Thursday, September 2, 2010

Carlos '97 free kick no fluke, say French physicists

Ω

Roberto Carlos' free kick goal against France in 1997's Tournoi de France is thought by many to have been the most skilful free kick goal - from 35m with a powerful curling banana trajectory - ever scored; but by others to have been an incredible fluke.



Taken in 1997, a year before the French won the World Cup, Brazilian Carlos's goal held France to a frustrating draw but, now, a group of French physicists – perhaps with a nostalgic eye to a happier time for French football – have computed the trajectory and shown that Carlos' goal was no fluke.

The research published today, Thursday 2 September, in New Journal of Physics (co-owned by the Institute of Physics and German Physical Society), explains why French goalkeeper Fabien Barthez made no move for the ball (but why a ball-boy ten metres from the goal did duck to safety) as the ball made a last moment sweep left and landed in the back of the net.

Using tiny plastic (polypropylene and polyacetal) balls and a slingshot, the French research team from the École Polytechnique in Palaiseau varied the velocity and spin of balls travelling through water to trace different trajectories.

While their research quickly confirmed the long-known Magnus effect, which gives a spinning ball a curved trajectory, their research revealed fresh insight for spinning balls that are shot over a distance equivalent to Roberto Carlos' free kick.

The friction exerted on a ball by its surrounding atmosphere slows it down enough for the spin to take on a greater role in directing the ball's trajectory, thereby allowing the last moment change in direction, which in the case of Carlos' kick left Barthez defenceless.

The researchers refer to their discovery as the 'spinning ball spiral', comparing the spiraling effects of Roberto Carlos's kick with the shorter-distance (20-25m) 'circular' free kicks shot by the likes of Beckham and Platini.

As Christophe Clanet and David Quéré, researchers from École Polytechnique, write, "When shot from a large enough distance, and with enough power to keep an appreciable velocity as approaching the goal, the ball can have an unexpected trajectory. Carlos' kick started with a classical circular trajectory but suddenly bent in a spectacular way and came back to the goal, although it looked out of the target a small moment earlier.

"People often noticed that Carlos' free kick had been shot from a remarkably long distance; we show in our paper that this is not a coincidence, but a necessary condition for generating a spiral trajectory."

Ω

Wednesday, September 1, 2010

Men and women use different leg and hip muscles during soccer kick

Ω


Significant differences in knee alignment and muscle activation exist between men and women while kicking a soccer ball, according to a study published this month in the Journal of Bone and Joint Surgery. Data reveals that males activate certain hip and leg muscles more than females during the motion of the instep and side-foot kicks – the most common soccer kicks – which may help explain why female players are more than twice as likely as males to sustain an Anterior Cruciate Ligament (ACL) injury.

Soccer is one of the fastest-growing sports in the United States with approximately 20 million registered players and an annual participation increase of more than 20 percent , according to statistics from the National Collegiate Athletic Association (NCAA) . Women also are playing this sport on more competitive levels. Prior research shows that females are more prone to non-contact ACL injuries than males and though many theories exist, a direct cause for the disparity is unknown.

"By analyzing the detailed motion of a soccer kick in progress, our goal was to home in on some of the differences between the sexes and how they may relate to injury risk," said orthopaedic surgeon Robert H. Brophy, MD, study author and assistant professor of orthopedics, Washington University School of Medicine in St. Louis. "This study offers more information to help us better understand the differences between male and female athletes, particularly soccer players."

Dr. Brophy and his colleagues from the Motion Analysis Laboratory and Sports Medicine Service at the Hospital for Special Surgery in New York used 3-D video-based motion analysis and electromyography to examine the differences between 13 male and 12 female college soccer players during the action of kicking a soccer ball.

Using eight to 10 video cameras, 21 retroreflective markers and 16 electrodes simultaneously, researchers measured the activation of seven muscles (iliacus, gluteus maximus, gluteus medius, vastus lateralis, vastus medialis, hamstrings and gastrocnemius) in both the kicking and supporting legs; as well as two additional muscles (hip adductors and tibialis anterior) in the kicking leg only. Five instep and five side-foot kicks were recorded for each player. Muscle activation was recorded as a percentage of maximum voluntary isometric contraction.

They found that male players activate the hip flexors (inside of the hip) in their kicking leg and the hip abductors (outside of the hip) in their supporting leg more than females.

In the kicking leg, men generated almost four times as much hip flexor activation as females (123 percent in males compared to 34 percent in females).
In the supporting leg, males generated more than twice as much gluteus medius activation (124 percent in males compared with 55 percent in females) and vastus medialis activation (139 percent in males compared with 69 percent in females).
"Activation of the hip abductors may help protect players against ACL injury," said Dr. Brophy, a former collegiate and professional soccer player and past head team physician for the former St. Louis Athletica professional women's soccer club. "Since females have less activation of the hip abductors, their hips tend to collapse into adduction during the kick, which can increase the load on the knee joint in the supporting leg, and potentially put it at greater risk for injury."

Brophy said that although the study does not establish a direct cause-and-effect relationship between muscle activation and knee alignment and ACL injuries, the data "moves us toward better understanding of what may contribute to differences in injury risk between the sexes and what steps we might take to offset this increased risk in females."

The current research in the area of ACL injury prevention has shown some promise. For example, in 2008, the Centers for Disease Control and Prevention published a study that found a new training program called the Prevent Injury and Enhance Performance (PEP) program, was effective in reducing ACL injuries in female soccer players. Developed by the Santa Monica Orthopedic and Sports Medicine Research Foundation and supported by the American Academy of Orthopaedic Surgeons (AAOS) among other medical and athletic associations, PEP is an alternative warm-up regimen that focuses on stretching, strengthening and improving balance and movements and can be conducted during regular practice time and without special equipment.

"Programs focusing on strengthening and recruiting muscles around the hip may be an important part of programs designed to reduce a female athletes' risk of ACL injury," said Dr. Brophy. "Coaches and trainers at all levels, from grade school through professional, should consider using strategies that demonstrate potential to prevent these injuries."

He said that additional research is warranted to investigate how the differences in hip muscle activation and alignment between the sexes may relate to differences in the risk of lower extremity injury among athletes in soccer and other sports.

Monday, July 19, 2010

Major League Pitchers 34 Percent More Likely to be Injured than Fielders

Ω

Watch out if you are a Major League Baseball (MLB) pitcher prior to the All-Star break. Pitchers are 34 percent more likely to be injured than fielders, according to a study presented today at the American Orthopaedic Society for Sports Medicine’s (AOSSM) Annual Meeting. The study looked into the epidemiology of MLB players’ injuries from 2002 – 2008. It also found that 77 percent of all injuries to pitchers happen before the All-Star Game.

“Even though baseball is a passion of many people and our national pastime, there is very little information about the epidemiology, characteristics or distribution of injuries in Major League Baseball,” said Maj., Matthew Posner, MD, orthopaedic surgeon at the William Beaumont Army Medical Center in El Paso, Texas. “This study attempts to evaluate Major League injuries over the period of six years.”

The study authors analyzed Major League Baseball disabled list data from a single internet website for the years 2002 – 2008. Then they calculated the frequency and proportional distribution of injuries by anatomic region, league, time of season and position. The study found that upper extremity injuries accounted for 51.4 percent of all injuries. Lower extremity injuries accounted for 30.6 percent, while back injuries accounted for 7.4 percent and core muscle injuries accounted for 4.3 percent.

Pitchers had a 34 percent higher injury rate than fielders prior to the All-Star Game, according to the study. Not surprisingly, pitchers experienced 67 percent of the injuries to the upper extremity compared to fielders while fielders also had a greater proportion of the lower extremity injuries and injuries to other anatomic regions, according to the study.

The study also noted that pitchers also spent a greater proportion of days on the disability list (62.4 percent) when compared to fielders (37.6 percent). But both pitchers and fielders spent significantly more days on the disabled list for upper extremity injuries than for lower extremity injuries.

National League or American League? The study found that the distribution of injuries by anatomic region was nearly identical between players in the National League and the American League when all players (pitchers and fielders) were considered. National League players injured their upper extremities 51.7 percent of the time, lower extremities 30.7 percent and other anatomic regions 17.7 percent.

American League players injured their upper extremities 51.1 percent of the time, lower extremities 30.5 percent and other anatomic regions 18.4 percent, according to the study.

As for the timing of the injuries, 74.4 percent of all MLB players’ injuries occurred before the All-Star break. Pitchers sustained 76.5 percent and fielders sustained 71.7 percent of their total respective injuries prior to the All-Star game. Seventy-nine percent of all shoulder and elbow injuries happened to pitchers before the All-Star game and 74.8 percent of all hamstring, quadriceps, groin and core injuries to fielders happened before the All-Star game.

Wednesday, July 7, 2010

Fouls go left: Soccer referees may be biased based on play's direction of motion


Penn study finds left-to-right readers more likely to call foul for right-to-left attacks


Soccer referees may have an unconscious bias towards calling fouls based on a play's direction of motion, according to a new study from the of University of Pennsylvania School of Medicine. Researchers found that soccer experts made more foul calls when action moved right-to-left, or leftward, compared to left-to-right or rightward action, suggesting that two referees watching the same play from different vantage points may be inclined to make a different call. The study appears in the July 7 online edition of PLoS ONE.

It's been documented that individuals who read languages which flow left-to-right are more likely to have a negative bias for events moving in the opposite direction, from right-to-left. In the Penn study of twelve members of the University of Pennsylvania's varsity soccer teams (all native English speaking), researchers found that participants viewing the soccer plays were more likely to call a foul when seeing a right-to-left attack

"The effects are impressive considering that left-moving and right-moving images were identical, with the only difference being that they were flipped along the x-axis to create right-to-left and left-to-right versions," said lead researcher Alexander Kranjec, PhD, a post-doctoral fellow in the Neurology Department at the University of Pennsylvania School of Medicine. "If the spatial biases we observed in this population of soccer players have similar effects on referees in real matches, they may influence particular officials differently: referees on the field will more frequently be in positions that lower their threshold for calling fouls during an attack, compared to assistant referees working the lines."

In real matches, referees and linesmen tend to be exposed to different quantities of right-to-left or left-to-right attacking plays, as referees employ a system to help them cover the field efficiently. Referees are encouraged to use a diagonal patrolling technique, choosing to run either a left or a right diagonal, while the assistant referees are tasked with running the sidelines.

Based on this study, the left diagonal system would favor the offense (viewing more attacks from right-to-left), and the right diagonal system would favor the defense (viewing more attacks from left-to-right). Given the relational opposition, the authors suggest that referees should avoid switching diagonals at halftime.

"There could be an unfair advantage if one team goes into halftime with a lead and the referees switch to a right diagonal system in the second half, favoring both defenses," said Dr. Kranjec. "However, because referees viewing leftward action may be more likely to see a foul when no foul was actually committed, as seemed to be the case when the referee disallowed what should have been the US team's third goal against Slovenia, the bias could work against the offense sometimes."

Study participants called approximately three more fouls when images of soccer plays where viewed from right-to-left (66.5 fouls) compared to mirror images moving left-to-right (63.3 fouls). Participants were statistically more likely to call a foul when seeing a right-to-left attack.

Previous studies suggest that similar directional effects are reversed in populations that read right-to-left languages, but other populations (e.g. Arabic or Hebrew readers) would need to be tested directly to see if the effects reported in this study correlate with reading habits.

###
The study will be available online at http://dx.plos.org/10.1371/journal.pone.0011667.

Friday, July 2, 2010

New World Cup Soccer Ball Will Unsettle Goalkeepers, Predicts Scientist

The new football that is being used for the first time in the World Cup is likely to bamboozle goalkeepers at some stage of the tournament, a leading scientist has warned.

The Adidas ‘Teamgeist’ football has just 14 panels - with fewer seams - making its surface ‘smoother’ than conventional footballs 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 football, 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 football 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.

Psychologists Link Hitting Skills to Vision

Why do some players hit it out of the park, when others can barely get it past the pitcher? Could it be that athletes playing well in a baseball game see the ball as a different size than it really is?

When heavy-hitter Paul Rugani steps up to plate, he's ready to knock a softball out of the park. "It's fun to hit. It's fun to get on base," Rugani says. "I like being up in situations where I can knock runners in."

Good players like Rugani can bring in home runs easily, and many athletes claim when they hit well in a game, the ball appears much bigger than it really is. Now, cognitive psychology student Jessica Witt sets out to find out if the theory is true.

"I watched players play, and after the games were over, I asked them to look at an array of different sized circles and pick which circle they thought best matched the size of the softball," Witt, of the University of Virginia in Charlottesville, tells DBIS.

Witt found players picking the larger circles performed better, proving that a player's perception of the ball's size is somehow linked to his performance. "It's hard to know which direction the effect goes," she says. "Do you see it as bigger and therefore hit better, or are you hitting better and therefore see it as bigger?"

She also found athletes who hit poorly see the ball as being much smaller than it really is. She says, "If we're a poor hitter, we see the world full of really, tiny, tiny, tiny balls that are really difficult to hit."

So to do well in a game, think big to hit big.

Witt recently conducted another study to find out if golfers who do well in a game see the cup as being bigger. Preliminary results suggest golfers do, indeed, see the cup bigger when playing well.

BACKGROUND: Perception and action -- the interactions between mind and body -- could be interlinked. Athletes often say that when they are playing well -- shooting hoops, hitting baseballs, catching football passes -- the ball appears bigger. When they are in a slump, the ball appears smaller. A new study by University of Virginia psychologists has found a connection between batting averages of softball players and how big or small they thought the ball seemed.

ABOUT THE STUDY: The scientists conducted their experiment at several softball fields in Charlottesville and asked players who had finished playing for the day to look at eight different-sized circles on a board, and to pick the one that best represented the size of the softball they had been trying to hit. They compared that data to the hitting percentage of the players for that day. The study found that when players were hitting well, they clearly perceived the ball to be bigger. And when they were hitting less well, they perceived the ball to be smaller. The scientists plan to continue their study on perceived ball size and batting averages under more controlled conditions.

HOW WE SEE "DEPTH": The human visual system is designed to allow us to detect fine detail, track a moving object, see colors, and perceive depth. All these components of a visual scene are processed and merged by the brain so that we observe them as one visual experience. How we recognize that different objects are at different distances from us depends on visual cues. For objects beyond 100 feet, the image that's projected on to the back of the eye is basically the same size to both eyes, so cues of depth perception would include knowing the relative range of sizes of objects in general. If one object partly hides another, we know that the object in front is closer. And as we move our heads and bodies, nearby objects will seem to move more quickly than distant objects, an effect called motion parallax.

For objects closer than 100 feet, we need three-dimensional vision. Because the eyes are separated by about six centimeters, each eye gets a slightly different view of the same object. So when we fixate on one object, we can tell if another object is in front of or behind it, because the object is located in two different places on the images that reach the retinas, or backs of the eyes. This is called disparity. Experiments have found that depth perception likely occurs in the primary visual cortex, where individual neurons receiving input from the retinas of the two eyes fire specifically when retinal disparity exists.

VISION PROBLEMS: If particular parts of the brain are damaged, people may lose some visual perception. They might not be able to recognize faces, for instance (prosopagnosia), or not be able to name colors (color anomia). And sometimes they can lose their stereoscopic vision (visual spatial agnosia) or lose the ability to see objects that are in motion (movement agnosia).

Science of Soccer: Ball Aerodynamics Focus of Research

With the attention of sports fans worldwide focused on South Africa and the 2010 FIFA World Cup, U.S. scientist John Eric Goff has made the aerodynamics of the soccer ball a focus of his research.

In an article appearing in the magazine Physics Today this month, Goff examines the science of soccer and explains how the world's greatest players are able to make a soccer ball do things that would seem to defy the forces of nature.

Goff's article looks at the ball's changing design and how its surface roughness and asymmetric air forces contribute to its path once it leaves a player's foot. His analysis leads to an understanding of how reduced air density in games played at higher altitudes -- like those in South Africa -- can contribute to some of the jaw-dropping ball trajectories already seen in some of this year's matches.

"The ball is moving a little faster than what some of the players are used to," says Goff, who is a professor of physics at Lynchburg College in Virginia and an expert in sports science.

For Goff, soccer is a sport that offers more than non-stop action -- it is a living laboratory where physics equations are continuously expressed. On the fields of worldwide competition, the balls maneuver according to complicated formulae, he says, but these can be explained in terms the average viewer can easily understand. And the outcomes of miraculous plays can be explained simply in terms of the underlying physics.

Goff also is the author of the recently published book, "Gold Medal Physics: The Science of Sports," which uncovers the mechanisms behind some of the greatest moments in sports history, including:

* How did Cal beat Stanford in the last seconds with five lateral passes as the Stanford marching band was coming on to the field?
* How did Doug Flutie complete his "Hail Mary" touchdown pass that enabled Boston College to beat Miami?
* How did Lance Armstrong cycle to a world-beating seven Tour de France victories?
* How did Olympic greats Bob Beamon (long jump), Greg Louganis (diving) and Katarina Witt (figure skating) achieve their record-setting Olympic gold?

The article "Power and spin in the beautiful game" appears in the July, 2010 issue of Physics Today and is available at http://www.physicstoday.org/beautiful_game.html

Thursday, June 24, 2010

Left or Right? Early Detection of Soccer Penalty Kicks

Ω

In the split second before foot meets ball, a soccer player’s body betrays whether a penalty kick will go left or right, according to recent research in cognitive science at Rensselaer Polytechnic Institute. Photo Credit: Rensselaer: Daria Robbins

In the split second before foot meets ball, a soccer player’s body betrays whether a penalty kick will go left or right, according to recent research in cognitive science at Rensselaer Polytechnic Institute. The findings could explain how some top goalkeepers are able to head off a penalty kick, diving in the correct direction in advance of the kick. It could also point the way to changes in how players kick, and goalies react.

The research, performed by Rensselaer doctoral student Gabriel J. Diaz, employed motion capture technology and computer analysis to identify five early indicators of the direction a ball would ultimately be kicked. Diaz said his research stemmed from an observation of real-world penalty kicks, in which players aim for the left or right side of the goal while hiding their choice from the goalkeeper.

“When a goalkeeper is in a penalty situation, they can’t wait until the ball is in the air before choosing whether to jump left or right — a well-placed penalty kick will get past them,” Diaz said. “As a consequence, you see goalkeepers jumping before the foot hits the ball. My question is: Are they making a choice better than chance (50/50), and if so, what kind of information might they be using to make their choice?”

Diaz tested 27 potential indicators of kick direction — 12 drawn from sports literature and 15 derived from a computer analysis of the kicks — and identified five as reliable indicators of the direction the ball will go.

In the second part of his work, Diaz also showed that four of the five early indicators he identified are used by people who are able to predict the direction of the kick before the foot strikes the ball.

Diaz used motion capture technology — cameras, sensors, and software — in Rensselaer Associate Professor Brett Fajen’s Perception and Action (PandA) motion capture lab to record the movements of three college-level penalty kickers. The technology is similar to that used to create realistic movement in computer-generated graphics.

More than 40 sensors placed on 19 major joints of the body (and the ball) recorded the movements of the kickers as they stood behind the ball, took two steps, and kicked either to the left or of the right side of a goal. Diaz recorded 126 kicks, half to the left and half to the right.

Then he tested the data he collected against the suite of 27 potential indicators.

Twelve of the indicators — such as the angles of the kicking foot, kicking upper-leg, and kicking shank — were movements of a specific, or “local,” area of the body highlighted by coaches and sports psychologists. Among them he found that two — the angle at which the non-kicking foot is planted on the ground, and the angle of the hips as the kicking foot swings forward —are reliable indicators of kick direction.

The 15 indicators identified in a computer analysis of the kicks were so-called “distributed movements” — patterns of coordinated movement throughout the body. Three of the “distributed” movements proved to be reliable early indicators, none of which appears to have drawn previous attention in sports literature.

Emerging evidence in the study of motor control has pointed to a significant role for distributed movements, Diaz said. He described distributed movement as a combination of movements developed over many repeated attempts to perform a task, in this case kicking in a particular direction.

“When, for example, you shift the angle of your planted foot, perhaps in an attempt to hide the direction of the kick, you’re changing your base of support. In order to maintain stability, maybe you have to do something else like move your arm. And it just happens naturally,” Diaz said. “If this happens over and over again, over time your motor system may learn to move the arm at the same time as the foot. In this way the movement becomes one single distributed movement, rather than several sequential movements. A synergy is developed.”

A distributed movement is complex, but, as Diaz’s second experiment indicates, some people may be using it — however unconsciously — to inform their judgment as to which direction the ball will go.

In his second experiment, Diaz played an animation of the motion capture data to a group of 31 subjects, and asked the subjects to pick which direction they thought the ball would go. In the animation, each body joint is represented by a dot, and movement of the body is easily recognizable as such. The animation runs from the standing-start until the foot reaches the ball, at which point the screen goes black and subjects pressed a button to the left or right of the screen, indicating which direction they thought the ball had gone.

Among his 31 subjects, all of whom were novices to the activity, 15 were not able to score above chance (50/50), even when given one-half second after the scene to ponder the outcome. Sixteen, however, did perform better than chance.

Diaz then looked for relationships between successful judgments on ball direction and each of the “local” and “distributed” movements he had tracked. His analysis revealed strong correlations between the two “local” and two of the three “distributed movements” that were reliable indicators of kick direction.

“The question is, knowing these potential sources of reliable information, what do people actually use?” Diaz said. “I found four reliable sources that were well correlated with subjects’ judgments.”

Another finding, he said, is that the 16 successful subjects waited longer than the 15 unsuccessful subjects to make their choices (if the half-second elapsed without a response from the subject, no result was entered).

“There is a clear relationship between response timing and performance,” Diaz said.

Diaz said his findings have set the stage for further exploration. He would like to create a training regime to guide subjects’ attention toward more reliable indicators of kick direction. He also wants to know if professional goalkeepers would perform better than novices on the task.

Similar studies using video data of penalty kicks among professional Dutch goalkeepers showed that not all professional players are better than novice subjects, he said.

“Only a subset are better than average. I want to know — what is it that these successful experts are doing better than novices?”

Wednesday, June 9, 2010

Sleep preference can predict performance of Major League Baseball pitchers

Ω

Pitchers who are 'morning types' appear to have an advantage over night owls

A Major League Baseball pitcher's natural sleep preference might affect how he performs in day and night games, according to a research abstract that will be presented Wednesday, June 9, 2010, in San Antonio, Texas, at SLEEP 2010, the 24th annual meeting of the Associated Professional Sleep Societies LLC.

Results indicate that pitchers who were morning types performed statistically better overall than those who were evening types. In early games that started before 7 p.m., the earned run average (ERA) of pitchers who were morning types (3.06) was lower than the average ERA of pitchers who were evening types (3.49); however, in games that started at 7 p.m. or later, pitchers who were evening types performed slightly better (4.07 ERA) than morning types (4.15 ERA).

"We were surprised to see that chronotype did affect pitching," said principal investigator and lead author W. Christopher Winter, MD, medical director of the Martha Jefferson Hospital Sleep Medicine Center in Charlottesville, Va. "We were also surprised to see that pitchers who were more 'morning type' seemed to do better overall."

Individual pitchers showed a trend toward higher ERAs in the late games. According to Winter, this supports previous research showing that the peak performance time for most athletes is between mid-afternoon and early evening.

The study involved 18 pitchers from five MLB teams: the Los Angeles Dodgers, New York Mets, Philadelphia Phillies, San Francisco Giants and Tampa Bay Rays. Sleep preference was determined using a modified version of the Morningness-Eveningness Questionnaire (MEQ). It identifies a person's tendency to be either a morning type who prefers to go to bed and wake up early, or an evening type who prefers to stay up late at night and wake up late in the day. Ten participants were found to be evening types, and eight were morning types.

The study used the players' statistics from the 2009 season, which provided about 728 early innings and 845 late innings for analysis. Game start times were adjusted for travel using the principle that for every time zone crossed, it takes 24 hours to adjust.

"These results are important as they are potentially giving insight into an entirely new way to grade or classify an athlete, in this specific case a pitcher," said Winter. "This study may provide insight as to which pitchers would be best in a given situation based upon when the game is being played. For example, a critical game being played in the evening might be a better situation to pitch an evening-type pitcher versus a day-type pitcher."

Winter also has studied the effect of travel across time zones on the performance of MLB teams. At SLEEP 2008 he presented the initial findings of a 10-year retrospective study that was later published in the September 2009 issue of the International Journal of Sports Physiology and Performance. He found that teams traveling from Western time zones to Eastern time zones were 14 percent more likely to win than teams traveling from east to west. Teams also won more than 60 percent of the games in which they had a three-hour "circadian advantage.

Tuesday, June 8, 2010

Will the new World Cup soccer ball bend?

Ω


Physics experts at the University of Adelaide believe the new ball created for the 2010 World Cup, called the Jabulani, will play "harder and faster", bending more unpredictably than its predecessor.

But why? And what will it mean for the game?

"The Jabulani is textured with small ridges and 'aero grooves' and represents a radical departure from the ultra-smooth Teamgeist ball, which was used in the last World Cup," says Professor Derek Leinweber, Head of the School of Chemistry & Physics at the University of Adelaide, who has previously written about and lectured on the aerodynamics of cricket balls, golf balls and the 2006 World Cup soccer ball, the Teamgeist.

Along with student Adrian Kiratidis, who is studying for his Master of Philosophy (MPhil) in Physics, Professor Leinweber has been reviewing the physics behind soccer balls and what that means for the Jabulani. Adrian is also a soccer enthusiast.

"While the governing body FIFA has strict regulations on the size and weight of the balls, they have no regulations about the outside surface of the balls," Professor Leinweber says.

"The Teamgeist was a big departure at the last World Cup. Because it was very smooth – much smoother than a regular soccer ball – it had a tendency to bend more than the conventional ball and drop more suddenly at the end of its trajectory.

"By comparison, the aerodynamic ridges on the Jabulani are likely to create enough turbulence around the ball to sustain its flight longer, and be a faster, harder ball in play.

"The Jabulani is expected to 'bend' more for the players than any ball previously encountered. Players are also discovering new opportunities to move the ball in erratic ways, alarming the world's best goalkeepers. By the time the ball reaches the goalkeeper, the Jabulani will have swerved and dipped, arriving with more power and energy than the Teamgeist."

University of Adelaide students have also put the new World Cup soccer ball to the test on the soccer field. Based on Professor Leinweber's theories, they've attempted to "bend" the Jabulani and have also kicked the Teamgeist and a regular soccer ball for comparison.

Tuesday, April 6, 2010

Scientists: Soccer improves health, fitness and social abilities

Soccer is a pleasurable team sport that provides an all-round fitness and can be used as treatment for lifestyle-related diseases. Men worry less when playing soccer than when running. Women's soccer creates we-stories and helps women stay active.



Photo from the study of women and soccer.
Credit: Mikal Schlosser

The above statements are taken from some of the results from an extensive soccer research project involving more than 50 researchers from seven countries. The researchers studied physiological, psychological and sociological aspects of recreational soccer and compared it with running. Led by Professors Peter Krustrup and Jens Bangsbo from the Department of Exercise and Sports Sciences, University of Copenhagen, the 3-year project covered several intervention studies involving both men, women and children, who were divided into soccer, running and control groups. The results from the studies are so remarkable that the Scandinavian Journal of Medicine and Science in Sports are publishing a special edition issue entitled "Football for Health" containing 14 scientific articles from the soccer project on Tuesday 6 April 2010.



Soccer training - older men
Credit: Mikal Schlosser

Soccer for Health

The researchers studied the physical effects of soccer training for untrained subjects aged 9 to 77 years. The conclusion was clear. Soccer provides broad-spectred health and fitness effects that are at least as pronounced as for running, and in some cases even better.

Study leader Peter Krustrup concludes "Soccer is a very popular team sport that contains positive motivational and social factors that may facilitate compliance and contribute to the maintenance of a physically active lifestyle. The studies presented have demonstrated that soccer training for two-three hours per week causes significant cardiovascular, metabolic and musculoskeletal adaptations, independent on gender, age or lack of experience with soccer".

Professor Jens Bangsbo continues: "The effects can be maintained for a long period even with a reduced frequency of training to one to two times one hour a week. Recreational soccer, therefore, appears to be an effective type of training leading to performance improvements and significant beneficial effects to health, including a reduction in the risk of cardiovascular diseases, falls and fractures. In a number of aspects, soccer training appears to be superior to running training. Soccer training can also be used to treat hypertension and it was clearly superior to a standard treatment strategy of physician-guided traditional recommendations".

The two researchers foresee a great perspective in using soccer as a health promoting activity: "The studies have convincingly shown that soccer training is effective to enhance fitness and the health profile for the general population. Future studies are needed to understand what is causing the beneficial effects of football, how well football can be used to improve heart health in early childhood and how other patient groups such as those with type II diabetes or cancer can benefit from playing soccer".

Soccer creates we-stories and helps women stay active

One of the many aspects of the study was to examine the level of social capital for women gained from running and soccer. Even though both the soccer players and the runners trained in groups, there were significant differences in the way they interacted and what they considered the most important aspects of the sport they were engaging in. The runners were more focused on themselves as individuals, whereas the soccer players developed "we"-stories as they began to see themselves as a team. From the beginning, most of the women, both soccer players and runners, thought running would be an easier form of exercise to stick to after the intervention programme was over. That turned out not to be the case:

- "The most important finding was the difference in social interaction and creation of we-stories between the groups, which may impact the possibilities of long-term compliance. A year after the study, many of the soccer players continue to play soccer, some have even joined an organised soccer club. Not many from the running group have continued their training. This can very well be due to the fact that the runners focussed on their health and on getting in shape, whereas the soccer players were more committed to the activity itself, including the fun and not letting down team mates", says Associate Professor Laila Ottesen.

Men worry less when playing soccer than when running.

Another study examined the exertion experienced during training for untrained adults and their experience of "worries" and "flow". This study, based on 6 groups of untrained men and women, showed that all groups experienced an overall high level of flow during the intervention, which underlines that the participants felt motivated, happy and involved to the point where they forgot time and fatigue. There was no difference in the level of worry for the female soccer players and runners, but the running men seemed to worry quite a lot more than their soccer playing counterparts.

- "The men that played soccer elicited lower levels of worry than during running, 2.8 vs 4.0 on a 0-6 scale, and although they are training at the same average heart rate they do not feel the exertion as strongly as during running" says Associate Professor Anne-Marie Elbe and adds: "Further research is needed to examine why men and women experience playing soccer differently but it could be that the men just have had more experience with football in earlier years than the women".

Tuesday, March 16, 2010

Tommy John” Elbow Reconstruction 95% Successful with Grown Teen Pitchers, Study Says

A new study presented today at the American Orthopaedic Society for Sports Medicine’s (AOSSM) Specialty Day in New Orleans, (March 13), found that 95 percent of skeletally mature high school pitchers were satisfied with their “Tommy John” elbow reconstruction surgery. Almost as many, (94.7 percent) returned to competitive baseball.

“Tommy John” surgery is a procedure where a damaged elbow ligament (ulnar collateral ligament or UCL) is replaced with a tendon from elsewhere in the body. The surgery is named for Hall of Fame pitcher Tommy John, who was the first person to have the surgery in 1974. John returned to the major leagues and went on to win 164 games after the surgery. Prior to this historic surgery, a UCL injury was a career-ending injury.

“High school kids have been a grey zone for this surgery,” said Michael J. Angel, MD, of Premier Orthopaedics of Westchester and Rockland. “Obviously, surgeons would avoid surgery on young patients whose growth plates had not closed. But this study can give surgeons the confidence to recommend this surgery to teenage skeletally mature athletes. It also gives the teen and their parents assurance that the surgery should go well.”

In the study, 20 high school baseball pitchers between 16 – 18 years old had the UCL surgery, 19 out of 20 reported being satisfied with the surgery (17 were very satisfied, 2 were somewhat satisfied). Eighteen of the 19 satisfied patients (94.7 percent) reported that they returned to competitive baseball. Of the 19 players, three reported that their highest level of competition was in the minor leagues, another 13 went on to play intercollegiate baseball and three returned to high school baseball.

Overuse injuries account for nearly 50 percent of all sports injuries in middle school and high school students, according to the National Center for Sports Safety. For high school athletes whose growth plates have closed, this study shows that the “Tommy John” UCL reconstruction is a successful option for teenage baseball pitchers who need it.

While the trend of young athletes to specialize in one sport remains controversial, sports medicine has developed innovative surgeries to repair and reconstruct overuse injuries that can result from specialization. However, the bigger problem is prevention of injury. AOSSM and several other sports medicine organizations, including the American Academy of Orthopaedic Surgeons, American Medical Society for Sports Medicine, American Academy of Pediatrics, National Athletic Trainers’ Association, National Strength and Conditioning Association and SAFE Kids USA have teamed together to help prevent overuse injuries in youth athletes. The STOP (Sports Trauma and Overuse Prevention) Sports Injuries campaign includes cutting edge information on sport specific injury prevention techniques for athletes, parents, coaches and healthcare providers. For more details, visit www.STOPSportsInjuries.org.

Wednesday, March 3, 2010

Soccer reduces risk of falls and bone fractures

An extensive research project has studied the effects of soccer on muscle strength, postural balance, bone mineral density and reflex response to a sudden push in the back among adult women and men. Five scientific articles are now being published in Scandinavian Journal of Medicine & Science in Sports showing that regular participation in soccer increases both bone mass and bone density, causes a significant improvement in standing postural balance and improves muscle strength. Together, these effects reduce the risk of falls and bone fractures.

The observed improvements in bone mineral density, strength and postural balance due to recreational soccer are of particularly interest for a large group of women but also for elderly men, says project leader Associate Professor Peter Krustrup, Department of Exercise and Sport Sciences, and continue "It is well known that the risk of falls and fractures increases with age as a result of weaker bones, poorer balance and attenuated ability to trigger rapid muscle force, but the present results suggest that soccer - and possibly other ball games - is an effective training method to reduce bone weakening that comes with increasing age".

Better bones from soccer than from running

A 14-week study in which women aged 20-47 years trained soccer twice a week showed marked increases in bone density in the left and right tibia. Furthermore, soccer training showed an elevated mass of the calf muscle, greater muscle strength, and an improved balance. A 16-months training intervention for the same subject group showed that prolonged soccer training for untrained premenopausal women elevates whole-body bone mineral density. The women who participated in the study had never played soccer before, implying that all can benefit from soccer. Interestingly the short- and long-term training effects on bone mineral density were greater for the soccer players than for a similar group of runners and an inactive control group.

- "During soccer training and games, the players perform many sprints, turns, kicks and tackles. This combination of actions help achieve a variable bone impact that appears to provide a better stimulus to bone mineralisation than running", explains project leader Peter Krustrup.

Little training required

Small-sided soccer games for 1 hour two to three times a week during 12 weeks for untrained men aged 20-40 years resulted in significant increases in muscle mass and leg bone mass, whereas no effects occurred for the inactive control group. The postural balance was improved as well. In a follow-up study on long-term effects of soccer for men, it was demonstrated that 64 weeks of training have an additional effect on both muscle mass and leg bone mineral density. These effects were observed despite the fact that the training volume was reduced significantly. After the first 12 weeks the training frequency was only 1.3 times per week, indicating that a relatively small amount of training can nevertheless affect bone strength in the longer term.

70-year-old men as fit as 30-year-olds

The research group has also examined muscle function and postural balance in a group of 65-75 year old men who have played recreational soccer most of their lives and compared the values with a group of men at the same age without specific training and a group of 30-year-old untrained men.

- "The research shows that 70-year-old men, who have played soccer most of their lives on a recreational basis, have just as good a balance and rapid muscle strength as untrained 30-year-olds and much better balance and muscle strength than their peers" says Peter Krustrup.

As an example, the untrained older men had more than twice as many falls in a one-leg balance test, compared to the soccer-trained older men and untrained young men.

About the project

Led by Professors Peter Krustrup and Jens Bangsbo from Department of Exercise and Sports Sciences, University of Copenhagen, 50 researchers from seven countries have studied the physical, psychological and social aspects of soccer and the results are remarkable. A number of scientific articles from the project are published on 2 March 2010 later this month the Scandinavian Journal of Medicine and Science in Sports will publish a special edition issue entitled "Football for Health" containing 14 scientific articles from the soccer project. The research project has received funding from FIFA - Medical Assessment and Research Centre (F-MARC), The Danish Ministry of Culture, TrygFonden, United Federation of Danish Workers (3F), The Danish Football Association, Team Denmark and The Danish Sports Confederation.

Further research plans:
The researchers have specific plans to examine the effect of soccer on other patient groups such as people with diabetes II and cancer. The research group is also planning follow-up studies of the long-term effects of soccer on preliminary stages of osteoporosis, on high blood pressure for middle-aged men and women as well as the cardiac and musculoskeletal health effects of youth soccer. A planned collaboration with an international network of researchers from, among others, England, Italy, Portugal, Switzerland, Germany, Norway, Sweden, USA, Kenya and Iran will examine the cardiovascular and musculoskeletal effects of soccer and other ball games such as basketball, handball, volleyball and floorball on inactive and overweight children and inactive elderly people.

Tuesday, March 2, 2010

Common Marathon, Half-Marathon Training Mistakes

Half marathons and marathons can be over in a matter of hours, but runners, both newbies and elite, often spend months training for the 13.1- and 26.2-mile races. Robert Chapman, director of the Human Performance Laboratory in Indiana University's School of Health, Physical Education and Recreation, and coach of Brook Team Indiana Elite, discusses four common mistakes runners make when preparing for these major races.

Mistake #1: Discounting the importance of the weekly long run
.

For the half-marathon and marathon, the weekly long run is one of the most important components of training. The adaptations that take place physiologically and psychologically during the long run are critical in helping the runner complete the race distance, as well as helping the runner achieve a goal time. Key adaptations that take place with the weekly long run:

* Increased storage of muscle glycogen. Glycogen is the primary storage form of carbohydrates in the body, and the amount of glycogen the body can store is limited. In a typical person, there is enough glycogen present to fuel about two to three hours of moderate exercise. When glycogen stores get low or run out, the runner "hits the wall" and will struggle to finish the event. However, glycogen stores can increase as a result of training, and stores improve significantly as a result of including long runs each week.

* Improved psychological ability to handle the race distance. With each weekly long run, there is an improvement in the runner's ability to mentally tolerate exercising for long periods of time.

* Improved ability to absorb and tolerate the "pounding" the legs will take during the race. Feet, joints, tendons and muscles are all gradually strengthened over time from the overloading they receive from the weekly long run. Many runners who fail to finish a marathon do so because of leg pain and discomfort, resulting from the weight-bearing pounding over 26 miles.

* Chapman recommends a long run once each week, starting early in training at about 20 percent of overall weekly volume. From there, athletes in the half-marathon should aim for a minimum long run distance of 8-10 miles, ideally completed at least twice before their race. Marathoners should aim for a minimum long run distance of 15 miles, completed at least twice before the race, with at least two long runs of around 20 miles being ideal.

Mistake #2: Selecting a race without considering the weather or lifestyle considerations for training.


Most marathons are held in the spring or fall because of the milder temperatures in the Northern Hemisphere. Most experts recommend a training buildup of 10-16 weeks for most experienced runners prior to a marathon, perhaps a few weeks less for a half marathon.

For athletes who select a spring race, this will mean completing a large portion of their training during the thick of winter -- where cold temperatures, snow and ice, and limited daylight hours can all have a dramatic effect on the quality of training and motivation for completion. Runners with work and family commitments, who have to train in early morning or evening hours, may find preparation for a spring marathon challenging. For athletes who select a fall marathon or half marathon, the bulk of the training load will come during the heat and humidity of summer. For most runners, training in extreme heat is more challenging than training in cold weather, where additional clothing can be worn. While it may be considerably easier to get runs in during early morning or late evening hours, summer is typically full of family vacations and weekend outings that can make sticking with a rigid training routine more difficult.

In the end, when deciding on a marathon or half marathon, each runner should take a look not just at the time of the year of the race, but the logistics of how well they will be able to complete their training in the three to four months prior to the event.

Mistake #3: Failing to "practice" the race day routine.


After weeks and weeks of training, many runners end up failing to finish or meet their goals -- often due to some simple, small detail that was overlooked regarding race day routine. Here are some examples:

* Not being used to running in the early morning, when most races start.
* Logistics such as bus departure for the race start, parking, proximity of race to hotel.
* Breakfast decisions, such as what and when to eat.
* Clothing, shoes, socks -- will they cause chafing or blistering?
* Uncertainty about the sports drink provided by the race and whether it upsets runners' stomaches.
* Shoe choice -- newer or older pair.

Many of these questions can be worked out during weekly long runs, such as clothing and breakfast choices. Runners also can contact race organizers for details about sports drinks and then try out the drinks during training. The weekly long run is not just an important component for training adaptations. It is also a great "dry run" for the race.

Mistake #4: Starting the race too fast.


Three athletes who Chapman coaches qualified for the U.S. Olympic Marathon Trials and another won the Columbus Marathon in her debut at the distance. In all four cases, the athletes executed a "negative split" strategy -- where the second half of the race was faster than the first.

Based on the paces completed in training, runners should have a strong idea of what pace they are capable of executing for the race distance, with slight modifications based on changing race day conditions such as weather. Once that pace is determined, Chapman recommends a conservative approach, especially if the goal is simply to finish the race. Even if a runner has a goal time in mind, a conservative, negative split approach will often lead to best performances, typically without the late race discomfort that normally accompanies a more aggressive pacing approach.

Starting out at a conservative pace can often be a challenge with the excitement of the race start, the bands and music, and even fireworks that are present when the gun fires. However, the most common recipe for disaster in a marathon is going out too fast.

Tuesday, February 2, 2010

Play Soccer for Your Health!

Play yourself healthy

A just published research experiment on inactive men with high blood pressure shows that just 3 months of soccer practise twice a week causes a significant fall in blood pressure, resting pulse rate, and percentage of body fat, and is more effective than the doctor's usual advice on healthy diet and exercise. Other parallel experiments on both women and men further demonstrates that a regular game of soccer affects numerous cardiovascular risk factors such as maximal oxygen uptake, heart function, elasticity of the vascular system, blood pressure, cholesterol and fat mass far more than e.g. strength training and just as much if not more than running.

Each of the experiments was controlled randomized studies where the soccer groups were compared to other exercise groups and inactive controls. The soccer experiments are part of a large-scale research project on soccer and health carried out at the University of Copenhagen, four Danish University Hospitals, the Swiss Federal Institute of Technology and the Schulthess Clinic in Zurich.
Project Leader and Associate Professor at the University of Copenhagen Peter Krustrup recaps the results: "Our research shows that soccer is a versatile and intense form of exercise that provides a positive effect on cardiovascular risk factors in a large group of untrained adult men and women," and continues: "Based on the results, soccer can be recommended as part of the treatment for high blood pressure and as broad-spectred prevention of cardiovascular diseases."

Small games, big gains
When untrained children, teens, adults and older people play soccer, their pulse rate remains high and they perform multiple intense actions like sprints, turns, kicks and tackles.
"Our analyses also showed that the pulse rate and activity profile is the same in small-sided games where only 4, 6, 8 or 14 people play. In other words, it is very easy to obtain a combination of cardio and strength training with soccer," concludes Krustrup

Research partner Lars Juel Andersen from the Clinic of Sport Cardiology at Gentofte Hospital, Denmark, believes that the results are good news for the millions of people worldwide, suffering from high blood pressure: "It is well known that physical inactivity is a substantial risk factor in developing cardiovascular diseases in itself, but it is new that a pleasurable team sport like soccer is effective in treating high blood pressure". Furthermore, associate professor Peter Riis Hansen from Gentofte Hospital suggests that football may have other favourable effects on the vascular system, namely a reduction of arterial stiffness, which has been associated with improved cardiovascular outcomes.
About the project
Led by Professors Peter Krustrup and Jens Bangsbo from Department of Exercise and Sports Sciences, University of Copenhagen, 50 researchers from seven countries have studied the physical, psychological and social aspects of soccer and the results are remarkable. A number of scientific articles from the project are published on 2 February 2010 at a seminar at the University of Copenhagen and later this month the Scandinavian Journal of Medicine and Science in Sports will publish a special edition issue entitled "Football for Health" containing 14 scientific articles from the soccer project. The research project has received funding from FIFA - Medical Assessment and Research Centre (F-MARC), The Danish Ministry of Culture, TrygFonden, United Federation of Danish Workers (3F), The Danish Football Association, Team Denmark and The Danish Sports Confederation.

Further research plans:
The researchers have specific plans to examine the effect of soccer on other patient groups such as people with diabetes II and cancer. The research group is also planning a follow-up study of the long-term effects of soccer on high blood pressure and preliminary stages of osteoporosis. A planned collaboration with an international network of researchers from, among others, England, Italy, Portugal, Switzerland, Germany, Norway, Sweden, USA, Kenya and Iran will examine the cardiovascular and muscular-skeletal effects of soccer and other ball games such as basketball, handball, volleyball and floorball on inactive and overweight children and inactive elderly people.

Thursday, January 28, 2010

Taller Soccer Players More Likely to Be Accused of Fouls

In this World Cup year, when football (soccer) passions are running high, supporters might be forgiven for objecting to every decision to award a foul against their team, made by referees. But they might also have a point. Researchers at Rotterdam School of Management, Erasmus University have researched all recorded fouls in three major football competitions over seven years. They discovered an ambiguous foul is more likely to be attributed to the taller of two players.

Dr. Niels van Quaquebeke and Dr. Steffen Giessner, scientists at Rotterdam School of Management, Erasmus University began their research by transferring their insights from decision making in business into the arena of sports. Specifically, they wanted to investigate whether people consider the available information in such ambiguous foul situations in an unbiased, i.e. subconsciously unprejudiced, way. Based on evolutionary and linguistic research which has revealed that people associate the size of others with concepts such as aggression and dominance, Van Quaquebeke and Giessner speculated that ambiguous fouls are more likely to be attributed to the taller of two involved players. Results indicate that respectively taller people are more likely to be perceived by referees (and fans!) as foul perpetrators and their respectively smaller opponents as foul victims.

To put their assumption to a test, the scientists analysed all fouls recorded by Impire AG in seven seasons of UEFA Champions League (32,142 fouls) and German Bundesliga (85,262 fouls), the last three FIFA World Cups (6,440 fouls) as well as data from two additional perceptual experiments with football fans. For all seasons, leagues, and data collection methods, their analyses revealed the same picture confirming their initial assumption: taller people are indeed more often held accountable for fouls than shorter ones -- even when no actual foul was committed.

A scientific article based on their research will be published in the Journal of Sport & Exercise Psychology in February 2010. This article can also be found on hdl.handle.net/1765/17827.

Van Quaquebeke said: "We chose football as the context of our studies because the sport often yields ambiguous foul situations in which it is difficult to determine the perpetrator. In such situations, people must rely on their 'instincts' to make a call, which should increase the use and thus the detectability of a player's height as an additional decision cue. Furthermore, the use of referee assistance technology and adequate referee training is frequently debated in association football. Thus, by providing scientific insights on potential biases in refereeing, our work might help officials weigh the options."

Both researchers say, however, that it is not their call how to derive conclusions for football practice.

Monday, January 25, 2010

Soccer Injuries: Cleat-Natural Grass Combination May Be Less Likely to Result in Anterior Cruciate Ligament Injury

SAthletes put less strain on their anterior cruciate ligament (ACL) while making a cut on a natural grass surface while wearing a cleat.

This is the conclusion from a study by investigators at Hospital for Special Surgery (HSS) that tested the strain placed on the ACL of four different shoe-surface interactions: Astroturf/turf shoe, modern playing turf/turf shoe, modern turf/cleat, and natural grass/cleat. The study appears in the January 2010 issue of the Journal of Biomechanical Engineering.

"It appears that a similar cut made on four different surfaces, the best strain profile is in grass/cleat combinations," said Mark Drakos, M.D., formerly an orthopedic fellow in the Sports Medicine and Shoulder Service at HSS. "So, there is less force occurring at your ligament for the same cut on that particular surface using this model."

He added that the study investigated noncontact injuries. "These are injuries where an athlete plants his or her foot while making a cut and blows out his or her knee," Dr. Drakos said. "The reason that I think this is so interesting is because there are still environmental factors, which have yet to be optimized. We don't know all the science behind why ACL injuries may be more common on turf than on grass. This study starts developing some of the science behind that, so that it can be looked at more closely because, at the end of the day, I think we need to optimize some of those environmental factors."

Previous studies have suggested that increased traction at the shoe-surface interface may increase the risk of sustaining an ACL injury. While the majority of studies reveal that ACL injuries are more likely to occur on artificial turf, there are some studies that have shown that injuries occur more frequently on grass fields. So, investigators have concluded that confounding factors, such as weather and footwear, must play a role in injuries. Some investigators have constructed models to test how the shoe-surface interface impacts loading conditions at the level of the foot, but no studies have investigated how the interface directly impacts the knee.

To fill this knowledge gap, investigators at HSS used a cadaveric model to test various shoe-surface interactions; they used the lower extremities (knee, foot, and ankle) from eight cadavers. One at a time, each specimen was positioned in a box-like structure, rigged to be in a standing position. The knee was positioned at a 30 degree angle, the flexion angle where the anterior cruciate ligament is most sensitive to strain. Investigators constructed an apparatus that placed weight on the leg, to simulate the weight of a body. Underneath the foot was a turf box that housed whatever turf they wanted to test and underneath the turf box, they placed a force plate that registered how much load was being placed on the shoe-surface interface. A lazy Susan was placed underneath the force plate that allowed the force plate and turf box to rotate. In this way, researchers could simulate a cut or a person pivoting in, for example, a soccer game.

"Our model looks at how forces travel up the kinetic chain, and that is something that should be looked at more closely, meaning you can't just look at the knee injuries by looking at the knee in isolation," Dr. Drakos said.

The investigators found that the natural grass/cleat combination placed a statistically lower maximum strain on the leg than any of the remaining three groups. All other combinations placed a greater amount of strain compared to the natural/grass cleat combination. The Astroturf shoe was 80.2 percent greater, modern playing turf/turf shoe was 47.5 percent greater, and the modern playing turf/cleat was 45.1 percent greater.

"As a former football player. I was always curious about why I was more sore after playing on artificial surfaces than playing on grass, and I wanted to find out the reasons behind that using a biomechanical model," Dr. Drakos said. "There are basically 200,000 ACL injuries every year in the United States alone and this [type of playing field and type of shoe] is an environmental factor which has been shown to play a role in injury, but has yet to be optimized. I think it is a scenario that deserves attention and further research."

Astroturf can be thought of as a carpet with ½ inch fibers on a 5 millimeter foam pad. The newer, modern playing turf consists of two inched fibers with a crumb rubber infill, three pounds of infill per square foot of turf. Investigators used fresh Kentucky bluegrass sod for the natural grass samples.

Saturday, January 23, 2010

Study: Perceived Ball Size Correlates With Batting Average

Athletes often say that when they are playing well – shooting hoops, hitting baseballs, catching passes – the ball appears bigger. Likewise, they say that when they are in a slump the ball appears smaller. When Mickey Mantle hit a 565-foot home run he said, "I just saw the ball as big as a grapefruit." But Joe "Ducky" Medwick of the St. Louis Cardinals said during a slump that he was "swinging at aspirins."

Appearances may be reality, in a sense.

A new study by University of Virginia psychologists has found a correlation between batting averages of softball players and how big, or small, they perceived the ball to be. The study documents that when the players were hitting well they clearly perceived the ball to be bigger. And when they were hitting less well, they perceived the ball to be smaller.

The interactions between mind and body – perception and action – may be as interlinked as athletes believe them to be, according to Jessica K. Witt, a cognitive psychology doctoral candidate at the University of Virginia. Witt and U.Va. psychology professor Dennis R. Proffitt describe the batting average and apparent ball size correlation in a paper that appears in the December 2005 issue of the journal Psychological Science.

The full article can be accessed online at: http://www.blackwell-synergy.com/doi/full/10.1111/j.1467-9280.2005.01640.x

"It's interesting that all the optical information is the same – the ball is only one size – but that it looks differently depending on the individual performance of the athlete," Witt said. She is interested in understanding if there is a feedback loop between perception and performance. "It's clear that the way we see the world affects the way we perform in it," she said. "I'm trying to get a glimpse into the role perception plays in streaks and slumps."

Witt and her colleagues conducted their experiment at several softball fields in Charlottesville, Va., and asked players who had finished playing for the day to look at eight different-sized circles on a board and pick the one that best represented the size of the softball they had been trying to hit. They also checked the hitting percentage of the players for that day. They found that the players who were hitting well were picking the larger circles, and the players who were batting .500 or above – those hitting safely at least half the time – were picking the largest-size circle.

The finding did not surprise Witt, a world-class athlete who competed last July for the gold medal-winning U.S. Ultimate Frisbee team at the 2005 World Games in Duisburg, Germany.

"As an athlete I've always been intrigued by how an athlete's physical performance can affect her state of mind," Witt said. "This study was designed to test what ball players have long been saying about how their performance is correlated with the way they are perceiving the ball."

Witt has experienced this herself as an athlete. She notes how she feels much more confident when she's throwing a Frisbee with the wind as opposed to against it. "The player I'm throwing to seems so far away when I'm throwing against the wind, but when I'm throwing with the wind it seems to be a short toss even if it's far," she said.

Witt plans to continue her study on perceived ball size and batting averages under controlled conditions. She hopes to obtain funding or regular access to a batting cage and competitive baseball players to design experiments that would allow her to closely monitor hitting performance, perception and the mental state of players. She is also interested in documenting whether or not visualization techniques – such as repeatedly imagining hitting a ball before going up to the plate – have any effect on performance in actuality and on whether the ball will look bigger.

Witt says such studies have implication in all areas of life – job performance, relationships, abilities and disabilities. "Perspective and perception play a big role in what we do and how well we do it," she said.

Thursday, January 21, 2010

How does an outfielder know where to run for a fly ball?

While baseball fans still rank "The Catch" by Willie Mays in the 1954 World Series as one of the greatest baseball moments of all times, scientists see the feat as more of a puzzle: How does an outfielder get to the right place at the right time to catch a fly ball?

Thousands of fans (and hundreds of thousands of YouTube viewers) saw Mays turn his back on a fly ball, race to the center field fence and catch the ball over his shoulder, seemingly a precise prediction of a fly ball's path that led his team to victory. According to a recent article in the Journal of Vision ("Catching Flyballs in Virtual Reality: A Critical Test of the Outfielder Problem"), the "outfielder problem" represents the definitive question of visual-motor control. How does the brain use visual information to guide action?

To test three theories that might explain an outfielder's ability to catch a fly ball, researcher Philip Fink, PhD, from Massey University in New Zealand and Patrick Foo, PhD, from the University of North Carolina at Ashville programmed Brown University's virtual reality lab, the VENLab, to produce realistic balls and simulate catches. The team then lobbed virtual fly balls to a dozen experienced ball players.

"The three existing theories all predict the same thing: successful catches with very similar behavior," said Brown researcher William Warren, PhD. "We realized that we could pull them apart by using virtual reality to create physically impossible fly ball trajectories."

Warren said their results support the idea that the ball players do not necessarily predict a ball's landing point based on the first part of its flight, a theory described as trajectory prediction. "Rather than predicting the landing point, the fielder might continuously track the visual motion of the ball, letting it lead him to the right place at the right time," Warren said.

Because the researchers were able to use the virtual reality lab to perturb the balls' vertical motion in ways that would not happen in reality, they were able to isolate different characteristics of each theory. The subjects tended to adjust their forward-backward movements depending on the perceived elevation angle of the incoming ball, and separately move from side to side to keep the ball at a constant bearing, consistent with the theory of optical acceleration cancellation (OAC). The third theory, linear optical trajectory (LOT), predicted that the outfielder will run in a direction that makes the visual image of the ball appear to travel in a straight line, adjusting both forward-backward and side-to-side movements together.

Fink said these results focus on the visual information a ball player receives, and that future studies could bring in other variables, such as the effect of the batter's movements or sound.

"As a first step we chose to concentrate on what seemed likely to be the most important factor," Fink said. "Fielders might also use information such as the batter's swing or the sound of the bat hitting the ball to help guide their movements."

Monday, January 11, 2010

Program may prevent knee injuries

A soccer-specific exercise program that includes individual instruction of athletes appears to reduce the risk of knee injuries in young female players, according to a report in the January 11 issue of Archives of Internal Medicine, one of the JAMA/Archives journals.

Soccer is a dominant cause of sports-related injuries in part because of its increasing popularity, according to background information in the article. Between 2000 and 2006, the number of female soccer players around the world increased by 19 percent, to 26 million. "The most frequent and severe type of injury among soccer players is to the legs, especially the knees. The anterior cruciate ligament (ACL) injury incidence is highest among young athletes," the authors write. "Knee injuries, and especially ACL ruptures, may have long-term consequences, including a long absence from soccer, incomplete recovery and secondary osteoarthritis of the knee."

Ashkan Kiani, M.D., of Uppsala Primary Care, Uppsala County Council, Sweden, and colleagues assessed an intervention program specifically designed to reduce the risk of soccer-related knee injuries among 1,506 13- to 19-year-old Swedish female players. The program featured strengthening exercises designed to achieve an improved motion pattern, reducing strain on the knee joint. The training sessions were integrated into the regular soccer practices and required no additional equipment. In addition, players, parents and team leaders attended a seminar to raise awareness of injury risk.

During 2007, 777 girls on 48 teams participated in the program and 729 players on 49 teams served as controls. Three knee injuries, including one non-contact injury (not involving another player), occurred among players participating in the program, compared with 13 knee injuries and 10 non-contact injuries among girls in the control group. Therefore, the program was associated with a 77 percent reduction in the incidence of knee injuries and a 90 percent reduction in the incidence of non-contact knee injuries.

"The rate of injury was not only lower among teams participating in the preventive program but the injuries that did occur were also less severe," the authors write. All three injuries in the intervention group were categorized as major, but all three players regained full activity within six months. Among the control participants, most injuries were severe, and only four of the 13 regained full activity within six months.

Coaches reported their teams' adherence to the program at two time periods, after the preseason training period and after the competitive season. Of the 48 teams participating in the intervention, 45 (94 percent) reported a high adherence of at least 75 percent. "The high compliance rate in this study suggests that the program is easy to implement and incorporate into regular soccer practice," the authors conclude.