factors of non-contact quadriceps and hamstring strains in soccer: a prospective study of 100 professional players. British Journal of Sports Medicine, 45: 709-714.

Heiderscheit BC, Sherry MA, Silder A, Chumanov ES, Thelen DG (2010) Hamstring strain injuries: recommendations for diagnosis, rehabilitation, and injury prevention. Journal of Orthopedic and Sports Physical Therapy, 40: 67-81.

Kraemer R, Knobloch K (2009) A soccer-specific balance training program for hamstring muscle and patellar and Achilles tendon injuries: an intervention study in premier league female soccer. American Journal of Sports Medicine, 37: 1384-1393

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