Monday, August 11, 2014 Sports Path’s Technical Report on the 2014 World Cup

The World Cup is over and Germany are still celebrating. And the first detailed analysis of the recently completed has arrived! Robin Russell of Sports Path and his colleagues have compiled their “World Cup Technical Report 2014”. In the first of which will likely be many analyses, their detailed look at the numbers offers some interesting observations.

The report team was comprised of analysts, coaches and coaching education specialists. They analyzed all of the matches played and prepared a report that is targeted for coaches who are interested in practical lessons from the World Cup. The team presents a wealth of interesting statistics. More importantly, they use those data to offer a number of implications for coaching, provide “common sense” answers to questions about their data and highlight what separated the winners from those who when home early.

Here’s a short summary of they key findings:

Teams, which scored 3 or more goals in a match, had a 100% win probability.

The “Gold Zone” (GZ) – a box extending a few yards outside of either post and to the 18 yard line.

80% of the goals were from strikes taken inside of the GZ. However, most of the attempts were taken from outside of this area.

A greater percentage of shots taking within the GZ were on target compared to outside of the Gold Zone

Thus, strike attempts taken inside the GZ were more effective and more accurate.


The most productive zones for delivering the ball into the GZ were the areas identified as the Central Attacking Zone (CAZ – the box on top of the penalty area) and Box Pass Zone (BPZ – the two boxes just outside of the Gold Zone). That is, balls delivered from these areas were more likely to result in retained possession and higher rates of conversion.

However, teams relied more on deliveries outside of the CAZ and BPZ as well as corner kicks.

Transition and Scoring

In open play, 49% of all goals were scored within 5 seconds of regaining possession and over 80 % of goals were scored within 15 seconds of regaining the ball.


Effective distributions by Goalkeepers played a role in securing attacking-third possessions. Teams should develop the technical and tactical abilities to transfer the ball from the defending to attacking third

Teams that directed their throw-ins away from the congested area and into a more spacious area were more effective in securing a possession in the attacking-third.

These are the highlights. There’s more, much more. To download a free receive copy of the Sports Path World Cup Technical Report 2014, visit Robin’s e-Learning Blog (CLICK HERE).
Posted by Jay Williams, Ph.D. Email ThisBlogThis!Share to TwitterShare to FacebookShare to Pinterest
Labels: Original Research, Strategy

Tuesday, March 11, 2014 Player Perceptions of Artificial Turf

The use of artificial turf (AT) playing fields continues. Despite recent research on performance and health issues surrounding AT, debate over injury risks and heat still swirl around the topic of “playing on plastic”. The safe use of AT is a complex issue and perceptions can influence how players perform as well as their susceptibility to injury. A recent study shows that professional players generally view AT negatively and feel that it raises the risk of injury and results in more delayed-onset muscle and joint soreness. Some of their perceptions may be rooted in evidence while some may not. However, it is important for coaches and trainers to understand how players feel about playing and training on AT.

The researchers collected surveys from 99 professional players from six MLS teams. They asked them to recall their experiences playing on AT and grass.

The survey yielded some important findings:

97% felt that playing and practicing on AT resulted in greater muscle and joint soreness.
90% felt that it took more time to recover after playing a match on AT.
94% felt that AT raised their risk of sustaining an injury.
Most players felt that AT was stiffer, had greater friction and exacted a greater metabolic cost than grass.
A large percentage agreed that the quality of the AT was an important factor in injury risk.

Overall, players had a negative perception of AT. They felt that AT increased the risk of injury and resulted in greater muscle fatigue and soreness. These perceptions seemed to be due to the mechanical properties of the turf.

The authors of the study mentioned that pre-established bias and personal experience may have shaped their opinion of AT. No doubt that a large percentage of public comments made by athletes and in the press about AT is negative. This can easily shape ones opinion of a particular playing surface. Also, comments provided by the players suggested that many have had negative experiences on AT: “All my 3 biggest injuries have happened on turf matches”, “Coming off back-to-back ACL tears… I feel mentally scared to play on turf”, “fear of having a cleat stick in the turf” and “The first time I played on (turf), I broke my 5th metatarsal”. Thus, it’s not surprising that players generally view AT negatively.

Are the player’s perceptions of increased injuries correct? We recently conducted a review of eight research studies looking at the rate of injuries on AT and grass. We found that playing or training on AT did not raise the risk of injury. This held for male and female players and for young and adult players. In fact, some injuries were actually lower on AT. Thus, from a research perspective, there is no evidence that playing on AT results in more injuries. However, this is a complicated issue.

Earlier research suggests that the player’s perception of greater fatigue and effort may be correct. The game does change when played of AT. Ball movement, passing sequences and playing tactics are different on AT compared to grass. For example, more short passes are attempted on AT along with fewer slide tackles. This is something that could increase effort, cause more fatigue and increase delayed-onset muscle soreness.

Fatigue along with muscle and joint soreness that persists 24-48 hours after a match can impact both performance and injury risk. In youth and college competitions, multiple matches are often played with limited time for recovery. There’s little debate that fatigue raises injury risk. If fatigue and soreness, either real or perceived, is greater after competing on AT, there is the possibility that injuries could occur during subsequent match, whether played on grass or AT. Regardless of the surface, injury risk may be increased due to greater fatigue or changes in movement patterns resulting from soreness.

Unfortunately, we could find no research on muscle soreness or markers of muscle damage after playing on AT. Injury studies classify an “injury” as something that prevents a player from participating for at least one day. While muscle soreness may hinder play, it usually doesn’t force a player to the sideline or count as an injury. Thus we can’t confirm the player’s perceptions of muscle and joint soreness after playing on AT. Neither can we discount them.

The authors of the study point out that it is important to understand player perceptions of AT. For example, if players routinely report more fatigue during the match as well as muscle and joint soreness 24-48 hours after a match, coaches can make adjustments in playing time and training schedule. Strategic substitutions and increased recovery may help players avoid injuries that result from short- and long-term fatigue. This is particularly true for teams where a Friday-Sunday schedule is played.

This study will not end the debate over playing and training on AT. It does confirm what many have long felt, many players prefer playing on natural grass and feel that it is a safer surface. It also emphasizes the need for more in-depth research into the use of AT fields. Understanding issues such as delayed onset muscle or joint soreness, effects of a congested calendar and long-term fatigue can go a long way in either confirming or allaying player perceptions.


Poulos CCN, Gallucci J, Gage WH, Baker J, Buitrago S, Macpherson AK (2014) The perceptions of professional soccer players on the risk of injury from competition and training on natural grass and 3rd generation artificial turf, BMC Sports Science, Medicine and Rehabilitation, 6:11

Monday, December 3, 2007 Fitness Training With Small-Sided Games

Peak performance during a soccer match involves many different factors. The most obvious are technical skills and tactical abilities. However, the factor that influences a player’s ability to perform over the course of a 70-90 minute match is his or her fitness level. From a scientific standpoint, fitness is defined as maximal oxygen uptake (VO2max) and represents the maximal amount of oxygen that an athlete can breath in and convert into energy. The most common ways to increase VO2max is through either continuous running at around 50-60% of maximal heart rate or interval running using short, high-intensity bouts at about 80-90% of maximal heart rate. These types of training have been used by coaches for years to improve player’s fitness.

Coaches usually have limited practice time with their players. So, it is difficult to squeeze in a 15-20 min running session when the technical and tactical abilities of the individual players and the team need to be addressed. One strategy that coaches use is small-sided training. This involves short matches using 2-8 players per side in a small grid. Several 2-5 minute games are played with a short rest periods in between. The idea behind small sided training is to incorporate all three aspects of soccer in a single drill: technical, tactical as well as fitness.
One way to judge how well a training program improves fitness VO2max is to determine the physiological demands of the drill. Most research studies show that during small sided training, heart rates can reach as high as 85-90% of maximal. Blood lactic acid levels can also reach 4-5 mmol/l and ratings of perceived effort typically describe the games as very difficult and near maximum. The heart rate, blood lactate and perceived effort responses to small sided games are all well within the responses found for interval running and higher than continuous running. That is, small sided games can be as physically demanding as performing repeated bouts of high intensity running.

One characteristic that distinguishes small sided training from interval running is the coach’s ability to vary the intensity of the training (Rampinini et al. 2007). By changing the number of players, the size of the grid, the match length or recovery interval, intensity can be increased or decreased. A recent study examining these variables found that 3v3 matches played on a large grid (18x30m) elicited greater heart rates than those played on a small grid (12x20m). As the number of players increased from 3v3 to 6v6, the intensity of the effort tended to decrease, especially if the grid size remained small. Coaches can also elevate the overall intensity of the drill by increasing the match duration to around 4 minutes and by using an active recovery interval of 2-3 minutes. They can further change the intensity of the drill by providing verbal encouragement or by simply letting the players play. Thus, the intensity of the small sided games can be varied by changing a few variables. This allows the coach to tailor the practice to meet the needs of the team.

The effectiveness of small sided games is seen in the fitness improvements over the course of a season. Recent research shows that following an eight month season where players trained with small sided games, fitness was markedly improved (Impellizzeri et al., 2006). The distance covered during a Yo-Yo test was increased and VO2max improved. Also, a recent study out of Italy found in soccer players who trained using small sided game training had similar improvements on endurance tests and match performance as did players who trained by running. Based on this, it is clear that small sided games can improve fitness and that the changes are similar to those caused by interval and continuous running.

From a practical standpoint, the coach should vary the intensity of the games based on a session by session basis. Intensity should either be increased or decreased based on the players needs: their current level of fitness, recent training session or match intensity and overall level of fatigue / tiredness. In general, players should not be training at the highest intensity every session. This is particularly true after intense matches. Repeatedly training players at the highest intensity can lead to “burnout” and can increase the risk of injury. Rather the intensity should be tailored to the situation at hand. A few guidelines are provided in the table.


Variable High Intensity Low Intensity
Number of players 3 v 3 6 v 6
Grid Size Large grid Small grid
Number of Matches 4-5 3-4
Duration 4 minutes 3 minutes
Recovery 2-3 minutes of light jogging 3-4 minutes of rest
Coaching Verbal encouragement Let the kids play

All of the available research indicates that small sided games are very effective at improving the player’s level of fitness. The physiological improvements and match performances after this type of training are similar to those that occur with interval or distance running. The advantages of small sided training are numerous. The intensity can be easily varied by the coach to elicit an optimal training response. The technical and tactical aspects of the game are stressed. Lastly, the players seem to prefer the competitive nature of the activity as opposed run training. Thus, there is a string case for using small sided games as a way to improve player fitness.

Further Reading:

Rampinini E, Impellizzeri FM, Castagna C, Abt G, Chamari K, Sassi A, Marcora SM. (2007) Factors influencing physiological responses to small-sided soccer games. Journal of Sports Sciences. 25:659-666.

Impellizzeri FM, Marcora SM, Castagna C, Reilly T, Sassi A, Iaia FM, Rampinini E. (2006) Physiological and performance effects of generic versus specific aerobic training in soccer players. International Journal of Sports Medicine. 27: 483-492.

Thursday, September 4, 2008 Cutting-Edge Research: PK Shootouts, Pressure and Choking

Choking under pressure is far too common at all levels of sport. Choking occurs when players under perform in situations where there is a high degree of importance. In soccer, the highest-pressure situation is the penalty kick shootouts. Individual efforts can often mean the difference between winning and losing a championship. Some players step forward and bury their kicks. Others choke, sometimes missing the goal entirely.

What causes some players for succeed and some to choke during high pressure situations? Drs. Geir Jordet and Esther Hartmen of the Norwegian School of Sport Sciences addressed this question in a research article published in the August 2008 issue of the Journal of Sport and Exercise Psychology. Their study focused on the success and behavior of players taking penalty kicks and pressures surrounding their effort.

The investigators viewed video tapes of penalty kick shootouts that occurred during matches played in the World Cup, European Championships and Champions League competitions between 1972 and 2006. Overall, there were 36 shootouts involving 359 kicks and 291 players.

They focused on three key variables that affected success. The first was “valence”, an indicator of the perceived pressure. Many times, the outcome of the match is not directly dependent on the success of the attempt. The shootout goes on whether the kicker is successful or not. For example, the match is neither won nor lost on the first attempt in a shootout. This is referred to as a neutral valence. At some point during the shootout, a player has the chance to end patch with a successful kick. With a goal, his team wins. But with a miss, the shootout continues. This is defined as a positive valence because of the possible positive outcome. On the other hand, players are faced with the situation where a missed kick would end the match and result in the team losing. This is negative valence because of the possibility of a negative result.

The second variable was “avoidance behavior”. Approach looking players placed the ball at the penalty mark then walked backwards, facing the keeper, in preparation for the attempt. Avoidance looking players, placed the ball, turned and walked away with their back to the keeper.

The final variable was preparation speed. This was defined as the time from when the referee signaled the kick to until the shooter began his run-up. This is a time period that can be controlled by the player.

The investigators found several interesting relationships between these variables and success of the penalty kick. In the situation of negative valence, when losing the match was a possibility, players more often avoided looking at the goal keeper and took less preparation time. As for performance, players were far more successful in the situation of positive valence. When making the kick meant victory and a miss meant continuing the shootout, players were successful 92% of the time. However, when faced with negative valence, players made only 62% of their shots. Thus, the possibility of a negative outcome results in more misses than the potential of a positive result. This condition also seems to cause players to alter their approach to taking the shot.

Success in penalty kicks seems to be dependent, to some extent, on how the player perceives the outcome. Most researchers feel that the negative valence situation is more pressure packed. That is, fear of being a goat is more stressful than the possibility of being a hero. This study bears this out. Players are more likely to choke when a miss means losing a match. They seem to respond poorly when they may be punished for failure as opposed to rewarded for success. It is possible that this fear of failure causes players to change the way they approach their shot. Players that choke during pressure packed situations tend to avoid looking at the goalie and when they take kicks quickly after the referees signal. This may reflect a lack of confidence in their ability.

Choking under pressure is a very complex phenomenon. Many, many factors contribute to performance under pressure situations. This study provides a small glimpse into how and why players playing at the highest level sometimes fail.


Jordet G, Hartmen E (2008) Avoidance motivation and choking under pressure in soccer penalty shootouts. Journal of Sports and Exercise Psychology, 30:450-457.
Posted by Jay Williams, Ph.D. Labels: Goalkeepers, Psychology

Thursday, December 2, 2010 Pitch Size, Fitness and Technical Training

Small-sided matches are often used by coaches to develop fitness of his/her team. The advantage is that fitness can be improved within the context of the game. This type of training also emphasizes both technical and tactical abilities. A number of variables can be altered when designing a small-sided game such as the number of players and rules modification. Another key component of small sided matches is the size of the playing area. A new study from researchers the University of Basque County in Spain highlights the ability of small sided matches to improve both physical and skill performance by varying the pitch size. This investigation shows that by changing the playing area, fitness or technical skills can be emphasized.

Ten 16 year-old boys played 5v5 matches (plus a goal keeper) on pitches of three different sizes. The large pitch was 62 x 44m (roughly half of a full-sized pitch), the medium pitch was 50 x 35m and the small pitch was 23 x 23m. Matches lasted 8 minutes and players were instructed to play without input from the coaches. Each player was fitted with a heart rate monitor and portable GPS to track physiological and physical profiles. Matches were also filmed to determine technical behaviors such as tackles, dribbles, passes, etc.

The physiological responses varied based on the pitch size. The large pitch elicited slightly higher heart rates and players spent 50% of the match exercising at more than 90% of their maximal heart rate. On the small pitch, only 41% of the match was spent exercising in this heart rate zone. During the large pitch matches, players covered about 1000m compared to slightly less than 700m on the small pitch. Also, the large pitch required the players to perform more high-speed sprints per match (6 versus 1). Thus, small-sided matches played on a large pitch elicit greater physiological responses. That is, they are more taxing on the cardiovascular system compared to matches played on a small pitch – a key to developing cardiovascular fitness.

The lower physiological response to the small pitch matches may be due to the amount of time the ball was in play. Over the course of all matches, there were several stoppages for goals, fouls, throw-ins, etc. On the large pitch, the ball was in play for 82% of the 8-minute period, compared to only 68% for the small pitch. Thus, when on the large pitch, players played for over a minute more than when on the small pitch. The investigators assume that when the ball is not in play, players generally stop moving, thereby reducing the demand on the cardiovascular system.

On the other hand, matches played on the small pitch required more technical skills. During these matches, number of interceptions, ball control, clearances, restarts and shots were all greater than when playing on the large pitch. For example, on the small pitch there were about 11 interceptions per match compared to only 6 for the large pitch. Thus, small sided matches elicit a greater number of technical skills.

This study’s results suggest that coaches can the demands of training by varying the pitch size of small-sided games. Expanding the size will emphasize fitness components whereas shrinking the pitch forces players to focus on technical skills. Previous studies also emphasized that the physiological intensity of small-sided matches can also be affected by varying the recovery interval between consecutive matches and by using verbal encouragement (see previous SSO article). Technical skills and tactical awareness can be further stressed by providing constraints such as two-touch rules.

In the end, this study provides more evidence that small-sided games can be a very effective training tool. They can be used to improve fitness and technical skills and tactical knowledge. The key is for coaches to design their training session and vary the games to meet the needs of their team.


Casamichana D, Castellano J (2010) Time-motion, heart rate, perceptual and motor behavior demands in small-sided games: Effects of pitch size. Journal of Sports Sciences, DOI:10.1080/02640414.2010.521168

Posted by Jay Williams, Ph.D. Labels: Current Research, Training

Monday, August 30, 2010 Antioxidant Supplements – Are They Needed?

Everyday it seems that new supplements are appearing on the market. One group of nutritional supplements that has received a lot of attention in the past few years is antioxidants. Vitamins such as C, E and beta-carotene along with fruits like blueberries and strawberries are considered powerful antioxidants. Some claim that these have many health benefits including enhanced exercise performance. Is this true? Can antioxidants benefit athletes? Dr. Scott Powers of the University of Florida is one of the leading researchers on exercise and antioxidants. He has published a review article focusing on antioxidant supplementation and performance. In his review, he concludes that there is actually little scientific evidence in favor of supplementation and that supplementation with high doses may do more harm than good.

What exactly are antioxidants? Antioxidants are a class of compounds that fight off reactive oxygen. Chemically speaking, reactive oxygen (or oxygen radicals) is formed when oxygen molecules lose an electron. This makes the molecule highly unstable and reactive. These molecules can then damage proteins, membranes and DNA. Such “oxidative damage” can lead to cell death, and is linked to many disorders including some cancers. Antioxidants scavenge reactive oxygen and protect cells from damage.

Reactive oxygen is formed during the normal course of metabolism. Some conditions lead to greater production and a condition known as oxidative stress occurs. Cells are equipped with its own antioxidant defenses so that most conditions of oxidative stress are easily handled by the cell. In some pathological conditions, oxidative stress can be very large greater or the cells own antioxidant defenses are suspect. Under either these conditions, reactive oxygen accumulates and the damaging to various cells can be severe.

During exercise, metabolism increases 10-20 times normal. As a result, the muscle cells undergo a period of oxidative stress and there is a rise the in amount of reactive oxygen produced. However, this rise is relatively small and very temporary compared to clinical conditions. Nevertheless, some researchers have linked this exercise-induced oxidative stress to exercise performance. They feel that it plays a key role in fatigue during prolonged activity lasting more than 30 minutes. By providing greater defense against reactive oxygen through supplementation, fatigue can be delayed.

On the other hand, many researchers point out that normal, healthy individuals have more than enough natural antioxidants to protect against oxygen radicals. This is especially true during exercise. Enzymes and antioxidant compounds found within muscle cells are more than capable of fighting off reactive oxygen. In fact, one of the benefits of exercise training is enhanced protection against oxidative stress – training builds greater defense. This adaptation leads this group to argue that reactive oxygen plays little if any role in the development of fatigue.

Given this debate, will do antioxidant supplements improve exercise performance?

The compound N-acetylcystine (NAC) may have some positive effects on performance. A few laboratory studies show that NAC delays fatigue under some conditions. Unfortunately, the methods used in these studies raise questions about the practicality of using NAC. For instance, one study shows positive effects after 35 minutes of intravenous infusion of NAC. Needles to say, most athletes cannot nor should not take such a pre-match approach. A few other studies show little or no effect of ingesting NAC on performance. So while there may be some potential for NAC to delay fatigue, there is not enough evidence to suggest that athletes use it as a performance enhancer.

As for nutritional antioxidants such as vitamins C, E or beta carotene, the research is much clearer. The vast majority of scientific studies show that supplementation with these vitamins has very little effect on performance. The vast majority of research studies all agree on this point. Further, a review of more than 68 clinical trials emphasize that dietary supplementation with these vitamins does not appreciably improve health. As it turns out, a well balanced diet that is high in fresh fruits and vegetables provides plenty of antioxidants and little benefits are gained by supplementation.

In his review, Dr. Powers emphasizes an important point. New evidence indicates combating exercise-induced oxidative stress may actually do more harm than good. Reactive oxygen seems to trigger the muscle to adapt to training. The brief rise during exercise stimulates the muscle to produce the machinery needed to improve function (and to combat oxidative stress). This includes muscle proteins as well as mitochondria and enzymes needed for energy production. Two recent studies emphasize this point. Both show that supplementing the diet with large amounts of vitamin E and C (~16 times the RDA for an adult) blunt the training adaptation to exercise.

The bottom line is that antioxidant supplements are not needed for otherwise healthy athletes who have solid nutritional habits. The only exception is athletes who do not eat a proper diet. Those who skip meals, don’t eat proper servings of fruits and vegetables or try to lose excess weight by cutting calories may benefit from a vitamin supplement that contains antioxidants. Otherwise, a healthy diet will provide more than adequate defense against oxidative stress and allow training adaptations. Supplementing the diet with antioxidants will not provide an added training benefit.

Finally, it should be pointed out that nearly all of the studies addressing the ability of antioxidants to improve performance were carried out with adult subjects. There is little if any research on adolescents or pre-adolescents. This makes it even more difficult to recommend antioxidant supplements to young athletes. Neither the positive nor potentially negative effects of short- or long-term use are understood. Thus, at this time, young players should focus on proper nutrition rather than supplement use.


Stear SJ, Burke LM, Castell LM, Powers SK, Kavazis AN, Nelson WB, Ernst E (2009) BJSM Reviews: A-Z of nutritional supplements, sports nutrition foods and ergogenic aids for health and performance Part 3. British Journal of Sports Medicine, 43:890-892.
Posted by Jay Williams, Ph.D. Labels: Current Research, Nutrition, Supplements

Thursday, March 11, 2010 Recreational Soccer: The Magic Pill for Adult Health?

Many adults are engaged in a never ending search for the “magic pill” that will improve their health and wellbeing. This is the focus of many fitness products and nutritional supplements that advertise extraordinary gains in health with little effort. Others spend countless hours pound away on the treadmill, stationary bicycle or elliptical machine in an effort to lose weight, improve fitness and avoid health complications. While we may never find that magic pill we may have found a balance between monotonous exercise and the lure of a quick fix. A recent research review argues that sedentary adults who participate in recreational soccer programs reap the same benefits as those who engage in more traditional exercise routines.

This post focuses on a review article by researchers at the University of Copenhagen. The article is a part a special issue of the Scandinavian Journal of Medicine and Science in Sports that is devoted to the health benefits of soccer. In weeks to come, we will be discussing other articles in this journal. For now, the focus is on adults and recreational soccer programs.

The researchers analyzed research studies focused on the health and fitness effects of recreational soccer. The approach they took was rather unique. Most agree that placing sedentary adults in ANY type of exercise program, including recreational soccer, will improve fitness and other health markers. In this review, the Copenhagen researchers also compared the effects of soccer to the effects of other types of exercise, specifically jogging, interval running and strength training.

In general, the studies examined sedentary adult subjects who participated in recreational soccer programs. The ages of the subjects were not specifically listed but were identified as “adults”. Most of the available studies used male subjects but a few focused on women. The programs lasted between 10 and 24 weeks and subjects typically played 3 times per week for 30-60 min per session. Training session usually involved small-sided games but some used 11v11 matches.

What follows is a summary of the overall findings and conclusions.

Fitness: Subject engaged in soccer training improved their VO2max by an average of 13%. Improvements were made using both full- and small-sided matches. When compared to jogging or interval running programs of similar training hours, the improvements in fitness via soccer were similar.

Cardiovascular Effects: Soccer training lead to reductions in resting blood pressure and resting heart rate. The effects on blood pressure were most pronounced in subjects with the highest initial levels. In addition, the researchers concluded that the improvements have significant health effects for the participants such as reduced risk for stroke and heart attack.

Blood lipids were also improved through soccer training. LDL cholesterol (bad cholesterol) was lowered and HDL cholesterol (the good type) was elevated after training. In addition, improved glucose tolerance and muscle enzyme levels in Type II diabetic patients occurred when soccer training was combined with nutritional advice. All of the changes due to recreational soccer participation were similar to those found using other exercise programs.

Body Composition: The soccer training programs show small reductions in body fat and increase in lean body mass. The changes in lean body mass reflect increases in muscle mass and muscle fiber hypertrophy. Such changes are not normally seen after jogging or interval running. Muscle fiber hypertrophy observed after soccer training (~15%) was nearly the same as that seen after weight training in men of similar age (~18%). Soccer also elicited changes in neuromuscular control that may improve balance and reduce the risk of falls and joint injuries.

Bone Mass: A few studies found that bone health was improved after soccer training. Bone mass in the legs, hip and lumbar spine were all increased. The changes were much greater than those that occurred after jogging and interval running and similar to weight training.

Perceived Effort: Perhaps one of the most important findings was that ratings of perceived exertion during soccer training were lower than those recorded during running. That is, when exercising at similar work rates and intensities, soccer participants felt a reduced sense of effort – they didn’t perceive themselves as working as hard as the runners. This may be linked to factors such as the focus and enjoyment of playing soccer and the social interactions with teammates. The more participants enjoy their exercise program, the greater their level of participation and the greater the health benefits.

Injury Risk: On the downside, the risk of injury may be somewhat greater in soccer programs that in other exercise programs – especially given the movement patterns and potential for contact injury. However, this is a difficult comparison to make since many of the risk injury studies don’t consider the intensity of the program. The Copenhagen researchers calculated that in the all of the studies reviewed,


Krustrup P, Aagaard P, Nybo L, Peterson J, Mohr M, Bangsbo J (2010) Recreational football as a health promoting activity: A topical review. Scandinavian Journal of Medicine and Science in Sports, DOI: 10.1111/j.1600-0838.2010.01108.x
Posted by Jay Williams, Ph.D. Labels: Health, Training

Tuesday, June 17, 2014 Should We Have Expected John Brooks’ Goal?

Yesterday in a thrilling match, US defender John Brooks scored in the 86th minute to secure a win over for the Americans over Ghana. The goal came off of a corner kick delivered by Graham Zusi. An exciting play for sure and a critical 3 points for the US. But, at this point in the World Cup competition should we have expected a goal to come from a corner kick?

In the 2010 World Cup, 627 corners were taken that resulted in 9 goals. That’s an average of one goal scored for every 70 corners attempted. Graham Zusi’s was the 126th corner taken so far in this year’s competition. Prior to the US goal, Switzerland and German scored the only goals from corner kicks. Add the US goal and we have 3 goals scored from 127 corners (Ghana had one CK after the US goal). That’s an average of 1 goal every 42.3 attempts. Slightly less than the 2010 average.

Based on the 2010 statistics, should we have expected the US to score? The average so far is about nine corner kicks per match so the next corner kick goal should have come about three matches later, not in this match. Given that stat, should the US have played a short corner and kept possession? Obviously not! They clearly made the right call. All statistics have some degree of randomness, outliers that occur outside of what is expected. And this is what makes the game so exciting – goals coming at unexpected times from unexpected players. In this case, John Brooks and Graham Zusi created their own outlier – an unexpected goal that earned the US the win.
Posted by Jay Williams, Ph.D.

Thursday, June 12, 2014 Prepping for the World Cup

The 2014 World Cup is ready to kick-off. Four years of preparation for an event that demands players pay a heavy physical and psychological price for success. As fans and coaches, we’re excited when our team overachieves and secures unexpected points and advances to the next round. Unfortunately we’ve often seen our side underperform. They seem listless and lethargic for no particular reason, making rare and uncommon mistakes. Matches that should be easily won turn into losses. This is especially true during the critical times when multiple matches are played within a short span of time. Teams have trained on every aspect of the game and they are fit and ready to play. But is there something else needed for a team to play well? As it turns out, what teams do off the field and behind the scenes can impact success. On the Science of Soccer Online, we have talked about a congested calendar, recovery and refueling. In this post, I’d like to us the World Cup as a framework to briefly summarize four key issues: how diet, recovery, sleep and daily hassles can play critical roles in improving or undermining performance during the match. Links are included for additional info.

Fitness, technical and tactical abilities are clearly keys to winning in Brazil. However, matches can also be won or lost off the field. What should players expect when playing such a congested schedule? Each match requires a tremendous physical effort. During 2010, US midfielder Michael Bradley averaged ~8 miles per match sprinting, running, jogging and walking. Add to that, stops, starts, turns and jumps and the energy cost of a single match is quite high. If they make the finals, Brazil will play seven matches in 32 days. Belgium (Group H) would play seven matches in 27 days. To make things tougher, there are only three days of recovery between some matches. This is certainly the case as teams work their way through the knockout rounds on the way to the championship match. Given the physical demands and schedules faced, it will be important for teams think ahead in order to quickly recover and prepare for upcoming matches. This will help avoid injury and illness as well as performance.

Diet and Hydration: What types of foods and beverages should players eat and drink during the tournament? We’ve talked at length on the SSO and through the NSCAA about the need for high carbohydrates, about 60-70% of total calories. This remains true for the duration of the tournament – . However, given the amount of muscle damage that is likely to occur with repeated matches, it is also important to add additional protein to the daily diet. Pre-match suggestions hold true – a high carbohydrate meal 3-4 hours before kick off followed by high carbohydrate snacks as kick off approaches. The post-match recovery diet will be critically important. Players need to eat and drink plenty of carbohydrates soon after the final whistle. The key is the first 45-60 minutes – take in plenty of high carbohydrate foods and beverages along with a small amount of protein will “jump start” the recovery of muscle glycogen.

The climate in Brazil means that proper hydration will play center stage in the tournament. Because of the high temperatures, players will lose considerable amounts of fluid along with key minerals and electrolytes. Not only can dehydration affect performance, it can cause serious health issues and raise the risk of injury. Players should drink before, during (when possible) and after the match or training. Fluids need to be replaced on a daily basis. The rule of thumb is to drink 1.5 times the amount of fluid lost during the activity. Sports drinks can provide fluids, carbohydrates and minerals lost during training and matches.

Many players enjoy a cold beer or two after a match. There’s probably a psychological and social aspect to relaxing and having a beer with teammates. However, too much alcohol, especially liquor can increase muscle soreness and inhibit recover of muscle glycogen.

Recovery: Apart from the diet, what is the best way to physically recover from a match? There is no doubt that the intensity of the match will leave players with delayed onset muscle soreness. To limit soreness, a post-match cool down is essential. Also, light exercises the following day can help alleviate muscle soreness.

Two other strategies that we’ve discussed are ice baths and compression garments. Research into ice baths and massages is a bit confusing. Ice is thought to reduce muscle inflammation and massages are designed to stimulate blood flow and promote relaxation of sore muscles. Studies show differing results ranging from no effect to modest effects on soreness and subsequent performance. Much of the benefit of these treatments may be psychological, reducing the perception of pain rather than actually “healing” the muscle. Perhaps the mental relaxation of a massage alleviates the discomfort. In no case has research shown adverse effects of ice baths and massage. So, while the benefits may be small, there is certainly no harm.

Compression garments are often used by players during a match to improve performance and limit muscle injury risk. Worn after a match, compression garments may offer some benefit by preventing muscle pooling. They could be particularly effective on a long plane flight or bus ride after a match. As with ice and massage, the research is not conclusive regarding positive effects but show no ill effects. So, it’s reasonable to suggest that players use compression garments and err on the side of a positive effect.

Analgesics are one of the most prescribed medications at previous World Cups. Non-steroidal anti-inflammatory compounds like ibuprofen, aspirin and acetaminophen are commonly used to combat muscle soreness and other mild discomforts. We’ve warned against relying too heavily on these drugs as they may mask a serious, underlying injury. Hopefully each team has a competent medical staff that can evaluate minor aches and pains and prescribe proper treatment rather than players self-medicating themselves.

We’ve also talked previously about the use of antioxidants to combat muscle soreness. While these offer some support for recovery, they may blunt a training effect. It’s important to note that athletes at the World Cup are not in training during competition – it’s too late to make major improvements in fitness. Thus, use of antioxidant vitamin supplements may be beneficial in limiting muscle damage and soreness during the tournament without impacting fitness. Vitamin supplements are also recommended to avoid possible dietary deficiencies due to varied eating patterns, training, match and travel schedules that could lead to illness.

Rest and Sleep: Part of the recovery process in sleep. Both sleep quality and quantity can affect performance. And, the schedule of events, travel and training can impact sleep. Travel, especially across multiple time zones often disrupts sleep patterns. In the case of the Brazil World Cup, most matches will be played in a single time zone. Only two venues lie in a different zone. So, time changes should not be a major problem. However, distance and time spent travelling can be an issue. The US will log nearly 9,000 miles flying between group-stage matches in Sao Paulo, Natal, Manaus and Recife. Research has shown that as the distance traveled increases, sleep as well as physical and mental performance can be impacted. This is especially true when discussing home field advantage. Since all teams will be travelling and there are no true home venues (except for Brazil), it will be interesting to see if travel and sleep patterns affect one team more than another.

Daily Hassles: Daily hassles are those small disruptions to your day – issues that crop up and have to be dealt with. Travel is a major daily hassle. Packing and unpacking, unfamiliar surroundings, different dining patters all create frustrations. Add to that meetings with the press, communicating with family members, and treatment for injuries means that players can expect stress-filled days. As the number of daily hassles grows, performance decreases, mental focus suffers and injury risk increase. Add to that, variations in player psyche, and it’s easy to see how scheduling can affect the player. A key for the support staff of each team will be to limit these daily hassles and keep disruptions of the daily routine to a minimum.

Bottom Line: The fittest and more technically and talented team may not be the most likely to add a star the their nations badge. The Champions may be the team that performs best off the field. Those who are prepare properly behind the scenes to insure players are well fed and hydrated, undergo proper recovery, maintain set schedules and limit daily distractions may be the sides that challenge for the trophy. Remember, failing to prepare properly can distract and disrupt even the most gifted side.

Wednesday, July 14, 2010 Penalty Shootouts, Mostly a Head Game?

Penalty kicks, especially taken during a shootout are high-pressure situations. This is true for both the shot take and the goalkeeper. Success, for each player depends on several factors, physical and mental. Previous posts on the SSO talked about the role psychology plays during the penalty kick. The defending position of the keeper, confidence of the kicker and even jersey color may influence whether or not a shot is saved or a goal is scored. Two new research studies published in the Journal of Sports Science examined other possible factors affecting penalty kicks. These studies show that the goalkeeper’s movements before the shot is taken and the kicker’s reaction after a successful shot may influence shot success as well as the outcome of a shootout.
The first study asked the question, “Does goalkeeper movement before a penalty kick distract the kicker?” A group of university players were asked to take penalty shots while the goalkeeper either remained stationary or moved by waving his arms up and down before each attempt. The goalkeeper was asked to remain in the center of the goal until the ball was struck (that is, he was not to “guess” which direction to move)

A moving goalkeeper resulted in more shots saved. Slightly more than 8% of shots were saved with a stationary keeper while the moving keeper saved about 22%. With a moving keeper, more shots were placed in the center of the goal compared to the non-moving condition. The researchers also found that when the goalkeeper was moving, players found in more difficult to focus on the target or the ball. More attention was directed at the keeper when he was moving.

It appears that goalkeeper movement does indeed distract the penalty taker. Movement results in shots placed more in the center of the target and more easily saved. It should be pointed that this was a very controlled experiment in that players took multiple penalty shots (as opposed to a single shot taken during a shootout) and keepers were given specific instructions as to how to react to the shot. Nevertheless a moving goalkeeper may prove to be a successful tactic.

The authors quoted Bruce Grobbelaar, Liverpool keeper during the 1984 European Cup final. He said that his “spaghetti legs” strategy used during the shootout was not a way to disrespect the opponent but a way to test their concentration under pressure. In the end, Liverpool won and Grobbelaar was right – distracting the opponent does indeed test the confidence of the penalty taker.

The second study asked if the player’s reaction after a successful penalty kick affected the outcome of the shootout. The researchers focused on all of the penalty kick shootout during the 1974-2006 World Cups and the 1972 and 2008 European Championships (a total of 325 penalty kicks). They analyzed the each player’s reaction to a successfully kick. Displays of pride (arms raised, fist pumped, chest expanded), enjoyment / excitement (broad smile on the face) and other reactions such as looking downward were all recorded.

After scoring, 66% of the players displayed celebratory movements with their arms raised. Only two of the players displayed enjoyment with a wide smile. Those who showed the prideful behaviors were more likely to be on the wining team. The reactions most closely associated with wining the shootout were – one or both arms extended over the head, expanded chest and both hands clinched into fists. Interestingly, players who looked downward after a successful kick were less likely to be on the winning team. Thus, celebrations with displays of pride are linked to a successful shootout performance.

The researchers point out two possible reasons for the link between displays of pride and shootout success. First, players displaying prideful behaviors may instill confidence in their teammates and raise expectations of making their shot. This likely translates into successful attempts. Second, attitudes of pride and superiority may make their opponents feel inferior and less confident in their attempts, lowering their expectations of winning the shootout.

Whatever the underlying reasons, displays of pride during a shootout seem to have a positive effect on ultimate team performance. This leads the authors to suggest that penalty takers should celebrate a successful attempt as it may increase the likelihood of winning. However, they emphasize that celebrating with their teammates is the key to enhancing teammate confidence and success. “In your face” types of celebration directed at the opponents or celebrations directed to the audience may not be as effective.

So, are penalty kick shootouts a head game? These two studies suggest that there is a very strong psychological component. Goalkeeper movements before the shot seems to distract the shot taker and increase the probability of a save. Prideful player celebrations with the kicker’s teammates after a successful shot may raise the team confidence level and negatively influence the opponents. Either strategy may enhance the chances of winning a penalty kick shootout.


Wood G, Wilson MR (2010) A moving goalkeeper distracts penalty takers and impairs shooting accuracy. Journal of Sports Sciences. 28:937-946.

Moll T, Jordet G, Pepping G-J (2010) Emotional contagion in soccer penalty shootout: Celebration of individual success is associated with ultimate team success. Journal of Sports Sciences. 28:983-992.
Posted by Jay Williams, Ph.D. Labels: Current Research, Goalkeepers, Psychology
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