Friday, March 30, 2007

The Iced Foot Effect

Science Magazine

"It was a dramatic finale. Only 9 seconds remained in the National Football League's 2004 Super Bowl, which pitted the New England Patriots against the Carolina Panthers. The score was tied. The Patriots kicker Adam Vinatieri was set to kick a game-winning, 40-yard field goal.

At that crucial moment, the Panthers called a timeout. The team hoped that this extra time would "ice" Vinatieri, getting him to think more about the situation he was in—and making him more likely to miss. The kicker had to wait 2 minutes before making his attempt. He made the kick, and the Patriots won the Super Bowl.

Football teams continue to call timeouts at such moments, always hoping to increase the chances that the opposing kicker will miss after the delay. Basketball teams apply a similar strategy when they call a timeout just before an opposing player attempts a free throw.

"Does making the kicker think about his field goal attempt for an extra 2 minutes alter his probability of success?" statisticians Scott Berry and Craig Wood ask in the current issue of Chance. In other words, does "icing" work?

To find out, Berry and Wood analyzed data about field goal attempts during the 2002 and 2003 NFL seasons (including playoffs). They recorded the kicker, the length of the kick, the score of the game, the time left in the game, and whether a timeout was called by the defense before the kick. They even noted whether the field was grass or artificial turf and the weather conditions (sun, clouds, rain, snow, average wind speed, temperature—unless the games were indoors).

In these two seasons, there were 52 different field goal kickers, combining for a total of 2,003 attempts. Of these kicks, 1,565 (78.1 percent) were successful.

Berry and Wood then looked at what they defined as "pressure" kicks—those that occurred with 3 minutes or less remaining in the game (or overtime) and would create a lead or a tie for the team attempting the kick.

There were 139 such pressure kicks, and 101 (73 percent) were successful. The defense called a timeout 38 times before the pressure kick, and 24 (63 percent) of these kicks succeeded.

To take a closer look at the data and take into account any physical factors that could affect the outcome, the statisticians created a mathematical model representing the probability of a successful kick.

In general terms, a successful kick depends largely on the distance. It's also useful to incorporate a factor that accounts for performance differences among different kickers. Weather may also influence the result.

Using this model, Berry and Wood obtained results using the 2-season data that matched certain expectations. A kick made indoors is more likely to be successful. Clouds also have a small beneficial effect on kicks. Rain or snow, on the other hand, reduces the chances of success. High winds also reduce the probability of success, but not as much as rain or snow.

In pressure situations, the odds of success change very little (a mean decrease of 1.8 percent). However, icing the kicker in such a situation has a pretty strong negative effect.

Using their model, Berry and Wood calculate that, for an average kicker, the estimated probability of a successful 40-yard kick in sunny weather is 0.759. The estimated probability under the same conditions for an average kicker who has been iced is 0.659.

"Reducing the probability of a successful kick from 0.759 to 0.659 is a very important difference," Berry and Wood report.

So, is calling a timeout a good defensive strategy? "The evidence is not overwhelming, but it is compelling," Berry and Wood conclude.

"Icing a field goal kicker on a pressure kick may decrease the probability of success," they add. "This implies that a psychological effect of pressure exists, and is compounded by more time to dwell on the kick."

Statisticians and fans have long argued about whether there is such a thing as a "hot-hand" effect in sports, where a player, such as basketball shooter, has streaks during which he's more successful than expected. Now, there appears to be evidence of a "cold-foot" effect!"

The psychology of baseball

It’s the seventh game of the World Series — bottom of the ninth inning, your team is down 4-3 with runners on second and third — and you’re on deck. You watch as your teammate gets the second out. That means you’re up with a chance to win a championship for your team...or lose it.

You’re known as a clutch hitter, and you’ve hit safely in 22 straight games — an impressive streak to be sure. But as you step into the batter’s box, your hands are sweating and your mind is racing. You think about the last time you faced this pitcher and the curveball he threw to strike you out. You look at him standing on the mound and he looks tired. You try to pick up clues from his body language. How fast is his fastball today? Will he tempt you with that curveball again?

Psychologists are asking different questions: Does your recent hitting streak really matter? Is there even such a thing as a clutch hitter? Will the pitcher’s curveball fool you? And then there are the more basic ques-tions: How is it possible to hit a 100 m.p.h. fastball without being able to see it for more than a split second? How is it that even sandlot players — mere children — can intuitively do the complex geometry needed to get to precisely the right spot to catch a fly ball?

University of Missouri psychologist Mike Stadler uses research from dozens of behavioral scientists, plus some of his own, to try answering these complicated questions in his new book, The Psychology of Baseball. "Baseball turns out to be a good laboratory for studying psychological phenomena," Stadler says, "because you’re pushing the human system to its limits. And that’s a good way to see how the system works."

Psychologists have been studying baseball players almost as long as the Red Sox had been disappointing fans in Boston, and much of the attention has naturally focused on the most heroic part of the game: hitting. Baseball’s great sluggers, such as Babe Ruth, Ted Williams, and Albert Pujols, make it seem so effortless, which makes it hard to accept the scientific consensus that hitting is basically impossible. That’s right, impos-sible. Why? A ball thrown by a major league pitcher reaches speeds of 100 m.p.h. and an angular velocity (the speed in degrees at which the ball travels through your field of vision) of more than 500 degrees per second. A typical human can only track moving objects up to about 70 degrees per second. Add to this the fact that it takes longer to swing a bat than it does for a pitch to go from the pitcher’s hand to the catcher’s mitt, which means a hitter must start his swing before the ball is released and has less than a half a second to change his mind. All that equals impossible.

Not surprisingly, professional baseball players are able to keep their eye on the ball longer (up to 120 de-grees per second) than the average human being. In one study, pro players who were asked to keep their eyes on the ball did one of two things. They either watched the pitch until it reached speeds too fast to keep track of — the farthest a player could track a pitch was 5.5 feet in front of the plate — or, less commonly, they watched for the first few feet and then quickly moved their line of vision to where they thought the ball would end up and watched it as it crossed the plate. So it turns out that your little league coach’s advice — watch the ball until it meets the bat — is actually physically impossible. But even the worst Major League hitters succeed two out of every 10 trips to the plate. Are the hits they get just pure luck? Not exactly.

"I guess what interests me most in some ways is that even though we have the perceptual limitations and even though we have the reaction time limitations, there’s still enough mental machinery there to help us solve the problem," Stadler says. Hitters must make some assumptions and guess where the ball is going to be and when it is going to be there in order to make contact. Because the barrel of the bat is long enough to cover the entire plate but is only a few inches thick, predicting where the ball will end up horizontally across the plate is much less important than pre-dicting where it will be vertically. And a large portion of predicting at what height it will cross the plate has to do with predicting the speed of the ball.

Arizona State’s Rob Gray has used a virtual hitting simulation — something he describes as a "purposefully simplified" video game — to help determine what cues help hitters make contact with the ball. In a 2002 study, he varied the speeds of the virtual ball randomly from about 70 to 80 m.p.h., and hitters failed miserably, with batting averages of about 0.030. That’ll get you cut from a T-ball team. But in the same simulation, hitters fared much better — with batting averages of 0.120 — when pitches were thrown at just two different speeds: slow (75 m.p.h.) or fast (85 m.p.h.). It’s the randomness, not an over-powering fastball, that fools hitters. Gray’s conclusion: "It is clear that successful batting is nearly impossible in the situation in which pitch speed is random and in which no auxiliary cues (e.g., pitcher’s arm motion or pitch count) are available to the batter."

So, back to you now in the batter’s box. You can at least take comfort in knowing that the pitcher you’re facing only has a few pitches: a fastball, a changeup, and maybe a slider or a curveball. You’ve practiced hitting each of those pitches thousands of times during your career, and can draw on your knowledge of those at-bats. There are also cues like the pitcher’s arm speed and the rotation of the ball that help you make an educated guess about what pitch is coming. You may need to get used to a pitcher’s speed, but you have a decent idea of where the ball is going — at least enough of a good idea to succeed at your job 30 percent of the time.

Now the question is: Are you going to perform in this clutch situation, with the game and the championship on the line, or will you choke? Research dating back to a 1984 study by Florida State’s Roy Baumeister (an APS Fellow) and including work by Michigan State’s Sian Beilock suggests that if you put a player in a pressure situation, he develops a greater than normal self-focus — what we colloquially call trying too hard. When you learn a process like a baseball swing, it is important to practice it step-by-step, and novice hitters actually think through their actions of shifting their weight, rotating their hips, and so forth. But experts do this naturally. Indeed, Gray used his hitting simulation to show that when expert hitters were asked to focus on a particular part of their swing, it adversely affected their performance.

"If we force you to go back and think about each stage of what you’re doing, you actually start interfering with this procedural knowledge, this motor memory, and you start messing it up," Gray says. "It’s like tinkering with a machine that’s running really efficiently. You start trying to control everything yourself and it messes it up and it hurts your performance."

It’s hard to imagine a more pressure-filled situation than the World Series, so it wouldn’t be a stretch to think the hitter might overthink his swing. But what if he’s a clutch hitter? What if he’s been on a hot streak the last few weeks? The scientific consensus is that there is no such thing as a streaky hitter; though try telling that to anyone who’s been on the losing end of one of David Ortiz’s 15 walk-off hits with the Red Sox or Derek Jeter’s 14 consecutive World Series games with a hit. Still, the statistical analysis seems to show that streaks and clutch hitting could just be a result of simple probability.

Physicist Ed Purcell of Harvard did a statistical analysis and concluded that all streaks and slumps except for Joe DiMaggio’s remarkable 56-game hit streak fall within what could be expected by chance. Think of it this way: If you flip a fair coin a couple million times, it’s not hard to imagine that there might be times when it comes up heads 20 times in a row.

There is additional support for this view. Dick Cramer, baseball statistician and founder of STATS, Inc., hy-pothesized that if baseball did have clutch players, they would be consistent from year to year — much like the league’s best home- run hitters are consistent across years. What he found in fact is that a player might be one of baseball’s best clutch hitters one year, then plummet to the bottom the very next year.

Not everyone is ready to discount clutch hitting. Gray, for example, thinks clutch hitters might know how to relax and not try too hard in situations where there is a lot on the line. So maybe it’s not so much being a clutch hitter as it is being a nonchoker. A study of bowlers lends support to this idea. Professional bowlers, the study showed, are much more likely to bowl a strike after a series of strikes than they are to bowl a strike after a series of nonstrikes. That was true for weekend sports, like horseshoes, as well.

It could be that too much of baseball is decided by factors other than the hitter — the pitcher and the fielders certainly have some influence — to be able to accurately determine whether hitters are clutch or streaky. What happens when a "streaky" hitter comes up against a pitcher who’s also on the top of his game? Or what if the hitter makes good contact during two of his at-bats but is robbed by spectacular fielding plays both times?

"Everything ultimately comes down to the hitter succeeded or he didn’t," Stadler says. "But there’s a lot more behind that number in the box score that the box score just doesn’t capture."

So, let’s say you’re back at the plate, and you’ve fallen behind in the count 2-2. The next pitch comes and, like you predicted, it’s another curve ball. You’re ready. You give a good swing. The ball sails deep into the outfield. The centerfielder takes off to his right immediately, tracking the ball with ease. He’s not actually com-puting any complicated formula in his neurons while sprinting, but he seems completely sure about where the ball is going to land. Then, whack! He runs straight into the outfield wall, and the ball flies over his head for a game-winning home run.

Like hitting, fielding also seems like it should be a mental and physical impossibility — which makes it fas-cinating to psychology researchers. If you put a player in the outfield and make him stay put, he is actually quite bad at predicting where a ball is going to land, yet he will run effortlessly to that spot when allowed to do so. How?

One of the first theories developed to explain fly-ball catching was developed by physicist Seville Chapman, who hypothesized that fielders used the acceleration of the ball to help them determine where the ball will land. To simplify the problem for experimental purposes, balls were only hit directly at the fielders, who then moved either forward or backward in order to keep the ball moving at a constant speed through their field of vision — so, they started with their eyes on home plate and then moved in a way that kept their eyes moving straight up at a constant speed until they made the catch. If they moved too far forward, the ball would move more quickly through their field of vision and go over their head. If they moved too far backwards, the ball would appear to die in front of them.

This theory seemed too simple to Mike McBeath, a psychologist at Arizona State. For one thing, Chapman’s model predicted that fielders would use the same process for balls hit to their left or right, simply making a sideways calculation along with the basic speed calculation. But that would mean balls hit to the side should be harder to catch, and McBeath (and every sandlot outfielder) knows that’s simply not the case. Any outfielder will tell you that a ball hit directly at him is the most difficult to catch, so McBeath reasoned instead that, when a ball is hit directly at a fielder, the fielder lacks some crucial bit of information for making the catch. He came up with a method that was similar to Chapman’s but included an extra piece: He hypothesized that fielders kept the ball moving through their field of vision in a straight but diagonal line. So if the outfielder is looking at home plate when the ball is hit, he then keeps his eyes on the ball and runs so his head moves along a constant angle until the ball is directly above him, which is when he snags it. To test this, McBeath had fielders put video cameras on their shoulders, and the cameras moved in this manner.

Yet ask any Major Leaguers about this, and you’ll get blank stares. McBeath did talk to pro outfielders, and responses ranged from "Beats me" to "You’re full of it." That’s because there’s no conscious processing in-volved; it’s all taking place at the level of instinct, even though the geometry is sophisticated.

It turns out that outfielders aren’t the only ones who operate according to McBeath’s strategy. Dogs use it to catch Frisbees, bats and insects use it to catch prey, infielders use the model — only upside-down — to field ground balls, and, now, robots use it, too. Because the algorithm for catching fly balls is actually so simple, McBeath has been able to work with robotics experts to program robots to catch fly balls. (Or at least to get to the right spot; catching is a different problem for a robot with no hands.)

"It’s neat," says McBeath, an expert on perception. "It’s not always true that the way humans and animals do things is the best way. The geometry of a moving fielder from the perspective of the fielder seems like it would be a nightmare of a formula. But what we’ve shown is that we can reduce it down to this really simple geometric solution."

Chapman’s model is still used to describe the special case of catching balls hit directly at the fielder. Both fly-ball catching theories require that the fielders make adjustments on the go, which explains why we’re so bad at predicting where a ball will go if we stand in one place.

It also explains why our World Series outfielder ran straight into the wall when tracking the game-winning home run. Using McBeath’s method, players tracking a fly ball only know that they are capable of getting to the spot where the ball will land. This intuitive geometry offers no insight into whether that ball is going, going … gone.

Are the good players born or made?

It’s tempting to assume that there is some innate ability involved in becoming an elite ball player. Baseball playing does seem to run in families — think Ripken or Bell or Bonds. Plus, studies have shown that baseball players are a select group of athletes with amazing skills such as being able to track objects moving at ex-tremely high speeds of angular velocity.

Back in 1921, psychologists at Columbia convinced Babe Ruth to take a series of tests and found that he re-acted faster to sound and visual signals than the average human being. His hand-eye coordination was better than most of the population, and he could perceive information significantly better than the average person.

"The secret of Babe Ruth’s ability to hit is clearly revealed in these tests," wrote Hugh Fullerton, the author of the Popular Science Monthly article that described the tests. "His eye, his ear, his brain, his nerves all func-tion more rapidly than do those of the average person."

Similar tests were recently done on St. Louis slugger Albert Pujols and, not surprisingly, he also ranked near the top of the human population. But psychologists haven’t been able to determine a causal link between this superior physiological functioning and succeeding at baseball. These characteristics might make people better at baseball, but it could be that baseball players with these abilities are better because they practice hitting base-balls all the time.

Mike Stadler, University of Missouri, subscribes to a set-point theory, meaning that players are born with a certain range of talent, but they get to the top of their range through hard work and practice. For most of us, no matter how hard we practice, we won’t make the Major Leagues. Others have the talent to make it, but need to develop their skills to become superstars.

Certainly speed, reflexes and hand-eye coordination are important, but there are other factors as well. All fielders seem to follow Mike McBeath’s theory to help them catch fly balls. But McBeath, Arizona State Uni-versity, found that some are naturally more aggressive, trying to stay ahead of the curve, so to speak, and these fielders tend to be more successful getting to balls that are difficult to catch. Others lag behind, wait for the ball to move off the straight line and then must make adjustments, which slows them down.

Baseball teams use personality tests — the most famous of which are William Winslow’s Athletic Motiva-tion Inventory and the Athletic Success Inventory, which is based off AMI — to help them weed out the great players from the good players when it becomes draft time. Instead of looking at players’ heights and speeds, these tests distinguish between their levels of ambition, coachability and leadership. Baseball teams don’t like to give away their secret formulas, but University of Washington’s Ronald Smith and others have looked at the correlation between these tests and success in professional baseball. Smith’s studies found a few characteristics — achievement motivation, coping with adversity and peaking under pressure —correlated well to a long career in the Majors, but, in particular, hitters with higher self-confidence are more successful Major League players. This characteristic doesn’t seem to be as important in football or basketball, probably because the whole team is more responsible for a successful outcome in those sports. In baseball, it’s just the pitcher against the hitter.

"For hitters, failure is such a commonplace experience that you have to have people who maintain confi-dence through even a long string of failure," Stadler says.

Does a fastball rise and a curveball curve?

The terms "rising fastball" and "off-the-table" curveball have become part of the baseball lexicon. But most psychologists and physicists agree that neither really exists. Because of gravity and because a pitcher throws from a mound a few inches above where the batter stands, it is impossible for a fastball to rise — even for a sidearmed pitcher.

Still, many hitters swear they’ve seen — and even been struck out by — these tricky pitches. As a graduate student working on his PhD dissertation at Stanford, Mike McBeath, now at Arizona State, was intrigued by this contradiction and took a month off from his research to write a paper on the illusion of the rising fastball. What he came up with is a model that explains how a fastball could be perceived to have risen even if it had in fact dropped a few feet from the time it was released.

If a batter misjudges the speed of a pitch and is expecting the ball to be slower than it actually is, he expects that it will fall farther by the time it crosses the plate. So he swings where he thinks the ball should be crossing the plate, but that swing is actually a few inches under the ball. Because it is impossible for him to follow the ball from the time of release to the time of contact, the result is a ball that appears to have been so fast that it jumped up over the bat.

The opposite is true for the curveball. The batter assumes the ball is coming faster than it actually is, so by the time it gets to the plate, it’s lower than the batter expected, giving the impression that it fell a few inches.

"The curveball definitely does curve some," McBeath says. "There’s been high-speed photography verifying that. It’s just that it appears to curve in funnier ways than it’s verified to do."

Side-to-side curvature has very little impact on the batter because the bat is big enough to cover the entire plate. Misjudging the speed, however, can cause the batter to swing over or under the ball So, maybe players should really be talking about "rising" and "off-the table" swings rather than pitches.

Monday, March 19, 2007

Prevention of injuries

The aims of this thesis were to study the incidence, severity and pattern of injury in male and female elite football players; to study time trends in injury risk; to identify risk factors for injury; and to test the effectiveness of an intervention programme aimed at preventing re-injury.

All studies followed a prospective design using standardised definitions and data collection forms. Individual training and match exposure was registered for all players participating. Time loss injuries were documented by each team’s medical staff.

The amount of training increased by 68% between the 1982 and 2001 Swedish top male division seasons, reflecting the shift from semi-professionalism to full professionalism. No difference in injury incidence or injury severity was found between seasons. The injury incidence was 4.6 vs. 5.2/1000 training hours and 20.6 vs. 25.9/1000 match hours. The incidence of severe injury (absence >4 weeks) was 0.8/1000 hours in both seasons.

The Swedish and Danish top male divisions were followed during the spring season of 2001. A higher risk for training injury (11.8 vs. 6.0/1000 hours, p<0.01) and severe injury (1.8 vs. 0.7/1000 hours, p=0.002) was observed among the Danish players. Re-injury accounted for 30% and 24% of injuries in Denmark and Sweden respectively.

The Swedish top male division was studied over two consecutive seasons, 2001 and 2002, and comparison of training and match injury incidences between seasons showed similar results. Players who were injured in the 2001 season were at greater risk for injury in the following season compared to non-injured players (relative risk 2.7; 95% CI 1.7-4.3). Players with a previous hamstring injury, groin injury and knee joint trauma were two to three times more likely to suffer an identical injury to the same limb in the following season, but no such relationship was found for ankle sprain. Age was not associated with an increased injury risk.

The effectiveness of a coach-controlled rehabilitation programme on the rate of re-injury was studied in a randomised controlled trial at amateur male level. In the control group, 23 of 79 injured players suffered a recurrence during the season compared to 10 of 90 players in the intervention group. There was a 75% lower re-injury risk in the intervention group for lower limb injuries (relative risk 0.25; 95% CI 0.11-0.57). The preventive effect was greatest during the first weeks after return to play.

Both the male and female Swedish top divisions were followed during the 2005 season. Male elite players had a higher risk for training injury (4.7 vs. 3.8/1000 hours, p<0.05) and match injury (28.1 vs. 16.1/1000 hours, p<0.001) than women. However, no difference was observed in the rate of severe injury (0.7/1000 hours in both groups). The thigh was the most common site of injury in both men and women, while injury to the hip/groin was more frequent in men and to the knee in women. Knee sprain accounted for 31% and 37% of the time lost from training and match play in men and women respectively

Friday, March 9, 2007

Risk of injury for young goalies using adult soccer balls

Risk of injury high among young goalies using adult sized soccer balls

Eager young goalies run a significant risk of injury, trying to make 'a save,' when using an adult sized ball?a practice that is all too common?finds research in the British Journal of Sports Medicine.

There are an estimated 200 million soccer/football players worldwide. In England and Wales 2.25 million players are registered with the Football Association. Of these, 750,000 are youth players, and an additional large but unknown number of children and young adults play informally throughout the year.

All children and young adults attending a fracture clinic in one hospital were monitored for 17 months. Those who had been injured while playing football, and who had sustained a wrist or hand fracture, were asked how the injury had occurred.

Among the 1920 new patients seen at the clinic, 29 wrist fractures were seen in 28 goalies who had been trying to "make a save." One of the goalies had fractured both wrists on separate occasions.

The average age of the injured players was just under 11 years. Most injuries occurred during the summer months, and on grass. Two thirds were sustained during informal play. In almost three quarters of incidents, an adult (size 5) ball had been in play. A junior size ball (size 4) was involved in a further 14 per cent of incidents. In 26 cases a plaster cast for around three weeks successfully treated the fracture, but three fractures required additional manipulation under anaesthetic.

An adult size 5 soccer ball weighs up to 450 g, and can be kicked at speeds of up to 25 m/second. The impact from a stitched ball, particularly when wet, is greater than that from a moulded ball. And goalkeepers are especially vulnerable to impact injury as they repeatedly take the full force of the ball on their hands.

The Football Association made recommendations on the use of appropriately sized soccer balls for young players in 1993, advising a size 4 ball for 8 to 11 year olds, and a size 3 for younger children. But these recommendations do not seem to be widely followed, say the authors.

Pediatric soccer injuries - 1.6 million ER visits

First national review of pediatric soccer injuries finds 1.6 million ER visits over 13-year span

Study finds higher injury rates in girls and very young players

Girl soccer players may be sustaining more injuries than boys, but boys are twice as likely to be hospitalized for their injuries, according to the first comprehensive look at U.S. emergency room data on youth soccer injuries. The review appears in the February issue of The American Journal of Sports Medicine.

Coauthors Robert E. Leininger, Christy L. Knox, MA, and R. Dawn Comstock, PhD, of the Center for Injury Research and Policy at Columbus Children's Hospital, Columbus, Ohio, found startling differences in age, gender, injury rate, diagnosis, and disposition of injuries in their analysis of youth soccer injury statistics.

Past research on soccer injuries has tended to focus on pro players, injuries to specific body parts, and age- or gender-specific soccer injuries. This study is the first to investigate soccer-related injuries among the entire US pediatric population.

The authors reviewed pediatric, soccer-related data from the US Consumer Product Safety Commission's National Electronic Injury Surveillance System (NEISS), a nationally representative sample of 100 US hospital emergency departments (EDs). The NEISS collects information such as patient demographics, injury type and injury event and is updated daily. Though only a sampling of injuries seen in US EDs, data are weighted and the results extrapolated to calculate the numbers of injuries treated in all US emergency departments. The researchers reviewed 1.6 million soccer-related injuries to children ages 2 to 18 years of age seen in EDs participating in the NEISS from 1990 to 2003.

During the 13 years studied, the overall pediatric soccer-related injury rate did not increase significantly, though it reached a peak in 2000. Over the same time period, however, there was a statistically significant increase in the number of injuries among girls 2 to 18 years of age. The increase in the girls' injury rate may reflect a sharp increase in female participation in soccer, the authors theorize.

Overall, girls sustained more ankle and knee injuries and were more likely to have sprains or strains than boys. The number of sprains/strains and lower extremity injuries increased with age, and upper extremity injuries were most common in children ages 5-14. Concussion was the most common injury in players 15 to 18 years of age.

"Future research is needed to further examine soccer-related injuries by gender," the authors write. "Society norms in the US, which may allow very young boys to be more physically active and to engage in activities such as soccer with less parental supervision whereas very young girls may be less likely to do so, may explain the gender difference."

The researchers studied 4 specific age groups: 2-4 years, 5-9 years, 10-14 years, and 15-18 years of age. They found a 4-fold increase in the percentages of injuries occurring in players ages 10-14 (49% of all injuries) from those aged 5-9 years (12.3% of all injuries). "It is possible that the middle school-aged player is bigger, stronger, and playing harder, leading to an increase in the likelihood of injury," says Knox.

Injuries to the face, head, and neck were more common in very young soccer players (2 to 4 years of age) than in older children. The youngest players (especially boys) were also more likely to be hospitalized for soccer injuries than their older counterparts. "In general, younger children have great difficulty expressing themselves in words," says coauthor Christy Knox. "When that child is injured, it seems prudent to hospitalize and observe that child."

"Children 2 to 4 years of age should be closely supervised while playing soccer because of the risk of head injuries and rate of hospitalization," the authors write. "More research needs to be done on soccer helmets to see if the risk for concussion and other head injuries can be decreased, and heading should be minimized among younger players."

The authors call for the establishment of a national database of all soccer participation and injury data. "With increased knowledge of the epidemiology of soccer-related injuries for all pediatric age groups, prevention and training can be improved, and the endemic rate of injury can be decreased even as participation increases," they say.

"Compared to contact sports, soccer has a fairly low injury rate. We want children to stay healthy and active, and to be safe when playing any sport. Parents, players, coaches, referees, soccer organizations, and the medical community should work together to ensure a safe and enjoyable experience for all participants," the authors conclude.

Heading into difficulty?

New soccer studies show short and long-term consequences of common practice

Dr. Frank Webbe has spent more than a dozen years of his life as a soccer referee and coach. He's also a professor of psychology at Florida Tech, with an emphasis on sports psychology. These two worlds came together with his research into the neurocognitive effects of heading in the sport of soccer.

Webbe, who has studied the effects of heading since the early 1990s, recently published two studies with different collaborators. Both studies researched the effects of frequent headings over time, while one focused further on the short-term effects of recent soccer heading. In the research, brain function among soccer players who had played for varying number of years was compared with the brain function of subjects who had never played. In his study with Shelly Ochs, Webbe also compared the functionality of players who had recently played soccer with those who had not.

The results of both studies should further fuel the debate on the safety of this common soccer practice. The results of his recency study were the most clearly defined.

Webbe found that recent heading by players who headed with "moderate-to-high frequency" led in some cases to weaker neurocognitive performance. This lessened performance includes a decline in cognitive function, difficulty in verbal learning, in planning and maintaining attention and a reduced information processing speed.

"What we found is that if Bill plays soccer on a Thursday night, and is a frequent header, he's more likely to score lower on a neurocognitive test Friday morning than a similar player who heads the ball only occasionally," said Webbe.

While recent heading is not guaranteed to decrease functionality, Webbe said it presents a strong enough risk factor to warrant further study.

The two studies seem to contradict each other on the long-term effects of soccer heading. Webbe's work with Ochs reports that, "no significant or strong effect was found for lifetime heading on neuropsychological performance." But, his study with Adrienne D. Witol reached an opposite conclusion, noting "players with the highest lifetime estimates of heading had poorer scores on scales measuring attention, concentration, cognitive flexibility and general intellectual functioning."

Webbe acknowledged the apparent contradiction, but said that the research with Ochs does support the concept of long-term harm.

"Inside the groups of testers, we found that more individuals were likely to be impaired in the frequent heading groups than in the less frequent heading and control groups," he said. "The difference was three or five out of 20 impaired among the lifelong frequent headers as opposed to one or zero out of 20 in the control groups."

After these studies, Webbe is more convinced than ever that soccer heading affects brain function. He has an idea of why this activity can be so damaging.

"Generally, we accept the premise that if you head the ball with proper technique, then your risk for brain injury is lower. However, we have to acknowledge that during a game things happen to make the heading situation less than ideal," said Webbe. "If you leave your feet, or are challenged by an opponent, you may not be able to head the ball correctly. As a result, when you head the ball you are putting yourself in a position to sustain an insult to the brain."

Soccer referees do favor home teams, study shows

Academics have proved what football (soccer) managers in the English Premiership have been complaining about for years – that referees are inconsistent and favour home teams.

Analysing over 2,500 English Premiership matches, researchers discovered that referees were statistically more likely to award yellow and red cards against the away team – even when home advantage, game importance and crowd size were taken into account.

They also found clear evidence of inconsistency between referees – with some referees significantly more likely to punish players than others.

The academics behind the study, which has been accepted for publication in the Journal of the Royal Statistical Society Series A, hope that their research will give the football authorities the firm evidence they need to help improve football refereeing.

"The decisions made by referees can influence the result of games and their actions can have important financial consequences for the clubs and individuals involved," said Dr Peter Dawson, a Wigan fan and lecturer in Economics at the University of Bath.

"Managers have been right to highlight inconsistencies and controversial decisions in games, but without a proper analysis of refereeing decisions over a period of time, their comments look like the usual post-match gripe, especially if they are on the losing side.

"The evidence we have collected and analysed provides a firm factual foundation that will help football's authorities debate what positive action they might take to ensure fair and equitable refereeing of matches in the future.

"This could include encouraging referees to avoid what is presumably unintentional home team bias in their decision making, and examining the extent to which corrective action is allowed to vary between officials."

Researchers, from the universities of Bath (UK), Otago (New Zealand), St Andrews (UK) and Wales, Bangor (UK), analysed all 2,660 matches occurring in the English Premiership seasons from 1996/97 - 2002/3 for disciplinary offences (in terms of the number of yellow and red cards awarded) for home and away teams.

They then developed equations to account for the many different variables that could account for the variation in the number of disciplinary offences. For example, they allowed for teams to play better when they were at home and more aggressively when away, for games, such as top-of-the-table clashes, to be more keenly contested, and for larger crowds to (potentially) exert more influence on referees.

As well as finding a distinct home bias in refereeing disciplinary action and inconsistency between referees, the research also highlighted that:

underdogs tend to incur a higher rate of disciplinary sanction than favourites
the number of disciplinary offences tends to be higher in matches between evenly-balanced teams, in matches with end-of-season outcomes at stake and in matches with higher attendances
home teams appear to play more aggressively in front of larger crowds
the crowd size did not appear to influence the incidence of disciplinary sanction against the away team
there was no evidence that the behaviour of either teams or referees is any different when the match is televised.
"The football pitch is like a laboratory for crime economists," said Dr Dawson, from the University's Department of Economics & International Development.

"You can introduce a new rule or increase the severity of a punishment and then see how long it takes for the referees and the players to adjust their behaviour.

"In many ways this mirrors criminal behaviour on the streets where it takes criminals and law enforcers time to adjust to the implementation of a new law.

"One example highlighted in our findings is the introduction of the automatic red card for tackles from behind in the 1998/9 season.

"This season saw a rise in the number of bookings and sending-offs, but by the end of the season referees had learned how to implement the rules effectively and players had adjusted their behaviour accordingly."

This kind of learning behaviour has also been observed in college basketball in North America. When two referees were introduced there was an immediate tail-off in the number of fouls called in a game, suggesting that as referee competence increased, with fewer fouls being missed, the actual 'crime rate' must have decreased by even more than is suggested by the fall in the number of fouls called.

Such increased monitoring of games, including the use video replays, is clearly something the governing bodies of football need to look into despite the obvious costs involved.

"Football needs the same kind of in-depth analysis if we are to see improvements in the consistency of the important decisions made by referees," said Dr Dawson.

English football (soccer) is 30 times more boring

English football (soccer) is 30 times more boring than football (soccer) games in rest of world

Analysis of just English premier football league and cup games showed that English top division football is in fact 30 times less likely to have high scoring games than the rest of the world taken as a whole, and could thus be seen by some people as 30 times more boring.

In summary their analysis revealed that a total score over 10 goals in any one game occurs approximately only once in every 10,000 English top division matches (once every 30 years) but in top division matches world-wide, such a score is seen once in 300 games (about once every day).

Knee injury in women soccer players = early osteoarthritis

Knee injury in women soccer players linked to early osteoarthritis

One of the fastest growing team sports in America, particularly on college campuses, is women's soccer. Of the more than 17 million players participating in organized soccer nationwide, 7 million are female. While offering an equal opportunity playing field for student athletes, soccer has one unfortunate gender bias: women are more susceptible to knee injury. One of the most common is tearing of the anterior cruciate ligament (ACL)--the ligament in the center of the knee that provides stability. In Sweden, where soccer is wildly popular and women have a shot at playing in a professional league, the risk of ACL injury is 3 to 4 times higher per game hour for young female players than for their male counterparts.
As too many soccer players know, tearing this pivotal ligament brings immediate pain and swelling, followed by a nagging fear of the knee suddenly giving-way. A recent study, published in the October 2004 issue of Arthritis & Rheumatism (, provides compelling evidence of serious risk of knee osteoarthritis (OA) and potentially crippling long-term consequences of a torn ACL for young female athletes. Conducted by a team of researchers at Lund University Hospital, and supported, in part, by the Swedish Soccer Federation, this study focused on 103 female soccer players, between the ages of 26 and 40, who had each suffered an ACL injury 12 years earlier, when they were between the ages of 14 and 28.

Each woman consented to knee radiographs, as well as answered questionnaires about her knee-related quality of life. More than half of the women were assessed as having OA of the knee, accompanied by persistent pain and functional limitations. What's more, 60 percent of the players had undergone reconstructive surgery of the torn ligament soon after sustaining their injury. Using various analyses, the researchers found that surgical reconstruction had no significant effect on knee pain or disabling symptoms. The surgical techniques used today for this injury might be more effective in preventing OA, but this has not yet been proven in scientific studies.

The study's leading researcher, L. S. Lohmander, M.D., Ph.D., describes the very high prevalence of pronounced OA among these young ACL-injured women as "alarming," with serious implications for their future. "For many of these women, the OA disease process can be expected to progress over time and the need for an osteotomy or knee arthroplasty may arise well before the age of 50 years in many of these subjects," Dr. Lohmander speculates. "Although joint replacement may be an efficient treatment for knee OA, the risk of aseptic implant loosening and revision is more than 3-fold higher in the patients operated on while younger than age 65 years, than if older than 75 years."

The first long-term study of the risk and complications of OA linked to this common and serious knee injury specifically among women soccer players, its findings emphasize the need for improved efforts at prevention and treatment of this torn ligament. "Randomized, controlled trials are needed in which different surgical techniques and rehabilitation protocols are compared directly with the best nonsurgical treatment," Dr. Lohmander concludes.

Score-celebration injuries among soccer players

New study indicates score-celebration feats result in serious injuries among soccer players

In one of the most popular sports worldwide, extensive attention is given to the "trademark" score-celebrations performed by professional top-level soccer players. While the Federation Internationale de Football Association (FIFA) devotes a page of their website to these dramatic celebrations, there has been no mention of the sometimes serious injuries and loss of playing time that have followed these events.
In a recent study published in the July 2005 issue of The American Journal of Sports Medicine, researchers examined these events among professional soccer players in an effort to prevent future injuries.

Dr. Bulent Zeren from the Center for Orthopadedics and Sports Traumatology in Turkey, teamed up with Dr. Haluk H. Oztekin, to report on 152 male soccer players from professional leagues in Turkey who had been treated for injuries incurred during a competitive match. Over the duration of two playing seasons, 9 of the 152 players had injured themselves while performing a post-goal celebration. The injuries ranged from ligament and muscle strains as a result of 'Sliding' across the field to rib and clavicle fractures as a result of the players 'Piling Up' on each other. The most severe injury was an ankle fracture that required surgery. These injuries took place in 9 separate games where the field was natural turf and was dry in all but the incident requiring surgery. Although each patient was enrolled in an early rehabilitation program, the average playing time lost was 5 weeks.

The researchers of this study conclude that exaggerated celebrations after making a goal, such as sliding, piling up, and tackling teammates, can result in serious injury. Not only should general guidelines be in place to prevent injuries, but coaches and team physicians should teach behavior-modification to minimize injury risks. In addition, the research suggests that stricter rules should be enforced for penalizing this type of behavior in an effort to prevent score-celebration injuries.

The article "Score-Celebration Injuries Among Soccer Players" can be found on The American Journal of Sports Medicine's website at

New World Cup soccer ball will unsettle goalkeepers

New World Cup soccer ball will unsettle goalkeepers, predicts scientist

Scientist backs claims of top goalkeepers

The new soccer ball that will be used for the first time in the World Cup's opening game on Friday (9 June 2006) is likely to bamboozle goalkeepers at some stage of the tournament, a leading scientist has warned.
The Adidas 'Teamgeist' soccer ball has just 14 panels - with fewer seams - making its surface 'smoother' than conventional soccer balls which have a 26 or 32 panel hexagon-based pattern.

This makes it aerodynamically closer to a baseball and, when hit with a slow spin, will make the ball less stable, giving it a more unpredictable trajectory in flight.

"With a very low spin rate, which occasionally happens in soccer, the panel pattern can have a big influence on the trajectory of the ball and make it more unpredictable for a goalkeeper," said Dr Ken Bray, a sports scientist at the University of Bath and author of the new popular science book How to score – science and the beautiful game.

"Because the Teamgeist ball has just 14 panels it is aerodynamically more similar to the baseball which only has two panels.

"In baseball, pitchers often throw a 'curve ball' which is similar to a swerving free kick and the rotating seam disrupts the air flow around the ball in much the same way as a soccer ball does.

"Occasionally though, pitchers will throw a 'knuckleball' which bobs about randomly in flight and is very disconcerting for batters.

"It happens because pitchers throw the ball with very little spin and as the ball rotates lazily in the air, the seam disrupts the air flow around the ball at certain points on the surface, causing an unpredictable deflection.

"With the world's best players in Germany this summer, there are bound to be plenty of spectacular scoring free kicks.

"But watch the slow motion replays to spot the rare occasions where the ball produces little or no rotation and where goalkeepers will frantically attempt to keep up with the ball's chaotic flight path."

The ball, which has been used by teams competing in the World Cup in practice sessions, has already been criticised by England goalkeeper Paul Robinson and Germany goalkeeper Jens Lehmann for its light-weight and unpredictable behaviour.

Female Soccer Players Perform Best On A High-Fat Diet

Female Soccer Players Perform Best On A High-Fat Diet, UB Study Finds

Female soccer players were able to perform longer at a higher intensity on a diet composed of 35 percent fat than on diets of 27 percent fat or 24 percent fat, researchers at the University at Buffalo have found.

The higher-fat diet, achieved by adding peanuts to the athletes' normal diet, had no effect on weight, percentage of body fat, heart rate or blood pressure, findings showed.

Peter J. Horvath, Ph.D., associate professor in the Department of Physical Therapy, Exercise and Nutrition Sciences in UB's School of Health Related Professions, presented the study here today (April 19, 1999) at the annual meeting of the Federation of American Societies of Experimental Biology.

"The women went 1.2 to 1.5 kilometers farther before reaching exhaustion while doing very-high-speed intermittent exercise when on the high-fat diet, compared to the lower-fat diets," said Horvath. "That is really a striking difference.

"Women are better fat metabolizers than men. Our earlier dietary studies with male and female competitive runners showed that while both improved their performance on a higher-fat diet, women benefited more than men. One implication of these findings is that dietary recommendations for women athletes should be different from men's," he said.

The study involved nine female collegiate soccer players who ate three diets in a randomized crossover design -- their normal diet, normal diet plus 415 calories of oil-roasted peanuts per day, or normal diet plus an equal amount of extra calories from carbohydrate-rich energy bars. The women consumed each diet for seven days during the luteal phase (the second half) of the menstrual cycle, when a woman's ability to metabolize fat is greatest, Horvath said.

Carbohydrate intake was highest -- 63 percent of total calories -- during the energy-bar diet, and lowest -- 51 percent -- during the peanut diet. Fat was highest during the peanut diet -- 35 percent -- versus 24 percent on the energy-bar diet. Protein and calorie intake, and caloric expenditure remained essentially the same across the three diets.

Endurance testing was designed to mimic soccer play, using constant speed running and running at different rates on a treadmill, plus forward running with a side-step maneuver performed on a force plate. The athletes were tested until exhaustion on the seventh day of each diet. Treadmill speed increased progressively, which meant the longer the athletes performed, the harder they had to work.

Results showed that the soccer players traveled about 15 percent farther on the peanut diet than on normal diet with or without energy bars, with no lessening of muscle performance, as measured by the force plate.

"When women consumed the high-fat diet, they performed longer at the highest intensity," Horvath said. Distances were 11.2 km on the high-fat diet, 10 km on the normal diet and 9.7 km on the high-carbohydrate diet.

"These results support our thesis that supplementing the diets of female athletes with peanuts or other fat sources can help build up their energy reserves and improve performance," Horvath said. "A low-fat diet may result in a poorer performance for women in a long, intermittently intense sport like soccer, especially during the later phase of the menstrual cycle."

Heading ball finds no injury boost in soccer

Review study of 'heading' ball finds no injury boost in soccer

CHAPEL HILL - Contrary to many parents' concerns, soccer players who cause the ball to bounce forcefully off their heads in games or practices -- a technique called "heading" -- do not risk brain injuries, a new University of North Carolina at Chapel Hill review study shows.

And the younger a player is, the less chance he or she has of getting hurt "heading" because young opponents cannot put much force behind their kicks, the lead researcher says.

"Based on the literature, we'd say that purposeful heading of a ball is not something parents should be concerned about," said Dr. Donald T. Kirkendall, clinical assistant professor of orthopedics at the UNC School of Medicine. "In fact, parents of children under age 12 have little reason to be concerned because heading in children's games tends to be a novelty, usually off a bounced or thrown ball, and kids just can't kick the ball that hard."

Kirkendall reviewed every study he could find on the subject. A report on the work appears in the May issue of Sports Medicine, a scientific review journal.

"In the late 1960s or early 1970s people started talking for the first time about what they called 'footballers' migraine,'" Kirkdendall said. "Back then, this could have been a problem because when the old leather ball got wet, it could become as much as 20 percent heavier. The modern soccer ball doesn't absorb water even if you play in the rain."

Later, in the 1980s Norwegian scientists published several papers implicating heading in neurological deficits, he said. That work did not account for other factors that could have contributed to the deficits such as previous head injuries, drug or alcohol problems, learning disabilities and other factors.

"The consensus of what we see today is that the force of impact from heading a soccer ball is fairly low," Kirkendall said. "Players prepare for heading the ball by tensing up their neck muscles and, in effect, put their entire body into the heading motion. We're not talking here about accidents in which the ball strikes someone's unprepared head."

Head injuries are possible in soccer, of course, but they result chiefly from players falling down, kicking one another, colliding with someone or running into a goal post, he said. Compared with tackle football, soccer usually produces minor injuries. Most involve bruises or lacerations, and other studies have shown that most of the few concussions fall into the mildest category. All players who strike their heads hard against anything and feel or look groggy should be removed from play for at least 15 to 20 minutes for trainers to check for lingering symptoms of concussion. Such trauma can alter mental function, producing grogginess and need not involve unconsciousness.

People who suspect a player might be concussed should not ask about deep-seated memories, such as what school they attend or what their name is, but about things that happened just before the event, Kirkendall said. If a player can't say what happened moments earlier, he or she might have an injury and should be removed from play and checked by a physician. Himself a longtime soccer player, Kirkendall once suffered a partially detached retina from a ball hitting him on the eye.

"A neurologist friend of mine, who also is a coach, once was ejected from a game for trying to get a referee to stop play so that he could get one of his players off the field for a head injury," he said. "He did the right thing for the girl and didn't care that he was thrown out."

Negative impacts of long-term soccer pl

OHSU Researcher studies possible negative impacts of long-term soccer play

Lower Mental Skills Testing Scores for Amateur Soccer Players May Be Linked to Headers and Head Injuries

Years of rough play on the soccer field may have a negative impact on a player's mental function. That's according to research reported by Dutch Neuropsychologist Erik J.T. Matser and Oregon Health Sciences University researcher Muriel D. Lezak, Ph.D., professor of neurology, School of Medicine. The conclusions are printed in the Sept. 8, 1999 issue of The Journal of the American Medical Association.

"Headers -- hitting the ball with one's head -- have always been part of the game," Lezak said. "Matser has pointed out that, in addition to these subconcussive blows, many players have also suffered concussions on the playing field."

To learn the possible effects of these injuries, Lezak worked with a research team in the Netherlands to search for an answer. The resulting study showed amateur soccer players scored lower on tests for planning and some aspects of memory than athletes involved in non-contact sports.

A total of 60 athletes were involved in the study. Thirty-three soccer players were tested along with 27 control athletes. The control athletes were in the same physical shape, age group and education level as the soccer players. Both groups of athletes had been involved with their sport for an average of 17 years. However, the control athletes had not received repeated concussive and subconcussive blows to the head.

When compared to the control subjects, researchers found the soccer players exhibited impaired ability on tests relating to planning and memory. On the planning tests, 39 percent of soccer players had scores that indicated impaired performance compared to 13 percent of control athletes. On the memory tests, 27 percent of soccer players had test scores that showed impaired performance compared to 7 percent of control athletes. In addition, researchers found a relationship between the number of concussions incurred by soccer players and lower test scores.

The study is released as soccer enjoys growing popularity across the United States. Worldwide, more than 200 million athletes play the game. Here in the United States, the sport is popular among youngsters and adults alike. This past July, more than 40 million television viewers watched as the U.S. team beat China to win the 1999 Women's World Cup.

While the study's conclusion suggests the impact of heading and other soccer-related head injuries may be linked to decreased mental performance, the research indicates that the impairment appears to be mild.

"One or two bumps on the head are not going to seriously hurt anyone," Lezak said. "However, numerous subconcussive or concussive injuries present a medical and public health concern."

Broadcast Rights to the Italian Serie A

Fox Soccer Channel Acquires Exclusive, English-Language Broadcast Rights to the Italian Serie A Through 2010

America’s Preeminent Soccer Destination Becomes Exclusive Television Home to International Powerhouses AC Milan, Juventus, Inter Milan and AS Roma

Fox Soccer Channel today announced the acquisition of the exclusive, English-language broadcast rights to Italy’s world-renowned professional soccer league, Serie A. Beginning this August and running through the 2009/2010 season, Fox Soccer Channel’s in-depth coverage of Serie A will feature up to three live matches each weekend, plus a mid-week match when scheduled. Fox Soccer Channel will also introduce its first-ever, dedicated Serie A highlights show; recapping the weekend’s action, the half-hour program will air on Mondays. On-air commentators, and the complete telecast schedule, will be announced at a later date.

The rights were acquired from Media Partners & Silva, the international sports agency that owns and distributes the Italian Serie A media rights worldwide. As part of the agreement, Fox Soccer Channel will become the exclusive English-language television destination for Italian Serie A in the country.

“We are thrilled to be the only English-language network to bring to fans across the country the excitement, passion and glory of top-flight Italian soccer,” said David Sternberg, executive vice president and general manager of Fox Soccer Channel. “This new deal with the Italian Serie A, coupled with our renewed agreements with the English Premier League and Major League Soccer, is not only the perfect complement to our already strong offering of the most in-depth and comprehensive coverage of domestic and international soccer, but it also reaffirms Fox Soccer Channel’s position as the sport’s preeminent broadcaster in the U.S.”

While Fox Soccer Channel has offered coverage of a limited selection of Serie A matches during the past two years, starting this season, the network will telecast approximately 140 matches and more than 140 hours of additional live Serie A programming yearly, including coverage of Italian powerhouses AC Milan, Inter Milan, Juventus and AS Roma. With the addition of complete season coverage of Serie A, Fox Soccer Channel will now offer more than 1,600 total live programming hours each year.

“We are delighted to expand our partnership with Fox Soccer Channel as we work together to extend the visibility of the Italian Serie A on America’s premier soccer destination,” said Riccardo Silva, president of Media Partners & Silva. “We strongly feel that this new partnership will increase the popularity of the Italian game in the U.S., as well as enhance Fox Soccer Channel’s offering of world-class soccer.”

About Fox Soccer Channel

Fox Soccer Channel offers the most comprehensive coverage of world-class soccer available in the United States, including Major League Soccer, the Barclays English Premier League, Argentine First Division and Italian Serie A; as well as global tournaments such as the UEFA Cup, UEFA Women’s Championship, English FA Cup, FIFA Club World Cup, CONCACAF Champions’ Cup and FA Community Shield. The Official Broadcast Partner of the United States Youth Soccer Association, Fox Soccer Channel also televises United Soccer League and NCAA Division I college soccer matches. The channel reaches more than 29 million cable and satellite households in the U.S. and Caribbean.

Tuesday, March 6, 2007

Goalie may influence direction of penalty kick in soccer

Goooal! New study shows goalie may influence direction of penalty kick in soccer

A penalty kick places a goalkeeper at such a disadvantage that only approximately 18% of penalty kicks are saved. However, some soccer fans think goalkeepers might save penalty kicks more easily by standing marginally to the left or right.

It turns out they're right! In an article published in the March issue of Psychological Science, Professors Rich Masters, John van der Kamp and Robin Jackson of the Institute of Human Performance at the University of Hong Kong found that penalty takers are more likely to direct the football to the side with more space.

After observing 200 video clips of penalty kicks, including those in World Cup and African Nations Cup matches, European Championships, and Union of European Football Association (UEFA) Champions League matches, the researchers found that goalkeepers stood marginally left or right of goal centre 96% of the time. While the mean displacement of the goalkeepers was 9.95 cm, there was no association between the side to which the goalkeepers stood and the direction in which they dived (94 out of 190 dives were to the side with less space). So goalkeepers weren't standing off-centre as a strategy.

Remarkably, despite all of the factors that can influence the direction of a penalty kick, more penalty kicks were directed to the side with more space.

After conducting experimental studies and carefully evaluating the results, Professor Masters and his team concluded that it is feasible for a goalkeeper to influence perceptions of space and consequently the direction of penalty kicks by standing marginally to one side or another of the goal centre. The goalkeeper can then strategically dive to the side with more space.

Extrapolation of their data indicates that the optimum displacement of the goalkeeper in real life is from 6 to 10 cm. Their results suggest that the penalty taker is unlikely to notice a displacement in this range, but is at least 10% more likely to direct the penalty kick to the side with more space than to the side with less space.